Transome size?

[lvl]

I was planning on replaceing my transome this winter. I've looked at quite a few posts here and they are very helpful. This is my question. I saw a post where the person cut the new wood 1/2 to 3/4 of an inch smaller then needed and filled the gap with peanutbutter type resin. Is this the standard when you replace a transome or should the wood be as snug as possible to the sides of the boat? If that makes sense.

Thanks
Bryan

 

[ondarvr]

Re: Transome size?

You already paid for the plywood, purposely cutting it smaller and then filling the gap will cost more money because now you need to buy more supplies to mix up putty to fill it. But...you won't be able to make it fit perfect even if you try to, so you'll still need to fill the small gap around it.

 

[HVAC Cruiser]

Re: Transome size?

Well, im not as versed as others on the topic but I can tell you what I did on my own boat be it right or wrong, I personally think it was right.
Listen to what ondarvr said for he is right, and I will try to elaborate and add my own 2 cents for what its worth.
When I cut the material for my transom ( I used Coosa board, but now I think it wa a waste of money to do it again, I would use 2 peices 3/4 ACX insted ) I left a real small margin around the sides then parged it in with peanutbutter.

For the bottom I kinda made a dam of peanutbutter to bed it. I basically did it like I was doing brickwork to make sure I had full adheasion to the sides of the boat.

I hope that helps, others might have better insite based on experience.

Bill

 

[evildocrsx]

Re: Transome size?

I just used two 3/4 inch plywood and glued them together with weatherproof carpenters glue. I glassed the edges and coated the whole transom with resin. I don't know how long it will last, but I didn't want to over do it.

 

[HVAC Cruiser]

Re: Transome size?

I just used two 3/4 inch plywood and glued them together with weatherproof carpenters glue. I glassed the edges and coated the whole transom with resin. I don't know how long it will last, but I didn't want to over do it.

Hi evildocrsx, he's asking about the reveal around the edges

 

[evildocrsx]

Re: Transome size?

Hi evildocrsx, he's asking about the reveal around the edges

Reading owns me!!

 

[HVAC Cruiser]

Re: Transome size?

Reading owns me!!

Hahaha lol, Hey lvl im sorry, and I don't mean to hyjack by any means, but I have no idea what you mean evildoc, maybe I have drank to much wine this afternoon Lol

 

[lvl]

Re: Transome size?

LOL No prob I think he means he didin't really read the question all that good. So what should I use for plywood? I'm thinking not that OSB type chip board. Maybe some kind of real wood type outdoor grade plywood from the Depot.

Thanks for the info guys
Bryan

 

[HVAC Cruiser]

Re: Transome size?

LOL No prob I think he means he didin't really read the question all that good. So what should I use for plywood? I'm thinking not that OSB type chip board. Maybe some kind of real wood type outdoor grade plywood from the Depot.

Thanks for the info guys
Bryan

Hey Bryan, I would use ACX, its stronger than OSB or chip. From reading here and elseware I used ACX for my deck and stringers. I bought it from lowes not home depot, simply because they always advertise that they have an indoor lumber yard. What that means to me , be it right or wrong is that their lumber is kept indoors and dry. I have had great success with ACX, and alot of folks here have used it for their decks and transom.
With whatever you deside to use, the main key is to seal the wood, edges and all with resin to prevent moisture from infiltrating
I hope that helps some.

Regards,
Bill

 

[andgott]

Re: Transome size?

Cut it as close as you can get it, but you won't get a PERFECT fit. I adhered mine to the boat and filled the gap around the edge with Epoxy resin mixed with Phenolic filler powder.

Don't even think about using OSB or chip board! Use outdoor grade BC ply. You'll want to 'pick' the stack a bit too so you can find the better pieces- I am amazed some times at how bad some sheets can be.

 

[bigredinohio]

Re: Transome size?

Here are you basic options for your transom rebuild:
Exterior grade ply (I use BC grade but I'm cheap)
Treated ply
Marine ply
Composite (something like coosa)

I agree with the Lowes wood statement. They have nicer wood to pick from! Definitely don't use OSB or partical board.

 

[VeroWing]

Re: Transome size?

You may, or may not, be referring to my thread on transom rebuild.
http://forums.bateau2.com/viewtopic.php?f=10&t=19949

The reason(s) I left a 1/2"-3/4" space around perimeter of cut plywood is two-fold:

First is, epoxy/wood & fiberglass flour paste needs to be pushed into the crevice created and then radioused out, because when you wet in fiberglass, it will not conform to a square corner, and it will create air pockets(weak spots). By leaving an opening around perimeter of plywood, when you fill with epoxy paste, you are bonding and sealing plywood ends, existing hull, and newly wetted in fiberglass from future water intrusion.

Second reason applys more to stringers than transom, but is a good rule to follow anywhere on your boat. That is that you should not install plywood where the edge directly pushes against existing hull fiberglass. This creates hard spots that are subject to cracking when boat hull is stressed and flexes during use. Below is a "how to" section I copied from a boat building site that helped me out during my transom rebuild.

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There are two points to pay attention to when installing the stringers in the hull.
There should be no hard spots and the top of the stringers must be in the same plane.

Hard spots are points where a part pushes hard on the hull. (This happens only with plywood stringers.)

This picture shows a frame with hard spot.

Hard spots concentrate loads and are dangerous. They can lead to cracks or hull failure. A stringer should distribute loads evenly all along it's length. The ideal way to install stringers is a little bit above the hull. Builders should start with a stringer that follows the shape of the hull within a 1/4?. They can use small pieces of foam to lift the stringer from the hull and fill the gap with epoxy putty while building the fillet.

-------------------------------------------------------------------------

Its' your boat, and you can do whatever you want, but you may want to get some more opinions from people who do this work day in, day out. Thats what I did. Mike

 

[ondarvr]

Re: Transome size?

Not allowing plywood stringers to contact the hull is a good practice, purposely leaving a larger than needed space around the transom and filling it with putty is of no value.

 

[VeroWing]

Re: Transome size?

Not allowing plywood stringers to contact the hull is a good practice, purposely leaving a larger than needed space around the transom and filling it with putty is of no value.

That would be your opinion, and my opinion is that it does have value, and for the reasons I pointed out above.

 

[ondarvr]

Re: Transome size?

There is no advantage to leaving a larger gap, please explain what you think you are gaining.

 

[VeroWing]

Re: Transome size?

I don't mean to imply that gap has to be as large as I made, only that there should be a gap.

 

[ondarvr]

Re: Transome size?

There will always be a gap because its difficult to cut it perfect and the space around the ply should always be filled. Its not always done on production boats though. It should be filled so the edges of the ply will be sealed and to have a radius to glass on. There doesn't need to be any extra effort made to make the gap larger though, having it wider won't increase or create any benefit.

You won't create a hard spot on the transom like you can with a stringer because the vertical glass transom is already creating a hard spot so to speak, but its in complete contact with the hull so its not a problem. Adding the wood to the already rigid structure won't make it stiffer in the vertical direction, its already as stiff as it can be.

On a stinger there is no support around the stringer, so any hard spot where it contacts the hull creates a flex point that may or may not have issues in the future.

The other thing that makes having a small section of a ply stringer in contact with the hull create a flex point, is that when the stringer is glassed over the laminate shrinks as it cures. As it shrinks it forces the plywood down into the hull with a good deal of force, which compounds the problem.

 

[VeroWing]

Re: Transome size?

Again, this is your opinion. I disagree and feel that there is value of having this seam and sealing edges from sides and bottom of hull creating uniform pressure throughout area. If seam is cut tight to hull sides and bottom then some sections may be touching, and others aren't, creating "hard spots" and unneccessary stresspoints to hull. Boats made of fiberglass bend and flex in all areas, not just in the stringers. Some areas more than others, but still flex all the same. You WILL create "hard spots" on corners of transom to hull side areas. You don't think that there is flexing and movement going on in the transom area, when hundreds of horsepower, 700-900lbs of twin outboards are riding on a fiberglass and wood transom pushing 4000-6000lb boat through 6-12ft waves.

I am confident, that on my boat, that there will always be uniform pressure throughout my transom area, and I am also confident that the edges of all the plywood installed is completely sealed and bonded together as one unit with the hull sides and bottom. I also know that my wetted in fiberglass on the inside of transom and running onto sides and bottom of inside hull is completely bonded to all areas and has zero air pockets, because of using the epoxy mix to radious out these corners.

Like I said in my first post, its' your boat, do what you want. I didn't just come up with this idea out of thin air. What I did was to talk to professionals, and searched information from persons that do this type of repair and rebuilds routinely.

We all have opinions, ours happen to differ.

 

[lvl]

Re: Transome size?

Great info guys.So i guess what I take away from all this info is that it is not critical that the plywood fit like a glove. However it is critical that all edges be sealed up tight with resin. Radius corners on the side and bottom where the glass will be transitioning from the transom to the sides and bottom of the boat. Most of all no air pockets.

Unlike vero wing I will only be hanging an 88hp single outboard on my 19Ft boat. hopefully I will never see a 12 ft wave on this boat or I will need to change my draws.

Thanks for all the help
Bryan

 

[ondarvr]

Re: Transome size?

You've got the idea, even on a stringer the standard gap is only 1/4 inch.