Discussion in 'Downeast Projects and Boat Building' started by Billyclub, Oct 8, 2017.
Leaky, I’m interested to know why you would go with marine ply vs synthetic Coosa or the like
I’m assuming 1708 would be the between fiber for laminating multiple sheets of voting together. I’m torn between using epoxy vs. vinylester resin. Increased cost with epoxy but great strength. Cheaper for vinylester resinand decent strength
BTW - I don't know what happened but marinepoxy apparently no longer sold at duckworks, but they do sell System III Silvertip..
1708 is just a type of fiberglass often used with 2 part epoxy, because the mat is stitched onto the roving versus held in with a glue that is meant to dissolve in solvent. It is good for quickly building strong fiberglass and has a heavy layer of roving.
As far as cores go - nothing trumps plywood in strength, period.
What you are doing here isn't something like a deck on a boat which is semi structural, it's holding a set of outboards intended to go smashing through seas and to have everything stay intact. It's already an old boat, presumably built with plywood in other places, a well done plywood transom is going to last forever in practical terms.
You do not laminate sheets of plywood together - you glue them, and that's why epoxy - just like the plywood nothing beats epoxy for doing that.
If you are putting any thought into coosa versus plywood, forget about the cost difference between Epoxy and Vinylester. A sheet of 3/4 coosa will run you like $300, a sheet of marine ply is like $100... 3X the cost coosa over plywood.
VE is not really that cheap - 5 gallons of VE runs a little less than $50 a gallon, 5 gallons of epoxy should start getting down into the $80 gallon range with Silvertip - not sure how much you need exactly, but if it was 5 gallons (which is probably too much) you'd save < $200 using VE over 2 part epoxy, and the difference in bonding can't really be compared.
For a 2nd opinion, you may want to stop by the scream and fly forum, ask those guys how they'd do it - the place is basically for go fast outboard powered boats - many projects like that are tackled and talked about, lots of good knowledge. The boat design forum is another one - lots of knowledge there, just it ranges all over the place and world.
Also gelcoat and epoxy don't work well together. You would need to paint. For glue try US Composites
I was planning on painting and was aware that epoxy sticks to polyester resin but not vice versa. I found a good source of information on vessel maintenace is “Boat works today”on youtube. I reached out to him last month and he stated he was going to be rebuilding a transom and the video will be out in February.
I guess my hesitation regarding using plywood again is another wet transom. I understand that if done correctly this tarnsom will never get wet again.
My 1989 seawolf in the picture, last time I drilled a hole in the transom it smelled like pine pitch, was probably home depot grade plywood, and it wasn't built with epoxy. Do dumb stuff and let water in and you got problems, even with coosa it might find a way to freeze/thaw and delaminate it - keep it sealed right and no problems.
Gel coat sticks just fine to epoxy - whoever says that simply has not done it or did not understand what went wrong. The problem is getting it to cure and it may only impact some little spot here or there, or may impact the whole job. There are ways to make it work, if you want to know I'll explain it, but basically the issue is there is a chemical inherently in the epoxy that interferes with polyester (or vinylester) resin curing, gel coat is a formulation of resin that normally does not cure as easily as straight resin or filler, and when you put these solvent based resins onto epoxy they tend to draw out the nasty stuff which undermines any cleaning you did to remove the contaminants... No matter what you do with epoxy - the key thing is before you paint, wash it with soap and water, not acetone, not solvent or snake oil, a brillo pad and water is perfect, because the residue I'm speaking of is cut with water (like bird shit, which also doesn't wash off right with acetone ).
The practical thing to consider though is have you ever tried gelcoating something after the fact and how did that finish turn out? Unless you got spraying gelcoat figured out (which is kinda voodoo), or you get how to sand and buff it to a shine (which is also kinda voodoo but mostly just lots of work), or are just tipping a small area with a paint brush that requires no blending, the odds are it looks like absolute shit when you are done. Gel coat simply is not made for re-finishing, it's good for initially building a part, small repairs here and there, but not a whole transom. When you are done with this the sensible thing to do is paint your boat - roll and tip, a two part paint if you want ultimate, a single part for a good and easy job.
By glue you mean epoxy?
I went on Composite on s website. Talk about confusing. Couldn’t find the product
"When I took off the trim tabs I noticed they had been moved and the old holes were never filled. I swear 5 gallons of water drained out of the screw holes"
Don't you just love uncovering shit like that? Every boat has it's well kept secrets unless a major rehab project like this uncovers them. It's the kind of thing that should only reinforce your decision to tackle this project first hand. Keep at it!
Epoxy : Epoxy Resins and Hardeners
kit for 3:1 or 4:1 depending on temps you have. After you navigate it a bit it pretty simple.
Finished cofre removal and sanded with 80 grit. Ready for Spring rebuild.
Need to make a decision on which bracket to go with Hermco (fiberglass), Armstrong (alum.) or others
If you decide to go with a Hermco, you should order one soon, I heard he's not making many more brackets, and is going to be closing up shop
Does the core go to the edges of the transom or is the 6" or so that you have left solid glass?
All that exposed wood you are trying to save needs to be sealed asap with poly or poxy.
I talked with the guy who owns Herco. He stated he was selling the buisiness and was going to be train9ing the new owner
No, the core stops at the outline cutout. What you see left is 100% f.glass
That bare fiberglass, no more wood there although it looks like wood. The rotting core discolored the glass
The inner fiberglass skin you see is about 1/4” thick
I was referring to the perimeter. Looks like wood.
Sorry, came onto your thread late. I have had luck with the pour in place stuff on a friends boat. You remove just the top edge of the transom, go in with your chainsaw and shop vac, pour the stuff in using a plywood trough, wait for it to cure and cap the transom off (or not, its optional) we capped his with a stainless "U" channel we had bent up special.
No fiberglass, no grinding, and strong as hell.
Funny, other than home made I've never heard of fiberglass engine brackets for the most part - what is the advertised benefit of them versus aluminum?
Brooksie is referring to "Sea caste". Expensive but will never rot.