GWS Zero conversion - RC Groups
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Feb 12, 2006, 04:37 AM
Pickin' an a Flyin'
Wufnu's Avatar

GWS Zero conversion

I've started a conversion of a GWS Zero to glow. Since I couldn't find many threads with specific details I decided to document my conversion as I go along (when I remember to do it, anyways). I'm doing a project about a mechanical dissection of any object and I decided to use my Norvel .061 BigMig. The project requires a demonstration so I had to buy a bit of stuff to get it going and bought a slope zero while I was at it. My thought was that if I spent that much money to get the motor running right I might as well stick it on a plane. School and money don't leave me with any free time so what I'm going to do is set aside $20-30 a month to buy stuff for the plane, as a reward for doing well in school, so it may be a looong time between updates. I only expect to work on it during the weekends, when I have parts to add to it. Depends on how well I can control my will.

As of now I've got the motor mount figured out and installed (that took me awhile deciding how I wanted to do it, and building it took a million times longer which makes no sense considering how simple it looked). I used a diagram of the motor measurements to design a simple motor mount. I used poplar for the mount, the first two broke due to trying to cut against the grain. The third one I finished I used clamps to keep the wood together long enough to cover it with epoxy then beef it up with another layer of wood. You can see in the pictures that the mount above the gws stick mount has two layers, I used two so the wood wouldn't split from vibration and so I could use longer mounting screws. I epoxied the whole thing onto the stick mount, aligning it on the mount so I could use the built in downright thrust. I figure the strongest force on the stick would be shear due to thrust, so I put in a small screw through the entire mount/stick setup (which the tip of is visible in some pictures). I have to mount the motor upside down, which I really don't like, because I didn't want the motor to stick out of the cowl and the stick mount is already on the top half of the fuse. Fiddling with the motor/cowl a bit I found that the back of the motor had to be just about right on the front edge of the fuse foam to have the proper length outside the cowling for prop clearance while keeping the cylinder off the cowl. This meant I had to trim the mounting stick by 1". You can also see in the pictures that I had to cut two small bits of foam from the fuse so that the back portion of the motor mount could be embedded into the fuse allowing the back of the motor to line up with the front of the foam.

I know the zero has cg problems so I'm sure the fuel tank will have to be on or forward of the cg. I prefer the center of the tank to be on the cg for fuel consumption balance reasons. That really, really limits where I can stick the thing, so I'm just going to put it in the canopy/battery area. Funny looking pilot, but there really isn't anywhere else to put it. I'm using a 2oz sullivan tank with clunk.

For battery power I am using a 4cell 350mAH rx battery pack which fits nicely into the stock battery tray. I'm unsure if I'll use a switch. I like the idea of leaving the battery inside the fuse to charge since I don't know how easy it will be able to remove with the fuel tank in the way.

Looking at the fuse tonight I'm 100% certain gws will have no problems doing rotary powered WWI aircraft, if they ever do them. This is a really snub nosed plane with a monster wing. Reminds me alot of my 109, only I think the wing has a much greater chord.

I would like to spray it with some water based poly-u, but I wasn't able to find any at Lowes. Any of you guys have a particular brand of foam safe spray can polyurethane I can use to fuelproof/resist the foam with and some places that sell it? I know glow doesn't eat foam, but running the Norvel on the bench my hand was covered in oil afterwards =/ Luckily I don't have to paint it, as I'm going with a white scheme, so just clear poly would be great. I covered the motor mount with 5 minute epoxy. Doesn't have the soaking 30minute does, and I didn't even thin it with denatured alcohol (because I don't have any), but I figure it'll do ok. I covered every spot with epoxy, just really thin amounts of it.

Also, anyone know of a good tubing to use for the exhaust port of the Norvel motor? My fuel tubing doesn't seem to fit.
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Feb 12, 2006, 08:41 AM
Registered User
twchdyn's Avatar
i had a mustang with an sc 12 up front. it was very fast!! the wings didnt like the Gs tho so use some carbon fibre spars in the wings and glass it all. oh and pin the hinges with cocktail sticks i lost an aileron in flight once, got it back down safe, lucky i guess. I put a ply firewall in and used a comercialy available mount. never had any problems with the mounting or running of the motor. Good luck with it..
Feb 12, 2006, 09:13 AM
Pickin' an a Flyin'
Wufnu's Avatar
What do you mean pin the hinges with cocktail sticks? I'm not familiar with the method. By cocktail sticks you mean those little plastic sticks that are a little bigger than toothpicks, right?

I'm using a Norvel BigMig .061, a little more poweful than a 400 sized motor, but actually weighs LESS. Well, before you add in all the epoxy I put on the mount. I may use cf for support as I have a few rods laying around, but I'm not going to glass it. The Norvel weighs less than their .049 , it's a very good motor for this plane I'm thinking. 230 watts from the gws 400 motor vs 231 from the Norvel .061 BigMig. The 230 for the 400 is found from the stall numbers on the gws motors page but if you look at the EDP section it shows around 100watts plus or minus 20-30 but the Norvel gives .31 at 22500rpm which isn't that much higher than average max power rpm. The Norvel weighs an oz less than the 400, then subtract alot of battery weight, add in fuel and servo weight plus the spray on poly-u for fuelproofing (if needed). Should be pretty close to stock weight, especially since there's no green paint on it.
Feb 12, 2006, 11:33 AM
Team Me!
P-38J-Lightning's Avatar
your going to cover this right? the glow will kill the foam
Feb 12, 2006, 12:20 PM
Pickin' an a Flyin'
Wufnu's Avatar
Glow doesn't eat foam, gasoline eats foam. The oil will soak into the foam over time, however, and cause the outermost layer of foam "pellets" to become loose and fall off. I'm more concerned over gained weight than anything else. Either way, no covering. That's what the spray polyurethane is for if I could find some Just fill in the gaps to keep what little bit of oils gets on the plane from soaking in. I've read that foam doesn't soak up as much as balsa, nor does it soak all the way in just a short ways.

PS - I love that episode of Family Guy.
Feb 12, 2006, 07:30 PM
Team Me!
P-38J-Lightning's Avatar
The one with the monkey? i love family guy too. the best one is when he explains why the monkey is evil lol
Feb 12, 2006, 07:50 PM
Pickin' an a Flyin'
Wufnu's Avatar
I meant the one with that guy "I'm just doing my thing!" The monkey is great too. Favorite show... well, tied with Futurama.

Ran my motor today on the test mount, to make sure it'll work for class. Stupid muffler came apart, I thought I glued it with something (a year ago, I don't remember). Everyone uses JB Weld or a screw, right? I HAVE to have a muffler, it's a school. The motor ran perfectly, however. Also, what size fuel tubing are you guys using on the muffler exhaust port tube nipple thingymajig? AND, has anyone gotten the muffler to make a good contact and not leak all over the place?

Glows are so much fun This whole "wait till March before spending any more money" is torture.
Feb 13, 2006, 12:20 AM
Registered User
Glad to see you converting a great gws bird. I did this conversion a couple of years ago with a norvel 061. I cut down the nose and added 3/32" ply then mounted engine. You will love it. Flys so slow, slower than a crawl and has unlimited vertical. I like flying mine in 20 mph winds "like a kite" . Don't worry about the fuel and foam because by the time the fuel starts to mess with the foam you'll have many flights. Advice, if I had to do it again, I would put an 074 on it for balance purposes. IF your not using landing gear than glass up cowl because the thin black one will crush on your first flight. regards, Eric
Feb 13, 2006, 05:01 PM
Pickin' an a Flyin'
Wufnu's Avatar
Thanks for the tips! I considered just whacking the nose and putting a flat piece of ply on there but I don't have a foam cutter and figured getting the right angle of the firewall would be impossible for my meager building abilities. I always go for the easiest route which was, for me, making a motor mount that mounts to the stock stick.

Did you happen to notice any added weight from oil soaking over time? I'm not worried about how it looks so much as having a fat bird. If I don't have to worry about alot of added weight then all I need now is to sand the foam down, buy one servo (going to get two from my SS), get some #3 screws for the motor, and put in the fuel tank to have it flyable. I didn't know I had so much stuff laying around. I might just spray it with poly anyways. "just in case." Maybe give it a better shine. Who knows

Where did you put your rx battery? I'm going to have mine as forward as possible to try and help with the balancing. I've never used clay in my life but if I can keep it below maximum stock weight then I might just have to clay it up. *shudder* I have lots of gws clay sticks laying around the house

Any pictures from it?
Feb 15, 2006, 01:46 AM
Registered User
Hi, I'm pretty new to this hobby, but I've converted a couple of GWS birds to glow.

I'm assuming you've seen the discussion on this thread already?

Some good info there. Personally, my preference is to cover the entire model with Iron on covering. True, the glow fuel and exhaust doesn't react with the foam, but I find that over time, the bare foam model gets harder and harder to clean. Also, if you have to make repairs, you'll find that it's hard to get any kind of tape to stick to foam that has been repeatedly doused with fuel/fumes.

On my corsair, I have to use a 700mAH battery instead of my usual 400mAH to maintain balance. I'm attaching a photo of how I did the engine mount there just for interest.

Feb 15, 2006, 06:50 AM
Registered User
twchdyn's Avatar
yeah toothpics the wooden or plastic kind, after you have glued the hinges in and they are dry drill a hole same dia as the toothpick and glue the toothpick in the hole then just trim and sand on either side.
Feb 15, 2006, 11:02 AM
Pickin' an a Flyin'
Wufnu's Avatar
Yah, I've seen the RCU threads before, I've been looking into it for awhile. Not until comparing the nose of the zero in my hand to the pictures of those corsairs did I realize that the Corsair has a honkin' big nose.

Did you use any down/right thrust? Is that any special tubing on the exhaust? I was hoping to get something flexible I could run out of the cowling (although if I can't get the stupid muffler to seat without leaking all over the place that's kinda pointless).

Have you ever covered the plane with polyurethane or thinned epoxy? Still hard to repair even with those used?
Feb 16, 2006, 05:09 AM
Registered User
Hi Wufnu, The Corsair does have a huge honker! Found the best flying prop was a 7 x 3 APC. If I were to do it again, dun think I'd go with the GWS version. Actually, I already have plans to scratch build a balsa version some way down the road.

I put in a tiny bit of right thrust/down thrust by adding washers when bolting on the Dave Brown mount. Actually, after flying the plane, I don't think it's that significant for this particular plane.

The tubing is just a exhaust deflector. My little Wasps spew plenty of exhaust, and I generally try to keep it as far away from the plane as I can. Yes, the deflector will move most of your fumes out of the cowling, but as you point out, the muffler is a little leaky. Did have some joy with a little plumber's tape. Semed to cut the leakage by about half.

For the F4U, the fuel tank and part of the battery compartment was coated with thinned epoxy ( 3 coats worth). I think overall, the iron on is still MUCH easier to clean, maintain and repair. It also makes the whole airframe a lot stiffer. And, I'm guessing it's lighter than epoxy.

Hope that helps.
Feb 16, 2006, 10:58 PM
Pickin' an a Flyin'
Wufnu's Avatar
Thanks for the help! That's alot of specific info that's good to know, especially for those down the road that need specific answers.

Speaking of which, I was able to find some water based polyurethane in a spray can at Lowes. I was going to get brush on, but it was $15. I happened to see a blue Minwax spray can that said water based. I bought it and it does not eat the foam, covers the foam nicely. I used a block of foam from a cardboard box to test it out on and no matter how close it was it wouldn't eat the foam, although I keep it at 12" per the directions to get the best coverage. I've got three coats on the fuse, two on the wings and elevator, and one on the rudder. Will finish up tonight and take a picture.

By the way, sanded the entire thing to get as smooth as possible with 240grit sandpaper. My arms are tired, my lungs are probably full of dust (I covered my face, but still). Talk about a chore! That was not fun.
Feb 17, 2006, 04:25 AM
Registered User
Oh yeah, with your 061 your gonna have to play with your incedence alittle. If you don't your zero will climb on throttle. Remember it was built for lift and slow fly. I put an 074 on the corsair with a mas 4.5x4 prop. It was fun. I don't remember what size battery I used in the zero but it was all the way forard and I used the opening in the cockpit for my throttle servo and ran the throttle tube next to the battery out to the engine.Keep us posted. regards, Eric

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