Split board joints.

[tonyart]

Hi, I now have my boat packed up for winter. Although she has been on the water a couple of times, and with new timbers and ply marine sheeting. I now have 2 joint splits in the hull. 1st one is on the bottom of the transorm that joins onto the main V structure timber. This joint is leaking and is letting water through. Only noticed as boat had water inside and had it tipped up to keep the water at the back so I could bail it out, and saw it running out though the crack. Also a 2nd crack along the side of the hull, quite a long crack where the ply boards meet.

What is now the.best way to fix? Sand down the paint to bare wood re seal and paint? And seal from inside as well?

Also what would be the best sealer to use? It would need to beable to move with the timbers so would need tome elasticisity to it

 

[Poignard]

Deleted. I misunderstood the question

 

[Fr J Hackett]

I am not a boat builder but a ply edge to edge joint is going to be a bugger to seal and especially reseal. Sheathing in GRP would do the trick. You need a large surface area to make effective edge joints but as Poignard says some pictures would help including one of the boat so the context can be established.

 

[Hacker]

The correct repair for the transom really depends on the structure of the crack. As @Poignard says photos are needed. If the hull crack is on the edge of a ply board then water is likely already in the laminate. If you want to keep the boat for a long time then you are likely to need to cut out the damaged area and replace with good marine ply. Sheathing in GRP will give you a very short term solution as the roast will continue under the sheath. We only sheath boats when new and absolutely dry.

 

[tonyart]

Hi, I'll upload pics later when I'm on my pc, this site says my pics are too large, also boat in question is a lysander. It's design is ply boarding. The boat had a full rebuild over the last 2 years, and had the best marine ply available.

 

[Tranona]

Really does depend on how the ply was fastened to the frames. The norm now is to use a really good waterproof glue, usually an epoxy, so it would be unusual for a glue line to fail. whatever you do they will need throughout drying out as probably water has got into the ply inner cores - even the best ply needs the end grain protected to prevent water ingress.

 

[Poignard]

This book, published by West Resins, contains a lot of information on repairs to plywood boats :
Woodenboat Restoration and Repair (Available in Print or free PDF)

Instruction

 

[tonyart]

Items Shared on 11-10-2021

Photos attached, no expense was spared in restoring her, from the detailed notes epoxy resin was used, also the boards were screwed in.
due to the amount of boards that attach to the hull, and most of them are cut to shape, the rest of the boats hull are fine, just in 2 places.

 

[Tranona]

That is disappointing to have failed so soon. Rake out the split seams, dry completely and fill with a thickened epoxy mix. The West instructions in post#7 will provide further information on how to use epoxy and fillers. Probably a goof idea to strip back the paint either side of the seams about 25mm and epoxy that (mask it off well so you do not get runs over the paint) and when cured repaint.

 

[johnlilley]

The photo of the transom does appear to suggest that the transom board or plank might be a bit suspect at the base where the plywood connection is failing causing possible fastening security failure. Have you confirmed that this area is sound and hard both internally & externally.

 

[tonyart]

The photo of the transom does appear to suggest that the transom board or plank might be a bit suspect at the base where the plywood connection is failing causing possible fastening security failure. Have you confirmed that this area is sound and hard both internally & externally.

I will have to recheck, outside its all good & solid, inside I had a brief look when I bought it and all looked and sounded solid. Im not 100% sure if the transom is the original or replaced. I do know that ALL the damaged timbers & boards were replaced on the boat.
Im not sure that if the water inside the boat caused the failure of the joint. As prev said I had quite abit of water inside. After trying to remove the cover for the first time it started to rain, lasted about 10 mins, when it stopped I removed the cover, but forgot about the water laying on the cover, after untying about 10 gallons of water spilled into the boat. I managed to bail out most of it.
It could be possible that the water on the inside caused the issue, from swelling and shrinkage.

As for the crack on the side, I believe this is where the hull was repaired as on restoration there was a large hole in that area, and from the photos the inner main frame was reinforced and to allow it to be recovered and secured with the new ply.

 

[debenriver]

A lot depends on how the original repairs were made. At the chine (where two planks join at an angle) it looks as if the planks are screwed regularly to the chine piece inside (the chine piece is the longitudinal member bevelled to receive the two planks that join on it). The real question is whether the planks were glued (preferably nowadays epoxy bonded) to the chine piece or just screwed and bedded.

If they were epoxy bonded, then it's safe to rout out the seam a little (perhaps 5mm width max), make sure it's clean and dry, then wet out with epoxy resin, then fill with epoxy resin modified with colloidal silica or similar. I would recommend using WEST system materials.

If they were simply screwed and bedded on, it's better to use a flexible sealant/filler. Just clean out any loose material and trowel the filler in. International make a flexible topsides filler (white – the red is for underwater).

The same really applies to the transom. The structure is usually that the transom is stiffened around the edges (called "fashion pieces") to give the hull planking a wider area to land on and be fastened to. The hull planking would then be screwed and bonded – or screwed and bedded – to the fashion pieces.

I doubt that you letting water get in there caused the problem - boats are meant to be in the water and usually have some inside as well from time to time.

If it leaks through the crack between the transom ply and the hull ply, then something is likely coming adrift there and you need to establish what the problem is. The most likely is perhaps the fastenings from the hull ply into the fashion pieces (and at the bottom, the backbone) are bad – insufficient, corroded, or lost their hold.

You need to tap the structures inside and prod them with a small bradawl or similar, to make sure they are sound. Good wood rings when tapped with a small hammer – rotten or saturated wood sounds very dull. The bradawl shouldn't be able to penetrate the wood (or only marginally) when just pushed against it.

Do the same with the ply transom, inside and out – but be a bit circumspect with the bradawl!

If the timber seems sound, then I would try to find the heads of the fastenings from the hull ply into the fashion pieces and backbone. Clean out the stopping over the heads and withdraw one or two fastenings. If they are slotted head screws, clean out the slots carefully. Then insert the screwdriver and give it a sharp tap or two with a hammer. Try tightening the screw a small bit before loosening it. Other head types (specially Philips) are a bit more difficult to clean out – but boat screws usually have slotted heads.

If the fastenings are OK, then you can probably use a flexible sealer/filler same as for the topsides. From the look of the crack and the fact that water just ran out, I would say that it's unlikely that the hull planking was epoxy bonded to the transom, fashion pieces and backbone – just screwed and bedded. Again if the fastenings are OK, perhaps there are not enough of them, or not enough down at the bottom. In that case you can bore off for, and drive, additional screws.

Whatever, you do need to discover what's going on there. And perhaps get more information from whoever did the refit etc.

Cheers -- George

 

[DownWest]

As John Lilley noted, there appear to be some areas of the lower transom than need a look at. The slightly shadowy:wavey areas could use a push with George's bradawl to see if they are soft.
Boats of that era were usually glued with Aerolite resin glue, which might be a bit degraded now and it is not easy to sort it out without major work. Really depends on what the restorer managed.