TOPIC: Plexiglass transom sheathing?

I need to replace the entire transom in my del Mar...fiberglass and all. It occurs to me that it would be much simpler to cover the new marine plywood with a sheet of plexiglass, screwed and bonded with 5200. The edges could be feathered-in with fiberglass resin and maybe a little fiberglass cloth where needed. The whole nine yards could then be sanded to 400 grit then primed.

Has anyone ever done this? Will fiberglass resin stick to the edges of the plastic sheet? If so, can anyone think of a down side? If not, does anyone sell sheets of fiberglass that could be used instead of plexiglass? All bright ideas/solutions considered/appreciated. No dumb ideas needed...I have plenty already!

I'd be really scared about that. The continuous fiberglass is what gives the boat rigidity. I'd just bite the bullet and do the glass job.

I agree. Plexiglass tends to crack when too much pressure is applied, as in mounting the motor and any movement when the boat flexes. I have cracked it just putting it in a window frame.
Bill

With age plexi does get brittle and has a ability to come unstuck. It moves with the heat a lot too. Fiberglass would be much better.

OK...in that case, does anyone know a source of smooth fiberglass panels? I'd really like to avoid laying it up from scratch with cloth and resin and the resulting semi-endless sanding, etc.

I've made smaller fiberglass panels myself, by laying them up on a formica countertop that has been well waxed (NOT in the kitchen, though!!), you could probably do the same on a larger scale...

I just make them a little larger than I needed, then cut them down to size. I used Epoxy in mine, but you could do it just as easily with polyester. You could probably even spray gel coat down first, then do the layup on top of that, and end up with a panel that is gelcoated. Might be worth some experimentation.

-Andrew

I would be concerned about the thermal expansion. Plexiglass expands a full 1/16" per 100 deg. Boats kept outdoors experience a lot of temperature swings.

www.eplastics.com/Plastic/Plastics_Library/Coefficients-of-Thermal-Expansions-of-Plexiglass

If you apply fiberglass from scratch onto it, it will be bonded very nicely to the boat.

Nautilus wrote:

OK...in that case, does anyone know a source of smooth fiberglass panels? I'd really like to avoid laying it up from scratch with cloth and resin and the resulting semi-endless sanding, etc.

I'm not sure I understand the statement about the sanding. When laying up layers of CSM and 1708 biaxial cloth there is usually no sanding. The only sanding I do is feathering the tabbing into the hull and that is very minimal. It is very important to have these resinous layers of glass on the wood to aide in the bonding to the hull. IMHO there are no shortcuts when installing a transom. It is probably THE most critical component of the boat.

(( IMHO there are no shortcuts when installing a transom. It is probably THE most critical component of the boat. ))

I agree, and isn't the transom on a DelMar curved ?

I would avoid anything but fresh glass like the plauge, I am not sure if you mighthave a motorcoach/ boat MFG or repairer in your area, but you might hunt someone down who could shoot and layer it with mat and spray chop, I usualy use roving and spray chop to repair large fiberglass areas. Sounds Spendy but usualy it's not to bad our local motorcoach mold shop wll shoot a 16ft open bow floor for cost +100.00. Cost my friend john 200.00 to have his floor shot and rolled.
As for doing your transom if your not pretty good with resin mixing/ application you might want to find a helping hand if you going to glass a large area, as to hot it will crack/ crystaize, to cold it will just get gummy. Hope my 2cents helps just don't be afraid to shout out if you need advice we are all here to help each others insanity!