Fibreglass Finishing Questions

hi, i recently replaced the transom on my 1987 Mako 224 i cored out the old wood material with a arbor bit and refilled core with trk2000, built up inner and outer transom with 4 layers of 1708 with poly laminating resin, and thought i had everything smoothed out pretty well, but after applying the 2nd and 3rd gelcoat layer, i can see that alot of the weave is showing thru in areas, And im unsure as to best solution. Do i sand off the gelcoat and add a surface layer of resin to fill in the weave more ? add another layer of 6 oz. cloth, then gelcoat ?
or is it ok to simply keep adding more layers of gelcoat until the weave is filled in. i know gelcoat shouldnt be that thick, but what is considered acceptable ? I'm pretty sure i should not add a resin layer over the gelcoat to fill, then gelcoat over that again ? any help is greatly appreciated.

 

Hi Mike, for canoes & kayaks the glass & layers are fine. Larger fishing & runabouts have a rougher weave. It's Ok to add a few layers of gel coat until all the fiber weaves are filled. May take 2+ coats to achieve that depending on the thickness of your weave.

 

Welcome

Pictures are worth thousands of words.

How thick was the gelcoat applied?
How was it applied?
How much texture remains?
How deep are the valleys, pits?
What color?

Hard to give good advice with incomplete information.

 

Use a high build polyester sanding primer to get the surface smooth again, this will be much easier to work with than gel coat or resin, and don't use straight resin, it won't work well.

The other option to make an easier sanding filler with the resin you have, micro-spheres and Cabosil will make something you can work with.

 

While it may take creativity for some craft that aren't made of developed surfaces there's a trick using, IIRC, Mylar and a real good squeegee or roller to compress down the fibers that may help reduce that.

 

Yes that's a good trick. Generally it takes a few coats though on a flat surface. Below is a good video (pardon the elevator music).

 

Many years ago I stepped onto an elevator completely unprepared for what I was about to experience: a full choral in harmony version of AC/DC's Hell's Bells with tinny silver bells.

I'm not a fan but it was just wrong on so many levels. A friend who was fan just shook his head in disgust.

So it could be worse I suppose.

This has been an Official Rurudyne Totaly Random Digression (tm).

 

thanks for reply's, i have been applying gelcoat with a short nap 4" roller and layers are going on fairly thin, rolling it out so no lines, its leaving a slight stipple, but i know thats un-avoidable. id have to say depest part of weave may be 1/16 to 1/8" max i already have rolled on 4 layers of gelcoat, sanding between layers to knock down any high spots and have been having issues where after just a min. the nap starts pulling off roller and gets stuck into work, where i have to pick it out and try to re-roll over it without making a mess of area, coats 3-4 filled in weave quite a bit,so as long as its ok, will keep adding more coats, will prob. stop after next 2 coats and call it a day. i did spread some epoxy/aerosil mix that i had extra from another project into the thickest weave parts as filler, will sand and give it 2 more coats of gelcoat today if weather holds. thanks for all your advise. will try to post pics tomorrow a.m. then on to next project, rebuilding dash....
cut out slant area, now have to get backing board and seal it up with glass, the fun never stops...

 

darkened some of the pics to show more contrast, let me know what u guys think - thanks

 

Me thinks you forgot the fairing step of the process.

Forgive me for not scrolling back to the start. Did you say if you ate using waxed or straight up gelcoat?

How close to flawless perfection are you striving for?

 

Hopefully you used gel coat with no wax in it.

Don't use a roller, use a squeegee (yellow plastic Bondo spreader type thing), apply some gel coat to the surface any way you can, it will be a little difficult on a vertical surface. Use the squeegee and spread the gel coat onto the surface, this fills the low spots and doesn't add anything to the high spots, a roller adds more material to all surfaces. You can put it on with the roller then squeegee it.

You may need to do this a couple of times.

Thickening the gel coat slightly helps, you can get even better results by using micro balloons in the mix along with cabosil, easier to apply, easier to spread and easier to sand.

That will get rid of the glass pattern, but you may still have a somewhat wavy surface, to eliminate the waves and irregularities you need to use higher build fillers and a long board. This would be done before doing the prior mentioned work.

The good thing is you are the only one that needs to be satisfied with the results, so you can stop at any stage and call it good enough, then bolt the motor back on.

 

You have to fair the area with a fairing compound. Best bet for a area that size is a epoxy fairing compound. Gives you way more working time then a polyester compound and holds up better. Youll never fill that weave in with gelcoat. Also you should spray the gelcoat, rolling it with a roller will not produce good results.

 

Polyester fairing will produce acceptable results. It will be difficult for the gelcoat finish to adhere to epoxy.

 

thanks for all the replies. I'm not going for perfect, just reasonable good looks. when i was doing initial sanding, the weave didn't look like it was going to take much to fill it, but turns out had alot of sanding dust apparently, and once i got 2 gelcoats on, and yes its laminating gelcoat, no wax, i could easily see the weave pattern was too deep in spots for my taste. i think i will give it a 80 grit sand then use the poly Lam. resin with q-cel and put it on with a spreader, i was considering this initially with gelcoat but wasn't sure if it would make gelcoat too thick. but will do skim coat today after sanding. thanks everyone.