Spindrift 12 setback: plywood fracture.

[Ambler]

I've Emailed Graham about this, but it's Friday evening, and meantime any & all comments/advice are welcomed.

Trying to pull the bottom panels of spindrift 12 together at the bow needed a lot more force than could be got from twisting stitch wires. A clamping method was devised but before the points of the panels could be brought into contact, one side broke :cry: :cry: about 3" back from the tip. The wood is 1/4" marine okume and I see no internal defect where it failed. Of course when it let go, a number of stitch wires also tore out of the wood and it's quite a mess.

2, no; 3, well; 4 questions:

Anybody else had this happen?

How do most folks get the bottom panels to mate at the very bow?

How should I repair the panel?

How can I complete the boat without re-fracturing after repair?

[Ambler]

All in due course. I'm a Luddite - still using FILM.

Pictures, We need gory, messy, heartrending Pictures.

[Designer]

Alexander,

Sorry to hear about your accident. I will answer you here instead of by e-mail so that it might help someone else. If only the front 3" broke off the bottom forward you can put it back on with glass tape on both sides and let it cure. I know that you decided not to use the butterfly method because of limited space, but I can't emphasise enough, how important it is to go back to the butterfly method.

The S12 is the easiest of the spindrifts to fold up. We currently wire the 2 halves all the way around the centerline to the sheer with the insides face to face and just open it up like a book. The reason that it works so well is that the maximum load is, as you found out, is at chine forward and the extra length of the sides gives you lots of leverage and you don't even notice the strain at the chine bow area.

As a bonus the butterfly method gives you a nicer looking bow, as it is hard to avoid a bump or unfair bow profile putting it together your way. It is so easy to fair the bow area to a sweet curve after you join the bottom to the sides and before folding.

As frustrating as you feel right now (believe me I have been there many times before) just piece the bottom back together and join the sides to the bottom forward and you will have a nice hull in no time. If the wires did not pull too much wood away when it blew, you may be able to drill new holes and the epoxy will fix it when you fillet and tape. I don't know how limited your tight space is but it does not take up that much extra space to butterfly it.

[Ambler]

Apolgies if this is double-posted: My computer seems to be acting up (What ELSE is new??)

Thanks, Graham, for your swift reply stating, in part;

"I can't emphasise enough, how important it is to go back to the butterfly method. The reason that it works so well is that the maximum load is, as you found out, is at chine forward and the extra length of the sides gives you lots of leverage and you don't even notice the strain at the chine bow area."

Which is pretty much what my wife said tonight.

Sheesh!!

I'll post some follow-up once I recover my aplomb.

Alexander.

"Take it easy, but take it" - Pete Seeger.

[mustangermatt]

Sorry to hear about the problem.

I am also building in a limited space (CS 17 in a 17 x 10 floor space). I found that the place that I needed the most room for unfolding was the overhead as the "top" side swung over. This was because I wanted to keep the side and bottom aligned pretty well to prevent undo stress while swinging it. Once the ceiling was cleared we could warp the side panels inward gently to fit within the space.

Note that I said "we". I had myself, my wife, and four kids to maneuver things. I think lots of help and a plan of where things are going before hand make it possible to complete the unfolding in very tight spaces.

Good luck

[Terry Dunn]

Sorry to hear about your problem.

I broke two pieces of plywood of plywood while stitching my Spindrift 10. My problem was caused primarily by not following the directions properly. I used the butterfly method but did not stitch the centerline all the way up. I was using cheap fir plywood.

The good news. I reparied the panels with fiberglass and epoxy and the fractures are not obvious.

When I built my CS 20, I think I did the butterfly as intended and it folded out so nice.

Good luck

[Ambler]

Thanks, Mustangermatt, for the condolences & info.

The fractured panel is now in splints & curing as per Graham's advice. It was a bit painful to undo all that stitching and get back to pre-assembly status.

How much headroom do you think the CS17 needs, to "unfold as it should?" Of course I'm already fantasizing about a bigger boat. I wonder what it would need to unfold a CS20 javascript:emoticon(':P')

Did you build the one in the picture? Now THAT's a boat.

Ah, just saw the encouraging post from Terry Dunn. Thanks, Terry. So we both have trouble following instructions, eh? javascript:emoticon(':?')How much headroom did you have?

What a great forum this is.

Alexander.

"Many people believe they are thinking when they are simply rearranging their prejudices"[/img]

[Tom Lathrop]

Too bad about the break and hope that it will work out fine next time. I am sure Graham is right about the building method but there a couple of things you can do to prevent breaks when bending plywood.

All breaks start at some weak point in the ply so the idea is to stop the fracture from beginning. If the surface of the area to be bent is sanded on the outside of the bend and then squeegee on a THIN coat of epoxy, the epoxy will bond the surface fibers and stop a fracture from starting. You can also attach a batten on the outside of the bend will spread the stress out and prevent the fracture from starting. I have used both methods and they do work.

[Garry]

Hi Ambler,

I just unfolded a Spindrift 11 and found it much less difficult than I feared. We did it in my living room which has 8 ft ceilings. We could not do it while it was on the horses so we set it on the floor. We stood the two halves vertically on the center seam and it just about fell open. The sides are very flexible so we could place them where we wanted as it folded open. It was easy to gradually tighten the wires to pull things into alignment then. We had to double up the wire for the last one at the stern bottom seam.

Check out the attached photos.

[attachment over 4 years old deleted by admin]

[Steve Day]

I have to put a few words in here. I stitched my Spindrift 10 using the butterfly method all by myself. It was "interesting" to do it that way and I would encourage anyone to get at least one other person to help.

However, I did get it done by myself with no major problems. Once I got the general shape, it was a matter of tightening a little here and there to gradually pull the bow sections together. I believe I got a fair hull. Reading Graham's advice and using my own experience, I would highly recommend the butterfly method.

Good luck on your repairs.

Steve

[Ambler]

I have fresh disasters to report - very embarassing! Details will be posted in a couple of days, with photographs (assuming THOSE aren't screwed up!!) We're having a "Let's not look at the boat" day tomorrow. But never fear, we're stubborn and will be back at it soon.

Meantime thanks to all for your good wishes and good advice.

"If, at first......."

Alexander - & Pat - Miller

[bwb]

Hi guys,

Just chipping in with a bit of an experience I had with a reluctant section of ply. I could not get a bow section to pull up to a pram dinghy bow transom. This was using 3/16" sides and 1/4" bottom sheets, and I had already given them one coating of resin on what would be the inside faces, while they were all still flat on the floor.

Even with 3 wires together in some holes, I could not muscle those sheets together, not even close.

I rang the plans supplier, who also sells the ply and resin, and asked his advice. According to him, the solution was to 'steam' the ply.

Following his instructions, I turned the hull upside down, and laid some towels over the front 1/3 of the dinghy. I then poured copious amounts of almost boiling water onto the towels, and quickly covered those wet towels with more dry ones, to keep in the heat. The steam bath was kept on for 20 minutes or so, with a top up of hot water after about 10 minutes - the time it took to boil some more water.

I quickly laced up the bow once the towels were taken off, and the hot, damp timber pulled up very sweetly.

I was concerned about wetting the 'raw' ply, but it suffered no ill effects, and a day or so later when it was dry, I glued, filleted and resined the ply with no problems, with the net result being a very acceptable bow section.

Sounds drastic, but it worked.

Now, a few months later, the dinghy has had a lot of use and abuse but shows no signs of the way it was 'treated' to build it.

I subsequently found Graham's site, and after reading his methods of lacing from the bow, realise that to build that way saves a lot of grief, muscle and hot water! I actually bought his Catspaw dinghy plans to compare the design and building of the two boats.

Regards,

Chris.

(Divas, Catspaw 8' and Spindrift 10')

[Klaus]

The word "butterfly method" was used in some of the replies and I am wondering what exactly is meant by that? Perhaps I know it under a different name :wink:

So, please enlighten me, a full size picture would do fine :wink:

Klaus, down under

[Garry]

Hi Klaus,

Here is a picture of the butterfly method in progress from the B and B Yachts web site.

There may be some more info on the site.

On my Spindrift, the bottom and side panels were taped together for the first 11". Then the bottom seam was loosely sown together with the port and starboard sides laying on top of each other (as shown). Then the sides were "unfolded." Since the bottom seam was sown together, the bottom and bow started taking shape as it was unfolded. Then the sides were sown to the unfolded bottom.

Hope this helps, Garry

[Ambler]

Thanks everyone for your input here. Sorry I haven't reported for a while - been workin' on (fighting with) my boat.

First I want to say I thought Mustangermatt deserved some kind of award for undertaking a 17 foot boat in a 17 foot space. But that was before I saw Garry's pictures of his boat being unfolded in his living room. WIth female help, no less. Sorry, Matt - you've been upstaged.

Well, as to the fresh disaster details I promised: we patched the broken piece back onto the bottom bow panel and proceeded to do the butterfly. Damned if the same panel didn't fail again on stitch-up, about 10-12 inches further aft. (Tom Lathrop is right - the failures have always started at a stich hole.) It didn't break right across the piece, but about two-thirds of the way, leaving a sprung jagged bit sticking out on the exterior of the bow. Crude attempts to force this back in place resulted in yet another crack starting to form behind it. I phoned Graham and he suggested perhaps I was not paying enough attention to tightening stitches gradually and symmetrically - probably true.

So we abandoned the now deeply traumatised forward bottom panel: Cut it off and spliced on a pristine piece. This time we reinforced the forward panel edges with glass & epoxy where the highest-stress stitches would be before proceeding through all the steps till we were ready to unfold again. Well, I guess we were a bit impatient or cocky or just careless, but in unfolding we created a (much smaller) crack in the same old area, this time at the rear edge of the fibreglass that holds the side to the bottom panel a la butterfly. We re-folded and repaired the crack by filling it with epoxy as best we could, then sandwiching it between glass/epoxy patches. Allowed it to cure, again unfolded the boat and began stitching the sides to the bottom. Almost got that finished before the repair let go. The crack gaped outwards again, but this time less so, being somewhat restrained between its fibreglass patches.

Being thouroughly fed up with folding & unfolding, stitching and unstitching, we decided the boat would damn well go together this time, regardless. So first a mess of epoxy was poured down the gaping area, between the inner & outer glass patches, then the offending area was sandwiched between two pieces of 1/4 ply, bolted right through; the inner piece bonded to the hull with epoxy and the outer one dry with poly protection to keep it from getting stuck. Once the epoxy cured, stainless countersunk screws were used to screw the hull to the inner plywood patch, and the bolts were removed. Gobs of thickened epoxy are being used as fillets and sanded so that the inside seam taping can traverse the patch smoothly.

The result is an ugly plywood patch which will never be seen, inside the fwd flotation space; and an almost-fair seam on the outside, which will be filled and sanded till it looks OK.

As of this evening our hull finally has its stitches removed and is filleted ready for inside seam-taping tomorrow. It's been a long haul and I think we've stitched & unstitched most of the boat 4 times.

But hey, it looks good !!!!!

On balance I think most of my problems stem from not proceeding cautiously enough. Unfolding and stitch-tightening require great care - even a heightened state of awareness. If you don't have it, you will develop it !!

Steve Day, you unfolded your boat single-handed? I'm awestruck.

Thanks again to all here,

Alexander Miller.

Two or three pictures are attached but they're all of the earliest disasters - after a while it gets tiresome to keep recording the failures.

[attachment over 4 years old deleted by admin]

[Greg Luckett]

Ambler,

Could you provide a close up of the edges of the plywood where the break is at? How many layers are in the plywood?

Thanks,

Greg.

[Ambler]

Sorry, Greg; I don't have any better pictures of the plywood break(s) than the ones I already posted. I guess you were hoping for an edge-on look at the plywood? After the second fracture I kind of lost my enthusiaism for photographing them. The novelty definitely wore off !!

The material is 5-ply Okume (6mm) purchased here on Vancouver Island where it's hard to find. When you can get it you take what there is. The sheets had handwriten labels attached, some saying 6566 and some 1088, but there was no such "official" stamp or imprint on the wood; so who knows? Am I naive to think that if it was to a British standard - especially 1088 - there would be a BS certification stamped on it ?? Where it broke I saw no obvious internal flaw, although the major part of each break seemed to run in a remarkably straight line.

I'm done filleting: Just a wee bit of sanding left before taping the inside seams, which I hope to do tonight.

I've got some questions about rope bumpers, watertight hatches and water ingress generally, but I guess this is not the thread where they should appear.

Happy building to all here!

Alexander Miller.

[Tom Lathrop]

Ambler,

A break like that looks like a plywood problem. Maybe the face plies are thinner than they should be. An interior void could also cause that but you said there was nothing obvious. Anyway an exterior batten would have solved the problem. Usually, the break is very ragged and over a much larger area, not straight across. The hot water tortue method also works.

[Ambler]

Interesting thet you mention the face plies, Tom. I've been puzzled & disappointed in their thickness ever since I got the material. I'd read that "proper" marine ply would have equal thickness plies, but to my eye this stuff definitely does not. I just decided my info must be in error. The two faces and the centre layer are noticeably thinner than nos 2 & 4.

I'll post a picture as soona as I can borrow my pal's digital camera.

So do the folks on this forum manage to get Okume that has equal plies ??

[Melissa Goudeseune]

The Meranti ply I used for the mini-paw is 1/4", 5-ply. All layers are almost equal thickness, and the wood behaves very predictably.

BTW, I purchased mine from Noah's in Toronto (www.noahsmarine.com). They do mail order as well, not sure about shipping charges for full sheets of plywood.

Michel