Transom Replcmnt WARPING?

[oceanpotion]

I just read a thread with the advice pointing towards cutting the old transom out from the inside. It said you could risk warping the hull if you cut the whole transom out and replaced it.

My question is.. if you were to cut the whole transom out, or the transom out to deck level say.. how could you avoid/prevent the hull from warping?

 

[erikgreen]

Re: Transom Replcmnt WARPING?

Good hull support.

Either do it on a bunk trailer, or better build a temporary frame to support the hull evenly and hold it straight. Use cross bracing if you really want to be sure.

Check out Oops' "hull extension with pics" thread to get an idea on bracing, he did some nice work there.

But basically all you have to do is make sure you provide enough support for the hull while you remove the transom and it'll be fine. Warping is actually more of a concern when you remove the stringers.

Erik

 

[ondarvr]

Re: Transom Replcmnt WARPING?

Why would you need to cut the whole transom out?

 

[oceanpotion]

Re: Transom Replcmnt WARPING?

i.o. o.b. conversion... cookoo cookoo

 

[Mark42]

Re: Transom Replcmnt WARPING?

That is going to be a neat project. I have not done one, but I spent a lot of time researching how to do it when I was thinking of buying a junk i/o and gutting the hull to build my own custom cabin cruiser.

Excuse me if I'm covering aspects that you already know, but in a nutshell, this is what I found:

1) remove and rebuild a new transom with splashwell. Be sure to use good knee supports to pass the load onto the stringers.

2) fill the i/o hole and add an outboard motor bracket. They often incorporate swim platforms, and you can get fancy and add a door to the transom.

The first option is probably the most labor intensive and the most economical choice.

The second option is probably the quicker and more common method, but the brackets are really expensive. There are great advantages to using a motor bracket: 1) Additional floatation from the motor bracket. 2) Swim platform is often part of the bracket, especially on larger motor brackets. 3) The brackets attach low on the transom where it is strongest and don't need much additional support except for possably adding some small knee brackets on the inside. 4) Lots more usable space is freed up inside over building a splashwell. 5) Setting the motor 2ft or more behind the boat greatly improves handling and stability of the boat.

If I were to do it, I would probably build my own bracket from ply and epoxy/glass to save the expense of a custom built or pre-built bracket.

So, what are your plans?

Here is an example. Photo is from dadmarine.com

 

[Tacklewasher]

Re: Transom Replcmnt WARPING?

That is going to be a neat project. I have not done one, but I spent a lot of time researching how to do it when I was thinking of buying a junk i/o and gutting the hull to build my own custom cabin cruiser.

Excuse me if I'm covering aspects that you already know, but in a nutshell, this is what I found:

1) remove and rebuild a new transom with splashwell. Be sure to use good knee supports to pass the load onto the stringers.

2) fill the i/o hole and add an outboard motor bracket. They often incorporate swim platforms, and you can get fancy and add a door to the transom.

Having done option 1, I wish I had done option 2.

 

[ondarvr]

Re: Transom Replcmnt WARPING?

Neither of the options require you to remove the entire transom, only the inside skin if the wood is bad. To keep the skin from warping, just clamp a straight edge or two on it when the wood gets glasses back in.

 

[reelfishin]

Re: Transom Replcmnt WARPING?

I am in the process of doing one right now, it was an older trihull with a Mercruiser drive. The transom was already 3" thick, reinforced with several aluminum gussets to the stringers, and in excellent shape. We are removing the upper half, rebuilding the gunwales as an open boat with a center console and building our own aluminum motor bracket. I will simply fill the hole and glass over the outer, maybe adding an inner layer for appearance since the boat will be completely open. The lower hull is very light, it's actually the first boat I've done that's made with double layer glass with a foam inner layer. It's got no foam below the floor, just a foam filled core throughout the hull. Sort of like they blew in the gel coat and outer glass shell into the mold, then foam, then a second layer of glass making the outer hull about an inch thick but very light. The bare hull only weighs in at about 400 lbs, maybe less and its 17' long by 7' wide. It will be a far better boat with the small outboard than it was with the heavy stern drive. The transom is also far thicker than any I've seen before, it's a single laminated layer of marine plywood, double what the equivalent outboard transom would be. The odd part is that the wood doesn't go all the way to the sides, it stops about 4 inches short on each side. It does have four large stringers though, each attached to the transom via a wood gusset and two large aluminum brackets glassed into the inner layer of the transom. The transom is very solidly attached to the stringers but not at all to the sides of the boat. I will be adding support here whether it needs it or not. I've just never seen a boat made this way before.
The main reason I chose this boat for this project was that it was a mint clean garage kept boat that most likely never saw rain, and the fact that I sold the motor and drive for far more than the boat was worth as a whole.