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Old Mar 10, 2015, 09:53 PM
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Question
Miss Kat Brat P51

I haven't looked through other forums on this, so I'll ask here as it is related.

Jim Vornholt designed a cool looking semi scale P51D Mustang particularly for pattern competition. It look good too. I wish I had picks to download, but I hope the following ling will bring you too it on facebook of all places. Scroll down to see it. https://www.google.com/url?sa=t&sour...w6zOG7We-l7Rjg

It was published in 1977 plan# 682.

Any opinions or experiences? I'd love to know.

Brian
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Old Mar 10, 2015, 10:03 PM
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Brian,

I know I have the magazine article on this. PM me with your email and I will scan it and send it to you if you want it. I believe I have the plans for it also if you decide to build one.
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Old Mar 10, 2015, 10:07 PM
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I'd appreciate the article. Thanks!

Sending you my info.

Brian
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Old Mar 10, 2015, 10:15 PM
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Brian,

Got it.

Leo
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Old Mar 10, 2015, 10:52 PM
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Leo,

no doubt your copy is better than this one but here's the article. Scanned plan leaves a bit to be desired. A good full size copy would be great to study. First impression: thick wing!

Brian,

downloaded and assembled from the link you provided...

Thanks for the read!

David
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Old Mar 10, 2015, 11:25 PM
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http://www.outerzone.co.uk/plan_details.asp?ID=5213

There's a link to the full size plans.

The wing is pretty thick. Easier to set up retracts though. Lol!

Thanks David.

Brian
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Old Mar 11, 2015, 12:29 AM
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I always wondered whether it'd be a handful with that pointy LE
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Old Mar 11, 2015, 08:41 AM
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Much better quality - thanks Brian!

I enjoyed reading the article last night. However, after thinking about it a bit, he mentions this is a 98% stand-off scale P-51 in planform except for the wing center section which he rendered semi-symmetrical in order for it "to fit" under the radiator scoop... Other than that, his pattern rendering I believe involves setting up the model at 0-0-0... I'm not sure how much this constitutes a classic pattern model but I suppose its all in the eye of the beholder.

Interestingly, the reference to pregnant guppies existed all the way back in '77! Funny to think that in the late seventies, some thought of models like the Curare, Arrow and Deception as pregnant guppies. They would be horrified if they had seen the pattern designs today!!

While the model is a nice and simple design including the provision for an inverted engine and properly placed fuel tank, personally I can't see this as being a good substitute for its contemporary brethren of the era like the pattern designs mentioned above. It is too short coupled and the thick sheet tail surfaces (mostly stab) don't agree with my idea of a good pattern ship. As far as a stand off scale model though, it looks like a great design - simple and effective! I can only envision a 90 4s or e-power on this design as a muffler or pipe sticking out the side would break all idea of both a pattern plane and a scale model on a P-51D IMO! Maybe a drop down header to put a pipe under the wing. A RE 60 engine might work too with some center wing mods and a thinner foil.

I can see the empennage being substituted for 1/2" sheet virgin foam (1/2" balsa is darn expensive especially when you are cutting out most of it and laminating 1/4" balsa is heavy and unnecessary) sheeted with 1/32" balsa - no need for 1/16". I like all the formers being either 1/8" ply or balsa. I would likely substitute some of them for lite ply. Fuse sides from 3/16" (or 1/8" if e-powered) and definitely 1/32" ply doublers as shown on the plans (not 1/16" as discussed in the article) for glow or lightened 1/32" (or 3/32" balsa) for e-power.

Not a big fan of "half wing plans" on semi-symmetric wings so I'd draw myself up a proper one and cut those ribs (and formers) with a laser to build it up in a jig. But... I would also likely return the wing to fully symmetric and go to 95% stand-off scale by reducing the airfoil thickness (and drag)...

The pointy wing LE is easy to sand out if desired.

What can I say, I'm a compulsive plan dissector.

David

P.S. 4-blade 3.5" P-51 spinners are hard to come by but Tower does carry a DB 2-blade. Maybe TT can custom make one (likely for the same cost of the models wood!)
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Old Mar 11, 2015, 08:53 AM
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Awesome response David!

It raised a few eyebrows for me as well. The designer also suggested using 1/8 balsa fuse side rather than the 1/4.

Whether or not it would be competitive, and I have doubts, it has some fun potential.

Fun read to read your response David. Thanks!

Brian
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Old Mar 11, 2015, 09:41 AM
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Quote:
Originally Posted by doxilia View Post
Much better quality - thanks Brian!
+1, that is a very clean scan.


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Originally Posted by doxilia View Post
As far as a stand off scale model though, it looks like a great design - simple and effective!
I was thinking the same thing. Even if it's not really a full on pattern model it sure looks like an excellent sport scale model.


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I can see the empennage being substituted for 1/2" sheet virgin foam (1/2" balsa is darn expensive especially when you are cutting out most of it and laminating 1/4" balsa is heavy and unnecessary) sheeted with 1/32" balsa - no need for 1/16".
I would build up the core from sticks and sheet it with 1/16" myself, but I do agree that taking a big piece of 1/2" balsa and then cutting out big chunks of it is wasteful and likely pretty heavy. It is hard enough to get nice, light balsa in thinner sheets, let alone 1/2" sheet.

I would also go with 1/8" fuselage sides. Current 2m pattern models use 1/8" and they work with big gas motors and extremely high power loadings. It should be more than adequate on a .60 sized model, especially with a 1/32" ply doubler in the front part of the fuselage.


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What can I say, I'm a compulsive plan dissector.
It makes me feel better to know there are others out there that do the same thing. I can't look at a plan without thinking how I would change things to my liking.


Mark
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Old Mar 11, 2015, 09:46 AM
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I'm sure I have the plans and article but have not looked at them in years. Am I correct that sides are curved? Might be something to consider.
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Old Mar 11, 2015, 11:15 AM
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I would build up the core from sticks and sheet it with 1/16" myself...
Mark,

yes, that would be another excellent alternative. Thing is skinning 1/2" flat foam is just so darned fast! And with 1/32" balsa, pretty light. If the model is covered, lightening holes through the foam and skins can also be made. Making holes in the foam alone is not a good idea with the thin skins but it could be done if skinned with 1/16". Frankly, 1/32" without holes is just as light with a couple of thin strips of CF under the skin - and the model can be glassed and painted!

Quote:
I would also go with 1/8" fuselage sides. Current 2m pattern models use 1/8" and they work with big gas motors and extremely high power loadings. It should be more than adequate on a .60 sized model, especially with a 1/32" ply doubler in the front part of the fuselage.
2m pattern is built a little differently than we build classics and uses a composite (glass/balsa/CF) stressed skin approach. Also, many of the designs use e-power so that requires much less structural strength. A 30-40cc gas motor requires considerably more tie-in with the fuse and a serious engine box unlike the e-powered versions.

That said, this plan and design could be built in the same stressed skin manner using 1/8" balsa sides even for 4 stroke glow. My first inclination would be to glass the inside of the fuse sides but since the formers are curved, a pre-glassed inner side won't do unless the sides are previously molded (I'm thinking aloud here...). A few tricks could be used to stiffen it if needed but honestly it doesn't look much different in design concept to Ron Chidgey's latest TT4 which also uses 1/8" sides and is designed for a 90 4s. Either 1/8" firm balsa formers or thoroughly lightened 1/8" lite ply in the rear. Keying all the formers with a 1/4" stringer along the side top would be helpful during construction in light of the curved formers which makes using a tab in groove key a little more complicated.

Quote:
It makes me feel better to know there are others out there that do the same thing. I can't look at a plan without thinking how I would change things to my liking.

Mark
Good to know there are similar victims out there Mark! After all, we do have 40 years wisdom on these designs...
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Old Mar 11, 2015, 11:36 AM
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...I am going to have to put this into my building cue. It will be a nice distraction from my Bridi obsession.
Building a foam core is perfect.
How about airfoiling the horizontal?
Great feedback. Anyone else feel they're going to be building one soon?

Brian
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Old Mar 11, 2015, 11:46 AM
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Quote:
Originally Posted by doxilia View Post
2m pattern is built a little differently than we build classics and uses a composite (glass/balsa/CF) stressed skin approach. Also, many of the designs use e-power so that requires much less structural strength. A 30-40cc gas motor requires considerably more tie-in with the fuse and a serious engine box unlike the e-powered versions.
I agree that E-power is easier on the airframe. I was referring to several of Mark Hunt's designs, the Insight, Hindsight and Pentathlon. They use 1/8" balsa sides with a heavily relieved 1/16" ply doubler from the wing tube forward, but no carbon at all and they have been very successful with gas and glow power. You do have to be careful how you support the motor box with gas power, though and soft mounts are a necessity.

Dick Hanson used to build very light Cap 232's (among others) with gas power and no soft mounts, but I am not at all in his class when it comes to building (or flying, for that matter) and I don't have the time to build piles of airframes to experiment on as he did.


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Keying all the formers with a 1/4" stringer along the side top would be helpful during construction in light of the curved formers which makes using a tab in groove key a little more complicated.
I hadn't looked closely enough at the tail formers. Those curved sides would definitely make things trickier. I think I would be tempted to add a small flat to each former for indexing the sides before having to curve and clamp the top and bottom edges in place. Your stringer idea would be very helpful as well, keeping things straight and true while wrestling with the sides. I can't imagine trying to get 1/4" balsa to meet those formers, even 1/8" can be stubborn enough at times.


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Great feedback. Anyone else feel they're going to be building one soon?
I might add it into the queue but the list is many years long at this point. It is a great find for a sport scale P-51, looks much, much better than the Top Flite kit design I was expecting to build at some point.


Mark
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Old Mar 12, 2015, 07:40 AM
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How do you guys think heat will affect the on board equipment? I would imagine the fuel cell will block a lot of it.
Curious about cooling.

Brian
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