Seeking Advice - 1978 Larvo Drift Boat Build

[ondarvr]

Where did you buy the gel coat?

 

[Pac12AfrerDark]

What was your plan after this coat, was this the final coat, or were you putting another one over it.

You need a 50/50 mix with the Duratec clear for it to cure tack free, less than that can leave the surface tacky.

Also, did you use the epoxy primer?

Plus polyesters don't bond that well to epoxies, so you have a few things working against you.

My plan was an additional coat (if I'm being honest I should go back to fairing steps - its Bumpy), I still have some lighter spots showing through.

(I'll come back to the duratec suggestion)

I did use epoxy primer. I was reassured (twice) from the maker of the primer that leaving a week to dry prior to shooting gel coat would eliminate any amine interaction issues.

Now, it's been about a decade since I took organic chemistry, but a week for it to surface and a 2x wash + solvent wipe seemed reasonable to mitigate that.

I purchased the gel coat from sea hawk. I think they are just a reseller, not a producer - tough to attest to their qc. Who knows- I am sure its user error.

The gel sets up rock hard in the cup, with a tacky surface on the air facing side.

So, here is what I did- because it was driving me insane.

Wiped down a small panel of the boat with acetone, wet sanded, cut and buffed, then waxed. Turned out ok, but still a bit tacky.

My current plan of attack is this:

1) order new gel and duratec clear
2) "finish" the rest of the boat by the same method described above
3) Get it on the trailer and get my wife her spot back in the garage for mother's day (did the bunks today)
4) get to work on the top side while the duratec and gel ships. Bigger issues up there.
5) re shoot the outside of the boat.

I'm all ears!

Thanks,

-Josh

 

[ondarvr]

You didn't say whether you sanded the epoxy or not.

The gel coat left in the container will cure differently due to the difference in mass.

Adding pigments to gel coat can inhibit the cure. And Sea Hawk gel coat is a rebranded product from someone else.

Its better to stick with one type of chemistry, and/or system from one supplier than to mix and match with little experience to guide you.

 

[Pac12AfrerDark]

I did sand the primer prior to the wash and set.

What you are saying makes sense - I think that my specific issue is a culmination of little things all tracing back to my lack of experience with fiber glass and gel coat.

The pigment, the mixed systems and lastly the spray. I noticed on the other side of the hull the gel is "striped" in some areas it's set up perfectly and and in the shiney areas it is still tacky.

Do you agree?

I realized I never drilled the new nose out to 2mm prior to shooting, so I probably applied it very thin.


I am going to give the duratec clear a shot, can you confirm this is the right product?
Duratec® Clear Hi-Gloss Gel Coat Additive https://www.fibreglast.com/product/Duratec_Clear_Hi_Gloss_Gel_Coat_Additive_1040/Gel_Coats

Either way, fun to learn all this - that's for sure.

Thanks agin,

-Josh

 

[Pac12AfrerDark]

I wet sanded, cut and buffed one of those dry spots on the otherside... all other things equal, I think it was my spray that was the problem.

 

[ondarvr]

The cheap Harbor Freight spray guns used to be great, now they're far less handy.

The old version could be drilled to 2.5mm and was a low cost workhorse.

The newer version doesn't work well once you take the nozzle out, its sealed in place and very difficult to reseal.

I havent checked you tube for any videos on a fix yet.

You definitely need a larger tip than the 1.4 it comes with.

 

[Pac12AfrerDark]

Thank you - I drilled out a spare nozzle.

I am going to just practice on the underside of a seat with gun setup to make sure things are perfect before trying again.

Oh well, boat is on the trailer - going to do the top side glass work while I'm waiting on the gel & duratec.

Encouraged thst I'll probably get it right next time.

Thanks again

 

[Pac12AfrerDark]

This project slowed a little with the re opening of fishing. Slowly making interior progress.

Got the shape, burned to chamfered the side. Unfortunately the 'wing's curves in two axis, slightly out matching my wood working abilities.

 

[Pac12AfrerDark]

My buddy lent me a belt sander. Made shaping that part so much easier. I have the geometry on the one side, I think I'm going to glass this side in so I can use any learnings for the other side.

Fishing season is in full swing, so progress has slowed to a trickle.

 

[Pac12AfrerDark]

Back to work. Got the fins shaped in. Trying some gun techniques on the seat before shooting the interior.


I dried out the HF nozzle, also purchased a few 2.5mm guns to try too. Shot this side with the drilled out HF, tried sealing half with PVA since I could only get a film thickness of about 16mil.

Oh well, i will keep trying new things. Most the threads that have "gel coat problems" never post an answer- so I'm flying blind.

-Josh

 

[Pac12AfrerDark]

Just in case someone stumbles upon this thread:

Harbor freight LVLP drilled to 2.3mm duratec at 10% - 16 mil thickness: set up great, better than most anything else I shot. Was a little waxy on top. But fully cured.

On the other half I added PVA after shooting. I rinsed the pva off and it is rock hard, no waxyness.


Because I couldn't help myself, I shot the other side with a 2.5mm top feed ebay gun, did 2 8 mil layers with 15 minutes to flash off inbetween. Sprayed with PVA after the second coat. Will update how that turned out.

Very happy I solved my cure issue. However, I bought WAY too little gel coat.

 

[ondarvr]

10% Duratec won’t do much to help with the surface cure, you need closer to 50/50. That can just be in the final pass if desired.

 

[Pac12AfrerDark]

10% Duratec won’t do much to help with the surface cure, you need closer to 50/50. That can just be in the final pass if desired.

I was wondering about that after rereading your replies earlier in the thread.

If that is the case, and I can assume the 10% I added was a moot point, then my previous problems were either 1) bad gel 2) epoxy primer related or 3) nozzle size (application related).

I dont think the epoxy primer did me any favors- but my money is on the nozzle.

Thanks again - I am waiting on polyester resin to glass the fins, then I'll post some more progress.

 

[Pac12AfrerDark]

Made some very nice progress this weekend. Got the wings almost fully glassed in.

It was definitely easier to run a layer on the top, and wrap the "whisps" around the edge to interlock with each other. Feels nice, can pick up the boat by either wing. Should be solid enough to hold the rowing seat.

I tried rolling all the air pockets out, but it looks like there are still a few. I was thinking about drilling a hole in them and injecting with resin.

Who knows, anyway- getting closer.

 

[Pac12AfrerDark]

Got the wings in, turning my focus 5o the back delaminated deck.

Looks like it went, glass, wood, glass. I'm wondering if I should lay some csm, then a layer of wood, then csm?

Or just resin, wood, csm?

Or.. epoxy, wood, then csm

I assume the wood was included in the design originally for a purpose.