Formula 27 Filler

[MEJETSKI2000]

Just how strong is this stuff ? Using it to replace some damaged gelcoat and sanding flush with the existing gelcoat before coating everything with new gelcoat. Have some stress cracks on the seats that I want to repair before recoating.

[marshmat]

This stuff?
http://www.westmarine.com/1/1/14084-formula-27-filler-pint-from-evercoat.html

Looks like generic brand Bondo to me. Polyester based, fast setting. I haven't used this particular brand, but have tried very similar products from several other suppliers. They're OK on a car, great on anything dry and stationary, but I don't trust them around water. Or vibration, for that matter.

Stress cracks are hard to cover up. Their presence is often an indication that the fibreglass underneath is too thin / too flexible for the loads it is subject to. You can patch and cover them, but unless the part is made more rigid, they come back....

[MEJETSKI2000]

I'm reinforcing the radius on the bench thwarts with fiberglass mat where most of the cracks have occured, as well as the flat surfaces where people will step when boarding. Basically using as a "spot putty" more or less I guess.

Oh, the boat is a 45 y/o Flying Junior, so I guess some wear and tear is par for the course, they built 'em pretty light back then LOL.