Transom Questions

steve_h7

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I'll preface this post with the fact that I'm working on my first restore so take this with a large grain of salt :)... but my transom area looked similar and, although mine is set up for an outboard and uniform thickness wasn't really a concern, I wasn't sure if I should keep grinding that off or if that was normal and I was going to end up grinding too far. I chose to keep going (carefully) and I was glad I did because after I started to remove some more of the uneven resin I found larger sections of fiberglass that weren't wetted out much at all and were almost completely dry. I just used my grinder like I had on the other parts of the transom.
Just fwiw...
 

sphelps

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I would grind out any of the loose glass ..The new wood may not bond very well in those area . You can glass in new patches In those areas before the transom install .
As far as wetting out the the ply before pb . It really does not matter . You can do that the day before or at the same time . If done the day before I would sand to roughen it up a bit first before pb .
‘The holes if you choose to do that can be around a half inch but I don’t see the need to make much bigger .
The thought is it gives a void for the pb to ooze and kind of make a structural through bolt or nail through the assembly .
Its an old school thing . Some do it others may not ...
Hope this helps !
 

JASinIL2006

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Another question on bonding the two layers of 3/4 plywood outside the boat. I have seen in some threads where people talk about adding "weep" holes to allow the epoxy to weep out under clamping. Is this necessary? If so, how big should the holes be and how many/how far apart?

I used 1/4” relief holes. I think they help in a couple ways, in addition to the mechanical bond sphelps mentioned. First, I think the holes help the transom shield from ‘floating’ on the PB so much, which makes positioning a bit easier. Second, it allows you to really slather on the PB so you can easily tighten the clamps to reach your target thickness.

The downside is this can be a bit messier, but it was worth it to me.
 

76SeaRay

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Thanks. I was thinking I would probably grind off the lower lip that is not bonded and then patch it after I grind down the thicker portion to get to a consistent thickness from the top to the bottom at 7/16 inches thick.

On the weep holes, would you use them when bonding the two layers of plywood by drilling holes in one sheet only? Then, once the two layers are laminated together would you drill holes again through both layers of plywood before bonding them to the transom hull? I assume you don't mean to drill holes through the transom hull to the outside.
 

sphelps

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No don’t drill through the transom to the outside ! LOL ! I guess you could drill the holes in one sheet for the lamination if you want . Not sure if I have seen that done . It’s usually done when installing to the transom skin . I don’t think there is a preferred spacing . I think I put them like every 6“ or so once ..
 

Scott Danforth

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I dont use weep holes.

I use a box of drywall screws with washers.

start in the middle, and make a circular pattern going outward about 5-6" on the spacing. it clamps the two panels together, and holds them when laminating, while squishing out the excess out the sides. then again, most of my laminating is done with the tite bond III
 

JASinIL2006

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Weep holes aren't needed when gluing the two sheets together; they are for when you attach the transom core to the hull. I drilled mine about 6" apart, too, and I drilled them after gluing the sheets together.

For gluing the sheets together, I also used drywall screws and Titebond III. (I don't think I used washers, though...) I removed the screws after the glue dried/cured and filled the holes with PB before I skinned the transom core. Drywall screws aren't the best to cinch together two pieces of wood, so I stood on the plywood pieces as I screwed them together to get a good tight joint.
 

76SeaRay

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Thanks, I haven't been able to decide between Titebond and Epoxy between the two sheets. I wasn't sure how strong the Titebond is compared to epoxy or PB between the two... Seems like Titebond III would be easier and save some money at least if it does all that is needed. So, if you use Titebond are you buying it by the quart and troweling it on? How much do you typically use (my transom is about 20 sq ft)?
 

zool

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A properly clamped Titebond lam will be as strong, if not stronger than the wood itself, as is epoxy.....I used epoxy because i was precoating the wood afterwards anyway..I also left the screws in for added measure....durarock coated screws really grab.
 

Scott Danforth

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look at it this way.

plywood is little thin sheets of wood glued together (with a 90 degree bias to each layer) with what is essentially tite-bond III

so taking two thicknesses of plywood and glueing them together to make a thicker section, all that is needed is tite-bond III, any other glue is simply another method (some more expensive than others)

as zool stated, the glue will still be stronger than the wood

so it is up to you..... use what you want
 

76SeaRay

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Thanks, I think I will go with Titebond III, save a little money, be easier to do, and a little longer working time.

Another question is the big OMC hole. When I put in the new transom plywood and cover up the hole, is it best to layer some CSM between the new transom plywood such that it covers the opening and extends in between the new transom plywood and the hull say 6 inches out around the hole. The mat would hang loose in the hole area until ready to bond when patching over the hole from the outside. This would be like putting on a bandage from the inside that is just larger than the hole. When the patch goes in, then there would a layer of CSM between the patch and the new plywood anchored inside the plywood hull lam area that can be wetted when the hole is filled in.. I won't cut the new Mercruiser keyhole until I have the transom done.
 

chevymaher

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I got my popcorn I am waiting and been wondering what the right answer to this one is.
 

sphelps

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I’m no expert on I/O but just me thinks that the layer of csm like you suggest is not really necessary. I would not want to add any thickness to the assembly to start .. Do that after you cut the new key hole .. I may be wrong ..
Hey Chev ! Save me some popcorn !
 

76SeaRay

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I am kind of back and forth on adding the CSM "bandage". However, I guess if I was going to do that then I would just put a layer of CSM over the whole area covered by the plywood. It will be a couple of weeks before I put in the new transom ply...

Going to cut out and bond the two layers of 3/4 ply tomorrow. Still haven't found how much coverage you get out of the Titebond III. Guess I will pick up a gallon since it seems two of the 16 oz bottles might run short for 20 sq ft of transom..
 

JASinIL2006

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I bought a gallon for doing my transom and I still have about 3/4 of it left. I would guess a 16 oz. bottle would be plenty. Two would be more than enough.
 

76SeaRay

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Well, cut out and laminated the two layers of plywood this last weekend. Hope I used enough Titebond, rolled it on as a heavy coat (used just less than a quart for the 20 sq ft). Got started on grinding the inner hull flat. What a PITA... For some reason it looks like the factory tapered the hull starting just about halfway down from the top then to the bottom so trying to get it to the same thickness. A lot of grinding to do....
 

76SeaRay

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Got tired of the grinding and dust so took a break and pulled all of the fittings and hand rails off the boat for later when the outside gets restored. Also removed the top deck of the hard top to eventually remove all of it and the upper and lower windshields. Some wood to do there plus refinishing the gelcoat on the outside. I will post a few more pics of the transom in a day or two. I work about an hour and a half north so have an apartment during the week for work. I might go down tonight or again this weekend to hit the grinding on the transom. I picked up a couple more flap disks and a hard disk for steel grinding to see if those work better. I may do up a picture and post it on how I am planning on clamping the new ply to the transom for some opinions on that.
 

76SeaRay

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In my bid to learn before doing, I am looking for feedback and comments/suggestions on clamping the new plywood transom to the hull. Here is what my current plan is:

Edit: Oops, realized one of my measurements was shown wrong. Revising the pic and will re-post......
 
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