Ply trimaran - which repair, if any?

Angelique, it is just your terminology or translation which is wrong. Starboard tack is with the wind (not the sails) on the starboard side.

 

Some more leeboard support pictures, the below boats are Botters*, these are Dutch fishermen boats which were in use about a century ago, part 24 is the leeboard support...

* all links are in Dutch, except the third.​

pic source​

It's a well-boat, note the shown fish well #21 and the well circulation grate, here as item #27.​

Explanation of the figures in Dutch, since it's too difficult and too long for me to translate all the jargon:​

pic source​

This boat heels not so much here, but it seems to be modified for more sail and more heeling, maybe the fish well is now ballasted and closed to the outside.

1 Broadened leeboard support, to keep the leeboard vertical when heeling more.
- Note the broadened leeboard support part is thin, I think this is since it goes through the water with increased heeling.​

2 Added part to bring the leeboard more outwards on its way down, BTW this part ploughs through the water when much heeled, so a part of the gain is sacrificed there.​

3 Block to protect the leeboard in collisions, which is a standard item.​

 

Note in my previous post that the main frame (item #20), that holds the leeboard pivot pin, and carries the main forces when the board is down, is extra strong and heavy, just like the modification Adrian has made to his boat in post #1.

 

Many thanks for the time you have all taken with the helpful comments, reassurances, research and good wishes.

I shall tackle a full repair after the trip, incorporating most of all your suggestions - belt and braces!

I've attached some rough sketches. The proposed leeboard sketch section is viewed from the bow, looking sternwards.

I've not detected any signs of shear or crushing failure around the pivot itself, either outside or in. The leeboard is a substantial chunk of pine (I think - happy to be corrected) and the small external plate and pressure plate are about 15mm thick solid timber, not ply.

I've indicated the position of the original failure. To the best of my interpretation, because the original reinforcement didn't go down far enough, but was well adhered to the hull ply, the turning moment applied by the lee board bent/twisted the hull ply below the pivot, the smaller original reinforcement possibly concentrating the forces around its lower point, and this fractured/delaminated slightly the ply in the position shown.

I hope by incorporating your suggestion of a larger external plate, Angel, which extends below the chine and filleting underneath to bring the loads to the second hull plank, this will not happen again.

Doug, I'll put glass in between the hull, the internal and external plates when I resin them in place.

I shall try to find a larger washer for the lee board, but I'm not overly concerned as there doesnt appear to be any damage here.

I'll disregard the brass screws idea Corley.

The sawing out and back filling with thickened epoxy - so, If I understand correctly, a small area of the hull around the pivot hole would be epoxy instead of ply?

I've never used tow - my glassing skills are pretty basic. Are you suggesting stitching as you would in sewing fabric - weaving the tow though holes in the ply hull and internal and external reinforcing plates?

Blue Knarr - thanks for your kind comments. Yes, there is wear to the meeting faces of the external plate and the leeboard. I'll experiment with some wearing faces, though I need to retain some level of friction to hold the lee board in the up position.

I think the cracks around the existing external plate that you and Angel identify must be caused by flexing - and presumably on the starboard tack, as Latestarter suggests.

Zilver - Much as I love the Solway Dory boats, I've not found them keen to get involved with repairs and modifications much! The two directors have in fact just retired, and the new business owner seems to be moving in an all composite boats direction.

The extra layer of wood on the external plate is, I think, just there to give clearance to the leeboard and handle, by the gunwhale, and reduce the risk of squished fingers!

This boat was one of two made, in fact the largest boats they have ever made, and I think perhaps pushing the size of the hull up without making it too heavy, has meant that there is less strength in the shape (curvature, chines...) than in the smaller boats. And the leeboard is a beast!

I really love the rig. Its light and dead simple - reefs by spinning the masts. The reefed sails are notably less good on one tack than the other, so I try to remember to reef the two sails in opposite directions. I love the both the practicality and the control it gives. I have to say that it points really well. I've always attributed that to the powerful leeboard.

Angel - many thanks for the time you have taken with the research, thinking and sketches - really helpful.
I love the drawings and pictures that you share too - much appreciated.

I will make the new external plate the same width as my internal reinforcement, and extend it as far down below the chine as I reasonably can without catching too much water, as you and Alan have suggested.

The one thing I'm keen to do is to put perhaps 6 large stainless steel bolts through the external plate, hull and internal plate, above and below the chine, while the new resin and glass layers are wet, and use them to draw the layers together to get good adhesion, and encourage them to act together structurally. I'm thinking M8 (8mm dia) with countersunk heads, which would be perhaps 20mm diameter. Large washers on the inside.

I had thought to leave these in, bedded in something masticky, but they could be removed after the resin has cured, and the holes plugged.

Adrian

 

Oh blimey! apologies for the monstrously hairy drawings - in my defence, I have done them on my phone!

 

For a moment I thought it said ‘‘damn age’’ there, I yet have to read the rest of the post though . .

Damn phone ! -

 

Thanks for clarifying Alan, my mistake was caused as a jargon translation issue, since any kind of jargon is one of the hardest parts in a foreign language.

For everyone who came this far in reading the thread, everywhere before where I've said ‘‘port tack’’ I've meant ‘‘starboard tack’’ and vice versa.

 

Now that Alan has cleared my terminology mist in English, I'm wondering too about any kind of relation between the post #6 pic 1 crack/slit and the only on port tack occurring cracking noises.

post #6 pic 1​

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(note post #22: ‘‘everywhere before where I've said ‘‘port tack’’ I've meant ‘‘starboard tack’’ and vice versa.’’)

But if it's not this crack/slit, then what is causing the cracking noises, and why on port tack only . . ?

 

Its my best guess, Angel, that my repair, although robust in the wood work, was not good in getting the new inside reinforcement to adhere to the hull, and the cracking I hear when the boat is under pressure is the delamination of my reinforcement from the hull. So I'm pretty confident that the external plate that you and Alan recommend combined with glass between the internal and external plates and the hull when I resin it in, will solve the issue. But I would like to use the bolts, at least while the resin is curing, to squeeze it all together.

 

And Angel - don't worry about the terminology - I think you have better command of technical terminology and jargon in not your first language than anyone else I know!

 

Done properly stitching is amazingly strong basically drill holes around say the perimeter of the external mount. You can think of the glass tow like thread and the edge as a surface you are lashing. The advantage is it basically makes the whole skin, reinforcing and internal support one piece removing the skin load issues. I've found the spacing can be reasonably wide and still effective. The good thing about it is that you fill all the holes with resin which forms a very strong and completely waterproof structural join. It even works really well for holding on quite heavily loaded parts like sail tracks.

 

Thanks all for your advice on this. I ended up puttin a bunch of stainless bolts through, set and coated in a clear PUR adhesive as a quick and dirty bodge. I had a wonderful camping trip in the boat; some days up to F5, and the repair was totally solid except a tiny amount of flex on port tack from the top chine up to the gunwhale where my rubbish glassing had failed and the hull was no longer attached to the ply gussets. I plan to replace the wooden quarter rounds behind the cup holders with aluminium angles mechanically fixed into gusset and hull. Still an ugly bodge. One day I may get round to a proper and pretty repair with enlarged cup holders to fit the jet boil.

Here's an album of the trip with a couple of pictures of the repair. many thanks all.

Snufkin round about Mull https://flic.kr/s/aHskJM3sUd

 

Great pictures, beautiful scenery. The nearest I've been is Isle of Skye. Were you plagued by midges?

Also I had a quick look at the thread again and noticed the drawing showing leeboard attachment on a Botter (post 16 Angelique). The post seems to be shaped so that the leeboard can "hinge" upwards and outwards if it accidentally gets left down on the windward side. Using the same movement it looks as if the crew can also remove the leeboard from its' post easily for maintenance or when mooring on that side. It looks like a well thought out arrangement.

 

Thanks Alan - it is a glorious part of the world. We didn't manage to circumnavigate Mull - the conditions were too marginal to tackle the unforgiving West coast of the island in such a little boat, and we had a tight time window, but we still had a terrific time. Im lucky enough not to be too bothered by midgies, and if they are about they seem to find my sailing mate Paul rather juicier than me! Its the damn ticks I can't bear...

 

Looks like a really great trip. Wish I had that scenery around me.

And the boat.

That was a monstrous repair. Like they use to say at work - go big or stay at home!