mixmkr
Well-Known Member
I wouldn't mix poly and epoxy. Use one or the other. As far as a mold for repair...if the front foot or more of the bow was missing, a mold might be helpful. With the size repair you have, I don't see a problem guestimating the original, as you have enough there to still give you a good idea. As mentioned previously, making the strength on the inside, now the boat is open and then extra glass layers on the outside and fair it out smooth.
On the topic of strength, although epoxy resin has better bonding than polyester, the resin itself is not the "strength" but instead the fiberglass cloth and how it is laid and applied. As I mentioned previously as well, bonding can be more than sufficient with polyester, if the surfaces are correctly repaired.... sanded well and clean. A good mechanical bond will be basically impossible to rip apart.
I only suggested poly previously, mainly on the basis of seeing too many failures of gelcoat applied over "unprepared" West System finishes. West System creates a "blush" that CANNOT be sanded off completely (unless you remove a lot of product!), but must be scrubbed of sufficiently with soap and water. If you're painting, a good primer and paint, ..the decision is less important which you use.
On the topic of strength, although epoxy resin has better bonding than polyester, the resin itself is not the "strength" but instead the fiberglass cloth and how it is laid and applied. As I mentioned previously as well, bonding can be more than sufficient with polyester, if the surfaces are correctly repaired.... sanded well and clean. A good mechanical bond will be basically impossible to rip apart.
I only suggested poly previously, mainly on the basis of seeing too many failures of gelcoat applied over "unprepared" West System finishes. West System creates a "blush" that CANNOT be sanded off completely (unless you remove a lot of product!), but must be scrubbed of sufficiently with soap and water. If you're painting, a good primer and paint, ..the decision is less important which you use.