Doubling up cross planked bottom?

[Ron Carter]

Still looking for a solution to the need to soak up a cross planked bottom when the boat will have to be trailered. The plan calls for 3/4" cedar planking. I'm considering reducing the scantlings and double planking the bottom with staggered seams and some kind of bedding between the layers. Chapelle suggests canvas or flanel soaked in heavy paint or white lead. I want to retain the traditional construction without the need to soak the boat for an afternoon cruise. Any alternatives to plywood and epoxy welcomed.

[Paul Scheuer]

The very traditional Yankee Yender (Issues 30-31) has double 3/8 cedar cross planking, clench nailed and sealed with bedding soaked muslin. The inner bottom is inside the planking with a cotton wick to the chine logs, attached with ring-shank nails. The outer bottom is clench nailed every three inches or so, about 1/2 inch from the edges, and screwed at the ends. If I did it again, I'd go heavier on the bedding compound. I still have to let her take up some, mostly in the one seam where I didn't nail on both sides because I would have had to get too close to the edges. When I get caught up on other stuff, I'll take the keel off and replace the poorly planned plank.

http://www.imagestation.com/picture/sraid18/p00e06597f13faf772b160b6497ffa382/fdcc7410.jpg

http://www.imagestation.com/picture/sraid18/p003a07450c054bd0dc4e0e2aeebcfb67/fdd396c7.jpg.thumb.jpg

[landlocked sailor]

Yep, that's how I built my Heidi skiff. http://www.imagestation.com/picture/sraid173/pc7270fc6cad5f4a53e4fe577fb590ddd/f3a92110.jpg
Harry Bryan uses a variation for his Daisy dory-skiff. The inside is crossplanked, while the outer bottom is planked fore and aft. Either way, the first layer is put on the chines BEFORE the side planks, so the ends are covered by the side planks. The outer bottom is applied AFTER side planking. Each layer is 1/2 the total bottom thickness; 3/8" in my case. Rick

[Ron Carter]

Exactly the kind of information I was looking for. Can either of you tell me what bedding you used and where you got clench nails. I recently finisned replanking a wood canvas canoe so I'm way too familiar with a clenching iron. Chapelle has a formula for luting but I suspect real putty and white lead are both on the endangered species list today.

Love this place! Only took 30 minutes to find out that white lead is still available. The boat I'm building has a keelson and sister keelson's so the clench nailing would be minimal in the spans between them.
Ron

[ 11-01-2005, 10:03 AM: Message edited by: Ron Carter ]

[Ted Ford]

Hi Ron-

Harry Brian - the ultra traditionalist who lives and works "off the electrical grid" in New Brunswick Canada uses thickened epoxy to join the two layers. He also uses epoxy on the edges of the first and second layer and beds the lenghtwise planks to the cross plaks with the same. He states that using relatively thin cedar allows you to get away changes in dimension with swelling. He compares the bottom to home made plywood.

I suggest you consult WB 126- pg. 82 for his "how to do it" article on Daisy and details of how he uses temporary screws to join the layers. If you don't have access, let me know and I can probably fax you the info.

Ted

[Ron Carter]

Ted,
Thanks for the information. I'll add #126 to my growing list of back issues I need to order. While I'm far from an "off the grid" traditionalist I'm leery of epoxy for 2 reasons. First my shop is marginally heated and will return to outdoor temperature hours after the fire goes out. With winter approaching an appropriate temperature for epoxy is almost impossible to maintain. Second I've developed contact dermatitis to common solvents like mineral spirits, gasoline and recently possibly latex. Given these problems I'm hesitant to risk the consequences of epoxy.
Ron

[landlocked sailor]

Ron, I got my nails from Strawberry Banke Museum.
http://www.strawberybanke.org/ They have an antique machine for making the real deal, but I used anchor fast ring-shank nails for the bottom.
I used Harry Brian's method of epoxy between the layers but would not do that again; I'd used the muslin between the layers as described by Paul. Rick

[Bob Smalser]

Plain old caulking seams in new, 7/8" planking will work fine in a trailer boat providing you don't moor it for extended periods.

Double planking provides the option to leave it in the water for a few weeks before retrailering.

[Paul Scheuer]

It was twenty years ago. I don't remember what the bedding compound was. It must not have been anything too special.

I remember chasing the nails. This was pre-internet - I did most of it through the mail. There was a guy in the NW that had an old nail making machine, a good story including the history of The Nail, but no nails after about a year. I finally got the clench nails and the rivets and roves for the laps from Wm Cannell.

[Ron Carter]

The inboard engine I intend to use is a early 1900's single cylinder two stroke. It is marginally balanced based on running it on the floor of the shop on skids. I'm thinking that the vibration even on heaily built stringers is going to be an issue with keeping the cross planking tight. Double planking might be beneficial for this reason also. Sure appreciate the continuing help.
Ron

[RonW]

As a alternative to epoxy, why don't you simply use a polyurethane caulk. Most of these claim to have over a 50 year life span.

I would not reduce the scantlings, and keep the planks relatively on the slim side, not too wide.
Look at these pictures on the popsicle stern by mike, he used a polyurethane caulk, and I have too, it works great.

http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=012327

[BrianY]

copper clench nails are also available through Faering Designs
http://www.faeringdesigninc.com/index.html

[Ron Carter]

Ron W Are you suggesting single planking or are you saying to double the bottom thickness? There is some good reasons for using narrow planks from the standpoint of minimizing the amount of dimensional change due to moisture content. Lots of extra labor but I'm self unemployed so that isn't a major concern.

[RonW]

Ron C.
Either or, it doesn't matter, just use polyurethane caulk instead of epoxy.
As I understand, your plans are already designed for a 3/4 inch single bottom, then the plans must have enough support for single cross planking.Just use poly between and under the planks. The stuff works really well.Just as mike did in his.

And if you wanted to double plank, use poly between the plank edges, and the same with the second layer of planking, and bed the second layer between the first layer with poly instead of canvas and lead, and it will be a cold day in hell before it leaks.

Personally I would prefer heavier single planking.
And as you say the plans already show it, so why complicate matters.Stop and buy a tube of pl window and door caulk, or a tube of vulkem, and I think mike mentioned another brand. This stuff is 1/4 the price of 3m5200 and a whole lot better product.

I am not saying that poly caulk can replace epoxy, as it doesn't create as much bond strength, although you might be surprise as to how strong it is, and with old fashioned framing can be a alternative to epoxy.

I will stick my neck out though and say that polyurethane glue, the right ones, can be a replacement for epoxy under a lot of situations. You may want to get a tube of pl premium construction adhesive, it will bond very well and permanently.

[Keith Wilson]

I bet roofing tar and fabric would work fine for keeping the water out. It would be much less expensive than any of the alternatives, and not nearly so permanent as polyurethane or epoxy. Workboats traditionally used it for seam compound. Only disadvantage I can think of is a tendency to bleed through light-colored paint. I haven’t tried it, so take this for what it’s worth. Myself, I’d use plywood.

[Ron Carter]

I have used polyurethane glue in my laminated paddle making for the last 4 years. 25 paddles some of them in service all 4 years and no sign of a glue line problem to date. I'm a big fan of the poly glue. The container says not for below waterline use. I called Borden's technical support folks and was told that the lawyers required the statement but the techies were satisfied that it was totally waterproof. Using self mlilled wood, air dried, I like the fact that 15% is the optimum moisture for urethame and it will work up into the low 20's so exact drying isn't an issue. Cost of 5200 had already eliminated that from my consideration. Will absolutely try the low price spread.

[Bob Smalser]

Felt and tar or felt and oil-based white lead bedding compounds were used for a good reason....the bottom could be dismantled for repairs.

Glue it or goo it together with adhesives and you'll have most of the disadvantages of plywood with none of the advantages.

[ 11-03-2005, 01:21 AM: Message edited by: Bob Smalser ]

[TimothyB]

What Bob said smile.gif

I really like the idea of a layer of Xynole (thick weave polyester) and Hot Patch roofing tar.. the stuff you have to heat up to get soft. Since you have a layer of planking over it, you dont have to worry about bleed through.

You coat the cross planking with tar, staple the Xynole down, apply more tar liberally and until the weave cant take anymore, then a bit more than that, and then plank over fore and aft. In the olden days they attached the outer planks with lots of round headed non tapered bronze screws from the inside.

Chapelle covers this in "Boatbuilding" as far as technique, as I recall...

[Ron Carter]

Lots of good information here. I'm still looking for cedar for planking. Molds are set up and will pick up the stock for the structural longitudinals on Tuesday. Probably will cross plank both courses simply because long cedar is darn hard to come by around here. Sides will be scarfed as required. Most likely will be using some form of fabric and bedding between the layers. Thanks for all of the input.
Ron

[Gary E]

Originally posted by TimothyB:
What Bob said smile.gif

I really like the idea of a layer of Xynole (thick weave polyester) and Hot Patch roofing tar.. the stuff you have to heat up to get soft. Since you have a layer of planking over it, you dont have to worry about bleed through.

You coat the cross planking with tar, staple the Xynole down, apply more tar liberally and until the weave cant take anymore, then a bit more than that, and then plank over fore and aft. In the olden days they attached the outer planks with lots of round headed non tapered bronze screws from the inside.

Chapelle covers this in "Boatbuilding" as far as technique, as I recall...Does anyone actually DO that with a staple gun?
I can just see all that goo under the fabric ozzing up and into the works which will stop working very soon.

Or maybe it's the kind that shoots like a pistol from a foot or 3 away to keep it clean?

I saw a 40 ish foot boat bottom covered with roofing tar, then tar paper, then more tar, then copper sheets were nailed on, and that was no eazy job, I can just imagine the staple gun.

[Stephen Hutchins]

I've seen skiffs cross planked before the side planking that were left out in the winter and the ice pushed the side planks off the chine. I've since thought it better to plank the bottom after the side planks: one, to help prevent the above from happening and two, It seems that the water pushing up on the bottom planking with a larger faying surface for the plank landings makes more sense. -Any comments on this?

[Bob Smalser]

Originally posted by Stephen Hutchins:
...It seems that the water pushing up on the bottom planking with a larger faying surface for the plank landings makes more sense. If I'm reading you right:

The inner planks are fastened to the chines with screws, and the outer planks to the side edges with screws then to the inner planks with clench nails. Sounds like lots of faying surface to me.

Ice can break chine joints by the bilgewater freezing and expanding, pushing sides outwards with huge forces. Faying surface area won't stop that.

[ 11-05-2005, 10:11 AM: Message edited by: Bob Smalser ]

[RonW]

I for one do not understand the suggestion of tar at all. Yes it may have been used 50 years ago, when every dollar spent on a work boat, was a dollar out of the family budget that was already stretched to the breaking point.

But in todays world I do not see it as a viable answer at all, there just are too many goos that work far better and will last 20 times as long.

The hot tar which is coal tar is hard as a rock and has to be heated to be pliable, then it is put on in multiple thin layers with felt between and topped off with rocks to help prolong it's life. That is why today they use rubber membrane, because tar just doesn't last that long with out repairs.And there is buckets of thick stuff which is asphaltum. And when you use it to patch your roof, in a few short years it is leaking again. Just not a answer in todays world.

[Bob Smalser]

Spend the money for Dolphinite if you don't like tar. Or make your own putty from linseed, whiting, white lead, etc.

But I've used inexpensive and effective tar many times without significant bleedout here in a cold climate.

Just don't use anything adhesive or you'll have another one of these unrepairable boats waiting for an early bonfire.

[Stephen Hutchins]

Hey Bob,
I should have mentioned I was speaking of one layer of bottom planking, but even still, I should have taken into account that ice could push side planking off the chine. I guess I was thinking more of screw and glue construction.
Thanks for the reply.
Steve