Transom layup

[lelandtampa]

So i just bought a 78 20' MA and it needs a new floor and transom. Here is how i plan to layup the new transom. any thoughts would be appreciated.It will be all epoxy resin and engine will be transom mounted.

OUTSIDE TRANSOM SKIN
LAYER OF Chopped MATT AND RESIN TO FILL IN GRINDING GAPS
DOUBLE 3/4" MARINE GRADE FIR PLYWOOD laminated with epoxy putty
1708 ACROSS THE TRANSOM TABBED 2" TO HULL
1708 tabbed 4"
1708 tabbed 6"
1708 tabbed 8" repeat with 1708 (until factory thickness of inside glass is built up)

[pelican]

Originally Posted by lelandtampa

So i just bought a 78 20' MA and it needs a new floor and transom. Here is how i plan to layup the new transom. any thoughts would be appreciated.It will be all epoxy resin and engine will be transom mounted.

OUTSIDE TRANSOM SKIN
LAYER OF Chopped MATT AND RESIN TO FILL IN GRINDING GAPS
DOUBLE 3/4" MARINE GRADE FIR PLYWOOD laminated with epoxy putty
1708 ACROSS THE TRANSOM TABBED 2" TO HULL
1708 tabbed 4"
1708 tabbed 6"
1708 tabbed 8" repeat with 1708 (until factory thickness of inside glass is built up)

chop strand matt and epoxy doesn't play well together...epoxy and gel coat - it can be done,but....


using wood core - the holes will require overboring,filling with a thickened epoxy,then having the holes drilled through the epoxy - to protect the coring from water intrusion.water intrusion into wood is never a good thing.plywood will absorb water,like a sponge."saltwater preserves wood,freshwater rots wood" -


using a composite board,like Penske board/coosa board avoids all that and allows the use of polyester compounds to laminate;along with the composite being a dense foam,with glass fibers on the outside,this composite will absorb nothing,weighs 45%less than wood and it will last indefinatley


there's other options sir....including a half ceramic/half Penske/coosa board transom core - lots of manufactures use that approach,which seems to work out very well

[kmoose]

Spend the money on 3/4 Coosa for the transom over marine ply. It is amazing to work with and 30% lighter were you need to save weight. I would also recommend Nidacore for the decks. Full dressed Nidacore is a quarter of what marine ply weighs before you even glass it and both products are forever with zero rot or water intrusion issues.

[jorgeinmiami]

I'm almost done with my transom. I also went from the out side dug out the old wood cleaned it up and replaced the skin I cut out. I went with a product called Arjay which is a pourable material. I needed 3 buckets for mine. After it cured it's hard as a rock. I did layer the skin back on with 3 layers of 1708 and am now in the fairing part. If you plan on keeping the boat for awhile use some kind of composite materials. It lighter stronger and will never rot.

And I also replaced my floor with nida core and it's a lot better than wood . Lighter stronger and never rot. Just leave some wood to attached the console and t-top

[lelandtampa]

on the Arjay did you use 15 gallons ? did you pull the outside skin off? how did you pour it in with no skin?

[DonV]

"how did you pour it in with no skin?"......very carefully!


"I did layer the skin back on with 3 layers of 1708"

Please note the above quote in Jorge's post. It took 17 gal to do my 23, all the way to the very top on both sides.

[jorgeinmiami]

Yes I put the skin back on 1st and I used 3 buckets of 5 gallons . I thought about some duct tape but it was a little too redneck for me.

[DonV]

Here ya go Mr. lelandtampa,

Skin off and wood removed, skin back on, poured and ready for the engine.

[lelandtampa]

got it i couldnt figure out if you used the original skin or layed up a new one on a table then glassed on. thank you for the visual.

[jorgeinmiami]

Mine was a little different since I raised my transom to 25 from the factory 20

If your going thru the effort raise it to 25. But actually since you have a MA a fellow member advised me to to 26 1/2 because of the splashwell and the mounting bolts of the engine would have a issue