Re: Gelcoating fiberglass... but not a boat...
There is 2 ways to do it bud.
First off ....and the hardest is a one off method.....In your pm you mentioned mass production....if so.,...this is not the way to go
Basicly, scuff the drums....and shoot gellcoat over it.
The thickness if the gellcoat is 35 thou.....that is more than what the wikipeida mentioned....lol....way more.
its more like 3 mim.
After you spray it you will need to sand it.....gellcoat does not come out of the gun smooth like paint.....it has heavy orange peel.
The auto body painters go crazy because, they think orange peel is caused by improper gun settings.....with gelloat it is caused by the thickness of the material.
To scuff the kit.....just use 100 grit sand paper.....then wash the kit with acetone.
To spray....use a standard pressure pot set up and a gun with the biggest tip you can find. even a harbour freight gun will do.
Use waxed resin....and add Mekp at 2%....if you use the metric system....it is super simple... if you use 100 mil of gellcoat...(one can of beer is 355 ml) you add 2 ml of mekp.
When you spray....keep the gun moving and lay an even coat you will need to make 3 passes to get the gellcoat to the thickness you need.....if you have to sand it....shoot at 55 thou thick....then when you fair it it will take it down to the 35 thou..
If the gellcoat is too thick or too thin....it will crack.
Start the sanding process at 320 grit.....sand the drum till most of the orange peel is gone......then 400.....by 600...all of the orange is gone....
When the orange is gone.....you are basicly polishing it. Keep sanding till you are all the way up to 1500 grit......then take the buffer to it with a gellcoat polishing compound like farecla or 3m compound.
The other method....is one that is more prep....but you can mass produce the drums fast......Did I say fast?....I meant very very fast.
This method will deal with making a mold.
Ok...lets build the mold.
Take mould release wax.....and shine that drum kit till it gleams......about 6 or seven coats.
Using tooling resin...and mekp at 2 % glass the outside of the drums with the thinnest finishing veil fiberglass cloth you can get.....
This is a woven roving and looks like silk....make sure it has a really tight weave...
Then after that layer is on.....no air bubbles....wrap it with 2 sucessive layers of 1.5 csm......then a layer of 1708 bi axe....another csm...and a final layer of the 1708.
Let that tack off.....now.....take a thin flexable material.....anything will work....foam ....wood....metal....and make 3 reinforcing circles....around the drum....kinda like circular stringers....one in the middle...and one at each end of the drum....then.....glass them on to the drum....using the csm.....at least 3 layers.
This is for mold stiffness.
Roll the air out.....and let it cure....
This exact same process is used in boat building......its called pullling a skin.
After it is cured......you will need to remove the drum from the mold....this could be tricky....but after a few whacks with a rubber mallet, the drum should slide out of the tube.
If it does not.....cut the new tube on opposite sides...then you can pull the skin off easily.....you will have 2 "c" shaped fiberglass parts.
If you have jagged edges of the glass on the mold.....you can either leave then jagged or cut it off with a router. (anything will work....even a table saw....just roll the drum over the saw blade.
Ok....we have our mold !
Now....we have to prep the mold.......
The inside of the mold is the outside surface of the drum...so it needs to be really smooth.
Take that release wax again......and shine the inside of the tube till it gleams.....use about 12 coats.....
If you had to cut the mold in half to get ti off the drum....duct tape the two halves together...or you can get fancy with metal bands.
Lets make some drums !
Using the same tools mentioned above the pressure pot and gun...
shoot UNWAXED gellcoat into the tube. (mekp at 2%)
let that almost cure....let it start to get hard...and add 2 layers of 1.5 csm
then....one 1708.....another csm....and another 1708...one csm.....
Now add 4% wax to the remaining resin.....and then add the finishing veil....this can all be done at the same time.
(you have to watch when you are glassing that you don't glass too much all at once...the resin gets too hot and will cook....getting very brittle)
Let fully cure.......i would actually keep the curing glass hot by using quartz lights. keep the glass at about 150 deg f (190 is best for 6 hours)
Now pull your drum form the mold....
As before...if there is a jagged edge on the drum....just use a saw or router to cut the jagged edge off....and light sand the edge.
To drill into the gellcoat to add the hardware.....place green tape over the hole location....and run the drill bit backwards till you get thru the gellcoat.......then switch to forward to go thru the fiberglass.
Add your skins.......tune the drum.....and your done !
When doing the gellcoat......you can use several different methods or products...like metal flake or multi color gellcoat.
each of these processes are somewhat involved....but after you do some single color sets...you will get the hang of it enough to try different gellcoating colors and methods.
BTW....if you get rich at this..... I expect a kickback....lol
Cheers
oops
