fixing transom to top seam on old witchcraft

[FMP]

When my transom core material was shot wet soft the layers didn't do anything but flex and crack the more the core degraded so I'd say the core does do more than nothing and mostly everything. Quite the difference when replaced with 1 3/4 " Marine ply properly bonded and layer finished to sides strings and bottom.

[colinJ]

So I did bond the transom sections together with epoxy and let me say that coosa holds onto resin really well . I followed the 2 stage laminating process recommended by west systems using the local suppliers epoxy (pro glass). I calculated the amount that would be used ahead of time, I came up with 8 ounces for a 10 thou bond line. I mixed up about 12oz for each bond. It took 6 ounces to wet out both sides to be bonded to a nice shine then mixed in fumed silica as a thickener to mayonnaise with the remaining epoxy and layed that on with a flexible plastic putty knife to have an even glaze. Pieced together then weighted with 400 pounds evenly applied I had a small but even amount of seepage.

If I could do this again I would have used vinyester but following the same process. Even with just a tiny bit of seepage it was allot of work to sand off. The bond here does not need to be extremely strong. I mean there is about 1200 square inches of area moreover there will be 1/2 stainless bolts for the outboard rigging as well as trailer eyes that would have to fail in order for these parts to slide. Even a weak bond would be far stronger than the underlying material.

[colinJ]

Hey XStream Whats the best technique to use when laminating 1708 with vinylester over large flat surfaces?

Most references seem to indicate that about 1 quart of resin per square yard of 1708 is the correct ratio. What I am finding is I have to use like 50% more to get it nicely wet out otherwise I get some entrained air.


What I am currently doing:

1. Wet out core material as much as possible with neat resin.
2. Lay down 1708 mat down and smooth it out using gloved hands.
No break in time (should I wait a bit on this first step)?
3. lay resin down with a large plastic squeegee, again going for about 1 quart per square yard not counting the initial wet out.
it takes allot of work to get the glass saturated.
4. grooved roller across the entire thing.
5. Repeat the process with another layer (no real waiting in between, the first layer is still pretty wet).

In layer 2 after I get it all rolled out it looks fine however when I return to it It seems like the vinyester has outgassed some and I see air bubbles under the layup.

I am using 1.5% catalyst, temperature is about 75 degrees. I am done with the pot long before it gels. So far I have only done the bottom of the deck. I am trying to improve my process before I move on to the top and transom.

I did a small section where I mixed about 1.5 quarts per yard and that looked much better, however it was also a single layer.

[colinJ]

Here is a picture to show what I am talking about. I also think that the dark color of the coosa material highlights this far more than with wood.

[XstreamVking]

Wet out real good under the glass, wet out the glass real good. (under and over) I like to use a 3/8'' nap 3'' paint roller. Ignore the amount of resin per material ratio.(60-40) Wet out on top of the glass after application if you need to with the paint roller. Better to be resin rich than to have "dry" spots like you have shown in your pic. You can pre coat your core material and let that set up before you glass over to stop the resin from wicking into the core material. This part of glassing has to be done by"eye" and will take some experience to get exact every time. You are doing fine and will soon be getting it perfect. You may also be able to up the hardener ratio if the material is sitting for more than an hour before setting up. Ideally, you want to finish up with the application and have it harden within an hour. The longer it sits un hardened the more resin wicks into the under lying material.

[colinJ]

I have in the past pre wet the fabric only for vertical applications. I am having it harden within an hour the vinlyester I am using has a mix range between 1 and 2%.

I think your suggestion about letting the pre wet out dry first may be the key here, but I will give your full method a try.

Thanks,

Wet out real good under the glass, wet out the glass real good. (under and over) I like to use a 3/8'' nap 3'' paint roller. Ignore the amount of resin per material ratio.(60-40) Wet out on top of the glass after application if you need to with the paint roller. Better to be resin rich than to have "dry" spots like you have shown in your pic. You can pre coat your core material and let that set up before you glass over to stop the resin from wicking into the core material. This part of glassing has to be done by"eye" and will take some experience to get exact every time. You are doing fine and will soon be getting it perfect. You may also be able to up the hardener ratio if the material is sitting for more than an hour before setting up. Ideally, you want to finish up with the application and have it harden within an hour. The longer it sits un hardened the more resin wicks into the under lying material.

[XstreamVking]

When the glass is laying pre cut on a horizontal surface, roll some back and wet out and un-roll as you go. Wetting under/over and rolling the glass out then rolling some resin on top. Finishing as you go. This can be done with 2 layers of glass at the same time with practice.

[colinJ]

This method works and will be the method I use from here on.

One thing though this coosa really sucks up the resin. I pre wet an area, let it dry came back to it and half the surface area was dry. In order to get an evenly wet dried area it seems I will need to pre wet it twice.

In the past with wood that I was trying to really seal with polyester (house project not a boat) I have done up to 3 wet coats before any fiberglass went on.

[XstreamVking]

I can smell the vinylesther and coosa cooking from here....Haha They do put out a unique smell when laminated together.

[colinJ]

Hey Xstream,

Purely for aesthetic purposes I would like to tint the inside layer of 1708 on the transom and deck with black resin pigment. I have found that 1.5-2% by volume is sufficient for a nice color.

This is the pigment I am using: https://www.fiberlay.com/upload/tech...MENT%20TDS.pdf

I know that pigments can affect strength but is this anything to worry about at such low levels?

[colinJ]

Ok so I am ready to glue in the transom. What’s the protocol for this?

I was thinking basically a layer of csm on each side and while it’s still tacky put on peanut butter with a notched trowel and get it situated and clamped so it squeezes out around the rim and form the squeeze into a fillet.

Also for the peanut butter should that be basically 1/3 each Cabosil, chopped glass and resin?

I have been finding that it takes an enormous amount of cabosil to make this stuff stick without slumping.

[XstreamVking]

Tint is fine...Sounds like your on the right track with the trans. Just follow the wet out, glass, wet some more. The putty mix thing is fine, or you can just use a couple of lays of 1.5 oz mat with a good load of resin. Either way is good.

[colinJ]

I got it in today, went decent. I did the 2x wet out with 3 ounce CSM on one side and really wetted in and on the other side I had thickened VE applied with a v notched trowel. I got nervous that it might have been starting to kick (not hot but the thickened epoxy applied with the vnotch felt firmer than expected) and I got them together as quickly as possible. Not as much squeeze out around the seam as I was hoping for yet I am still confident that the bond line is 90% resin. Also the external skin took exactly the same set that it had with the old wood transom (less than 1/4 inch or so inset along the center bottom) I thought I might be able to get the external skin flat but the lumber I used to spread the load conformed to the slight curve.

Now I did kind of bugger the fillet a bit. First it took like 2 liters of peanut butter to fully fill the area all the way around the transom which I did in about 3 different batches. I mixed in allot of 1/4inch milled glass (like 10 pounds) and the thickener I used was fumed silica). Once I had it flush I set about making the fillet but I got cocky and tried to do it in one batch. The result is that the fillet is pretty good across the center where I spent most of the time its ok on one side but ridiculously thick on the other (perhaps 3/4-1" thick at the thickest portion).

Take a look at the attached pictures.

I set-about sanding this smooth but this stuff does not sand well. It rips apart the sanding disks/belts (yes I tried a belt sander) I suspect its because it has so much glass in it.

Is this to thick, or would I be ok tabbing over this?
Starboard (kind of buggered the fillet on this side):


Center (pretty even 3/4" radius fillet)

[XstreamVking]

Just glass over it and keep going. Little extra weight, but no big deal.

[colinJ]

Hey so any advice on doing the tabbing? I have done some tabbing before and I had a hell of a time with bubbles trying to get the stuff to curve and also air trapped under an overlap. I was planning to tab from big to small to avoid the overlap and when I say big to small I really mean big to slightly smaller. For example 12", 11.5", 11" just a small change in size.

The other thing is the complex curves. Is it OK if I make a separate tab for each curved section to avoid the wrinkles and then just butt the tabs up together?

Finally, I am a little paranoid that I may not have gotten the best adhesion between the transom and old skin (ok if feels totally solid but there was very little squeeze out). So I am thinking I can double up the tabbing just in case (also knees etc). Would 6 layers of tabbing be overkill enough? I even considered drill a few small holes to inject resin just incase.