-
Transom laminating question
When laminating two 3/4" sheets of plywood together, what is the preferred method?
- Apply resin too both sheets, put one or two layers of 1708/cloth/Matt etc in between.
- Apply construction adhesive glue, clamp/screw sheets together, then apply resin/glass too the outside of the laminated sheets.
- Other ways?
Also, I saw a video on scribing a line onto plywood, from the transom. Now I can't find it. Using the old wood isnt an option, there was none left. Anyone done such?
Use cardboard/cheap plywood instead, too make a template?
-
Transom lamination or other project? If transom work are you building a core to butter in after complete or working the lamination in place in the transom?
-
Transom laminating.
Building core first, or build in place? Good question. What are the pro's and cons to each?
-
Personally for me it depends on the quality of inner transom skin, ability to clean out transition edges where new core is going, is it being slid in from the top, pushed in from the back (assuming you left a flange), or installing from the inside. Did you salvage the outer skin for re-lamination to core. How was the old core removed? A picture here would help me help you greatly. Please note, Only, Only, Only use epoxy to butter in a new core, laminate a core outside of a transom, and to re-laminate outer skin back in place. If you look at the transom work pictures I posted for my personal Champion restoration project you will see how clean things need to be for a rock solid repair. Ester resin adhesion 300 PSI - Epoxy resin adhesion 3000 PSI, big difference. Also epoxy is tough, will not fracture like ester resins.
-
1569930937931_0_IMG_20190924_203515520.jpg
Installing from the inside. Old core was removed with a shop vac, what was left of it. Inner skin cut out .
I'll look at your champion thread again.
-
It's clean enough, the picture is good. What is the milky material along the transition from bottom to transom outer skin?
-
I made a peanut butter mixture (epoxy) too fill in low spots. As I went, the bottom has alot more low spots then what I thought, wound up doing it all. Also, The old transom was 1-1.25" thick, I plan on a 1.5" thickness for the new transom. This extra thickness causing extra work..
You have a good eye!
-
Well you can go two ways, if mine I would be making the complete core as I did for my Champion and here is my argument for proceeding that way. Ester resin really don't like to stick over epoxy except gelcoat. The oils made by epoxy when curing must be washed off with a good soap and water. The introduction of water here is a absolute no-no. So after epoxying the 2 halves of the new core together (be sure to make oversized for later fitting) sandwiching one layer of 1708, only put epoxy on the aft side of the core to butter in, be sure after clamping to police up ALL the epoxy that squeezes out from behind the core. This is necessary to prevent contamination of the plywood inboard. I only allow just a minimum amount of epoxy past the core. After curing what epoxy that you didn't wash off while wet grind off now. This leaves a very small line of epoxy that your inner layers of 1708 saturated in vinylester resin to bridge. Since you went in from the inside you actually made more work for yourself in a transom repair. The other way is to build the transom in place as the manufacturer does but using epoxy you run the risk of contaminating a lot of area from your picture still needs work. Repair shops use vinylester to rebuild transoms everyday, us epoxy nuts can be accused of being 110%'ers. The epoxy you started with must be scratched well before buttering the core in too. I assume some of the vertical glass that has been removed was transom bracing? All of that is much easier to replace with vinylester. In my Champ I will be taking the hull stringers all the way back with epoxy but using a 1/4" Coosa 24 core in between the stringers and deck area allows me to transition back to vinylester for the glasswork to complete the repair.
-
You said I made more work for myself, by going from the inside. How would you have dealt with the sponsons, on the back? To build it
Also - The boat had four stringers, two approximately 66" long, two more approximately 128" long . I was going to use epoxy for them, 1708, and 1/2" plywood. The gap for the old stringers (the vertical glass, I think your referring to) measures 1/2".
Am I on the right track?
-
Transom cores can be epoxied in pieces, you leave about a 3in flange around the outside of the actual transom, skin the rest off, dig the wood out from the outside, I fit Coosa replacement panels in dry first, if the inside skin is not thick enough for me I add more before fitting new core then butter the inside channels, butter the backs & sides of core pieces, then clamp them in. Any epoxy that squeezes out is spread scraped off without smearing. Now if you get the core at the perfect level you can continue by buttering the back of the skin, fitting it back from where it came, clamp off very well until epoxy cures. Grind the seams to a 12 times grind, and use vinylester to glass the seams back. Does not help with rotten stringers but you can remove the wood from the bracing stringers to transom if rotten while the back is open. I prep, fit, and butter Coosa panels and epoxy them in before adding transom replacement core pieces. I am able to replace transoms with Coosa in 1/4 the time of going in from the front. It goes without saying the skin flake and gel must be repaired when going in from the back. I have that down to the point it only takes me a few hours to fix now.
I always epoxy in replacement stringers, buttering the channel in without trapping air, just being careful not to create a hard line where the skin can crack later. I bed the bottom of the stringer with a flexible epoxy bedding compound against the skin first to prevent a hard line from being created. The bedding epoxy can be a pain to find. Right now I'm looking for another supplier myself.
-
When you epoxy in (butter) the new stringers, do you put something like foam insulation? Cut from a sheet. Or is the "butter" good enough, too keep from getting a hard line?
-
A hard line is where something solid inside the skin is laminated against the outer hull in such a way that it provides a stress point next to it in the outer hull. Hulls flex when running, my understanding is over time just the flexing of the outer hull against the hard spot will weaken the skin. Most manufacturers float the stringers over the skin so an object striking the hull will not crack the skin against the hard line. I have used pieces of H-80 scored Divicell to float stringers in the past. If you look closely at how your existing stringers were glassed in only the fabric should be attached to the skin. Sometimes plywood type stringers will have a bevel on the bottom so solid full contact is avoided. Using 1/2in - 5/8in Coosa 26, with a single layer 1708, epoxied in is fairly flexible if floating the stringer 1/4in off hull skin. You want your restoration of the stringers to give the hull "Spine" not support a specific spot on the hull skin. It's hard for me to describe, turn your hand out flat palm up, under the stress of running across the water being pushed from the rear the hull wants to curl up like curling up the fingers on your hand. "Spine" in a boat hull refers to the resistance to curling up. Transverse reinforcement is to keep the hull in shape across the width of the boat. The new waffle type laminated stringer systems that are glued in are usually foam filled, no core other than the rigidity of the foam. I hope this is understandable, I'm a Marine Engineer not a lecturer.
-
Don't fill the void under the stringer with thickened epoxy then push the stringer down into it. That is only done in the voids replacing a transom.
I usually smear a little thickened epoxy into the pores of the Coosa material and wet the sides of the glass where I cut the old stringer out just to make sure I'm gluing the two pieces together.
-
Reply With Quote