Redwulf__34

Hey Bob,
Your right about your leading edge. I'll try to find the info I had. I had a great article someplace on leading edges. If I can find it again I'll post it. It went over all the differences in various leading edges.

Sean

N1EDM

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I remember someone making the analogy of putting your hand out the window (like we used to do when we were kids) and how twisting it just a bit made it go up and down 'with vigor' to simulate a 'sharp' Leading Edge.

But, if you balled your hand into a fist and tried the same thing, the result would be very different (blunt Leading Edge).

Good analogies - I wish I could remember who wrote that... was it you, Bob??

Bob

Mustang Fever

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Bob

I'm old, but not that old.

Riddle4U

I fly high performance sailplanes also. For years I have always sanded the last ten percent of the wing (toward the tip) to be a more blunt round shape with a progressively more streamlined (bullet) shape toward the root. This keeps the wing tips flying after the root has stalled in many cases. In this case you may avoid a spin, yet still notice an incipient stall that is visually apparent but perhaps recoverable. I tend to do this on my power planes also. The washout accomplishes basically the same thing if anyone is wondering. A little of both isn't a bad idea, and you can sand a more streamlined leading edge as you go toward the root to keep drag down (still with good stall charachter). Full size Corsairs, and many other aircraft incorporate a "stall strip" on the leading edge which also improves stall charachteristics (snap/spin).

smkrcflyer

Hi guys,
My son and I will both be building one of these. He's building the D and I'm building the B. I had intended to use a 120 4C but after reading Mustang Fever's posts on the OS 120 AX this looks like a good way to go. Thanks for all the information on this kit.

Mustang Fever

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That's great, smk.

Just so nobody misunderstands- don't use that silly Robart 121 retractable tailwheel. It is not near strong enough for a model like the 1/7 Mustang. I wish now I had built the fixed TW per the instructions. I nearly lost the airplane because of that crumby piece of plastic. Those big 531RS mains with struts, though, are perfect.

I'm getting the Sullivan fixed unit to replace it with, since I don't want to cut the plane apart. I'll mount it on a ply plate between the formers, and stick the hairspring on it and attached the other end to the plate so that it can castor, but the spring will try to keep it straight. Bums me out, but the original bird didn't have a steerable TW, either, so what the hey [:-]

Riddle4U

Thank you for the advice Bob. It is too late for me though... I'll have to take my chances?! I guess I'll hope the rudder has enough authority to keep'er straight. Just what fails on that Robart retractable piece? Do you have a pic of it broken? I have it installed in my old Royal .60 Zero also. Thanks, Eric

Mustang Fever

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Riddle:

I don't have my camera with me, but the right turn part of the steering arm broke off and the pivot broke away from the mounting bracket on the right side. Instant left turn. When I get it out I'll take a pic of it. The theory at the club is that I hit a goose turd. The place was carpeted with them.

smkrcflyer

Bob,
I read about 80% of this thread and I have made some notes. There was some concern over the CG. What is the correct CG? Is what shown on the planes correct?

Mustang Fever

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Steve:

I ended up using what the plans and instructions said, but I also lengthened the airplane by 1/2" at the TEs of the stab and fin. I ended up with considerable down trim after the first flight, with the gear up, about 3/16" at the widest part of the elevator. This says to me that the bird is verging on tail heavy, given the huge amount of downthrust that is built into it. I would suggest that you go about 1/4" ahead of the recommended C.G. point to begin with, then move it back. (Or maybe just balance it a few degrees "nose low" at the recommended point.) You'll find that with gear and flaps down, the bird is very docile and has plenty of elevator authority at the recommended throw, and will land so slowly that I don't believe being a touch nose heavy will be a problem.

Be prepared to pump in some down trim after retracting the gear. Mine with the gear down and flaps up wants to go nose low, but then steadies out after retracting the mains.

I almost forgot- I ended up with a fair amount of right aileron trim and some right rudder as well. This may be due to the tremendous torque of that 1.20, but be ready for it to turn left on you after takeoff.

Riddle4U

Not being critical in a negative way, that left turn incident would seem more related to unexpected torque effect (amongst three major left turn tendencies inherent in prop planes), than the TW?. I can't imagine a broken tail wheel careening the plane to the left, it just doesn't have that much impact on a tail dragger, traction wise. Particularly at any higher airspeed the rudder controls everything not the tailwheel! Just my opinion, but having flown even full scale tail draggers the tailwheel just doesn't have much authority on direction after the first two or three seconds of takeoff (i'm thinking two seconds). That said the P.O.S. apparently broke, that is sad. I certainly think they would have beefed it up if it happened a lot? They have made that part for thirty years after all. I am just puzzled (no..I don't work for robart..lol). I hope I have better luck, but you may well be right in your assesment of that part. I know thousands use it (in reading TF Mustang threads alone). ..Things that make you go Hmmmm? -Best wishes

Mustang Fever

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Riddle:

She wasn't going very fast, as I was feeding the power in really slowly. The tail hadn't even tried to come up.

smkrcflyer

Has anyone put a GMS 1.20 2C in this plane? Its putting out 3.3 HP at 13,000 RPM. The weight with muffler is 31oz. And at $140 the price is good.

Mustang Fever

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I've never used GMS, but it would probably perform about the same as the OS 120. I don't think you'd want to run it at 13000, tho. Put a big prop on it and keep it around 10000.

thedeuce

Hey,

Does anyone know anything about the bob violet T-33 retracts that are recomended if you want to install inner gear doors? Is anyone putting inner doors on?

John

Mustang Fever

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John:

There's some guys who have done it and made them work, but there's been no flight reports on those birds.

The pics and info are earlier in the thread, which is kinda big.

Riddle4U

the Deuce, I am someone to talk to on those BVM retracts and inner doors. I have put my TF on hold for some years, and we all understand how that happens. I also bought the BVM cylinders for my inner doors. Also, I bought an electronic piece that times the cycle for the P-51. I think the Bob Violett (BVM) suggestion was a pretty good suggestion. I just have to be honest and say I haven't finished my Mustang yet. I think their suggestion was good, and I followed it. I don't have a full, functional test of it yet though, is all. I have posted some pics here (albeit a year ago), I suggest reading the whole thread if you care. I know we are all a bit lazy, but there is a lot of existing knowledge on these threads! When I make my fiberglass doors (inner and outer), I will document them here. I am also trying to participate in a project here....It is named " Royal 1/6th Corsair group build" (well that is my memory of our name). Please check out the thread. We are scale nuts! I just wish we were moving faster on our builds, personally. Good luck, Eric!

thedeuce

Eric,

Thanks for your reply. I might rack your brain a few times during this build . Do you happen to have the part numbers for the retracts and inner door cylinders you used? Also are the retracts the 85 deg ones? I am for sure going to go nuts on the detail for this mustang. I have a tonne of books, pictures on the mustang. I have decided to do a A-36 version of the mustang(same as B version)(i'm sure you already know that, sorry), and adding the dive brakes into the wings, so i'll have to figure out the mechanics of the and runn them off of a servo or two. I just ordered the 'B' version kit from my local hobby store. I will keep posting with pictures as time goes on.

Cheers,

John

Riddle4U

Yes I think they are 85 degrees. I don't know if they have changed the manual, the manual I have actually talks about the BVM gear and seperate cylinders in a little detail. I think they are actually the T-33 jet mechanical retract mechanism from Bob Violett Models. I would start with their website, I will see if I have the packaging for the inner gear rams, but they are BVM also, and you just need to figure an appropriate length. I will let you know if I run into more info for you. A lot of my pictures were on film when I originally framed most of the kit, so it is hard to provide those pictures. I actually think there are quite a few differences between the A-36 "Apache" and the B model. Including: I think the inner wing break is non-existant (check the 3-views..it is nearly a straight leading edge), guns are all way different, the whole nose of the plane is quite different as it used an Allison engine, and had a scoop on the top of the nose, the location of the Allison prop centerline was lower I think changing a lot of the under nose shape (you probably couldn't use the T.F. cowl), the A-36 has a pronounced reverse curve with two cannon shooting from underneath the nose cowling, the entire "belly scoop" is different shape from back to front (including where it is less pronounced in curve behind the wing leading back to the fuselage, the B and D are longer overall in the nose to boot! Still, you could modify it for all of these differences and it would be very cool to those that can tell the difference; or just build the "B" model! I think the wing, scoop, and nose are the main differences between B and A-36 (and those are big). Really the "razorback" -B model is actually closer to the bubble top -D, then either are to the A-36 (surprisingly..I know). Modifying to that A-36 wing will be quite a bit of work I think (the fuselage root...and all)! Let me know how it goes. - Eric

p.s. I just checked BVM.. my gear is in the retracts section, and is still available. It is carbon fiber/nylon with aluminum link. It is expensive 90.00 a side 180.00 for two (I guess they sell them individually for replacement purposes). I found my old package for the BVM door cylinders: they are #5751 1 5/8" with 1" stroke, they are 27.50 a piece and still available (yea I know..expensive jet pricing). You will probably want to get the 5/8" air rams for operating the main gear mechanism from Robart along with their air control kit (unless you want servo actuated, which might be a thought actually). This is all premium stuff, and most would go a cheaper route

thedeuce

Eric,

Thats alot of great info, thanks so much. I have looked into the differences in the a-36 to the D model, there is a slight change in the wing which will be not to bad to change, luckely the size of the two planes are identical. I have a few pictures i will post soon. My local hobby store doesn't deal with BVM so i will have to go online and order them.

Cheers,

John

Riddle4U

Well, I just measured my three-views and your A-36 is actually a full 17 inches longer, than a B or a D (these look to be good 3-views of both the A-36 and B/D in my book: Production line to Frontline- North American Aviation P-51 Mustang -Osprey publication). I am not sure where that difference is, just pick your reference and go by that I guess. The spec page lists overall size as being essentially the same (as you said). Upon looking at my three-views you WILL need to mold a new chin scoop and toss the Top Flite part. Also you will need to toss the belly scoop part from Top-flite and mold your own (as well as redesign the lower-rear fuselage). Otherwise, you'll just be building a B with a funny inlet on top of the nose. Good luck, and maybe I'll do the A-36 after you've sorted it all out. It is a fresh departure from the usual mustangs and will impress if done nicely! [The 1/6th Corsair I am building is also an early variant]

thedeuce

I didn't think a full 17inches, because like u said the specs are the same. By the way i have the exact book. It's a good one. I guess i have alot of work ahead of me. It will look good though, like u said, different than the usuall D models you always see.

John

thedeuce

Here's a good picture.

Riddle4U

Yes, good picture...now get out your drafting dividers and start measuring to the micrometer (or pretty close)! Remember, all scale models are judged to their source material, and not to a constantly drifting number between factory drawings (never measure the same as the real breathing thing even), and a hundred books about a chosen subject. One of the main rules of documentation is that the factory drawings are often wrong (yup). In all of the beauacracy of war (even in peace), what is left is just sometimes lacking. Measure the real thing, and again you'll often be wrong against the best drawing (yes, the drawing is wrong). You can't present your exact living subject as documentation at a scale contest, though! You present a chosen drawing! If your model looks more like the real thing which is physically sitting on a ramp next to a competition, and in full view of the judge, than the drawings you have presented....well, you lose. That is the case in every major scale contest I can think of. Chances are that our book's drawings are slightly out of scale (but, they're all we got).

My edit here: and John I am not picking on you personally, that is an excellent choice of subject (difficult, a bit, for most contemporary R/C modelers), but I like to see the bar raised....so Bravo on your decision to do something more challenging! Can't wait to see how you modify the kit to match your source (I like that book, out of a number of Mustang sources I have, not that it is difinitive).

Here's fun pics from another book I have (less serious). I guess I'll say reference quoted on request. Two are A-36.

[Edit] second thought- the book is imaginatively called "Mustang" (patterson/perkins-Howell Press), it is full of some really nice photos (trully) and actually some pretty decent info. Sorry, I can't do justice trying to take a picture of a glossy pic (if they were too good I'd get sued). I recommend it for enjoyment (even if the "stunt" pilots in the book are thinking of other enjoyment)!

thedeuce

Eric,

Thanks for the help and info, of course i don't think that you are personally picking on me, i enjoy a good conversation. The more help the better, so don't be afraid to speak your mind. I do agree that i have chosen a hard aircraft to build(modify). I think it will be worth it, and fun to do. I forgot to tell you that i have another book that i have been going by, called, P-51 Mustang by Bert Kinzey by his company called 'A detail and scale aviation publication'. All of the drawings in the back o the book has all of the models from prototype through to the p-51C models.
They are all in 1/72nd scale. Was woundering what you think of this book or have you heard of it?

John