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Old Nov 28, 2012, 06:49 AM
Hey was that a Thermal ????
Joined Nov 2009
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Thanks Richard for helping out.

I have lost track of where I am (no sleep, lots of building) so if you have a plane on order but have no paid for it drop me a note. If you have sent funds I have a written record along with the PM's

Paul
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Old Nov 28, 2012, 09:40 AM
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Thanks for the help electrich.

I have one more quick question. I have bsi foam safe CA, 5 and 30 minute epoxy, and micro balloons. Will I need a less viscous "finishing" type of epoxy? If so, can anyone recommend one?
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Old Nov 28, 2012, 04:48 PM
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No, for basic assembly of the plane the 30 min stuff should work fine.

When you get to the point of the finishing strips of glass over the center joint of the wing you can just add a few drops of alcohol to thin the epoxy mixture a little.
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Old Nov 28, 2012, 05:17 PM
G_T
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Just note that thinning epoxy with alcohol greatly reduces its strength, and extends the cure time, often requiring heat to reach full cure (if it ever does). Just FYI.

http://www.seqair.com/skunkworks/Glu.../Thinning.html - might be worth reading.

I would suggest instead picking up a small quantity of West Systems 105 epoxy and their 205 fast hardener. Used in relatively small quantities and spread out thin so it doesn't cook itself off, it isn't fast. It is good for things like the center glass joining strip, or general delamination repair. It is thin enough to do the job, and slow enough to give plenty of working time. It is not really thin enough for aircraft laminating work except in despiration, but it is very thin compared to 30 minute epoxy! With additives, I use it as a glue. Additives being stuff like fumed silica, cotton flox, milled fiberglass, microballoons, various chopped fibers, that sort of thing. I even used dirt once for a field repair. West 410 lightweight filler is a good one to have. I prefer it to the hobby shop microballoons.

Gerald
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Old Nov 28, 2012, 10:17 PM
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Reedy Creek, Qld, Australia.
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Quote:
Originally Posted by G_T View Post
Just note that thinning epoxy with alcohol greatly reduces its strength, and extends the cure time, often requiring heat to reach full cure (if it ever does). Just FYI.

http://www.seqair.com/skunkworks/Glu.../Thinning.html - might be worth reading.

I would suggest instead picking up a small quantity of West Systems 105 epoxy and their 205 fast hardener. Used in relatively small quantities and spread out thin so it doesn't cook itself off, it isn't fast. It is good for things like the center glass joining strip, or general delamination repair. It is thin enough to do the job, and slow enough to give plenty of working time. It is not really thin enough for aircraft laminating work except in despiration, but it is very thin compared to 30 minute epoxy! With additives, I use it as a glue. Additives being stuff like fumed silica, cotton flox, milled fiberglass, microballoons, various chopped fibers, that sort of thing. I even used dirt once for a field repair. West 410 lightweight filler is a good one to have. I prefer it to the hobby shop microballoons.

Gerald
I like to use the slow hardener from West Systems, seems to make the resin less yellow (or is my fast hardener to old) and still full cures in 24 hours in warm temps.
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Old Nov 28, 2012, 10:53 PM
G_T
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West will yellow with UV, like most epoxy. Some other laminating resins such as MGS tend not to yellow. MGS starting out a very pale blue helps too... West starts out amber colored.

Gerald
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Old Nov 28, 2012, 11:27 PM
Hey was that a Thermal ????
Joined Nov 2009
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Gerald, I love your effort to help us out. The person who developed Resin Research's line is the one who suggested thinning. I have not had a problem getting thinned epoxy to cure at all. Okay so maybe it isn't quite as strong. So it drops from 5,000lbs of tensile strength to 2,000lbs, I don't see this as a problem. I obviously made those numbers up but you get the point.

Some companies even sell alcohol blends to thin with. RR quit doing that because denatured alcohol works just as well according to their lead Chemist.

Oh, on the yellowing. The blue tint is a whitening agent that brings out bright colors. RR has it available for one of their resins. Both have a UV inhibitor that is colorless. To my knowledge my wings don't yellow.

Keep the resins intended purpose in mind when looking at characteristics. RR was designed for applications similar to what we do. Many resins were originally designed for the boat building industry.

If anyone is looking for a REALLY nice 30-40min epoxy check our RR's Kwik-Kick!!! It is very friendly in every way, has a whitener and UV inhibitor in it. I have developed an epoxy allergy and nothing in the RR line bothers me at all.

LuapauL
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Old Nov 29, 2012, 09:36 AM
Ride, Surf, Fly, Sleep
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Originally Posted by G_T View Post
Just note that thinning epoxy with alcohol greatly reduces its strength, and extends the cure time, often requiring heat to reach full cure (if it ever does). Just FYI.
Flat out at work at present, but couldn't resist replying on an area in DLGs where I don't feel like a newbie!

Gotta go with Gerald on this as an ex-Composites R&D guy - but it doesn't weaken it much if you use it correctly and not enough to cause an issue in this application.

I've not used West being in the UK, but any proper laminating resin will be OK.

Personally, I'd go with a slow 60min hardner and then heat the resin (as you can't heat the foam without melting it). This will cause the resin to cure much faster and it will go very, very thin. This way you get strength and save cash on thinners.

Also, I'm not sure about modern epoxy systems but the destructive tests we did on aerospace resins circa 2001 show that slow hardeners increased the strength of the matrix compared to the faster systems. I can't remember the exact figures but it was by quite a significant amount. The chemistry showed that slow systems gave more time for longer molecules to form and polyform branching in the molecules was increased - basically think of spagetti; with slow hardners the strands of spagetti where longer and more intertwined/closer hence them making it more difficult for them to slide past each other.

Finally, If you are using thinners, make sure they're foam friendly - i.e. not acetone!

The other thing is note that the 30min or 60min hardners are rated for "pot life", i.e. how long you can work it. Not for cure time. This can be up to 10 x longer in a thin film (i.e. cure overnight to be safe with stressed parts). Also make sure you know whether the system mix ratio is by volume or mass (most are mass).

(PS. You'll love the FF - definitely go with D47's all round, also called SD100's etc, I have and they're an excellent compromise as a newbie myself, see the build in the thread)
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Old Nov 29, 2012, 10:12 AM
Hey was that a Thermal ????
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Originally Posted by quincross View Post
it doesn't weaken it much if you use it correctly and not enough to cause an issue in this application.

James once again you and I are on the same page. There is no doubt then lowering the percentage of solids will lower the strength. Even thinned it is still the strongest part of that center joint.

The FireFly is meant to be an easy to build, uncomplicated, high performance DLG. With that in mind don't over think things guys. I know of folks, not me mind you , who have used foam safe CA to wet out the glass on the center wing joint. Don't get so hung up on the shaft we miss the point.

PaulLuap ( I don't know whether I am coming or going)
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Old Nov 29, 2012, 10:51 AM
Ride, Surf, Fly, Sleep
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Originally Posted by The_Builder View Post
James once again you and I are on the same page. There is no doubt then lowering the percentage of solids will lower the strength. Even thinned it is still the strongest part of that center joint.

The FireFly is meant to be an easy to build, uncomplicated, high performance DLG. With that in mind don't over think things guys. I know of folks, not me mind you , who have used foam safe CA to wet out the glass on the center wing joint. Don't get so hung up on the shaft we miss the point.

PaulLuap ( I don't know whether I am coming or going)
Spot on mate - keep it simple - if it wasn't for the weight increase you could do that joint with polyester resin and it'd be fine.

Epoxy resin + slow hardner + heat with hairdryer - doesn't get more simple than that for a noob and the slow cure gives you time to screw it up and then fix it if you're not used to working resins.....or for peeps like me who are, but are just no good at it

As an aside I took a 30 min lunch break (first for 10 days) and flew the FF - 160' launches....OK I know that's not very impressive for an expert, but bear in mind I'm a complete noob, hadn't picked up a DLG until the FF and I've only launched it a handful of times since. I am seriously stoked

(I will post the promised full review from Mark and myself with the throws setup, I'm just a little over run at present work wise....)
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Old Nov 29, 2012, 11:38 AM
Ride, Surf, Fly, Sleep
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Originally Posted by RocketDog View Post
Hi all,
Battery
300mah 2s Eflite

I have this battery also, but I'm not sure if it has enough capacity? I plan on running the 2s straight with no regulator.
.
Just seen this - definitely go with a slightly larger capacity pack ~360mAh

I'm running 3 x D47's (SD 100's), FrSky 4ch Rx and a 360mAh pack straight into the RX.

After first flights totalling 1 hour the total draw was 130mAh which had dropped the nominal voltage quite low. Remember you're running at 7.2v (2S) which will drain the pack faster than if it was a 1S.

Also unless you're going to go to the extremes I went to (unplanned wing and planned tail shift) to get a low weight, with a 300 I reckon you'll be adding lead to balance with your listed setup. Pay a few $ and buy a larger battery as you may as well make the weight work!

Right....back to work! NNNnnnnngh...must keep away from thread even if bored out of tiny brain,,,nnnnnnnggggh
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Old Nov 29, 2012, 12:49 PM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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Originally Posted by The_Builder View Post

If anyone is looking for a REALLY nice 30-40min epoxy check our RR's Kwik-Kick!!! It is very friendly in every way, has a whitener and UV inhibitor in it. I have developed an epoxy allergy and nothing in the RR line bothers me at all.

LuapauL
Paul, Which RR epoxy are you using for your layups? The Kwik-Kick looks like it would work well for glass/epoxy over balsa on power plane wings. Thanks!

Ken
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Old Nov 29, 2012, 02:05 PM
Hey was that a Thermal ????
Joined Nov 2009
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Ken, The KK is quite thick. It rocks as an all around adhesive. It responds very well to heated cures is very clear when cures and is the highest strength resin in their line up. For laying up wings I use the 2050 with the 3100S hardener. The fast would work in the winter in my shop but might catch fire in the summer. The S gives me plenty of time and I get a very nice hard finish in 14-16hrs when the weather is decent and it will cure in 20 even when the outside temps drop into the 20's. I use a hot box but my shop is not heated at night.

On the battery subject I have been running a 600MAH 1S. I charge when I remember to.....
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Old Nov 29, 2012, 03:09 PM
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Joined Apr 2007
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I use the kwik kick thinned by one drop denatured alcolal per two grams of mixed epoxy for doing bagged tail layups. Can only do a single fin at a time due to the short working time, but the wet out goes just fine and the stuff cures hard as a rock AND resilient!

I only have KK and some 5 minute epoxy on my shop shelves. Don't feel a need for anything else unless I want to start making pods or wings.
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Old Nov 29, 2012, 03:34 PM
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Paul, that pretty much mirrors my experience with RR. I'm using the 2050 with the 3100S hardener as well. The stuff has absolutely zero odor, is nice and clear, and is the thinnest resin I've used. MGS might be thinner, but I've never used it and can't confirm. I've had a couple of longer layups where everything went wrong that could go wrong and it started to kick just before I was finished, but the 50 minute pot life is plenty of time. In fact, if I pour it onto a plate and let it spread out instead of keeping it in a cup it will last over an hour. I usually cure at room temp for 12 hours and then hotbox it at 125 for another 6 and they come out rock hard. My second Mystic wing was just 1.4oz glass over 15psi foam and it's surprisingly dent resistant. I love this stuff.
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