Sanding Gelcoat

[Sugarloafer]

Hi All,

I'm completely rebuilding my 1983 Hewes Bonefisher II.

Right now, I have it upside down on the trailer, and I've re-gelcoated the whole hull.

I'm at the point where I'll be spending the next 5 years sanding the orange peel to get it to a smooth finish.

Pretty good luck so far, as I've tested an area several square feet, moving from 220, 320, 400, 600, and 1000 grits, followed by compounding, polish, etc.

My question is: does anyone know why my gelcoat looks mottled (several shades of the blue I used)?

Prior to sanding, the gelcoat was completely uniform in color, and the multicolored effect (like blue camo) only appears after sanding.

Does anyone know what I'm doing wrong?

Thanks.

 

[ondarvr]

Re: Sanding Gelcoat

There can be a few reasons, but its not too common.

If there were several layers of gel coat applied, the mix may not have been the same each one. If more wax solution, patchaid, thinner of some type, or even catalyst at times is added, then the color can be slightly different from layer to layer, or from one mixed batch to the next.

Another reason can be from pigment seperation, different color pigments will weigh a different amount, this can create some separation at times, espesially if the gel coat is thinned with something like acetone.

It can also occur if the gel coat is sprayed at angle, this can blow the gel coat across the surface which can separate the pigment also.

 

[Sugarloafer]

Re: Sanding Gelcoat

There can be a few reasons, but its not too common.

If there were several layers of gel coat applied, the mix may not have been the same each one. If more wax solution, patchaid, thinner of some type, or even catalyst at times is added, then the color can be slightly different from layer to layer, or from one mixed batch to the next.

Another reason can be from pigment seperation, different color pigments will weigh a different amount, this can create some separation at times, espesially if the gel coat is thinned with something like acetone.

It can also occur if the gel coat is sprayed at angle, this can blow the gel coat across the surface which can separate the pigment also.

Thanks for your expertise!

Even though you say none of them are common, I'm probably guilty of all of them. This is my first time shooting gelcoat, and I did it in a series of 4x10mil sprays, and probably didn't use the exact amount of styrene, catalyst, etc. for each batch (all shoots did come from one 6gallon container of gelcoat, but even this I mixed myself using my own color formula). Also, since this was my first time shooting, I probably did spray at an angle more than once.

Do you think I should try to respray while avoiding these mistakes and see how it comes out, or just go with the water camo look?

Thanks!

 

[ondarvr]

Re: Sanding Gelcoat

I just recently inspected a re-gel coat job on a 30' sailboat, it was done by a very experienced fiberglass guy and it had the exact same problem, it was even blue, so I know what yours looks like.

If you started with a white tint base its possible that it was over pigmented by the time you added enough blue to get the color right. This can lead to pigment separation also.


If you respray it with the same mix (color) it may happen again, plus you will most likely sand through this new layer just like before, exposing the off color product under it.

Its up to you on what to do, I'm not sure what the best answer is.

 

[Sugarloafer]

Re: Sanding Gelcoat

I just recently inspected a re-gel coat job on a 30' sailboat, it was done by very experience fiberglass guy and it had the exact same problem, it was even blue, so I know what yours looks like.

If you started with a white tint base its possible that it was over pigmented by the time you added enough blue to get the color right. This can lead to pigment separation also.


If you respray it with the same mix (color) it may happen again, plus you will most likely sand through this new layer just like before, exposing the off color product under it.

Its up to you on what to do, I'm not sure what the best answer is.

I started with a neutral base, and didn't go over the recommended pigment guidelines that I've read.

I suppose I'll respray and sand, and I'll make do with whatever pigment(s) emerge. It doesn't necessarily look "bad," just after all that work I was hoping for something more uniform.

Thanks for all your help...at least I'm having the same problems that even experts have sometimes.

 

[marcortez]

Re: Sanding Gelcoat

I like it!!!!

A "camo" effect for the denizens of the deep.....

No doubt you will be getting mulitple hookups with your new "stealth" bottom.

Azure blue seas mottled with pearly white sand.....perfecto!!!!!

And the "ewwwws" and "ahhhhs" from the launch ramp crowd...asking you where you found that color combo!!!!