Glassing in new transom

[BOWTECH.JUSTICE]

So, on my 92 Celebrity i/o open bow ski boat, I have my transom and part of my deck stripped down of all wood and almost ready to start putting back together. Ive been doing alot of reading and watching videos to get this accomplished. My questions are, as I start glassing things in, how much thickness does a layer of glass add to the total? My outer hull is 1/4", and if I put two pieces of 3/4" ply glued together, Im at 1 3/4". Im planning on an adhesive of peanut butter resin against the hull. Will all that and a couple layers of 1708 get me to the thichness of 2" thats required? How long can I go between coats if I cant get right to another coat once I start? And, does the last coat need to have resin with wax in it for curing or can it be sprayed with an air inhibitor? Thanks ahead of time.

 

[alldodge]

Final thickness should be between 2 and 2 1/4 (IMO suggest try for 2 1/8 so you can sand on the inside)
Flatness outer surface 1/16
Flatness inner surface 1/8
Parallelism - inner to outer surface 1/8

What do you plan to use between the two layers of 3/4 ?

If your using Vinyl or Poly ester resin you can wait till the next day or so. Use more coats to get thickness.

No wax should be used with the resin even for final coat, nor spray. Wax is used with gelcoat

 

[BOWTECH.JUSTICE]

PL construction adhesive between ply.

So fiberglass resin cures out on its own?

And sorry, Im still a little confused on the thickness. Will I make it to 2" or more by the path I planned on taking?

 

[jbcurt00]

PL will take 72hrs minimum to off gas before you should consider covering it w glass and resin. And would be pretty far down the list of options I would recommend.

Fiberglass resin is either Polyester or Epoxy, best to use those terms to keep it straight. Resin could either.

As long as 'recent' polyester is tacky, you can add new layers of polyester and glass. If its not tacky, it needs to be well scuffed to provide better adhesion of the next layers. Wipe the surface w a little acetone and lay new polyester and glass


Wax can be used w poly resin or sprayed w PVA to cure the final layer. In some cases its not necessary. Warm climates and time will often be enough for polyester to cure hard and tack free. And either wax or PVA is also used w gelcoat.

Except for changing the PL in your layup schedule, and wrapping the 1.5in thick transom ply lamination w a layer of CSM before you install it, the rest will get you close to the desired 2.25in.

IIRC the spec is 2 1/8 min to 2 3/8 max for Mercruiser keyhole.

EDIT: As noted in AllDodges post below, 2in to 2.25in is the spec.

 

[jbcurt00]

Check this graphic to see a typical layup for a transom
http://forums.iboats.com/forum/boat...lamingo-splashed-w-pics?p=5550980#post5550980

Although for an OB, its the same for an I/O, just have to maintain the distance thru the keyhole and maintain parallelism so that the transom is perpendicular to the centerline of the boat.

 

[JASinIL2006]

I think aiming for a bit more than 2" is good advice. If you're going to err, better to err on the side of too thin; it's much easier to build up thickness by adding extra layers of 1708 than it is to remove material if you're too thick at the outset.

I used peanut butter (thickened resin) to attach the transom core to the hull. I trowelled on quite thick and the used the clamps to pull the transom core in to my target thickness - 1 15/16". Any PB that oozed out of the relief holes was scraped off right away and used to start the filletting, along with any PB that oozed out along the edges.

If you use PL adhesive to glue the two pieces of the transom core together, make sure you allow at least 72 hours before starting to glass in the core. An adhesive like Titebond III will allow you to proceed the next day.

Good luck with your project!

 

[alldodge]

Resin come in 3 types, Poly, Vinyl ester and epoxy

I used resin and a layer of CSM between the 3/4 ply

 

[BOWTECH.JUSTICE]

Sorry I didnt state that it is poly resin that Im using.
Is the PL a good choice if I let it cure the 72hrs? Already bought it and waiting 3 days isnt an issue at this time.
Not knowing how much resin I need for the whole project, my concern was that I wouldnt have enough and then it have it set up before I could get new shipped in. Anyone have an estimate for the amount of resin to bond the transom with the peanut butter, and to apply 3 or 4 layers of glass?

 

[gm280]

BOW, if all you are doing is the transom and nothing else like stringers and flooring, then I would think that one gallon would suffice. But honestly, without being there and visually seeing the project in hand that is only a WAG. I used Titebond III glue between my 3/4" plywood, but others have done theirs in many different ways. Is one way better then another? Maybe, but the main idea is to install a good quality solid transom. So anyway you can accomplish that, it is good. JMHO!

 

[JASinIL2006]

Sorry I didnt state that it is poly resin that Im using.
Is the PL a good choice if I let it cure the 72hrs? Already bought it and waiting 3 days isnt an issue at this time.
Not knowing how much resin I need for the whole project, my concern was that I wouldnt have enough and then it have it set up before I could get new shipped in. Anyone have an estimate for the amount of resin to bond the transom with the peanut butter, and to apply 3 or 4 layers of glass?

PL is fine; in fact, it's probably stronger than you need. The glue holding the plywood layers together would probably fail before the PL would That's why I went with Titebond III; you don't have to worry about the off-gassing like you do with PL and you get a glue with similar water resistance to glue used to make the plywood. The 72 hour wait with PL probably is a minimum... if you look around on some of the resto threads where PL was used, you occasionally will see someone who had problem with the PL off-gassing as it cured and ruining fiberglass laminations that were applied too soon.

I just looked at my original purchase list from when I did the transom and deck (not stringers) in my boat and I bought 15 gallons. I probably used a third of that (may a bit less) on the back end of the boat. I'd probably order several gallons - maybe even a 5 gallon tub - if it were me.

 

[BOWTECH.JUSTICE]

Thanks guys, all great info and very much appreciated.

 

[Woodonglass]

This might be of interest...Fabricating Decks, Stringers, and Transoms
My Guess-Ti-Mate for resin for your transom would be 3 gallons. You'll also need approx 6 quarts of cabosil and 2 cups of 1/4" chopped strand fibers to make enuf PB to glue it in and make your filleting materal. This is JUST for the transom Stringers and deck will take a lot more. You'll need approx. 5 yds of 1708 for the transom.

 

[mxcobra]

I built my entire boat with pl permian, and learned a thing or 2 along the way. first clamp them transom plates down very tight, and even... I used a hydraulic press, because that stuff is thick and will swell up, use a notch trowel to spread it on the plates. evan clamped as tight as you can its going to ad 1/4 to 3/8 of dimension to your 3/4 inch plates 3/4 +3/4 +1/4 for the pl, also 72 hours is not enough cure time using poly. Its more like 7 days. or the poly makes the pl bubble up for some reason. by the way pl is very strong and will never ever come apart.