Unidentified 1/2A Combat Plane

Looks like a George that I had made from magazine plans.  I think it may have been from the 70s because I was in high school then. I made another similar one with a stabilator too with the same diamond airfoil and a TD .049. The motor has a newer cylinder than from that time. https://www.vintagemodelplans.com/collections/model-combat-airplanes-plans/products/full-size-printed-plan-building-notes-half-a-combat-george-wingspan-22-inch-engine-1-2a  It looks quite similar to the other one I made which name escapes me. Kind of remember a school shop teacher getting the kids to make them in a school in Peralta. Wherever that is.

Unless the builder re-designed the horizontal stab, I do not think it is a 'George'. The 'George' has a one piece flying stab, whereas the OP's plane has a horizontal stab and elevator. Also, the wingtips on the unknown airplane are straight/squared, the 'George' has tapered wingtips.

I would have to dig through magazines for two days to find the article to get the name. The diamond airfoil was a great design feature with the leading edge at 45 degrees. It could be easily built on a board. I made it with a stabilator but likely took some artistic license.  Just can't remember the name.  It was 45 years ago.  I remember flying it all summer with over 45 degrees up and down, and doing squares and lots of eights and my own version of a clover leaf.  Then I had to rebuild the tail and gave it much less up and down.  It was so much faster on the turns that I could not do the same flying, so I sold it to a flying buddy.  He got a couple flights on it and destroyed it. Had a wedge tank. At any rate it will be a fun cheap date.

I like the diamond airfoils. Easy to cut out ribs, as one can use a straightedge. I have only built one, the 1/2a Circlemaster I believe it is.

Thanks for the replies. I took the engine off and rotated the tank so the vents are vertical. Also set the pickup tube to about 8:00. The engine mount is too narrow vertically to rotate the back plate to set the needle upright. The needle is more protected in the horizontal position anyway.

What are the groups thoughts on spraying the the plane with a coat of polyurethane to better protect the covering from oil soaking?

The pushrod seems to drag on the plastic ferrule where the rod exits the wing. This seems to limit the down travel on the elevator. Should I be concerned enough to do something about that?

If you think there is a couple coats of dope or whatever, on it, I would not add any more weight. Trimming the plastic ferrule may be a good idea. I spent 3 hrs. looking through old magazines and found the one I made.  It really looks like this.  5 1/2" chord, 22 1/2" span, same elevator, the differences are minor which makes me think it is this one even still.  The wingtips have a shallow triangle and the motor mount is sideways to that.  The name is the "Snip" from Model Airplane News April 1974.  There were full size plans in the mag. for the "short kit"

aspeed wrote:If you think there is a couple coats of dope or whatever, on it, I would not add any more weight. Trimming the plastic ferrule may be a good idea.  I spent 3 hrs. looking through old magazines and found the one I made.  It really looks like this.  5 1/2" chord, 22 1/2" span, same elevator, the differences are minor which makes me think it is this one even still.  The wingtips have a shallow triangle and the motor mount is sideways to that.  The name is the "Snip" from Model Airplane News April 1974.  There were full size plans in the mag. for the "short kit"

It does look alot like the Lil Snip, minus the wing tips and beam mount. Thanks.

The tank vents do need to be vertical however the NV can (and should) be left where it is. Then get best position for fuel P/U.

In this copy there are two options for mounts.  i'll try and load it in the plan section too.  It is really easy to make if someone is interested, and maybe I can find it easier than on my computer.

Mystery solved.  Thanks. The plans should come in handy if (when) I crash it.

The Snip build thread going on here motivated me to get this one out and see if the engine would run. It fired up quite easily. Possibly the first time the engine has been run. Temp broke 40f here today, but windy. Hopefully, I'll get this thing in the air soon.

Great pic of the Widow running there.

NEW222 wrote:Great pic of the Widow running there.

Thanks. The engine started easily, and ran well. I ran a couple of tanks of fuel through it, then cleaned the plane up, removed the engine, cleaned it up, reinstalled it and hung the plane back up. Waiting for warm, low wind weather. (Do we ever get that here?)

Didn't go well. I used Rusty K's folded carpet launch method. That worked ok. Got the plane in the air. Made it around about three times. Then the glue on the outboard side of the engine mount apparently failed. The engine tilted slightly inboard, the lines went slack, the plane came in at me. Had to dodge it. Then it crashed. Not good for waiting all summer for decent weather. Tried to fly the Skyray also. Engine wouldn't run more than a few seconds. Might have to get out of this hobby.

TLAnderson wrote:Might have to get out of this hobby.

Oh come on, really?  The adventure has just begun!

Bummer TL. That's a shame. I don't like to use wood screws, machine screws for me if at all possible. Not fun seeing one of these heading right for the eyes.

Rebuild it, if you have to use screws on that firewall design, replace with hardwood and go fly again.

One bad day isn't going to get you down! Pick yourself up, dust your self off and get right back on that pony.

Bob

I fixed the Snip and flew it again yesterday. I was flying over thick grass which acted as a cushion when the plane crashed. Out of about five launches, four resulted in an immediate loss of control and a crash. I was able to fly out a full tank of fuel once, only by holding the plane dead level. Any up input resulted in the lines going slack and a loss of control.

I don't know much about trimming these things, but it seems that this one needs some outboard tip weight, maybe some nose weight, and more right offset of the engine. Photos I've seen of some combat planes show the engine angled outboard by quite a bit.

So, where should the CG be? What's a ballpark figure for tip weight? How much should the engine be angled outboard?
That Black Widow runs great, by the way. After the one successful flight, I was so dizzy, I could barely stand up.

Seeing that you mentioned that your uncertain as to how this plane should be trimmed I will add what I gather from your post.

        1. What prop are you using? If your using a prop that's 6" this isn't helping your cause as it's making the plane want to porpoise due to being too large. Obtain a 5x3 and wind it up.  Think of it this way, if you had a small 12" wheel and you held it by it's axles and spun it and then tried to turn it what happens? It opposes your inputs, do this using a large bicycle wheel that's 27", the forces are more than doubled to try and turn it by it's axle. If your currently using a 5" prop terrific.

2.  More than 75% of issues from loss of line tension is due to a warp in the wing. From your post this is what I'm believing your problem is. Sight the plane from the rear holding it level about 2' out in front of you. Scanning your eyes from inboard to outboard take note that your not seeing the top or the bottom of either wing panel. Using 1/4" straight dowels ( Arrow shafts even better)  about 18" long rubber banded from leading edge to trailing edge and viewed from the sides will immediately show a twist. In addition, from both sides sight down the leading and trailing edges. Look for humps either up or down and make the needed adjustments. A twist is not always a easy task to remove, in the case of the Lil Snip, you have a continuous spar top and bottom your trying to twist and if glued improperly, it's a real tug of war relying solely on your covering to do so.

     Insure that your booms are aligned properly. If the wing is twisted from tip to tip will also cause one to be higher. Many times this goes unrecognized. One boom is higher than the other and the stab is now tweaked. While having it offset to one side can help, just make it level so that all incidences are on a level plane.

3. Cox equipment by no means is considered high powered. A wing needs speed to have it fly properly and stay out on the lines. While I'm not a fan of line rake, this plane might need the leadouts swept back SLIGHTLY!!  Prior to moving them, attach your flying lines to the leadouts of the plane and hang the plane like a plumb bob. Note the incidence of the leading edge to the ground as the plane is hanging plumb. The plane should be slightly angled out with it's nose pointing more to the ground. If the plane is actually level, this isn't actually bad, it's just until you get used to the plane, keep it nose down.  My plans indicate the first leadout exiting the inboard tip 1 3/4" back from the leading edge and the rear leadout at 3".

4.  Engine offset isn't needed. While others will tell you it keeps the lines tight, it slows the plane down. Referring back to #3, these planes need speed. Using offset to a slight degree isn't harmful but the plane really shouldn't need it and I would forego using it until other options have been tried. One small #2 washer on the inboard side isn't going to do any harm.

5. Tip weight is elected by the size and type of your lines. Tip weight is only a necessity upon launch and after that it's dead weight. Speed keeps the lines tight , not tip weight. 5-7 grams of tip weight is all that's needed in that plane. Adding more will assist the plane to fly outboard more lessening your chances of the plane coming in but if the wing is warped, your fooling the warp, causing more drag and not fixing the underlying problem. Your plane sounds like it's coming in when you give it input, this suggests to me that your outboard wing is flying high, if you had the ability to go inverted, it would be opposite. You need to fix the wing before you can trim anything. Having too much weight is very bad and causes extremely poor maneuvering. When the wing goes through a outside or inside maneuver, the weight wants to keep going straight in the direction it was pointed vs turning. During a inside loop for instance when you exit at the bottom with too much tip weight, the wing will drop drastically prior to going into level flight. This is usually what causes panic.  

6.  The CG is critical if the plane is on the tail heavy side. I dug out my Lil Snip plans and the CG is 1" behind the leading edge. Keeping in mind that this is a generalization so that most that fly the plane can do it successfully. It probably and more than likely is still slightly nose heavy which isn't bad. The plans also indicate the pushrod is in it's furthest outmost hole on the control horn. If you have a single hole control horn, insure that the hole is at least 3/4" from the hinge center line or pivot point as most refer to it as.  I would add only the needed weight to make it correlate to the CG I offered. Adding more is like running a marathon with 10 lb sneakers on.

7.  Using a heat gun, you can twist the surfaces to repair the warps if needed. When doing so, it's much easier with two people. Twist the surfaces the opposing directions and note the wrinkles in the covering when doing so. Heat the wrinkles until they completely shrink top and bottom and don't relax twisting for at least a minute until it's cooled. This may take repeated attempts.

8.   Now back to engine offset, while I mentioned it's not necessary most of the time, if you feel the lines are getting a little slack during maneuvering, add some. It causes a lot of drag as I mentioned. Line drag causes the plane to yaw inboard therefore some of this can be reconciled by adding engine offset. This is a small plane with a decent wing area and little drag compared to a full bodied plane. It should penetrate the wind well. The shortcoming of this plane is the fact that it has a diamond airfoil. I agree, it looks cool but they're not a good airfoil design. This plane will go like stink in level flight until the maneuvers start, then it's like hitting the brakes. Now if you do one loop every so often this might not be noticeable, but if you start into 8's after some other maneuvers, the plane is once again going to get light on the lines. IT NEEDS SPEED. This is why I'm suggesting not to use engine offset unless you have to. It's one more hurdle you need to overcome.

9.        Your handle is equally as important. You made no mention of your lines that your flying with. I personally fly these on .012's 35' long handle to centerline of plane. I also use Spectra Power Braid. Your handle spacing where your lines exit your handle should be no greater than 2", if so, your over controlling the plane. This becomes worse if the builder used the innermost hole on the bellcrank. This makes the surfaces deflect too fast. So verifying this is important, unfortunately it means cutting into the plane sometimes. Ken

Thanks, Ken, for the detailed, informative reply. I was hoping you would respond as I know you fly these combat planes. This plane appears to be covered with silkspan. I'm not sure if it will tighten up by heating, but I will definitely check for warps and follow your advice.

I was flying it on about 38 feet of 15# test Spiderwire. There was very little line tension even in level flight. I could see the lines were bowed from drag. There was no glide after engine stop. The lines would go slack, and the plane would nose up and stall.
I was using a 6x3.5 prop. I do have a 5x3, and will try that.

Thanks again.

When using a heat gun with silkspan, be careful. It will work but wave the gun and don't hold it on one spot too long. You can easily burn a hole in it or even worse set it on fire. When they burn up, they go fast. Last weekend, I was lighting a tissue covered Jetex plane. The model instantly went up but I managed to save it.

        Having your plane pitch up is a bit concerning lending itself to a tail heavy condition. However, I would follow the CG advice I offered and try again. If the plane is tail heavy enough to cause the nose to pitch up after the power cuts would suggest to me that you wouldn't of been able to fly it level. It would've been hunting all over going up and down. What I feel that might be happening is that due to the bow in the lines you mentioned, it's pulling the up line causing the elevator to make the plane pitch up.

         Old school wings can be quite funny. Nothing like modern flying designs. Taking off is usually the most difficult part. Until the plane gets up to speed about 3/4 of a lap its a wild ride. Your line length is also a bit concerning as 38' is not out of the question length, it's just that it makes the plane slower when flying on 35' lines.

Ken Cook wrote:When using a heat gun with silkspan, be careful. It will work but wave the gun and don't hold it on one spot too long. You can easily burn a hole in it or even worse set it on fire. When they burn up, they go fast. Last weekend, I was lighting a tissue covered Jetex plane. The model instantly went up but I managed to save it.

        Having your plane pitch up is a bit concerning lending itself to a tail heavy condition. However, I would follow the CG advice I offered and try again. If the plane is tail heavy enough to cause the nose to pitch up after the power cuts would suggest to me that you wouldn't of been able to fly it level. It would've been hunting all over going up and down. What I feel that might be happening is that due to the bow in the lines you mentioned, it's pulling the up line causing the elevator to make the plane pitch up.

         Old school wings can be quite funny. Nothing like modern flying designs. Taking off is usually the most difficult part. Until the plane gets up to speed about 3/4 of a lap its a wild ride. Your line length is also a bit concerning as 38' is not out of the question length, it's just that it makes the plane slower when flying on 35' lines.

Well, Ken nailed the problem. The wing is warped. Sighting down the trailing edge, the right side is warped down and the left side is warped up. That's got to be why the outboard wing wanted to come up. I had decent flying weather tonight after work, and no time to try to straighten the wing, so I tried something else. I put a trim tab on the outboard wingtip.
I know that's not standard practice, but I thought it was worth a try
.


Surprisingly, it did help. I was able to fly out three tanks of fuel. The plane was much more controllable, and the line stayed tight, even up high in wing overs. It would also glide after engine stop.
After the third successful flight, I made two more attempts but the plane went back to immediate loss of control on launch. I think because the hinges pulled out of the stab, and I didn't notice it until after the second crash.



The second crash was when the engine came off.



Those little wood screws just weren't up to the job. Broke the prop too.
The plane is fixable, and I had a ball flying it, so I'm not too bummed about the damage.

I flew the Snip again tonight. Had about a 50/50 immediate crash to successful flight ratio. I accidentally looped it right after launch on one flight.
I had to replace the stab and elevator. They were both cracked pretty badly. Those plastic hinges were too thick for the original balsa, so I used cloth hinges this time, and basswood instead of balsa.



I used a 5x3 prop this time, and put a rubber spinner on to cushion the crashes (hopefully). I've got two #4 washers between the backplate and firewall on the inboard engine mounting lugs.



I need to come up with a better engine mounting system. Those wood screws just don't do the job. They came loose a couple of times. Also had the backplate to crankcase screws come loose once while in flight. She dumped her fuel and quit running when that happened.

So, I got a few flights in, hopefully learned a bit more about flying it, and didn't need a trash bag when I was done.
The Snip lives to fly another day.

That's cool the trim tab worked for you Imay have to do that to my RM , the wing has a warp in it last time i checked it , Then it caught on FIRE with a fuel related insodent But it was repairable .. What i have done before with fuel soaked engine mount holes (not saying U have ) Is to clean up holes good and wood glue some toothpicks in there to refill the holes with a harder wood . What size screws are you using ? I think 1/2" length is appropriate.. You could also put a 1/16" lite ply block behind ur mount . The plane still looks good even after some ruff fly-ins .