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Bad, bad news. Rotten Transom


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Bilge pump seems to have given up on the boat so I removed it to see if it was dodgy wiring or a bad pump. While I was down there I had a dig about, something I should have done when I bought the boat.

Transom is rotten. It seems to be 2 layers of ply with fibreglass between. The guy we bought from has dug out the first layer which is rotten so on quick look you can see solid wood. If you put your hand a bit further along you can grab handfuls of rotten wood. 

Is there any chance/point in seeing if the rot affects the whole Transom? Can you cut out the rotten parts and keep the good or will we end up with a compromised Transom and we need to replace the whole thing? Could I remove the rotten bits, patch in with new marine ply, cover in fibreglass then put another layer of 12mm ply and fibreglass so have an 15ishmm thick Transom?

If I knew then what I know now I wouldn't have bought this boat but I didn't and I did so got to make it work. I just want to go fishing

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10 minutes ago, LostPiker said:

Can you cut out the rotten parts and keep the good or will we end up with a compromised Transom and we need to replace the whole thing? Could I remove the rotten bits, patch in with new marine ply, cover in fibreglass then put another layer of 12mm ply and fibreglass so have an 15ishmm thick Transom?

No, no, & no.

Yes, the rot will affect all the transom which is often made of 2 x 18mm ply panels bonded together.

The only way forward is to cut out the inner skin of the transom, either cut or lift the gunnels, and then take out the old transom panel.

Make a new panel from 2 x 18mm ply (resin bonded together) and then re fibre glass the inner skin.

Usually when the transom is rotten the floor is rotten as well, but that is only a few stringers and some plywood.

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31 minutes ago, LostPiker said:

Could I remove the rotten bits, patch in with new marine ply, cover in fibreglass then put another layer of 12mm ply and fibreglass so have an 15ishmm thick Transom?

 

You could do the following, which will allow you to use it during the summer season, however, I cannot condone this method, but lots of people do it.

Take the engine off and make a large Ali, or stainless plate for the outside of the transom. The plate needs to lip over the top of the transom and cover all 4 engine mounting holes by at least 50mm ................ then make a similar plate (not lipping over the transom) for the inside.

That will  allow you to do the job properly next winter.

 

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Very annoying for you, especially as the last owner mashed it up to hide the problem. But onward and upwards, don’t dwell on ifs and jeffs/Geoffs - bite the bullet and fix it properly. 

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My last boat has the exact same method of firming up the transom as GPS describes and there is no movement in it although I know the transom is shot because it's there. This thing had been used 3 or so seasons in that condition, floor was rotten too. But at least I was aware of these before I bought it. Only bought it for the engine and trailer but decided to take it on as a project

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Thanks.

I think I'll do it properly now, I don't want to be taking a boat out for the first time and worrying about the transom the whole time. 

just trying to find 18mm marine ply that doesn't cost the earth and take ages to be delivered. Found some videos on youtube but they all show the transom being cut out from the outside. My plan is to cut the floor back about 18 inches. Assuming its solid there and the stringers are solid that far back, cut out the inner fibreglass skin, hack out the wood back to the inside of the outer fibreglass skin. Cut the ply to fit tight with the fibreglass skin and around the edges. 

Then do I paint the wood with resin and let it go off. Then bond one layer of resin covered 18mm ply in, layer of fibreglass, then another layer of the resin covered ply and then fibreglass over the top taking the fibreglass 6 inches or so along the sides?

then put a new piece of floor in. Where the floor meets the sides of the boat, what supports it? Are there blocks on the side to sit the ply on or does the fibreglass over the top hold it up?

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5 hours ago, JonC said:

Very annoying for you, especially as the last owner mashed it up to hide the problem. But onward and upwards, don’t dwell on ifs and jeffs/Geoffs - bite the bullet and fix it properly. 

I never would and never did even comment on the repair method, I only sympathized with LP and wished wished him luck. You lot should all know me by now and know that as far as I am concerned the only way to do a job is to do it correctly. I would carry out the repair exactly as GPS said and leave the transom exterior in place and cut out from the inside. I am aware that some people have removed the outer transom GRP, but a far more professional finish will be achieved by leaving the outer skin intact. I would also drill a series of holes in the plywood sheet/sheets to allow the resin to bond through. Once again LP, I wish you luck and am still sure that you will get there!!! Geoff.

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18 minutes ago, Geoff said:

I never would and never did even comment on the repair method, I only sympathized with LP and wished wished him luck. You lot should all know me by now and know that as far as I am concerned the only way to do a job is to do it correctly. I would carry out the repair exactly as GPS said and leave the transom exterior in place and cut out from the inside. I am aware that some people have removed the outer transom GRP, but a far more professional finish will be achieved by leaving the outer skin intact. I would also drill a series of holes in the plywood sheet/sheets to allow the resin to bond through. Once again LP, I wish you luck and am still sure that you will get there!!! Geoff.

I don't think Jon was criticising you Geoff - simply using the phrase "if's and jeff's".

But then, I reckon you already knew that 😉

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1 hour ago, Andy135 said:

I don't think Jon was criticising you Geoff - simply using the phrase "if's and jeff's".

But then, I reckon you already knew that 😉

Paranoia is creeping in I think . I used a common phrase, with both spellings, the former being correct. 

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The boat construction is nothing like I expected. 

There is a cross member about 18 inches in front of the transom, the floor from at least there back to the transom is solid fibreglass. Looks like 2 lots as it hasn't bonded all that well. In total about 20-25mm thick. Below the deck level nothing attaches to the transom, I was expecting some stringers or similar. The transom below the deck level is bare ply, no fibreglass layer, unsurprisingly rotten. Seems someone put a couple of bits of batten on the transom to rest the deck on? I think I'll cut the deck out in one piece and refit it when I'm done - repairing the two great big holes I just cut in it to see what's going on underneath. 

 

I've got some pics but there are over the size limit so will shrink them and post them tomorrow

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On 4/20/2021 at 9:50 AM, LostPiker said:

just trying to find 18mm marine ply that doesn't cost the earth

Use external grade plywood (WPB), it will be way cheaper and easier to get.......B&Q, Wicks, etc

Also, the ply panel will be bonded together and then encased in fibreglass, so not open to the elements

Your engine bolts will be put through holes plugged with sikaflex, and the drain bung will also be sealed with either sikaflex, of drilled oversized, resin bonded, and then drill the correct size.

 

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59 minutes ago, LostPiker said:

The boat construction is nothing like I expected. 

There is a cross member about 18 inches in front of the transom, the floor from at least there back to the transom is solid fibreglass. Looks like 2 lots as it hasn't bonded all that well. In total about 20-25mm thick. Below the deck level nothing attaches to the transom, I was expecting some stringers or similar. The transom below the deck level is bare ply, no fibreglass layer, unsurprisingly rotten. Seems someone put a couple of bits of batten on the transom to rest the deck on? I think I'll cut the deck out in one piece and refit it when I'm done - repairing the two great big holes I just cut in it to see what's going on underneath. 

 

I've got some pics but there are over the size limit so will shrink them and post them tomorrow

Sounds a bit like the Trident I have, that was also full of badly bonded fibreglass. The whole crossbearer/central support was very poor, only 1-2 layers of CSM, not wetted out properly. The floor had been overlaid with another floor, both of which had had it.

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4 minutes ago, suzook12 said:

The ones that aren't there!! Duh!!!

 

Hang on... we've been here before...

What does Uncle Albert have to say about this? 🤣

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