Fibreglass Finishing Questions

[Glenn Tranchon]

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

I know you read alot that gelcoat wont adhere to epoxy but its just not true. I spray gelcoat over epoxy on almost a daily basis and its bulletproof once it cures up. You really just have to prep the surface right, clean good with acetone and youll be fine. Fairing fillers mixed with bare epoxy is your best bet. West system 410 fairing filler with a slow hardner is the way to go for a area that size

 

[mike marchetti]

*Update - put on skim layer with lam. resin and q-cel, but was really really hard to get it on the spreader then onto vertical surface, what a mess! i could see i wasnt going to be able to skim it nice and flat with the spreader so i just skimmed filled over the highest spots i could find, got about 60 % of transom, b4 both pots got hot. will sand with 80 and skim over any needed areas again tomorrow.

 

[mike marchetti]

thanks glen,will try that once i see how everything looks after sanding tomorrow.

 

[kapnD]

To be sure that your fairing putty is compatible, use your same gelcoat thickened to a trowelable consistency.
For large areas, I use a wide drywall trowel to minimize ridges and sanding.

 

[mike marchetti]

i didnt use any putty, instead i used laminating resin thickened with either aerosil or q-cel into a thick paste and spread it on with Spackle spreader took a few times to get the build up needed, but it looks all nice and level now that ive sanded the whole area back down. So now im trying to decide if i should buy a gel coat sprayer and spray the transom instead of rolling it.
i also have to redo 3 out of 4 sides on my center console, (Alot of spider cracks and holes with spider cracks from previous owner drilling a 100 holes into the dash) so figured would be faster and better looking to spray that too rather than roll, im about to buy the $140 spray gun off ebay that has the big 4.7mm nozzl... any thoughts on cheaper alternative ?
Gel Coat Spray/Dump Gun ES-100 E&S | eBay https://www.ebay.com/itm/Gel-Coat-Spray-Dump-Gun-ES-100-E-S/131780070311?hash=item1eaeb44ba7%3Ag%3AEREAAOSwJo1bVjFD&_sacat=0&_nkw=gel+coat+gun+&_from=R40&rt=nc&LH_TitleDesc=0
seems a worthwhile investment ? will be posting more pics soon.

 

[Glenn Tranchon]

Just buy the cheap full size primer gun from harbor freight (1.8 mm tip). Youll have 8-10 mins of working time to spray and clean the gun with acetone. Save alotta money and itll spray fine just thin with duratec high gloss additive or styrene. I spray gelcoat thru a 1.0 mm detail spray gun alot and it works fine. Save the money and just clean the gun within ten min of gelcoat bein cataliyzed

 

[mike marchetti]

I was going to do that but thought the bigger tip size would be better. but there is a big price difference. does thinning it 10% affect the thickness or effect the gelcoat ?

 

[Blueknarr]

Mike
The transom looks much better.
What are you using to sand with?
I don't see the need for you to buy a gel gun at this time. I think the stipple from a low knap roller will be equal to the orange peel of an inexperienced sprayer.

 

[Blueknarr]

I was going to do that but thought the bigger tip size would be better. but there is a big price difference. does thinning it 10% affect the thickness or effect the gelcoat ?

It makes a big difference.
I typically roll 2 - 4 coats on top of one another as soon as firm enough to not be moved around by next coat. Then I block sand fair with 80 and 120 crossing. One final coat wet sanding with 600 and 800.
Spraying small areas with a small tip is ok. But trying to cover large patches is difficult. If my repair zone is simple, I roll. If complex compound curved surfaces then I'll spray. There is little difference in final finish effort.

 

[mike marchetti]

thanks for the info blue knarr,
i was just going to roll the transom as i was doing before, i dont mind the stipple, as its not too bad with 1/4" nap roller, and easy enough to do light sand on top, but i have a ton of spider cracks and holes all over 3 sides of the center console, which will require lots of grinding, refilling areas with c.s.m. finishing etc. so with that much area and all the corners and angles on the center console, i feel like it would come out alot better with alot less sanding if i sprayed it.
and for sanding the transom, ive mostly been using a square palm sander with 80 and 120 grit paper, i just use long sweeps with light pressure, and make sure i change sanding direction all the time to prevent low spots. its come out very even sp far or i would have made a long block. i get the spray equipment this coming monday, so will do a small practice shoot on some outriggers i need to re-surface and see how it does and try to dial in adjustments before using on boat. the spider crack issue is going to be more challenging than i originally thought because the console layup on the sides is very thin and flexible, not much material there to begin with, i wouldnt be surprised if alot were all the way thru. if you guys have any ideas on how to build up these areas please let me know, i was just going to grind down past the cracks as ususal and then rebuild with c.s.m. gonna be labor intensive but dont know of any other proper way to do it. i also have my dash hole nice and sanded ready to glass my new insert in, but wanted to run all of my new wire harness and control cables thru from the stern while i have the big opening (way easier than crawling into console) i was going to peanut butter the sides then add 2 layers of 1708 to entire top of console to tie the insert into the surrounding area.
will post pics as i can. thanks everyone for your help. its very much appreciated.

 

[Blueknarr]

Mike,

I was concerned that some of the wavyness seen in your first set of pics may have been sanding induced. Some people try to speed the sanding process by tipping the sander and focusing it on a problem spot.
This aggravates and doesn't alleviate the problem. A flat surface is made by keeping the pad flat at all times. I prefer even passes in cross direction.

The spider cracks on console are almost certainly thru and thru. If the increase in weight is acceptable, try adding a layer to the interior before attempting gelcoat repair.

I could not see them in the second set of pics. I don't understand what insert your are referring to.

 

[mike marchetti]

hi blueknarr
didnt post pic of insert yet, but its the piece im going to insert into the hole i cut in the dash. i used a 1/2" piece of oak plywood, has 3 layers of c.s.m. on bottom and 6 layers of 1708 on top all glued up with west epoxy, then added 2 coats to edges of plywood to completely seal it. drilled out my hole to re-mount steering wheel, then re-coated hole twice with epoxy to seal where i drilled. i was expecting my spray equipment to been here already, but just got of the phone with harbor freight, 10 days later and they never shipped my stuff. ridiculous then tried to charge me full price again 10 days late... i made them give me free 2 day fed ex ship or i would have canceled and bought elsewhere. so now have to wait another week to get equipment to spray the gelcoat. always something.... lol
i might just sand the tabs off of the sides of insert so i can peanut butter in between the insert and dash cut out to strengthen, do you think thats necessary or over kill ? will tabs and top coat entire dash and cutout with 2 layers of 1708 and one layer of 6 oz to tie insert to dash be strong enough ?

 

[Blueknarr]

i used a 1/2" piece of oak plywood, has 3 layers of c.s.m. on bottom and 6 layers of 1708 on top

Certainly will be very stout

I wouldn't want to brush-n-roll that console

 

[mike marchetti]

anyone have any thoughts on doing the peanut butter between dash and insert or would it just be over kill, my main concern is that it will be supporting the steering wheel, and was concerned about the insert pushing thru the dash if someone was leaning hard on the wheel in some good chop. do you think the thickness of my tabs will be Strong enough ? and what do you guys suggest for top coat to tie into dash, i was thinking 2 layers of 1708 then one 6 oz cloth for smoother finish ? thanks everyone. going to try and run my new wire harness thru tubes today up to dash, so i can start glassing the insert in. also still digging the foam out from around filler neck in gunnel, its completely foam filled in there, i can see there is separation between the filler neck and the barbed part where hose attaches. so going to dig it all out and remove filler neck, vent tube, and piece of disintegrated fill hose then hopefully dig enough foam out to see where the interconnect hose attaches to hard metal pipe that runs thru gunnel and floor and into coffin box where gas tank is. ahhh the fun never stops...

 

[mike marchetti]

some early pics of when i first got the boat, will try and find some of the transom repair pics in case someone is interested.