Tight-seam construction in Port Orford Cedar

[dstreck]

Has anyone got first-hand experience doing tight-seam construction? Our customer is specifying this method for his rebuild, and we have 1600bf of Port Orford Cedar on the way. I have never done a non-caulked carvel hull before. The only reference I have found for it is in Chapelle, and he only gives it 2 paragraphs and concludes that it should only be used in small craft with light planking (this project is 38' LOD, planking is 3/4"). On the other hand, I think IODs were done this way, and they certainly aren't small craft.

Chapelle notes that a pair of rollers are used to crush matching v-grooves in the mating plank edges, then the planks are edge set together and fastened. Finally, the whole boat is washed with boiling water (!) to swell the planking tight. That ought to be fun.

So, I'm looking for anyone who has built with this method, or any references anyone can think of. I understand the concept, but the actual nuts-and-bolts are a little shaky. Any help is appreciated.

[Bob Smalser]

Y'all are taking on significant potential problems in return for a few cosmetics. Compare POC with others on a stability chart like this one. From the species with the least seasonal movement at the top to the species with the most at the bottom.

Obviously only a very few species at the top tier of stability can be used without the gasket effect of cotton caulking, and even then the hull becomes a house plant of sorts, sensitive to all the environmental and maintenance factors that cause compression set.

Given what's available today in vertical grain, I'd recommend only WRC or Khaya and a full-time boat house, or I wouldn't do the job. POC won't remain leak free very long.


Order of Stability in Wood Species
Percent Shrinkage Green to Oven Dry as an Indicator of Relative Stability

Northern White Cedar Radial 2.2 Tangential 4.9 (R+T)/2 3.5
Honduras Mahogany 3.0 4.1 3.5
Khaya 2.5 4.5 3.5
Redwood, 2d Growth 2.2 4.9 3.5
Western Red Cedar 2.4 5.0 3.7
Eastern Red Cedar 3.1 4.7 3.9
Atlantic White Cedar 2.9 5.4 4.1
Eastern. White Pine 2.1 6.1 4.1
Teak 2.5 5.8 4.15
Incense Cedar 3.3 5.2 4.25
Alaska Yellow Cedar 2.8 6.0 4.4
Purpleheart 3.2 6.1 4.65
South American Cedar 4.0 6.0 5.0
Iroko 4.0 6.0 5.0
Sassafras 4.0 6.2 5.1
Okoume 4.1 6.1 5.1
Spanish Cedar 4.2 6.3 5.25
Black Cherry 3.7 7.1 5.4
Black Spruce 4.1 6.8 5.45
Tamarack 3.7 7.4 5.55
Baldcypress 3.8 6.2 5.6
Port Orford Cedar 4.6 6.9 5.75
Dark Red Meranti 3.8 7.9 5.85
Black Locust 4.6 7.2 5.9
Sitka Spruce 4.3 7.5 5.9
Sapele 4.6 7.4 6.0
Douglas Fir 4.8 7.6 6.2
Longleaf Pine 5.1 7.5 6.3
White Ash 4.9 7.8 6.35
Black Ash 5.0 7.8 6.4
Yellow Poplar 4.6 8.2 6.4
Rock Elm 4.8 8.1 6.45
Slash Pine 5.4 7.6 6.5
Apitong 4.6 8.2 6.5
Light Red Meranti 4.6 8.5 6.55
Black Walnut 5.5 7.8 6.65
Tangile 4.3 9.1 6.7
Western Larch 4.5 9.1 6.8
Angelique 4.6 8.2 7.0
Ipe 6.6 8.0 7.3
White Oak 5.3 9.1 8.0
Live Oak 6.6 9.5 8.0
Greenheart 8.8 9.6 9.2

[Hank Bornhofft]

The Concordias and othere A&R or European boats were done this way. A thin bead of cotton was laid in the grooves. As the wood swells the compressed groove expands and seals with the cotton but no seam shows at the surface. The secret is very close control of seasoning and humidity to get prodicted results based upon what was learned from experience with the particular wood. A&R used mostly African mahogany but also some larch. I think you would have to do a few boats to get it right and I don't think the quality of wood available today. Too tight, planks buckle and frames crack, to loose and she leaks. I would call Peter Costa at Triad boat works in Mattapoisett MA who has worked on and rebuilt Concordias all his life. Mine had some re-planking, garboards and 5 planks up both sides done by Concordia Company in the late '70's and traditional carvel was used.

[MiddleAgesMan]

It is a recipe for cracked frames, sooner or later.

[dstreck]

Bob,

Thank for the info (again). For better or worse, tight-seamed planking was specified by the Naval Architect and seconded by the owner. I have a feeling we'll be reefing out those seams for cotton caulking next winter.

Hank: I'll give Peter Costa a try. I've met him a few times. Thanks.

In the meantime, I need to get up to speed on this method. Anyone used these "edge crushers" that Chapelle talks about? How about soaking the boat in boiling water? Sounds like a great way to end up in the burn ward.

[Bob Smalser]

Thank for the info (again). Unfortunately, tight-seamed POC was specified by the Naval Architect and seconded by the owner.

By all means get some other professional opinions. For wood suitability, refer the architect to a consulting wood technologist like Dr Richard Jagels at U.Maine or Dr Bruce Hoadley at Yale. Advice you have to pay through the nose for is more easily heeded.

POC is gorgeous and a joy to work, but is one of the worst possible choices for your application.

[Canoeyawl]

Most of the locally built “Monterey boats” were planked this way. Hundreds of them - many were very long lived and some more than a century old are still fishing today.
There have been several references to the “crushed groove” in the WoodenBoat magazine over the years.
If I recall correctly this was a Herreshoff technique and the procedure was to fit the plank, then crush the groove into the plank edge with a roller device and then lightly plane the same edge just back to flat. When the wood swelled the crushed area would raise above the plank edge insuring a watertight fit.

Edit to add; After noting Bob’s chart I see that Port Orford cedar is rated almost exactly between Honduras Mahogany at one end and Douglas fir at the other…
Both are excellent planking stock. Your N.A. may have a good handle on this.

[Bob Smalser]

After noting Bob’s chart I see that Port Orford cedar is rated almost exactly between Honduras Mahogany at one end and Douglas fir at the other…


It looks that way, but we can tie the comparison down a bit tighter.

The numbers shown are the percentage wood shrinks going from green to oven-dry both for pure qsawn wood (radial) and pure flatsawn wood (tangential). While little in the natural world is absolute, these shrinkage values correlate pretty directly to the degree wood moves during seasonal moisture swings, and are the only method available to determine relative stability. In its final form with primer and paint, wood won't move as much as in these tests done in the raw, but relative stability between species remains the same.

HM shrinks 3.0% radially and 4.7% tangentially going from green to oven-dry. The % for POC is 4.6 and 6.9....and for DF 4.8 and 7.6.

Assuming riftsawn planking stock with a 45-degree slant of growth rings, the extrapolated riftsawn shrinkage rates are 3.85% for HM, 5.75% for POC, and 6.2% for DF.

So in this application compared to HM, POC is around 50% less stable and DF is around 62% less stable.

[Rob Stokes, N. Vancouver]

Jeez - I wouldn't consider this method of construction for a kitchen cabinet due to the inevitable wood movement - I'm really curious how a boat hull can be built like this and expected to put up with the potentially massive swings in the wood's moisture content over the seasons, years and locations the boat's going to go through.

It seems so counter-intuitive to me...

Rob (who's waiting to learn more)

[dstreck]

We at the shop have expressed our concerns about this method of construction, and this material (although I actually preferred it to mahogany, thinking that a harder wood like HM would bust frames when it swelled, while softer POC would compress...which still might be the case) but the decision is out of our hands.

So, anyone have a pair of "plank edge roller crushers" they want to sell?

[michigangeorge]

Dave, when that boat has problems the owner will be sueing you first and it will be your $ and reputation that suffer. Some times you just have to turn down some jobs and walk away.

[George Roberts]

dstreck ---

It is poor practice to try to do work you have no experience in. Worse practice to accept the work and then shop for opinions on how to do it.

I guess I could work up some engineering, nuts d bolts, that would determine how to accomplish the desired effect.

[pcford]

Most of the locally built “Monterey boats” were planked this way. Hundreds of them - many were very long lived and some more than a century old are still fishing today.

My sympathies go out to the prospective builder. He sounds certainly capable enough to protect himself if he were to proceed with the project.

As for myself, I hate to be in a position to be putting the blood, sweat and tears into a project about which I would have serious misgivings. Legal problems aside...I would need to sort out the facts of the matter before I'd proceed...for my own psychic well-being.

With that said, I would certainly listen to those with real experience than to recitations from a wood engineering table.

[pcford]

dstreck ---

It is poor practice to try to do work you have no experience in. Worse practice to accept the work and then shop for opinions on how to do it.

I guess I could work up some engineering, nuts d bolts, that would determine how to accomplish the desired effect.

Shows little understanding of the real world. I once was talking to a professional boatbuilder; he remarked that he had never done the same job twice.

I do speedboats....mostly Chris-Crafts. After having done this for almost thirty years, I can say that I've done most everything on a Chris.

Right now I'm working on a little Garden gaff sloop. Beginning of next week I am going to go over to ask Peter and Steve at Jensen's about the transom structure. I am sure they've done the same.

[outofthenorm]

According to Woodenboat, Dick Pulsifer has been building his Hampton boats this way for many, many years using WO and pine. There have been at least 2 articles on his methods, including one in the current issue. There are ways to make it work, but the design has to be suitable.

- Norm

[Bob Smalser]

As long as I can find a definitive reference for the correct way to put together a tight-seamed boat...

You might ask Tom Jackson here at WBM if he knows of a New England yard with recent tight-seam experience. I'd also expect your Naval Architect to have a solid handle on who and where he's had such designs built and their track record.

If the boat lives in a cold climate, has a covered boat house, the boat house has a bubbler so the boat isn't hauled for more than two weeks annually, all coatings are kept up, and you get a dead match between the moisture content of your planking and local baseline moisture contents for similar boats planked in species that match POC's density of .39-.43 Specific Gravity, the planking won't move very much seasonally. Problem is, boats are rarely treated that well, and even with one that is, the first winter in the Caribbean will probably result in unpleasant surprises from a couple months of warm water and tropical sun.

[dstreck]

dstreck ---

It is poor practice to try to do work you have no experience in. Worse practice to accept the work and then shop for opinions on how to do it.

I guess I could work up some engineering, nuts d bolts, that would determine how to accomplish the desired effect.

George,

I didn't "accept the work." I was assigned the job by my foreman. I've planked boats before, carvel and lapstrake, and I'm confident I can do a fine job on this one. I just need to get more details about this particular method. Its not the kind of hull that I would build for myself, but thats not my call. For the record, I've never built a double-planked hull before either, but I'm sure I could do it if my foreman gave me the job. All I'm doing is trying to get as much information as I can before I start.

[StevenBauer]

Norm, Pulsifer's boats are strip planked. Not quite the same thing as tight seamed carvel.

Steven

[Jay Greer]

One reason the Monterey fish boats remained tight is that they were in constant use and they also laid gunny sacks soaked in sea water on deck whenever the boats were in port. I did put down a deck house on its sill, by using the crushed seam method, once. I made up a long handled bronze roller that had a bead machined in the center and a washer on either side to keep it centered on the plank. The long handle allowed me to apply a lot of leverage. I planed the Honduras plank down to the bottom of the crushed seam and bolted the whole works down. I never heard any complaints of leakage from the owner.
Jay

[dstreck]

One reason the Monterey fish boats remained tight is that they were in constant use and they also laid gunny sacks soaked in sea water on deck whenever the boats were in port. I did put down a deck house on its sill, by using the crushed seam method, once. I made up a long handled bronze roller that had a bead machined in the center and a washer on either side to keep it centered on the plank. The long handle allowed me to apply a lot of leverage. I planed the Honduras plank down to the bottom of the crushed seam and bolted the whole works down. I never heard any complaints of leakage from the owner.
Jay

Jay,

Did you crush both mating edges or just one? Chapelle mentions a matched set of rollers, one of which crushes the center of one plank edge, the other which (I think) crushes the outside edges of its mate. This creates a shallow "tongue and groove" which the application of boiling water swells together. Or thats how I interpreted Chapelle.

Gotta do more research...

[rbgarr]

Is this for replanking the Six Meter you mentioned before?

[George Roberts]

dstreck -

"I didn't 'accept the work.' I was assigned the job by my foreman.

I would expect your foreman to provide any needed instruction. I also expect that if you go off on your own and "discover" a method, you will be held to a higher standard.

---

PCford ---

"Shows little understanding of the real world."

I expect those people who designed and built the Titanic had the same issues dstreck is having. I expect his results will be less dramatic. (That was too easy and unfair in so many ways.)

[RonW]

Interesting. I have never done this, but have read about it.
Besides the description in chapelle's boatbuilding book as you already know of.
I did manage to dig out and find a description in a little book printed in 1941 called -build a boat for pleasure or profit- which I am sure is totally unavailable.

The method described is to crush the grain with a little tool by pecking on the tool with a hammer and sliding the tool along as you crush the grain. The diagram shows the center 1/3 of the plank being compressed into a round depression, then they say to plane the plank smooth to the depth of the depression.This is done on both planks after they are spilled, of course.
The tool looks to be only 3 or 4 inches long, but it is also made for the thickness of planking, so that it just sits there as you peck on it sliding it along leaving a depression in the middle 1/3 of the plank.

Hope I have described the diagram and method good enough.
I also remember this crushed edge being used by Rushton on his larger rowboats, but with a twist, they just compressed the edge after the plank was properly fitted with out any planning. In another words the whole edge was crushed.

P.S.- this does show both mating edges - as I understand to be crushed and planned, but only in a center groove crush, not a tongue and groove as showed by Chapelle. Maybe there where variations on the method back then, I would think the tongue and groove would work better, but then again maybe the grovve only so as to not create to much pressure by swelling. Surely the architect will give you a little detail drawing with a brief description..good luck and please tell us what the architect says..

[werner]

there doesn't seem much written information on closed seamed building method not even in the books from when that method was popular.
relative large boats were build + 40" were build with this method.Years ago spoke to a guy who had build his ketch >40" that way with khaya ,remember he said it was important to final plane the plank all the length in one go ( curl doesn't brake).
The international meters 6 and 8's were build that way most of them with Honduras mahogany and quit a few survived .I have an old photograph 1910 of an eight meter being build it looks like a chain and wedges were used to pull the planks together !

[dstreck]

Interesting. I have never done this, but have read about it.
Besides the description in chapelle's boatbuilding book as you already know of.
I did manage to dig out and find a description in a little book printed in 1941 called -build a boat for pleasure or profit- which I am sure is totally unavailable.

The method described is to crush the grain with a little tool by pecking on the tool with a hammer and sliding the tool along as you crush the grain. The diagram shows the center 1/3 of the plank being compressed into a round depression, then they say to plane the plank smooth to the depth of the depression.This is done on both planks after they are spilled, of course.
The tool looks to be only 3 or 4 inches long, but it is also made for the thickness of planking, so that it just sits there as you peck on it sliding it along leaving a depression in the middle 1/3 of the plank.

Hope I have described the diagram and method good enough.
I also remember this crushed edge being used by Rushton on his larger rowboats, but with a twist, they just compressed the edge after the plank was properly fitted with out any planning. In another words the whole edge was crushed.

P.S.- this does show both mating edges - as I understand to be crushed and planned, but only in a center groove crush, not a tongue and groove as showed by Chapelle. Maybe there where variations on the method back then, I would think the tongue and groove would work better, but then again maybe the grovve only so as to not create to much pressure by swelling. Surely the architect will give you a little detail drawing with a brief description..good luck and please tell us what the architect says..

Ron,

I like the idea of pounding (er...tapping) in the groove rather than rolling it. Seems like the roller could easily go astray and slip off the plank edge. Maybe I'll try to codge together a tool like you describe and do some testing. I'm also unsure if I should put a strand of cotton wicking in the groove, as was done with the Concordias. More questions for the NA...

[RonW]

I think you will get more consistent results by tapping then rolling.
Do you have a picture of this groove depressor in your mind.
It sits on the plank with legs that go down the sides a little ways so the tool can't slip off or go astray.

[RonW]

I keep drawing it, and it looks good, then when it gets posted the margin moves everything back, need more of a computer wiz then me.
It basically looks like a C clamp with a half round bump in the middle that compresses the groove........

[dstreck]

I keep drawing it, and it looks good, then when it gets posted the margin moves everything back, need more of a computer wiz then me.
It basically looks like a C clamp with a half round bump in the middle that compresses the groove........

Am I on the right track?

http://i88.photobucket.com/albums/k182/davestreck/edgecrusher1.jpg

[RonW]

You got it....Shorter legs... computer generated models and antique boat building methods all rolled in to one simple how to course....

[Hank Bornhofft]

A&R used two hardened rollers between which the plank was feed, grooving each edge. The planks were a little oversize. Then it was planed down to the root of the groove, leaving a smooth edge with compressed wood in the center. Again, it requires close humidity control and experience with the slected wood to predict the amount of swelling. You're playing Russian roulette--it just might come out right the first time, or not.

[Jay Greer]

Jay,

Did you crush both mating edges or just one? Chapelle mentions a matched set of rollers, one of which crushes the center of one plank edge, the other which (I think) crushes the outside edges of its mate. This creates a shallow "tongue and groove" which the application of boiling water swells together. Or thats how I interpreted Chapelle.

Gotta do more research...
This job was on the bottom edge of a deck house side so only one surface was rolled with the depressed groove. I did plane off the plank down to the bottom of the groove. Having the long handle on the tool allowed me to lay full body weight on the plank edge that was set low on blocks in the shop.
Jay

[merlinron]

i would go to my boss and ask him if went to the NA and asked him to sign off on his suggested or spec'd method of construction, giving him the burden of liability. i have done that before a couplee times with buildings..... it usually make the architect/engineer rethink his ideas....

[mike hanyi]

oh you guys are scared stiff about the unknown!

http://www.jakobstadsbatvarv.multi.fi/mallit_rakentaminen.html

most all sixes are built this way, make sure client agrees to 100% new framing as the old frames are most likely tired. in Finland and sweden this is common pratice.

glue the planks together, and sikaflex them to the rabbet, 2part epoxy paint the planking under the waterline, and bilges.

if there movement it will be cracks it will be from drying out, which is repaired with a spline in the crack. there are thousands of boats built this way in europe. if it is a six tell your client to fly you over to visit us in finland and get the low down on six restoration.

redsky in kotka

[RGM]

For crushing the groove try using a length of solid copper wire or if that doesn't hold up well enough use a length of round welding/brazing rod. I think that the Dutch have been doing this for a few hundred years or so. Lay it on your plank edge and scoot the thing along as you methodically beat on it. Keep it lined up in the groove as you move it, don't leaf frog around. Like most things in life and wood boat work practice a little on the planking material that you plan to use. The groove doesn't have to be exactly, perfectly in the dead center of the plank edge. Just really damn close. A little wavering is acceptable. Then as described earlier, plane down to the groove. Or if you're feeling lucky just lay a length of candle wicking or two in the groove and start planking. Once again Mr. Smalser provides excellent information. I hope some of you folks print his stuff out. Good luck.

[outofthenorm]

Norm, Pulsifer's boats are strip planked. Not quite the same thing as tight seamed carvel.

Steven

Not all that different. Pulsifer doesn't use cove and bead and doesn't put any glue or goop or cotton in the seams. The only real differences are that the planks are narrower and they are edge nailed. The overall expansion and contraction of an area of planking - and its subsequent power to break frames - is the same as trad carvel.

- Norm

[Bob Smalser]

The overall expansion and contraction of an area of planking - and its subsequent power to break frames - is the same as trad carvel.


Yes...but. An 6-point drop in moisture content will cause an 8-foot crossgrain expanse of riftsawn POC planking to shrink around 1 inch. The more seams that inch of shrinkage is spread over, the less likely the boat will leak. Similar happens during swelling, and consequently a stripper is slower to experience the eventual compression set that happens to every boat.

The only good news about this method of construction using POC is that the Boston humidity swings that determine MC change are similar to Monterrey, where (with great care) similar boats have been successful.

Boston averages 68-77% AM humidity and 58-60% PM humidity with no larger than a 5% change between months and no real dry season.

http://www.cityrating.com/cityhumidity.asp?City=Boston

San Francisco is damper and averages 82-86% AM and 59-68% PM with no larger than a 5% change between months and a mild dry season from July-October.

http://www.cityrating.com/cityhumidity.asp?City=San+Francisco

Seattle in turn, has much worse conditions for planking. It has PM highs of 78% in December that drop to 49% by July, with monthly changes as high as 11%, and a significant dry season from May-Sep.

http://www.cityrating.com/cityhumidity.asp?City=Seattle

[Roger Cumming]

I owned a tight-seamed Dragon class sloop built in Denmark for 5 years in eastern Long Island. Planking was fir on ash frames. Not knowing any better, I hauled the boat every winter and stored her outdoors. The planking opened up so much that she had to spend the first night every spring in the slings of the travelift. The shrinking and expanding of the planking loosened the fastenings. The boat would leak at first but then stabilize so that two weeks could elapse before the bilge had to be pumped. It was explained to me that the climate in Scandinavia is much more conducive to this boatbuilding technique than is the northeastern USA. The climate here is just too extreme. I think it is a very poor choice, offering no advantage over conventional carvel construction. The prospective owner should be made aware of this.

[py]

I hope I don't offend Dave by observing that the client who goes to a yard with an order for a boat to be built by a do-able but rather unusual and demanding method, and who's work is delegated to a boat builder with no experience in the method, is probably not getting the level of expertise that he thinks he is paying for. Good on you Dave for doing some research-probably in your own time. And no doubt you are looking at other sources in addition to this one. I hope it all turns out OK, but do have a terrible feeling that this will all end in tears.
Phil

[tonydezoc]

Dave, I would strongly advise you to ask the foreman how he would do it, and if he doesn't know ask him to find out himself, otherwise you will end up the fall guy. Your foreman is paid to make these decisions, not you, and if it works out well he will certainly take some of the credit. I have replaced single planks in "gentlemans launch" type boats built this way in the UK in the past, usually with the best air dried brazilian mahogany we could find and we usually used brown sika as a bedding compound between adjoining planks, for work below waterline we used cotton and seams. Tony.
ps "Bíonn caora dhubh ar an tréad is gile."what does it mean I haven't studied the native tongue since leaving cert 1982

[redbopeep]

The Concordias and othere A&R or European boats were done this way. ... A&R used mostly African mahogany but also some larch.

Was it Khaya or Sapele? Both are called "african mahogany." I'm curious about the stability of Sapele which we're using in re-planking.

[Bob Cleek]

I'm with the others on this one. Maybe it's the lawyer in me, but I'd give the owner and architect a written clear statement putting them on notice that you understand the method they are specifying and will do it, but that you cannot undertake any responsibility for its working nor warrant that the method is suitable for the use intended. Otherwise, no matter how good a job you might do, if there's any problem down the road, they are going to be blaming you. That letter will sure come in handy then!

[redbopeep]

er
I'm with the others on this one. Maybe it's the lawyer in me, but I'd give the owner and architect a written clear statement putting them on notice that you understand the method they are specifying and will do it, but that you cannot undertake any responsibility for its working nor warrant that the method is suitable for the use intended. Otherwise, no matter how good a job you might do, if there's any problem down the road, they are going to be blaming you. That letter will sure come in handy then!

Its good business to communicate questions back to the person who is responsible...too many people posture and "act" like they know what they're doing and then end up taking responsibility for something they never should have been asked to do in the first place.

This post started out about how to actually "do the deed" and its certainly headed in other directions regarding responsibility/legalities.

I used to work as a (building and infrastructure) construction manager and presently own a technology business where we custom build things all the time. Also have been an expert witness in trials regarding construction/structures and whether they were built to spec and met underlying expectations regarding performance. Can't tell you about how to build tight seams, but can tell that we're talking way off base here but its easy to get back!

Either your spec is a performance spec (says "keeps out the water, and performs like xyz under certain conditions...like coastal cruising or so on) OR it is a spec to standards/materials/methods. Don't go mixing up the two. If your company has a performance standard to meet, then they probably shouldn't have taken on a job that no one in the company has done before and then passed it on down to you to figure out something you've never done before either. On the other hand, if its a detailed spec by a naval architect, then what's your copy the construction method say? It should refer to common methods of construction or give you a detailed plan/spec where there is ambiguity. If it refers to this as a common method of construction and you think its not (common since you've never done it!)...kick it back up to your foreman with a question.

Whoever has the contract to build the boat (that would be your foreman or his boss? the yard?) has the "spec". Since it sounds like you're not the fellow making the decisions on this project, you're the guy doing the work--you need to ask your foreman how this tight seam is supposed to be done. Boat yards don't seem to be ISO shops, so you probably can't hope to have a yard standard for this method, you can only kick the ball back uphill to the ..um...people responsible for the contract. They're also probably the folks responsible for getting the right wood at the right humidity for the job, too. Right?

Those folks can send a letter to the NA asking for clarification, bringing up expected limitations of the wood/construction method mix chosen by the NA. The NA will come back with a clarification letter to add to the file or make a change to the spec....

...then life can go on without a bunch of folks on the WBF getting all bent out of shape. Its quite possible that this fellow (the NA and the owner) know what they're doing, expect to use the boat in a cool northern climate, etc, and that's all there is to it. Its also quite possible that whatever sales person at your company is dealing with the job doesn't want to admit that your company hasn't done this kind of work before OR may not even realize that there's a potential problem.

Too much posturing and not enough communication can lead to big problems. So, you tell the foreman your ideas about how it CAN be done (and your references) but tell the fellow you haven't done it before! Then, hopefully the foreman will kick it back up to the yard owner/sales folks...its a good idea for your bosses/salespeople whoever to just communicate with the NA about this and get to the bottom of it before things go wrong. Doesn't seem to have a lot to do with you. I think you've got a method and a lot of good folks here have given you examples of where they've done similar things. All in all, those examples are straightforward and clear and coming from experienced boatbuilders here on the forum and should be good basis for you to continue the work if the foreman says "do it."

In the meanwhile, regarding this building method--I know a fellow who built a folkboat (or is it called folkbote?) in Sweden. First boat he ever built (in the 1960's), hadn't done much woodworking before then either, did it tight seamed with a little roller dohicky like that which has been described above. Nothing went wrong, life was good, used the boat for 25 years. All was great. Sold the boat so I don't know how its doing now. He's in Florida now and I've been trying to talk him into visiting us in California to work a bit on our boat. :rolleyes:

Best of luck with your tight seam project!

[dstreck]

Ron, Hank, Jay, RGM, Bob, Roger, py, Tony, other Bob, and everyone else:

Thanks all of you. Excellent advice from this forum, as usual. It seems that the consensus is that this method is a poor choice for this boat. I tend to agree. The last thing I want to do is deliver a boat that is going to disappoint the owner. The best I can do is put together a well reasoned argument in favor of traditional carvel construction, augmented with all the information I've found here and elsewhere, and let him make the call. Both the owner and the NA know that, while I'm experienced in plank-on-frame construction, neither I nor anyone else at the shop has done this particular version of it.

In the mean time, I've built a prototype of my "seam pounder" and ran some tests today (in between building the transom framing, buying deck beam stock, and tracking down our POC, which seems to have been abducted by aliens somewhere between Oregon and here). I'm gonna soak my sample pieces and see how this swelled seam concept works. I'll post results and pics when I have them.

Once again, thanks to everyone who has chimed in on this. Any and all information, comments, etc. is welcome.

[dstreck]

.
ps "Bíonn caora dhubh ar an tréad is gile."what does it mean I haven't studied the native tongue since leaving cert 1982

"there is a black sheep in even the whitest flock"

[dstreck]

Here's my prototype seam crusher. 1/4" bronze rod epoxied into an oak block. The plywood fence keep the rod centered on the plank while you walk it down, whacking it with a mallet. Seems to work pretty good.

http://i88.photobucket.com/albums/k182/davestreck/DSC01465.jpg

[Rob Stokes, N. Vancouver]

Maybe make up a prototype "hull section" of dry planking stock and rib material using this method and leave it under a lawn sprinkler for a week.

Rob

[RonW]

Hey Dave.
That looks pretty good for a starter. The length seems about right compared to the diagram I have, about 3 inches long, I would think much longer would give too much support and cause excessive pounding. My diagram does have legs on both sides, but I don't see any reason one leg won't work, just have to be a little more carefull.
Do you have any way of having someone in a machine shop to mill one out of a piece of brass or mild steel, maybe even aluminum.

Another thing I was thinking of with this method, has much thought been put into the moisture content of the planking to start with?
Since everything in this method is dependent upon compression and then exspansion, it would seem to me that the lumber should be relatively stable to begin with, after all the swelling to create water tightness isn't all that great. Or am I just concerned about nothing?
What moisture content is the planking to begin with, out of curiousity.

[dstreck]

Maybe make up a prototype "hull section" of dry planking stock and rib material using this method and leave it under a lawn sprinkler for a week.

Rob

Thats the plan. Gotta get the planking stock first.


Another thing I was thinking of with this method, has much thought been put into the moisture content of the planking to start with?
Since everything in this method is dependent upon compression and then exspansion, it would seem to me that the lumber should be relatively stable to begin with, after all the swelling to create water tightness isn't all that great. Or am I just concerned about nothing?
What moisture content is the planking to begin with, out of curiousity.

The planking stock has been air dried, but until it arrives, I wont know to what %. I'm gonna put the meter on it as it goes through the mill for resawing.

I gotta figure out what the optimum moisture % is so that the wood swells enough but not too much.

[dstreck]

dave,

heat and humidity cycle that sample as many times as you have resources for. Soak, then put in an air conditioned room under a heat lamp.. repeat, repeat repeat. The low humidity then high humidity will be a great torture test. Heck, then throw in the freezer. you will learn loads about what combination of lumbers, groove depth, etc yield a good solution. this is practical applied science at its best. eventually, you will be the "Go to guy" on tight seamed construction, because you will know how it will behave, not just out the shop door, but down the road.

Engineers use the same approach using Environmental chambers which bake, freeze, flood, dry, vibrate, shock running machines for any length of time at almost any frequency. Highly Accelerated Life Testing will find the chinks in the armor of any mechanical device (and a boat is just that). It's the best teacher.

I'm going to make up a dummy section of planking, compete with frames and fasteners, and torture test it as you describe. Try to get a handle on the amount of swelling/shrinking we can expect, and consequently how much groove we should pound into the planks and how hard we should edge set them.

We're also toying with the idea of pushing for doing traditional caulked carvel BTW. Since we're planking down from sheer and up from the garboard, we'll have to do a shutter, and thats gonna be a challenge with these tight seams.

Planking stock arrives tomorrow (knock wood), so as soon as I finish the transom framing we can get to work lining the boat off.

[dstreck]

Planking stock arrived at the sawmill yesterday for resawing, and we brought it into the shop today. This stuff is fragrant. Smells like someone spilled about 200 gallons of Pine Sol in the shop. Moisture meter showed between 7-8% on the samples we tested. We're keeping it stacked and stickered inside (very dry environment).

I made up 2 sample sections of planking, which I left soaking underwater when I left the shop this afternoon. One has compressed seams that have been planed down to the apex of the "dent", the other has compressed seams with 2 strands of cotton wicking in the dent (held in with shellac). Each sample has one seam open .020", one open .015" and one seam tight. In both cases the planking is compressed on one edge only. Forgot the camera or I would have posted pics.

Now we see what a few days of soaking do.

[py]

Dave,
If I was getting a yard to build me a boat I'd like to have a guy like you doing the work.
Phil

[Bob Smalser]

Moisture meter showed between 7-8% on the samples we tested. We're keeping it stacked and stickered inside (very dry environment).



Does your shop routinely use planking kilned to 8%? What are the above and below-waterline MC's of local moored boats?

[dstreck]

Does your shop routinely use planking kilned to 8%? What are the above and below-waterline MC's of local moored boats?

Bob,

According to the vendor, the POC was air dried (standing deadwood) for 10 or so years. Forest fire killed, according to him, and never kilned. Based on his story (which I can't vouch for) I was worried about rot pockets, insect damage, etc, but its clear, clean and buttery smooth. You've got me on the MC of local boats. Not sure how to check at this time of year, since they're all hauled.

[dstreck]

Dave,
If I was getting a yard to build me a boat I'd like to have a guy like you doing the work.
Phil

Cheers, mate.

What do they pay shipwrights down there in Oz?

[Bob Smalser]

Not sure how to check at this time of year, since they're all hauled.

Check them on the hard then, both above and below the WL, and see if they are anywhere remotely close to 8%.

[py]

Don't know. Probably not much. There's precious little wooden boat building around anyway. I reckon if a guy wanted a carvel boat built here he'd be lucky if he had 3 or maybe 4 competent yards to choose from in the whole country. So, maybe there's an opportunity...

[tonydezoc]

There are some of us here still building, but we are few and far between, pay varies from approx $25- $45 ph depending on skill and experience and if you or anyone else reading is interested in working in West Australia feel free to contact me anytime. Tony

[dstreck]

Update:

Planking test pieces have been soaking since Thursday afternoon. Gonna give them till Monday and check them then. Here they are:

http://i88.photobucket.com/albums/k182/davestreck/DSC01487.jpg

Both sample pieces seemed to swell up nicely. I'll get the feeler gage on them on Monday.

Joe, our resident tinkerer, machinist, and all around mechanical genius dropped this on my bench this afternoon:

http://i88.photobucket.com/albums/k182/davestreck/DSC01482.jpg

He was watching me pound out the seams with my mallet and whomper block, and told me he had a better idea. Took him all of an hour to put together (I added the handles from an old Record #5...still have to grind off the stub of the handle screw). Roller wheel is 1/4" stainless, with the edge ground to a half-round. Base and fence aluminum. Works like a charm:

http://i88.photobucket.com/albums/k182/davestreck/DSC01484.jpg

Normal planing pressure puts a nice 1/32" groove in the plank edge, ready for either cotton wicking or planing:

http://i88.photobucket.com/albums/k182/davestreck/DSC01490.jpg

I'm hoping that by next week I'll be able to have some definitive data to pass on to the NA.

[Bob Smalser]

Both sample pieces seemed to swell up nicely.


Too nicely.

If you go out and check a few of those wooden hulls on the hard, I suspect even after 3 months out of the water, you won't find one with planking less than 12% MC. Below-waterline planking may even still be at the 16% plus or minus it was when it was hauled in November.

Assuming this boat has 8 feet of crossgrain planking expanse and 12 planks, if your planking was flatsawn like the samples shown and at 12% MC the hull would swell almost an inch in the process of going to 16%. Each seam will expand by around 3/32nd, tightening them up snugly, but not dangerously.

But your planking is at 7-8%, and the hull will expand well over two inches. That's pushing a quarter-inch expansion per seam, most of which will never rebound. Even if the frames don't break and a plank doesn't buckle, the compression set will be immediate, and severe.

Not being local, I could easily be wrong about your local MC's. But I'm not wrong at all about the effect of a 9-point rise in MC. It won't take long to check out local planking MC's, and I'd much rather be wrong than see y'all go out of business. What you can get away with using mahogany can be fatal in less stable woods.

[dstreck]

Bob,

The planking at its widest point spans about 7 feet/18 planks. Not sure if that makes much of a difference.

Also, I'm not sure how much to trust our moisture meter. The planking is definitely dry (the sawmill operator noted that he had to run extra kero lube to keep it from overheating when it went through) but frankly the meter looks kinda cheesy, and doesn't have any correction tables for different wood species. Its mainly used by the fiberglass guys to check for water infiltration into wood cores.

Basically, my plan is to soak the samples and check the real-world results. If they start to buckle or distort, we'll have to take it from there. Planking won't start for another week or so, so I have some time to let the samples really soak it up.

In the end, is all this debate simply a result of the specified construction method? All else being equal, how much more likely do you think tight-seams are to fail in this situation versus traditional caulked seams? Would caulked planks absorb 2" of swelling over 7 feet without complaint? I've planked boats with dry stock before (even KD, on one memorable occasion), and they've never torn themselves apart from stresses while swelling up.

Thanks again for all your help, Bob.

[Bob Smalser]

Bob,

1) The planking at its widest point spans about 7 feet/18 planks. Not sure if that makes much of a difference. Also, I'm not sure how much to trust our moisture meter.

2) All else being equal, how much more likely do you think tight-seams are to fail in this situation versus traditional caulked seams? Would caulked planks absorb 2" of swelling over 7 feet without complaint?

3) I've planked boats with dry stock before (even KD, on one memorable occasion), and they've never torn themselves apart from stresses while swelling up.



http://pic20.picturetrail.com/VOL12/1104763/3075040/214182916.jpg

1) Borrow a moisture meter with insulated pins that'll take an accurate reading from the center of the plank. Your lumber dealer will have one. They either have built into their algorithm or have tables to correct for species and temperature, although most are calibrated for Doug Fir which is pretty close to POC in density. Without accurate readings, you are strictly hit or miss on success. I do find it hard to believe that standing dead would be less than 12-14% MC in S. Oregon/N. California. 7-8% are outdoor MC's only in Arizona. But the lumber could have also been put thru the kiln just to kill the bugs either before shipment or to keep them from infesting their stack yard, which would have been prudent.

2) No planks will absorb much over an inch of swelling per 7 feet without damage somewhere. A caulking seam gains you less than a 16th of gasket effect. But that's only on the rebound as caulked planks are also tight to each other on the inside and suffer the same crush damage, although caulked seams don't touch full thickness like tight-seamed and would apply less force to the frames.

3) Look at the stability chart. POC is closer to DF and SYP than it is to Atlantic or White Cedar or mahogany. You may never have planked a boat with wood this unstable, and you're using it in the worst case scenario.


Order of Stability in Wood Species
Percent Shrinkage Green to Oven Dry as an Indicator of Relative Stability

Northern White Cedar Radial 2.2 Tangential 4.9 (R+T)/2 3.5
Honduras Mahogany 3.0 4.1 3.5
Khaya 2.5 4.5 3.5
Redwood, 2d Growth 2.2 4.9 3.5
Western Red Cedar 2.4 5.0 3.7
Eastern Red Cedar 3.1 4.7 3.9
Atlantic White Cedar 2.9 5.4 4.1
Eastern White Pine 2.1 6.1 4.1
Teak 2.5 5.8 4.15
Incense Cedar 3.3 5.2 4.25
Alaska Yellow Cedar 2.8 6.0 4.4
Purpleheart 3.2 6.1 4.65
South American Cedar 4.0 6.0 5.0
Iroko 4.0 6.0 5.0
Sassafras 4.0 6.2 5.1
Okoume 4.1 6.1 5.1
Spanish Cedar 4.2 6.3 5.25
Black Cherry 3.7 7.1 5.4
Black Spruce 4.1 6.8 5.45
Tamarack 3.7 7.4 5.55
Baldcypress 3.8 6.2 5.6
Port Orford Cedar 4.6 6.9 5.75
Dark Red Meranti 3.8 7.9 5.85
Black Locust 4.6 7.2 5.9
Sitka Spruce 4.3 7.5 5.9
Sapele 4.6 7.4 6.0
Douglas Fir 4.8 7.6 6.2
Longleaf Pine 5.1 7.5 6.3
White Ash 4.9 7.8 6.35
Black Ash 5.0 7.8 6.4
Yellow Poplar 4.6 8.2 6.4
Rock Elm 4.8 8.1 6.45
Slash Pine 5.4 7.6 6.5
Apitong 4.6 8.2 6.5
Light Red Meranti 4.6 8.5 6.55
Black Walnut 5.5 7.8 6.65
Tangile 4.3 9.1 6.7
Western Larch 4.5 9.1 6.8
Angelique 4.6 8.2 7.0
Ipe 6.6 8.0 7.3
White Oak 5.3 9.1 8.0
Live Oak 6.6 9.5 8.0
Greenheart 8.8 9.6 9.2

[dstreck]

Bob,

I'll try to get accurate MC readings next week. In the meantime, I'll just lie in bed every night staring at the ceiling imagining worst-case scenarios.

Do you have any good news for me?

[Bob Smalser]

Do you have any good news for me?

I'll just lie in bed every night staring at the ceiling imagining worst-case scenarios.

The good news is you have a bed to lie in because your current shop is still in business.

Over time with your spare tool money, gift yourself Bruce Hoadley's Understanding Wood, a USDA Wood Handbook, a good Delmhorst commercial meter with a wide range and start collecting local samples to get ahead of these challenges.

[MiddleAgesMan]

It seems you could compare the local boats on the hard with the meter in hand. If it's wrong on the new wood it will be wrong on the local boats. Of course an accurate meter would be best.

Bob has made several cautionary statements but I want to emphasize what I see as the most important: taking that lumber from 8% in your shop up to 16% once the boat is launched would be disatrous due to the total expansion the planks would experience with that change. I think he said 2" based on an assumed but realistic total width of cross grain wood in the hull. I don't think you'd have to wait long for something to give--like the frames!

If you find your new lumber is really that much drier than the local wood boats on the hard I think you have serious problems. Planking should not commence until you've either found other material or figured a way to bring your planking stock up closer to what it will be in use.

[tonydezoc]

Dave I have been thinking about your tests, did you measure the width of the test pieces before soaking? I would be interested to hear how much each piece swells overall and also whether they shrink back to their original size, also it might be interesting to fix blochs of wood to the ends of the "frame" pieces tight to the planks and repeat the process to see how they react when they are unable to swell.

[dstreck]

Dave I have been thinking about your tests, did you measure the width of the test pieces before soaking? I would be interested to hear how much each piece swells overall and also whether they shrink back to their original size, also it might be interesting to fix blochs of wood to the ends of the "frame" pieces tight to the planks and repeat the process to see how they react when they are unable to swell.

All the sample pieces I used to build the mockups were ripped to exactly 3" width, then fastened to the frames. I also threw some individual pre-measured pieces in. Gonna give them a few more days to soak, then do all my measuring.

The first moisture meter indeed was screwed up. A better (borrowed) moisture meter shows closer to 11-12% MC for the planking stock, although total variation is from 8-12%, depending on which part of the board we check. This makes me feel marginally more confident.

[dstreck]

Update:

As anyone who has followed this thread knows, we at the shop have been skeptical and reluctant to proceed with this "tight seamed" method. Experience with the yawls has shown us how much trouble this type of planking can cause, and further research has made us feel even less confident with it. Now, thanks to tireless lobbying by us and the expert opinions of as many shipwrights, surveyors and NAs as we could get to talk to us (including many folks from this forum) the owner has seen the light and has changed the method we're going to use to plank the boat. We are going with traditional double-planking, mahogany over cedar, bedded in shellac.

We're gonna have to take all our POC back to the sawmill for further resawing, but its worth it. Now the boat has a fighting chance of lasting more than just a few seasons.

Thanks again to everyone who chimed in on this. Now I can finally get some sleep. Im gonna celebrate by taking the day off tomorrow for the Maine BBS.

[George Roberts]

"Shows little understanding of the real world. I once was talking to a professional boatbuilder; he remarked that he had never done the same job twice."

Considering the outcome of this thread, perhaps more understanding than some.

[RonW]

Well, I think it has been a interesting thread.

I agree other methods would be much better. From what I have read about these compressed grain methods, as I understood them, they were more sucessfull on the small stuff, but really didn't catch on.
And I suspicion there are good reasons why they didn't catch on...

[tonydezoc]

Well fair enough but I would still be interested in seeing the results of your experiment. Tony

[dstreck]

Moot point now, since we're double-planking the boat, but for anyone who's still interested:

http://i88.photobucket.com/albums/k182/davestreck/DSC01510.jpg

Both planking samples (crushed and caulked, crushed and planed) managed to deflect 16" long 7/8" x 7/8" w. oak frame pieces by about 1/8" when swelling (a tiny bit more for the crushed and planed sample.) A single 3" wide plank sample swelled to 3 3/32".

Not a scientific test, by any means, but something to think about. Interestingly, a third sample I made up with traditionally caulked seams deflected just over 1/16".

[RonW]

Dave- thanks for taking the time to post the results. It would appear that the method works a lot better then anyone would have expected. I do seem to remember reading not to use anything between the planks, it would seem that your test samples bears that out. I do hope that you take all 3 samples and set them aside somewhere nice and dry and warm, for a week or two and see how they look then.. Do tell us what happens then....

[RGM]

Hi Dave, glad to hear that things worked out for one and all.