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General control line discussion => Open Forum => Topic started by: Sheldon Hartwell on February 10, 2011, 06:34:43 PM
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Hi fellow C/L'ers,
After spending some time on this forum and reading the amazing feedback on questions posted, I thought that I'd finally put one of my questions to the people of the Stunt Hanger. My question is:
I'm currently building a Sig P-51 Mustang; you know, the one with the foam wing cores. I've gotten rid of all of the the plastic components and made the balsa replacements. Each has been weighed and been well under the originals. ( I've weighed them. ) After all of this, she still feels like, excuse the expression, a real porker.
As per the instructions, I,ve already drilled it out for a Fox 35 ( and I had one on hand ). Is this going to be an adequate powerplant, or am I in trouble? I've built profiles for the same power rating and this is like night and day as far as the weight of the aircraft. Believe me, at this stage in the game, any input would be greatly appreciated.Thanks.
Marauder
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When I built mine, I also threw out all the plastic stuff. I hand picked the 1/16" wing sheeting too. However, I think the Sig foam cores are solid except for the two tunnels drilled for the leadouts. I tossed those in the trash too and used a set of much lighter triple cored wings.
I think a Fox 35 will be plenty of power if you can keep the plane under 45oz. (That's kind of a guess). The lighter the better! Mine weighs a tad under 41oz and uses a Brodak 40 so power is not an issue.
Just continue with your Mustang, but be very aware how much weight is going into it. It's a very small model, under 500 sq in. I think.
Post progress!
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Have you allready sheeted the wing? I just built one for my brother for chirstmas and it too is heavy. My brother got a new enya 40 xzs from Randy. He said that you could prop it to put more air over the wing. I had this set up for a fox 35. this motor will fit in the beems, and if you use the back holes for the front and drill new back hole you may only have to sand the nose ring a little. I even got the cowel to work out good. We think with paint it is going to come out at about 40oz. A lot of the weight was the wing. the skins were put on long ago. You can make it lighter by putting the epoxy on with a seringe along the front and back and a x patter in the center. We did this in rc and we could drop about 4oz. A liquid oz of epoxy is a lot more than a oz weight.
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How about cutting out parts of the wing aft of the high point. Do triangular holes (it will look like the latest geodetic structure, an added bonus) so that the wing will remain torsionally rigid. You ought to be able to get rid of several ounces that way. Lay it all out, use a forstner bit to do the corner holes, then connect the dots with a coping saw and very fine blade.
An alternate is to hot wire in bigger cavities in the wing. You already have starter holes!
Or do both! y1
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Ahh what's the weight ???
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I have seen two of these fly that flew very well with Fox 35's. I do not know what they weighed, but the Foxes were plenty of power. One is Jim Lee's, and the other is Mike Donovan's. Of course, you have to take into account that these guys can fly very well.
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I've had two of the SIG Mustang Stunters. Had to wait on the first one as the ad was in the magazine before kit was ready. Was built box stock and powered with trusty Fox .35 Stunt. It flew well for me until the bellcrank platform pulled loose. The second one was also built box stock except the pivot bolt for the bell crank was made longer to go past the sheeting. Was also bushed inside the wing to keep it centered. No plywood in the wing. Once in the fuse I put plywood plates over the pivot bolt/rod that fit inside the fuse sides and epoxied to the sheeting as well. Put many flights on that one with the old trusty Fox .35 Stunt. I think weight on both planes was 42 ounces ready to fly. By the way never hogged out the foam core either.
Now if you do a search for Jim Lee in the members section and PM him, he might tell you how to make a super stunter out of it. I think Todd won at the NATS with it in Senior and Advanced.
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Heres what I did to lighten my Mustang. After getting rid of plastic parts, and forming new balsa parts built new cowl and cut out wing as shown.
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I glue balsa to cores with Aliphatic resin, takes longer to cure and is MUCH lighter than the epoxy.
I have one of Sigs P-51s that came already built from a friend.
A little heavy on the scales, feels like a brick in the hand and with an S.T. C.35 and 10x6 it feels light in the air.
I was only able to put in a few flights while finishing breaking the engine in so this spring will see how it turns.
David
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As was mentioned, Jim Lee has some excellent, easy to do, mods for the Sig Mustang Stunter. Todd did win some NATS events, IIRC, with one and we built one using Jim's mods. I did not have a kit, but a set of "cored" wings and the kit plans. All I have heard of the kit, it flies well but can build heavy "out of the box".
Big Bear
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Hey guys,
Thanks for all of the input that you people have sent me so far. As per your request, I'm posting a few pictures of my progress at this point. As you can see in one of the pictures, the plane weighs in at about 25 oz. at this stage. I'm pretty far along in the construction as you can see , so there's really not a whole lot that I can do as far as weight reduction.
The finish on the plane is going to be a doped on silkspan with clear followed by the colored dopes as necessary. I haven't decided on a paint scheme yet.
Again, any info is greatly appreciated.
Thanks,
Sheldon
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Looks like you're too far along to change much now. I'm wondering if you did anything to beef up the landing gear, or did you just epoxy those blocks into the wing? Also, I can't tell if you made an engine crutch or assembled the nose as per plans. I notice the nose ring is the same width as the fuse (no taper). What size spinner is that going to use?
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Hi Clint,
Yes, the landing gear was one of my first concerns when I started building this kit. I wasn't too crazy about all of the landing loads being put in compression with the foam core alone and also the fact that the foam was the only thing holding the landing gear blocks in place. So what I did was to put ( 4 ) plywood sub-ribs ( approx. 1/3 of the chord ) into the foam wing core basically putting a saddle in ( 2 ) places over each landing gear block. This way, the ( 4 ) sub-ribs have to act in a shear function as well as compression.
The nose was built pretty much stock with the exception of a support for the fuel tank. The nose ring has just been glued-on at this stage, nothing on the entire airplane has been faired-in at this point. As for the spinner, I haven't even tackled that yet, just like the paint job.
Thanks,
Sheldon
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Hi Sheldon,
I think it should com in at a weight you can live with. Just don't go using a full gallon (before thinning ) for the clear coats like Championie does! LOL!!
Wow, paint schemes............ WWII markings from several countries , and there are hundreds of USAF WWII schemes. Korean War Markings, Israeli desert camo (sand and spinach with baby blue undersides) is awesome, civilian and air racing (which can be your own "phantom" markings!). Hard to pin it down! I liked Col. J.D. Landers' WWII ETO "Big Beautiful Doll" over 40 years ago before the Top Flite ARF R/C kits hit the market.. ;D Then there are the checker tail and checker nose squadrons, the OD/Neu. Gray like the "Tangerine", The "American Beauty" w/yellow and red striping, "The Millie G', OD/yellow/grass green fuselage w/aluminum wings and tail surfaces. Literally hundreds of great looking "fighters" alone! On my Rabe Mustang, I am going to use the Millie G scheme but substitute my Wife's name "The Patricia G". ;D
Big Bear