Epoxy coating bulbs

Can someone tell me how to coat a bulb and have it come out smooth? I tried pouring epoxy over the bulb and heating it with a hair drier but I get ridges and lumps(and it wastes a lot of epoxy). If I put it on with a brush I still get the ridges. When I try to sand the ridges I usually sand through the thin areas before it gets smooth. Does anyone have a slick method they are willing to share?

Don - Thicken epoxy to mayonaise consistency - thick, but still a bit creamy/runny. Coat bulb and stretch a balloon over it. Will still have a few creases, but works (sort of) like the German Rubber method for latex on hulls. Work out excess via the opening in the balloon. From my experience, this is a 50% proposition - sometimes it works excellent - other times it looks like a dog-turd filled with kibble! Still haven’t figured out what I do differently to have a good (or bad) finish. Still requires some sanding before painting.

Hi Don

If you have the ridges and lumps on the surface after the resin is cured, and wetsanding is the only way out, it often helps to apply a layer of tracer paint (Thin layer of spray paint). It makes it easier to spot when you have to stop sanding, but still it is allot of work.


Thanks guys
Working off Dicks idea, I’m thinking I might try wrapping it with surveyers tape. It would flex enough to follow the shape and (hopefully) leave minimal sanding. I hate sanding. I’m just not sure how to hang on to the thing while I’m wrapping the tape. Five pounds of slippery lead with a pointy end, hmmmm. How did you deal with the fin slot Dick. I thought of filling it with wax but that would compromise the final glue joint. Maybe balsa.
I’ve seen a bulb(Sails Etc, I think) that was covered in CF cloth. I’d like to know how the did that.

Hi Don.

This how I did mine.

After the lead was attached to the fin, I put the fin in a vice with the lead vertical. I thinned the epoxy and brushed it on with downward strokes. The epoxy flowed down the bulb and the excess dripped off. the last one (the Emo) came out well with practically no runs and needed very little sanding.


OK, the surveyers tape didn’t work. It kept sliding down the bulb.
John, I’ve tried that before but not with thinned resin.

As I now have a bulb with a coat of thickened resin on it I will get a chance to try Anders sanding method. After it’s sanded I’ll try a coat or two of thinned resin. It is a few grams underweight anyway.

OK, something I used on a badly cast bulb (it just wasn’t a good day for casting and i didn’t feel like doing it over), was a product called “U-Pol Dolphin Glaze Finishing Putty

It is available as most automotive paint suppliers. A little bit goes a long way. It cures quickly (around 30 min) and it is SUPER EASY to sand and doesn’t clog sand paper. It mixes up like 50:1 or 20:1 (can’t remember and don’t have the bag close by). It’s also light weight, so if you’re bulb is close to the desired weight it won’t mess it up.

I highly recommend it. Oh, it takes paint really well, also.

But you do need to sand it to get a smooth finish. But like I said, it’s really easy to sand, so it’s worth it.

Warm the bulb first,(until it’s quite warm to the touch… 50-60c) mount the bulb vertically, then lightly brush on the epoxy… You will end up with a nice thin even layer…

Once cured, use scotch- brite to key up the surface prior to painting. That way you do not sand through.

Don -

my bulbs are usually already attached and faired to keel. Thus I have something to hold and hang fro

If you think this is a challenge, try 19,600 kg!

Just slip into your red and blue underwear!!

The ODOM book tells you to clamp the keel into a vice or something similar, then paint on the epoxy and use a blow dryer to warm the epoxy and smooth it out.

Hi All

Being very simplistic why use Epoxy. Two Pack Polyurethane it gives you High Gloss colour and dry’s much harder. That what I always coat my Ballast in.