In reading the Depron Razor thread Angus mentions “Epoxide” as a waterproofing agent for balsa.

I’ve been using epoxy since it became available, but I’ve never heard of epoxide. Can anyone tell me if there is consumer packaged epoxide available in the USA and what it might be called?

Aside: How language evolves. I heard a guy say that he epoxied something with ordinary glue.


Epoxide is quite correct in this instance, describing the chemical formed during setting of the resin.

I don’t doubt the correctiness of the name, I just want a consumer level brand name that I can purchase at the local hardware or hobby shop.

I tried googling epoxide (there’s another example of language evolving) and I got chemical definition, descriptions of the molecule and all sorts of things I don’t need.

A brand name for some usable goop for waterproofing is what I am after, preferably measured in ounces rather than gallons.


Pete -

I’m a very strong supporter and user of WEST System brand epoxy products fro the Gougeon Brothers in Bay City, Michigan. You will need to purchase from a marine dealer/supplier as it seldom is carried in home improvement stores or hobby shops. I don’t like the 5 minute stuff from hardware stores as it isn’t formulated the same. Buy the mini pumps - saves lots of waste and measures the product correctly (normally 5:1 ratio for their base product)

Each pump stroke is already metered - so one push provides either a 5 part ratio or a 1 part ratio.


I have generally used what used to be British SP Systems epoxys - but that’s just because its cheaper here and technical support is better

I very much agree with Dick that ‘home handyman’ epoxides are pretty awful things. Bite the bullet and buy professional quality materials and tools (pumps etc.)

Sad to relate I have some ten year (or older) West System stuff around here someplace. Last time I looked the larger can contents were quite discolored (about like stout) and I am reluctant to try it at this point. I probably used less than two ounces. I really don’t want to buy another gallon or so and have it lie around ten more years.

Both of you are almost certainly right about the quality of this sort of thing versus the handyman stuff in a small tube, but the reality of it is that an ounce or two will last me a long time, as experience has shown.

The ordinary hobby stuff is okay but way thicker than convenient for smearing onto balsa.

I was hoping for something very liquid in a small container.

Right now I am at the stage of making a half model (built up) around which I will wrap some 1/64th ply. When I get the shape of the ply right I will tape it together a la Razor and have the start of a boat.

I will try to post a picture of the half model when I get it roughed out. Its built out of 3/32nd sections on a 3/32 profile.


The suitable epoxys for coating are available also a “wing-skinning” kits in aircraft modelling shops - its often SP113 resin and comes in fairly small amounts.

FWIW I hate all fast-cure epoxys - they do not cure for me into a solid, structural ,material so i generally use good old 24-hour araldite. This is a radical misnomer as it will cure happily in 5 minute when heated on a light bulb - or as I now do on a retired mosquito-killing heater.

These are a mains voltage PTC resistor which means that as they heat the resistance rises and they self-regulate to a set temperature - spot on for curing araldite.

Having said I have fast epozys I have discovered a type in a “pound” shop which costs a pound, smells and is completely reliable! I use this with microbaloons for lots of joining, fairing etc.

Pete -

According to epoxy tests by Gougeon Brothers, that WEST Stuff is probably still good, although not for coatings where you want the amber color. As I recall their technical test/article, there was virtually no different in holding power between new and old, discolored stuff. That burgundy color will happen in about a year - it’s the air that causes it.

I’d give it a try as you really aren’t stressing it as much as a full size boat!

Buy one of their “Fix-It” packs - I think it’s like 3-5 oz. of the stuff. I wrote technical article in one of the last AMYA magazines and listed the product number and cost at that time. Let me see if I can find it - or just Google WEST System and look for their handi-paks.

[LEFT] Shelf life[/LEFT]
[i]If the containers are kept sealed when not in use WEST SYSTEM resins and hardeners should remain usable for many years. Over time, 105 Resin will thicken slightly and will therefore require extra care when mixing. Hardeners may darken with age, but physical properties are not affected by color. Mini Pumps may be left in containers during storage. It is a good idea, after a long storage to verify the metering accuracy of the pumps and mix a test batch to assure proper curing before applying epoxy to your project.

Handi Repair pack #101 is $10.95 (US)
[/i]Six (6) Resin & Hardener Packets 101-T is $18.95
They also have the G/Flex stuff too

Thanks, The Fix-it packs sound like what I need.

I have piles of glass cloth and most of a gallon of West system epoxy and very little use for quantities beyond what I can mix with a match stick!

Amazingly, I also have some old but unopened Petit Hobby Poxy. I don’t think that has been made for ten or twenty years.

I made a tiny mostly working model boat a bunch of years ago that a girlfriend talked me out of. That was finished with Aerogloss model airplane dope and was really beautiful, but I think that stuff has gone the way of the dodo too.

I think one of the reasons I am hesitant about opening the West System stuff is the potential mess that I can create with pump full and the amount of cleaning.

I’ll work around for the time being, and probably get something in my LHS.


Another way of measuring (if you are careful) is to use smalll graduated polypropylene cups for admnistraton of liquid medicines. Cured eoxide does not ahere to them and they can be cleaned completely but just cracking the cured matrial free. Do the calculation properly, preferaby so that the volumes for the two components fall exactly on graduated lines. Fill them on a surface that is accurately levelled and sight across at eye level - but you know all this.

Thanks Angus,

I have a sleeve of those cups in my flying buddy’s house. His daughter calls them mixie cups. I guess I could use up my West epoxy a few drops at a time.

The stuff we use in my friend’s shop is quite thick and when you mentioned epoxide in the Depron Razor thread I though it was something I could more or less paint with.

Right now I using thin CA and I am gluing myself to everything in sight, but I have a hull coming along pretty fast. I guess I will have to mix some epoxy and find some very light glass to get the seams a little better.


The reason why I have traditionally used SP Systems epoxide is that it is less viscous than West. I once had my hands on dome French 'poxy whose name I cannot remember that ran like water: it was beautiful, but I can’t remember the name. You can get what used to be SP Systems stuff from http://www.freeflightsupplies.co.uk/ . They’re honest and its no harder than buying from the US - Paypal does everything.

For fillets, joint sealing etc, look at collidal silica and microballoons (also Free Flight)

Just let me mention again Burgess Wood Sealer, a water based resin product. It paints on like water, capilliaries into the structure of the wood and goes off (slowly) to give a resin skin. Very effective on balsa, which it penetrates quite deeply. Available, in the UK, from yacht chandlers. Probbaly also available elsewhere.


I find that Z-poxy finishing epoxy found at Hobby Shops mixes easily, flows very nicely and soaks right into balsa.

If you want water consistancy, pour your epoxy into a aluminum cooking dish, the throw away type. Take a heat gun or hair dryer to warm of the epoxy. Just take note it will have a shorter pot life. You may want to warm up your hull some also. Thin epoxy will go back to it’s orig. consistancy shortly after it is applied to a cold hull.

If your using an epoxy and it bubbles, after being applied to wood, common with some epoxies. A quick burst of heat across the boats surface with a heat gun, will burst the bubbles and level any high spots and or runs.

Another source of epoxies in the MAS brand.

Thanks Angus, Historyman and Roadtoad.

I have two varieties of microballoons, glass and phenolic. I will poke around looking for thinner epoxies now that I know they are available. I have Paypal and have bought things in the UK and Switzerland, so I’m set there, and will check the UK freeflight outfit for interesting things that havven’t made it to the USA.

The Burgess stuff sounds good. More or less what I want for quick and easy protecting of stuff like balsa which seems like the most vulnerable thing on a boat. I once tried some Grumbacher water based varnish made for artists painting with acrylic. I varnished a bookcase I made and it was slightly sticky forever! I think by now Burgess or Grumbacher or someone has probably solved that problem. I know there are guys finishing guitars with water based products of one sort or another. Brings to mind my worry about balsa though. I am somewhat worried about it expanding when wet and doing damage that way.

Thanks again, I’ve bookmarked the sites for now (under Footy) and will look at what’s available while waiting for glue to dry etc.


Don’t think of the epoxide as protection for the balsa. Think of it as the outer skin of what I call a ‘zoned sandwich’, i.e. sandwich structure in which the material of the core and of the fibre matrix of the composite skins is the same - they just fade into one another Once you start to think this way, you can start to build some incredibly light, stiff structures, but the depth of resin penetration (i.e. the thickness of the skins) obviously needs thinking about. The great virtue of epoxide is not hat it’s good paint (it mostly isn’t) but that it’s damned strong. Exploit that fact.

Makes sense. I wonder how stressed these boats are by sailing versus being stressed by handling.

I don’t know anything about sails at this scale yet, but I have a source for very thin mylar.


He lists 2, 4 and 5 micron clear mylar and iron-on adhesive 5 micron stuff in various colors. I’m thinking of mylar sails and iron on reinforcement in the corners and maybe to stick battens on and reinforce the leach against stretching.

Is this stuff too light for sails? Mylar is pretty tough stuff, so I’d like to give it a try. The only thing that worries me is that ironing the adhesive will probably also shrink the mylar unless it is well stretched out and taped down. Any experience with mylar in these weights?


Handling is by far the highest stress. As a very rough calculation, the maximum hydraulic load a Footy can put on its skin is roughly equivalent to free pouring water over he back of your hand from a height of a foot!

The art is not in making things strong enough - it’s finding materials that are light enough (in terms of size, thickness, etc) not to end up making the whole thing ridiculously over-strength and over-weight.

We’ve used the lightest Mylar Free Flight Supplies sell with good results.

Pete - I 've published this before - but the darn thing works extremely well for those very small batches of resin - just print out a bunch of these, lay wax paper over them and drizzle the resin and hardener onto the wax paper. Mix together and you’re good to go. Once the wax paper batch cures, peel off the left-over and discard, and use again. The extra copies of the below attachment are just for “in case” - best of all … no pumps needed! :wink:
DON’T dump your WEST supply though! :scared:

Thanks Dick,

I am curious to see what it looks like anyway. It is left over from Wing Bagging mania. My flying buddy and I were going to vacuum bag airplane wings, but somehow we never got around to it so it looks like the resin will wind up doing something close to what it was made for.

Cute idea, by the way.