Rot in Inflatables Transom

[davidpbo]

Whilst fitting some dinghy wheels I discovered some rot in the dinghy transom.

https://www.dropbox.com/s/ogwt764slbvw5ih/Inflatable Tender Transom Rot.jpg?dl=0

Tender is upside down.

I have cut it out leaving me with a gap 30cm by 5 and 10mm deep (To the right of picture) which I am going to epoxy some marine ply into. There is some shallower rot to the left. Would I be better to take this area out to the same depth and put one longer strip in. In one or two small areas where it is slightly deeper I will fill with epoxy.

It is a medium term repair until I either replace the transom or the tender.

 

[Graham376]

I would insert one long piece as each joint is a weak point. If you have a router, chamfered edges would be stronger than butt joints.

 

[davidpbo]

I would insert one long piece as each joint is a weak point. If you have a router, chamfered edges would be stronger than butt joints.

Rightly or wrongly butt joint it will be. There is still 9mm or so of the original 19mm ply behind that the new will be bonded to.

 

[TQA]

Your fix should be fine if the motor is a 2.5hp egg beater.

If it is a 15 hp then I think you will need to add further reinforcement to help transfer the forces to the floor and tubes.

 

[davidpbo]

3.5 Tohatsu.

 

[davidpbo]

My intension is to epoxy the wood strip in place. I don't haver any clamps with a deep enough throat tto clamp the wood in place in place while the epoxy goes off. I was considering drilling and screwing both to let any excess epoxy out and to hold it in place. Would I be best using brass or stainless countersunk screws? they will be covered.
Or I could just place a heavy weight on top.

The epoxy and hardenner I have is 2012. I probably should get some new shouldn't I?

 

[TQA]

Screws would be my solution. Bronze for perfectionists, brass or stainless will do.

 

[William_H]

The epoxy and hardenner I have is 2012. I probably should get some new shouldn't I?

Give it a go on a test piece. Hardener may be just fine. olewill

 

[davidpbo]

Having bought new epoxy at £40+
I did mix the old to dispose of a lump rather than liquid and it set ok although the hardenner was very pungent and dark. I suspect 2012 may have been the use by date.

Having epoxied in the replacement ply I have sanded the rest of the transom. Should I apply a coat of thinned epoxy as a sealer/primer?

What would people use to bind hypalon to the wood where I have peeled some back slightly where it overlaps the wood?

 

[davidpbo]

P.S. I have also relaced the sacrificial pad the outboard clamps to.

 

[davidpbo]

A second mix of new epoxy has not gone off. I have painted the transom with it and after 36hrs it has still not gone off although it is gelling. I suspect I got the mix wrong, it was also thinned with some acetone.

What to do? I am tempted to leave it and see what happens and maybe when it has set some more put another coat on possibly with a little extra hardenner in the hope that will encourage the first coat to set. The residue in the mixing pot has not set either although it is gelling.

 

[Boathook]

A second mix of new epoxy has not gone off. I have painted the transom with it and after 36hrs it has still not gone off although it is gelling. I suspect I got the mix wrong, it was also thinned with some acetone.

What to do? I am tempted to leave it and see what happens and maybe when it has set some more put another coat on possibly with a little extra hardenner in the hope that will encourage the first coat to set. The residue in the mixing pot has not set either although it is gelling.

With epoxy resin only mix at the correct ratio. Extra hardener does make a difference in that it may overheat and create bubbles in the mix as it cures and lack strength. I have never thinned epoxy and would only use a product recommend by the manufactures unless other forum members come up with some suggestions.

 

[Graham376]

West suggest warming the materials as best method for thinning. If solvents are used, IIRC only 5% should be added.

 

[davidpbo]

The first coat which was being used as a primer worked fine. This coat is going off just very slowly. I mixed a little hardenner with remainder of the mix in the pot which just to see what happens.

 

[TQA]

Getting the mix of resin and hardner crack on is essential.

if mixing small quantities get an electronic scale and some disposable cups. NB mix by weight can be different from mix by volume.

Warm up before mixing to thin. If you MUST use a thinning agent and I don't recommend it mix the resin then add the manufacturers thinning agent.

If you have the mix wrong it will never go hard and reach full strength but just go chewy.

 

[davidpbo]

Thanks folks for the advice on what I should have done, what I should have asked for was suggestions from anyone who had had epoxy not go off and how they rectified the situation. I suspect there was a problem with the electronic scales. My intension was to put on one coat of thinned epoxy as a primer which I have done successfully before, then a couple of varnish.

It is still very slightly tacky, at the moment probably too far gone to wipe off with acetone but not hard enough to sand without serious clogging. I think I will try another coat.

Unfortunately my wife has a very bad reaction to unset epoxy.

 

[davidpbo]

I decide to strip and start again. I had to use a hot air gun as sandpaper clogged badly. Fortunately the tubes are hypalon rather than PVC, I suuspect hypalon is much more forgiving of heat than PVC. Unfortuantely I found some more rot which I have removed and replaced with ply. This has now been coated with unthinned epoxy which will be sanded and varnished when set.