transom rebuild help

C

CharlestonSC

Member
The plot thickens, planed to just do some patch work but as I dug into it the whole thing was wet so I decided to rip it all out from the inside.
looking as I pulled it out looks like wellcraft made the transom out of 1.5'' thick plywood and put 2 relief cuts to let it curve a bit.
so I was think of just using 3/4'' and epoxing it one piece at a time and clamping it to the back of the transom?
any suggestion?
I have seen some pictures where other members make it in 3 pieces.
 
That will work fine....in fact, if you want it to bend even easier, use 1/2 inch ply and just add more layers...thickened epoxy will work great....pre-wet both sides. Use a notched trowel about 1/4 inch deep and sweep it in one direction to allow air to escape and the putty to spread and clamp it in one at a time...use as many clamps or through bolts as you can to spread an even load, just don't squish everything out...just enough to see the resin ooze...then the remaining layers can be glued and screwed with self tapping screws and fender washers....just like you see being used on boats being built over a frame with wood...when cured, remove the screws and do the next layer. Since your prepping/grinding the existing glass, I would replace what you ground out with a layer of 1708 to make up any lost glass thickness and uneveness....don't need anything between the layers of wood except epoxy. Post some work in progress pics!
 
Here's the start need to grind the thin layer of wood off so the epoxy has something good to bond to.

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Looks really good.......you're going to need to grind the sides of the gunwales as well to allow you to wrap around each layer of glass for the inner skin.....probably 4 to 5 layers with a 2 or 3 inch progressive overlap on each layer...you want the same total skin thickness or a little more than the original. Also once you get the core in place, make nice fillets around the perimeter with epoxy putty and then tab the perimeter with a few layers of 6 inch tape, then put on your full sheets over everything.
 
Yes, I'll grind the gelcoat on the sides to get a good overlap, fill in any voids with epoxy puddy. I have a a 60'' roll of 40oz cloth with heavy mat then a heavey cloth on top of that, looks as thick as what wellcraft used.
With fiberglass it is best if I do the edges then let that dry then do the large skin?
Meaning if you cover up something you just glassed after it has started to kick will it be best to let that cure out or can it be layered by another?
Thanks for the help, and I'll keep this updated
 
Actually, its better to go wet on wet to keep the chemical bond going....just because the resin begins to kick, its still considered wet on wet for a few hours...depending on who's resin you use, they will tell you how many hours you have to continue layering before its required to sand again.....if using slow hardener, you can go several hours after its kicked...even up to 12 hours on some brands depending on temperature....it usually takes up to 24 hours to fully cure.

Once the core is in place....pre-cut all your glass, the tabbing and full sheets and have them ready......then make your putty fillets and let it just start to set up and then add your tabbing tape...if you do it right away, you may squish out the fillet, so just let it set up a bit but still tacky. Wet out your tabbing and let the layers overlap a bit...in other words, if using 6 inch tape, one layer has 4 inches on one side of the joint and 2 inches on the other, then the second layer would be layed on the opposite side, creating the 2 inch overlap......let that start to tack up so it doesn't slide on you when putting on the full sheets....then pre-wet the core, let it start to tack and then add the glass and wet out completely.

The 40oz glass is pretty heavy...I like using 17oz for the sheets and 12 oz for the tape..you will use a lot of resin and it will take some time to completely wet through that heavy material, so be patient......make sure you have resin rollers, bubble rollers and plastic squeegees to spread the resin and remove the air pockets.....you will need to wait until each layer tacks a little before adding the next because of the weight of the glass.....it may want to slide on you being in a vertical position.....maybe you can use some type of plastic to clamp and hold the top of each sheet until it kicks.......but i wouldn't sweat it.....read the working and curing tables of your resin....you should have plenty of time....even overnight if you do a last layer late at night and continue the next morning.....all else fails, just let fully cure, sand with 80 grit, wipe with alcohol and keep going.
 
Update, dry fiting first layer of the transom waiting for epoxy to come in.
still have to do a bit more grinding to do.
Has a HF bisket joiner that I took the guard off of and that did a great job of getting the wood out.
IMG01320-20110314-1316.jpg


IMG01317-20110313-1554.jpg
 
I saw a good description by someone on a forum, might have been thehulltruth forum, where they wrote up a lengthy description on how to make the transom repair. I can no longer find it! Does anyone recall where that might be?
 
Update, 2 layers of 3/4 inch epoxyed in, will glass in today. Man that 2nd layer of 3/4 was a bear, I ended up having to use a fork lift with some weight on it and lowerd the forks on top of the wood to help push it down. also got the floor glassed in, used 40oz woven looks like what wellcraft used, it took 3 gal of resin to wet it out.

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IMG01348-20110319-1350.jpg
 
looks great. i can't tell from the photo, but if those thru-hulls are plastic, change them to stainless while you can get to them. they are a pia later.
 
find the one that matches what you had and bed it good with 5200 or something similar

sorry couldn't get the link to work, go to west marine and type in" thru hull fittings" in the search box.
 
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How much glass did you put on? Looks good, but a little light....you shouldn't see the wood as clearly as that...what was the original skin thickness? What type of glass did you use? Also, I would probably put a few more layers where the transom meets the stringers to tie it in a little better.....thats a key element for strength in a transom and allows transfer of load to the rest of the grid.
 
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I used 38oz plain weave with 1oz chopped strand stiched to the bottom of that, it measured .040 thick with some calipers.
I know it is thick as it took 3 gal of VE to wet out the floor and 1.25 gal of epoxy resin to wet out the transom.
I got the fiberglass direct from a mill here in SC that makes fiberglass products, it was for boat building, it was a 50'' wide 50' roll, I was suprised that you can see so clearly after resin was applided, the floor I used VE and the transom I used epoxy. So being so clear I guess that is just the good quality of the glass and resin from US Composites.
I used epoxy putty in all the gaps and used that to glue the stringer ends to the 2nd layer of the new transom.
I also used 6'' wide strips of that 38oz glass to tie the transom on the sides, bottom and around the stringer first, then covered the whole thing with one big piece of the same glass.
I think this should be very strong.
Let me know what you think.
 
Here is what I used the woven measure .025 thick and the chopped mat is about .012 thick
And the stiching to the woven I think adds strength.

IMG01361-20110321-0900.jpg
 
Looks like good quality material.....and you got great wet out on the tabbing and full sheet...no bubbles......but IMHO I think one or two layers isn't enough... .040 skin thickness is light.....decks are one thing, but most transoms are .125 to.250 thick, depending on the MFG'er and boat/engine combination....what was the original skin thickness you removed? You want to match and/or exceed the OEM skin thickness.
 
Inside transom thickness from the factory on my V was thin (One layer of heavy woven into one oz matt). They didn't throw too much at it and they didn't spend any time filling in the gaps with putty to smooth out the transitions. To me 38 oz. sounds about right with what the factory used. I don't recall them using much if any reinforcement around the perimeter where the real loading is. The outside (hull) on mine was about 1/4" to 3/8" thick. You could debate for hours on the layup schedule. What Richie Rich said, thumbs up!! I personally like to layup wet on wet if two or more layers are used. If the 1st layer is allowed to kick off and set, you then have to grind it out again to get a proper bond(at least with VE, not sure about epoxy). So you would be grinding away some of the long woven strands in order to layup a second layer and that would deminish the strength of the first layer. When wet on wet isn't possible and where weight isn't a concern I like to lay a layer of 1.5oz mat into the roving as a sacrificial layer that can be roughed up for the second or third layers of glass. My .02
IMO what you have done so far looks great. You need to spend some time on the top of the transom to ensure it is waterproof. With respect to the heavy weight fabric, it is very difficult to get it to make the tight radius where the upper edge of the plywood core meets the upper lip of the transom. You may want to get some lighter glass to reinforce the edges and push into the corners at the top sides and bottom of the transom. You have come a long way fast. Don't rush it too much, take your time and the results will be spectacular.
 
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