boat exploded !

[amess]

Just a few strips short of rolling the hull... cold snap in the mid-west. Dry air. Boat strips exploded loud enough to hear in the house upstairs (over 2-car garage).
Splits in cedar strips EVERYWHERE. one foot to two foot long... at least one shows daylight through the 1/16th inch split.
So - am I screwed?
Or can they be filled with epoxy without worry and go forward. Boat is 22-foot GlenL AMigo - will be glassed when hull planking complete so planking is essentially just core material... Sure id defeating filling... year's time and two grand to shatter like toothpicks.

Any advice (and support) will be helpful.

[JimD]

will be glassed when hull planking complete so planking is essentially just core material Huh? :eek: :confused: This is the glued strip plank version, right? Not the FG version? The strips are supposed to be edge glued with epoxy and nailed to one another. The planking is not 'just core material'. The planking, along with the bulkheads and frames, is the hull, the whole hull, nothing but the hull, pretty much, and the hull's integrety does not come from the fg sheath. Whatever happened to your boat (and I have no idea how that could happen) it may be a blessing that it happened now and not later as in after the boat is launched.

Bummer. Sorry to hear this.

[Bob Cleek]

How wet was the wood when it was glued up? If it was generally the same as the ambient humidity, things will likely return to where they were before the dry air. Don't fill the cracks with epoxy or the wood will bust again when it swells up. The swelling and shrinking of wood is cumulative. Strip upon strip shrinks just a tiny bit, but over the space of a whole hull, it adds up and will bust someplace. This is an inherent problem with strip building. While traditional carvel or clinker planking aren't to some folks' tastes, they do have the advantage of moving without tearing themselves apart like monocoque construction can.

[Ian McColgin]

In my albeit limited experience with strippers - helped in building six small boats and helped in repairing two roughly eight ton sail boats - the size of the stips is quite important.

For example, it was not a stripper but back in the '60's a fellow wrote a whole book on building a St Pierre dory with 2x2 glued diagonal. John Gardner's review in National Fisherman was scathing and he predicted a blow up. Some months later he reported the bow's spectacular deconstitution.

I don't recall if there's a real formula but strip planking needs to be quite narrow and thinner than it's narrow. Then, while expansion and contraction are, as Bob noted, cumulative, that cumulation does not occur on the seam lines which hold up perfectly under the limited shear, crushing and pulling strains to which they are subjected.

I am guessing that you have a combination of three different problems:

The wood was not correctly cured - or too much moisture from something - prior to gluing;

The wood was not suitable for stripping as it had too great a range of moisture uptake and loss; and/or

The planks were too big in either width or thickness.

I'd not attempt any repair until the actual causes in this instance were analized and a cure was even possible. This problem will not disappear under glass.

G'luck

[ 12-09-2005, 08:27 AM: Message edited by: Ian McColgin ]

[gert]

Post some pictures, that'll help

[TomF]

What an awful thing to happen. I'm so sorry.

Which way is the grain oriented in most of your strips?

Tom MacNaughton's approach is to use square strips, orienting each to show flat-sawn grain to the outside of the boat. Most wood movement is across the grain, so this orientation reduces the cumulative pressures that likely caused the failure you've described.

Tom Fetter

[brian.cunningham]

Ouch! :eek: Sorry to hear that. I though you were posting about a fuel leakage.

Is it still on the mould?

Strippers can be repaired, the biggest problem in one that's already in been launched is setting up the temporary mould. If it's still in it that's half the problem.

How dry were the stips when you installed them? I'm thinking the epoxy made them swell.

How many strips per day were you installing?

[Tom Lathrop]

One question that comes to mind is; did you attach each strip rigidly to the frames as you built? If you did not, it would seem that the whole structure would contract with lowering humidity instead of tearing itself open. Anchoring each strip to frames would create stresses as the planking tried to shrink. My few cases of strip building were done over temporary frames that the strips were not rigidly attached to and no such problem occured.

In any case, I hope you can find a way to work through the problem. A little splitting does not sound like a hull failure issue.

[George Roberts]

amess ---

As mentioned above, it sounds like the strips shrank becasue of the dryness and were constrained in some manner, either because they were fastened to the forms (perhaps by accident) or because of their shape.

1/8" strips change to equilibrium moisture content within minutes. 1/4" strips change within hours. 1/2" strips change within days. It is hard to lay up strips with the "wrong" moisture content.

I would do nothing except mark where the splits are. When the weather warms up do the repairs.

[JimD]

I'd ask Glen-L. If the splits are 'EVERYWHERE' as you say and the strips are edge nailed this does not sound like an easy repair job. I suppose the rationale against filling and regluing now is that you'll end up with compression problems when humidity rises again but with strip planking you already have a couple hundred lines of epoxy running the length of the hull so will a number of filled in cracks make a difference? I dunno. Just talking.

[ 12-11-2005, 02:14 PM: Message edited by: JimD ]

[helvit]

There have been some posts from builders who steamed cedar strips intended to be edge glued. Was that part of the process?

Before planking an Ocean Pointer I called Dave Stimson and told him my Atlantic white cedar was maybe too dry. The question was-- what's to keep it from trying to buckle or blow the deck off after it was in the water a while. Answer--- the drier the better; cedar is sufficiently compressible to accomodate the difference.

But apparently it doesn't work the other way. It sounds like this wood was too wet and split within the planks (not along the joints). If the drying is complete, the splitting finished and the splits one or two feet long as you noted, with access to the damage from inside and outside the planks-- it's terrible but how could it not be repairable?

[amess]

Thanks for the input.
More info - and not the worry I had first felt necessary
All splitting has occured because of drastic drop in temp and humidity. Building in Mid-MO summer humidty was always 90 percent of better - this week instantly cold and 10 percent.
SPlits occured in strips, not in glue seams.
and Yes, I had to steam the center section a bit to make the bends with the 3/4 x 5/4 strips.
I also suspect one of the pieces of lumber from my second order was greener than the others and I missed it because all the stip splitting is confined to one zone of laying strips.
ALSO - my mistake... strips are not perfect in grain alignment )end of boards where grain curves.... more quartering than parallel grain...
in any event I will just keep going and come back to fill, glue splits when humidity is more normal again.
The EXPERTS around here don't suspect any real structural damage. At first I was going to fix and seal everything with epoxy, as design requires. But I see your point here when you say to wait until the wood has again stabalized.
I'll keep plugging away.

[bukuboy]

Why not sell it or donate it to the boy scouts or something. Get yaself some Bruce Roberts plans for the Tom Thumb-- Built in steel. ---Bukuboy

[Howard Sharp]

Visited a guy on the Cape this summer who is building a beautiful Golant Gaffer. He has a well heated shop and exactly the same thing happened last winter. He had stripped the hull in the summer, and one day in the miidle of winter there were three or four very loud (like gunshots) cracks from the hull. He simply filled the cracks with thickened epoxy and is moving on. On thinking about it for longer I think I would do it slightly differently.
From the outside I would rout or chisel a plankgroove half the thickness of the planking to cover the length of the crack plus a few inches at each end, and overlapping the sides of the crack by, say, 3/4". Spile the plank, but before gluing it in, rout out the crack in the remaining halfthickness of planking so that it's a uniform width for the length of the crack. Now you can put a dutchman in the inner halfthickness, and put the spiled plank on top.
I've heard people say that winter in the Northeast can be drier than the desert. I once saw an English-built Vertue on the Cape that had been out of the water for a few months, and in the dead of winter the stem had cracks which I could quite comfortably get my hand into. Of course in the water most of those cracks will close up. The theory of cold molding is that the wood never gets as wet as that, but I think it's bound to absorb some moisture eventually, and this explains why some designers and builders insist on the three layer approach for cold molding. If it's any comfort, this kind of cracking is only going to happen when the boat is out of the water, in a heated shed in the winter, not when it's in the water in the summer.

[Craig Lekven]

If it were me I think I'd consider covering it with Kevlar instead of glass cloth. Small splits will be filled as you apply the resin to the cloth. Larger splits may need to be filled prior, though, or the resin will all run out the inside. After the hull was turned over I'd fill any remaining splits with epoxy while saturating the interior with epoxy.

The repaired splits become glue joints - you just end up with more "strips" than you planned. The Kevlar is your insurance policy.

[JimD]

The repaired splits become glue joints - you just end up with more "strips" than you planned. Only if the splits are open enough for the epoxy to penetrate. If the ambient humidity rises enough to swell the wood and close the cracks I'd bet not much epoxy is going to get into them. Wouldn't you still have kevlar over a boat with cracks in it?

[ion barnes]

I just happened to be reading John Gardner's Classic Small Craft and pages 142 - 144 talk about strip planking a Yankee Skiff of about 40' in length.

1) He says that at one time he shared the opinion commonly held by proffessional boatbuilder that strip planking produced rough cheap inferior boats, and there were cases to prove it.

2)He later had the chance to examine a vessel strip planked with 1-1/8 thick by 1-1/2 deep strips of mahogony. The strips were only nailed together with 3" stainles ring nails, 3" apart. The fit was wood to wood, no paint, sealant, glue or whatever. In addition,the strip are fastened to the sawn frames with the same nails. The frames were on 2' centers

3)He was very impressed with the result and added that he would definitely not recomend gluing.

I would also suggest that the grain direction could have contributed to your problem.

[Craig Lekven]

If the ambient humidity rises enough to swell the wood and close the cracks I'd bet not much epoxy is going to get into them. Wouldn't you still have kevlar over a boat with cracks in it?I'd imagine that without any additives added to the epoxy, and a decent ambient temperature, that you'd get enough epoxy sucked into the gap by capillary action to adequately fix the problem. You'd want to use the lowest viscosity epoxy you could find. Of course, you could do a test piece and see. If the option is to throw away several years of work, I'd give it a try.

[JimD]

I'd imagine that without any additives added to the epoxy, and a decent ambient temperature, that you'd get enough epoxy sucked into the gap by capillary action to adequately fix the problem. In my mind's eye I don't see that happening.

[Craig Lekven]

[ 12-16-2005, 05:08 PM: Message edited by: Craig Lekven ]

[JimD]

Originally posted by Craig Lekven:
Craig, you're very talkative today! :D

[sdowney717]

I would be more interested in filling the cracks now when the wood is dry. You will get the epoxy further into the crack and later on when the humidity increases the wood will only get tighter. And then when the humidity goes down it will be back where it was.

I did repair a crack in a mahogany board in the summer, and then coated the exterior of the board with epoxy. It has cycled thru a couple years with no problems at all. This is not an underwater board.

[Ron Williamson]

Where's Old Bingey when you need him?
Doesn't he heat up the shop,slop epoxy on everything,then crank up the air conditioner to suck the glop down into the pores and cracks,as the air cools?
R