Another Transom question

[intheboatshed]

I'm phaffing over how best way to replace significant rot in Token Gesture's transom.

The transom appears to be made up of 3 layers of 5mm ply - 2 layers cover the whole transom, and the third layer is a strip along the top edge of the transom, about 10cms wide.

The rot has been caused by a screw fastened through the transom at the top pintle to a knee that appears to have been added at a later stage (I guess to increase the transom's strength). Unfortunately, all 3 layers have rotted at this point. 

Secondly there is rot around the 2 small drain holes, at the bottom of the transom. Which I guess is the normal place to suffer rot.

Finally, I was thinking of reshaping the transom flap holes anyway, as the lower lip is so low the boat takes on water as soon as I so much as look at the transom, let alone go aft to lower the rudder - a 3 to 4inch lip would be more practical.

If I cut out a large section of the the transom all in one go, is this likely to cause the hull sides to splay apart? Would supporting the hull using a tightened strap be enough to keep its shape while I replace the part removed?

Can anyone share any hard earned lessons on doing this sort of repair?

Thanks

Tim

[Martin]

I think I would fit better seals to the transom flaps rather than make them less effective.....

[fat lad (Guest)]

If water’s coming in the transom flaps then you’re sitting in the wrong place.

[benb]

Im sure there are people more qualified than me able to comment, but I'd suggest that if you were going to cut away much of your transom, then I'd be tempted to put in some temporary support while you work. For example a piece of wood secured to both sides of the decks as close as practical to the transom. The problem with using a strap or something in tension is that you could actually pull the decks closer together at the back... A strap would stop it splaying but it might end up a bit narrower too! All could be preventable with a bit of wood and couple of clamps.
I'd be tempted not to change the size of the transom flaps. As Fat Lad suggests you could be sitting too far back. In your post you suggest that they leak when you look at them...  dont look at them - it will save you loads of time  
 
 

[chalky]

Hi Tim,
I have replaced 2 transoms  so far, both have in my opinion worked well. The first one was in 3022 my pipedream and the second was in  760 Bobtail. The 4 plank one was easier than the 8(?) plank  therefore the baggy should be simple. Assuming the remains of the existing transom are still bonded to the hull make a template of the transom on hardboard or thin ply allow for the hull and deck thickness. The inside face of the transom will be bigger than the outer face, you should be able to determine this by careful measurement on the inside and outside faces of the transom. 
Mark and cut your new transom to shape allowing for the bevel which wont be more than a few millimetres over the thickness of the new transom. This can be made from whatever you can source. 3022 was solid cheap and cheerfull ply (18mm?). Bobtail has something a bit nicer.
How to remove the old transom will clearly depend on how well fixed it is. Watch out for any staples that may have been left from the inner laminations...  I managed to remove the remains intact from Bobtail and this was my template. I fixed a timber batten between the side decks to hold the hull together. I also used a webbing strap to start with but soon found it wasnt doing much.
Keep trimming the new transom till it fits... a bevel gauge is useful. A perfect fit is not essential on the inside face as thickened epoxy will fill a reasonable gap and a small fillet will hide the inside joint. If the outside has a wide joint, paint it! There are pictures of Bobtail(760) on the database that might help. Refixing the knee(s) is quite straight forward. Epoxy  and mocrofibres are very forgiving.
Good luck and I accept no resposibility if it goes wrong!
John
 
 

[intheboatshed]

bend/chalky - Thanks for the tips and advice.
I was hoping not to replace the whole transom, although that might initially seem the most obvious thing to do, because the construction looks quite intricate at the transom / side deck join. I'm a bit worried that in attempting to split the join I'll cause more damage than I already have. 
I think everyone slightly misunderstood my comment about water coming in through the transom flaps - I didnt mean when sailing. I appreciate if water was coming in at that time it would be good indication that the crew weight is too far aft. I meant when getting ready to go sailing. I had noticed from pictures taken by the previous owner he had taped up the transom flaps, and I found by using duck tap across the lower edge of the transom flap holes, it gave just enough height to stop a lot of water coming when I have to go aft to lower the rudder ready for sailing, after launching the boat. But thanks for the comments anyway.

Tim