Coosa transom in Hydrostream

[NosBoss]

So, I’m completely redoing my Hydrostream Ventura 2 for the second time. I did it 10-11 years ago with all cheap plywood and polyester resin. I layered up the hull, skipped the core and went with stringers. I didn’t seal the wood very well and the stringers/floor rotted. I tore it all out and now doing complete coosa board restore. So, my question is how should I go about doing the laminating of the transom? Should I cut the three pieces of 1/2” coosa and glue them all together on the floor or get the first piece in the boat and laminate the layers it in there? I do not have access to the top of the transom as I filled in the splash well the first go around and do not plan to cut it out. My other question is, what is a good way to put pressure in the coosa once in the boat? I can’t clamp it like it. Do I drill all the motor mount holes and run some bolts through it? Maybe put a piece of 3/4” ply on the outside to even up the pressure? Any ideas would be helpful.

[CUDA]

I'd make a template or just measure and cut the Coosa board to fit, do as you said on the floor

install layers of mat between the cut pieces and use weight till it kicks, Epoxy is your friend

Drilling the holes and using bolts sound great.

[NosBoss]

I plan to layer one or two 1-1/2 ounce mat between the layers. Not sure why I typed “glue”. Drilling the holes and bolting it was the only option I could come up with to get a good bond to the original skin. It sucks working back in the area under the rear deck, but I’m not redoing the outside just to clamp it. Oh, I’m using vinylester resin this time.

[FUJIMO]

...core bonding compound. you can also use the stern-eye holes as well, to thru-bolt. as well as proper length scraps of wood to hammer/wedge between the back end of your stringers & the new transom core material. when using core bond compound(putty), drill about 100 1/8'' holes through the 1 1/2'' new transom core, before pushing it into place...

[VkingMike]

I would precut all of my Coosa to fit, 2 or 3 pieces depending on how thick you want to go. I would laminate them together outside of the boat first and then make a final layup with your 1 pre-cured piece.

Using the engine bolt holes, I would make 2x4 or 4x4 horizontal braces the width of the Coosa ( and outside) and through bolt those to spread the load all the way across. Once that cures you can do a final layer of glass to seal it all up.

[FUJIMO]

...you use a corregated metal tile grout trowel, the ones with the teeth on them, to spread the core bond. it gives you a perfect even depth application of the core bond. let the excess bonding compound push out the sides and bottom, and then add extra corebond at the sides & bottom to fill in the gaps, with a putty knife. try to leave a smooth putty surface or you will be grinding off too many humps & bumps, as the stuff does set up hard...

[FUJIMO]

...with a helper, lay down a large piece of cardboard, wet the cardboard out with a resin roller cover, lay down precut strips of 1708 biax on the cardboard, wet those out also with the resin roller. you can stack 3 or 4 at a time on top of each other and wet those out at the same time. lay down under the back & have you buddy hand you one strip at a time. push them up in place and smooth them out with your bare hands. they will look great...

[NosBoss]

I was working on my template and got it close. Need to do a little bit more trimming. I’ll cut the 3 pieces of coosa out and laminate them before putting the assembly in the boat. I think my best option is to use the engine mount holes to pull the new transom tight. I can also use the front side of the splash well to push off of. Maybe cut some 2x4’s to wedge in there.

[LakeFever]

Spreader clamps. Easy to make, clamp strong. No holes required so you can get your transom sealed with full lays

[NosBoss]

The top cap is completely enclosed. No way to get clamps on it.

[LakeFever]

Right. My buddy used a 2x12 and small screw jacks with long 2x4’s he wedged the 2x12 horizontally across the seat boxes and front floor area. He had a spider web of 2x4’s pushing back from the 2x12 against the transom. You don’t need crazy amounts of pressure, especially if you use corebond.

Bolts through and screws from the backside in are common on many builds I’ve seen. Some use stainless screws and leave them in. Others take them out, fill with thickened resin and then lay over. All probably fine. Imo it’s more critical to get a void free flat bond than it is to worry about holes. I put so many lays on mine I ended up with 3/8”’thick glass per side of the transom. Little holes underneath this would be nothing to worry about. Btw, good choice on vinylester imo

[NosBoss]

I need to come up with some kind of reinforcement to push off of. Right now the inside of the hull is completely gutted. The only thing to push off of right now is the front side of the splash well and the dash. I can probably fabricate something off the dash to get some pressure on the lower end of the transom. Maybe some long load locks out of a truck.

[LakeFever]

Yup that sounds like a winning plan. You should be able to rig up a fabricated backing plank or board that you can clamp to the dash. Make this board so the surface faces the transom at a parallel angle so your wood jacks won’t slip. Use whatever jack system you have access too. Not too much pressure to distort anything though.

[MattGreen]

...you use a corregated metal tile grout trowel, the ones with the teeth on them, to spread the core bond. it gives you a perfect even depth application of the core bond. let the excess bonding compound push out the sides and bottom, and then add extra corebond at the sides & bottom to fill in the gaps, with a putty knife. try to leave a smooth putty surface or you will be grinding off too many humps & bumps, as the stuff does set up hard...

Guys do it exactly like Fujimo laid out on each post. I did my Checkmate this way (with Coosa), it come out awesome. I mixed up an epoxy adhesive to exactly the consistency I wanted (slow hardener, no styrene to deal with under the splashwell) so I had lots of working time. If you make a nice custom putty knife/spreader you can make a clean fillet all the way around with minimal grinding. I laid up my main bulkhead first (a week earlier), and cut custom wedges to push in the lower part of the transom - braced against the bulkhead. I used all engine bolt holes and the stern eyes for bolts (wax them up good first); use big backing plates to distribute the load. Hint: leave lots of length on these (I used all-thread), if they still stick (likely at least a bit), heat the long end with a torch - the heat will conduct through the bolt enough to soften the glue/epoxy holding it in place.
Apply putty/adhesive to both the transom and your Coosa core material (sticky + sticky = good bond).

Matt

[FUJIMO]

...Apply putty/adhesive to both the transom and your Coosa core material (sticky + sticky = good bond)...

Matt

...yes on this...