Thread Tools
Old Jun 03, 2016, 03:07 AM
slowmatch is offline
Find More Posts by slowmatch
Registered User
slowmatch's Avatar
Joined Dec 2015
223 Posts
Discussion
Epoxy for Built up Construction?

I'm planning a built up 2 metre RES woodie with Allegro Lite type construction (bungee launch though). Please can anyone tell me roughly how much epoxy will be needed? And what type is recommended?

Has anyone used the Hobbyking 30 minute stuff? Seems about half the price of the similar Zap product.

http://www.hobbyking.com/hobbyking/s...dProduct=69121

Thanks!
slowmatch is offline Find More Posts by slowmatch
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 03, 2016, 04:03 AM
GordonTarling is offline
Find More Posts by GordonTarling
Supersonic Engineering
GordonTarling's Avatar
UK, Greater London, Uxbridge
Joined Mar 2001
3,477 Posts
If the airframe is all wood construction, why do you want to use epoxy? Epoxy adds a lot of weight and, in my experience, doesn't bond as well to wood as some other adhesives. Personally, I'd use a white PVA wood glue and possibly CA if there were any specific areas which required it. Everyone has their own favorites though.
GordonTarling is offline Find More Posts by GordonTarling
Reply With Quote
Old Jun 03, 2016, 04:14 AM
slowmatch is offline
Find More Posts by slowmatch
Registered User
slowmatch's Avatar
Joined Dec 2015
223 Posts
I'm very comfortable with PVA and CA but this design has carbon cap spars, kevlar wrapping etc. Plus the wing joiner construction.

In the fuselage, I'll be using epoxy for the carbon boom/pod connection and bits like wing bolt seat, launch hook etc.
slowmatch is offline Find More Posts by slowmatch
Reply With Quote
Old Jun 03, 2016, 06:40 AM
kzimmerm is offline
Find More Posts by kzimmerm
Kurt Zimmerman ≡LSF 4461≡
kzimmerm's Avatar
Montrose, NY
Joined May 2003
1,660 Posts
I use epoxy in areas that requires extra strength along with flexibility. All my spar construction is done with epoxy. I use epoxy to laminate carbon on the spars and for the shear webs. Any bonding to Fiberglas is done with epoxy.

I use very little CA only because it tends to make a brittle bond. I also don't like what it does to balsa making it brittle. I use carpenter glue on the remaining construction.

I have airframes that have lasted 20-30 years so I'm going to continue what works for me.

Kurt
kzimmerm is offline Find More Posts by kzimmerm
Reply With Quote
Old Jun 03, 2016, 08:23 AM
chawkins is offline
Find More Posts by chawkins
PBR Sailplane
chawkins's Avatar
United States, MI, Midland
Joined Jul 2012
376 Posts
For what it's worth, I rarely,if ever use epoxy. And only use CA for hinges. Wood glue on most everything
chawkins is offline Find More Posts by chawkins
Reply With Quote
Old Jun 03, 2016, 08:50 AM
hallo is offline
Find More Posts by hallo
Amateur Forever
hallo's Avatar
Norway
Joined Feb 2014
1,517 Posts
If you are just mounting or "glueing" something I guess any epoxy glue should work though there are different qualitys, some are for example made to sand more easily which in my experience makes for a brittle and otherwise low quality glue, some are perhaps less chemical resistant (fuel and such) and becomes like wax if exposed to it over time. But I guess the majority of brands are in practical use much the same.

If you are to make sparcaps yourself or use it to saturate fiberglass I would use some kind of laminating epoxy, the difference is that it is much thinner floating - this makes it better for saturating/penetrating and it is also easier to remove excess epoxy which is important. The quality (flexibility and strenght) might be a step up compared to some glues aswell, but it needs to be mixed with something like milled fiberglass or cotton or similar if it is to be used as a glue.

Dont worry too much about it, use what you get and make the best of it.
hallo is offline Find More Posts by hallo
Last edited by hallo; Jun 03, 2016 at 09:03 AM.
Reply With Quote
Old Jun 03, 2016, 09:05 AM
LJH is offline
LJH
Find More Posts by LJH
LJH
Moths do not fly inverted
LJH's Avatar
Greenwich CT.
Joined Sep 2000
4,996 Posts
I mostly use CA in my wood builds but I believe there are places where epoxy is a better adhesive. When I use epoxy I pretty much only use West Systems as it is a marine and aero space grade epoxy. The viscosity of WS is pretty low so it flows very well and absorbed into the fibers of wood. WS is also used extensively in the construction of carbon fiber race boats so you know it works with carbon. It is not cheap or fast curing but works great and the shelf life is quite long so you can use it for years to come.

Cheers,
Jim
LJH is offline Find More Posts by LJH
Reply With Quote
Old Jun 03, 2016, 10:16 AM
dankar04 is offline
Find More Posts by dankar04
Registered User
Tucson, Az
Joined Feb 2007
16,876 Posts
I agree with posts above ca. Titebond. Epozy slow cure for wing joiners is fine. Very heavy and not needed in general construction. My 2 meter Riser R/E came out under 20 OZ. flying weight.
dankar04 is offline Find More Posts by dankar04
Reply With Quote
Old Jun 03, 2016, 10:20 AM
Heddon125 is offline
Find More Posts by Heddon125
Registered User
United States, MN, Albert Lea
Joined Feb 2012
48 Posts
I have used Raka epoxy in the past for a couple boat building projects and have been happy with how it works. Used mostly for laminating fiberglass cloth onto wood but you can thicken it up with silica or other products and use it for gluing and bonding as well. Prices are pretty reasonable compared to some of the other bigger brands like West. One option - they have a trial kit here - (scroll to the bottom)

http://www.raka.com/epoxy_kits.html

$18 includes 12 oz of resin, fast and slow hardeners, plus some microballoons, silica thickener, and some glass cloth you could snip up into fibers for high strength bonds. It should be more than enough for what you are planning to build.

Most of the hobby store 5 or 30 minute epoxies work fine for gluing but are too thick for laminating fiberglass or carbon cloth. It can be done but not ideal. They should work fine for bonding things like precured carbon spar caps though.

I haven't tried the Hobbyking stuff you linked to but from the single review it sounds like it cures kind of rubbery/tacky. Maybe he just had his mix ratios off or didn't mix enough though. In my mind if you're going to put a lot of time into a build a few extra bucks for a product you have confidence in is worth it so I would say go with a brand you know.

Steve.
Heddon125 is offline Find More Posts by Heddon125
Reply With Quote
Old Jun 03, 2016, 12:19 PM
slowmatch is offline
Find More Posts by slowmatch
Registered User
slowmatch's Avatar
Joined Dec 2015
223 Posts
Thanks for the comments. Just to be clear - the question was which epoxy rather than whether to, or where to use it.

The spar construction will be similar to the Allegro Lite - so adding a filler to make a buttery consistency for gluing the carbon caps but also for wetting out the wrapped Kevlar tow.

I have used WEST on boat project but its a long time ago. More recently I've used 20 minute '2 ton' cheap stuff in small quantities, but its pretty thick.

Can anyone tell me how zap compares? Or suggest another brand at the budget end of the spectrum? I agree about getting what you pay for but this particular model is being built to a budget for sport flying from a bungee launch.

Also what sort of quantities would be required for a 2m allegro style build?

Thanks
slowmatch is offline Find More Posts by slowmatch
Reply With Quote
Old Jun 03, 2016, 01:08 PM
GliderJim is online now
Find More Posts by GliderJim
Registered User
GliderJim's Avatar
Michigan, USA
Joined Jul 2006
725 Posts
I've always just used my local hobby shop "brand" epoxy, which is made by Bob Smith industries. http://www.amazon.com/Bob-Smith-Indu...f=sr_1_fkmr0_1 I've used it to cap spars with carbon fiber and mixed it with micro balloons to fill joiner boxes, etc. Also as a straight glue for certain types of joints. I've also used it to apply fiberglass to small areas or to join wing halves. It's a little thick for fiber glassing so I usually warm it up a bit with the heat gun right after applying it which causes it to thin and allows it to wet out the cloth better.

I don't know exactly how much you'll need for your build. The link I gave was for the 4.5 oz. It also comes in a 9 oz. size. I can't imagine you'd need more than that.
GliderJim is online now Find More Posts by GliderJim
Last edited by GliderJim; Jun 03, 2016 at 01:14 PM.
Reply With Quote
Old Jun 03, 2016, 04:04 PM
kzimmerm is offline
Find More Posts by kzimmerm
Kurt Zimmerman ≡LSF 4461≡
kzimmerm's Avatar
Montrose, NY
Joined May 2003
1,660 Posts
There is West System, Pro Set which are great for glass lay ups. I typically use the LHS 20-30 min for most other work.

Very seldom I'll use 5-10 min but have it in my collection of adhesives.

Kurt
kzimmerm is offline Find More Posts by kzimmerm
Reply With Quote
Old Jun 03, 2016, 04:21 PM
jetmaven is online now
Find More Posts by jetmaven
Registered User
Joined Oct 2004
1,301 Posts
I regularly fly an Aquila built in 1978 . It was completely built with carpenters glue .
The only epoxy in it is in the spar center section and the tow hook area.
I totally agree that ca is not a good choice , too brittle . The stuff is way over rated .
I guess the instant gratification crowd thinks it's wonderful.
jetmaven is online now Find More Posts by jetmaven
Reply With Quote
Old Jun 03, 2016, 05:26 PM
Heddon125 is offline
Find More Posts by Heddon125
Registered User
United States, MN, Albert Lea
Joined Feb 2012
48 Posts
If you're really pinching pennies and don't plan on wetting out stuff like unicarbon or glass cloth I'd say just use whatever the cheapest 30 minute stuff you can get from your LHS or home store, and mix it with wood dust or silica. It will work for gluing down the kevlar wraps too, just smear some on, let it sit for a minute or two and wipe it off.

As far as quantities if you use more than two or three ounces (including the waste you wipe off) for the whole build I'd be surprised.
Heddon125 is offline Find More Posts by Heddon125
Reply With Quote
Old Jun 03, 2016, 08:43 PM
HIR/Cer is offline
Find More Posts by HIR/Cer
Registered User
HIR/Cer's Avatar
Joined Apr 2005
603 Posts
Purchased a house brand (D &J Hobby) 20 minute Bob Smith Industries epoxy in May 2006 (!), always stored in a cabinet, and have just being using it recently for a casual build of a Drifter II. Seems to be less viscous then when new and the good news is that it sets up like new after at least waiting overnight. It's been strong enough for a Wanderer's outer spar repair with a short 1/16" ply sandwich wrapped with dental tape.

For that Wanderer build years ago, a friend recommended Satellite City Hot Stuff ca, and baking soda for its gap filling ability, and used it for the majority of its build with some epoxy for the wing joiner tubes (my modification) and the wing spars. The Wanderer has not fallen apart yet

Don't care for the ca odor so have been using Titebond but will have the ca ready for quick repairs. Also, never was a prolific builder and emptied a bottle of ca before it becoming hard and useless.
HIR/Cer is offline Find More Posts by HIR/Cer
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product Plexidrone finally releases the specs for their "Built from the ground up" FC - klepper Multirotor Electronics 0 Mar 20, 2016 09:00 AM
Discussion re-making wing for a built up wing (gorilla bob) slo-stick danielphantom Foamies (Scratchbuilt) 11 Mar 13, 2016 06:43 AM
Sold Built ROYAL P6 Peashooter set up for a DLE 20 Gas engine Aerogasrc Aircraft - Fuel - Airplanes (FS/W) 3 Feb 15, 2016 07:25 PM
Link Built up CF wing construction links GaryO Composites Fabrication 3 Mar 08, 2011 08:26 PM
Sold 38% Christen Eagle Kit All built up wood construction $650.00 Brian Mitchell Aircraft - Fuel - Airplanes (FS/W) 3 Nov 14, 2009 11:55 AM