P-51C at ~70% scale as ultralight?

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Tangoavenger

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Mar 28, 2021
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I just went back and read this thread from the beginning.

A few comments.

Totally off topic, but I think a standoff scale Mitsubishi A5M perhaps with a 3 cylinder radial, would be a nifty project.

Getting down to pt103 weight is a challenge, Period.

The Shetland Pony plane is great! Cartoon vs. Authenticity? Give me cartoon. I really really like it. Inspirational.

Someone already suggested a silhouette scale model approach without the weight of an enclosed fuselage. Tube & gusset, fabric covered. The Ultracruiser long wing is proven, and you can paint the Mustang taper on or better yet, faux paint where you just suggest it's tapered. For example, white tapered paint on leading and trailing edge, and polished in the Mustang wing outline shaped area. That eliminates the actual root leading edge extension for the retractable gear you don't have, but keeps the look. Paint the bombs on the underside, etc. ....

re: medical & licences.

If you've never Failed a Class 3 medical exam, then you can self certify for a Light Sport licence if you have a valid driver's license and just don't brag about your problems. Ethically, & personally, both of us are mortal, doomed, and "might" have a medical condition that might cause us to fail a Class 3. Ethically, if either of us... Any of us, thinks we might be a danger to others, for example a condition that causes unexpected blackouts, then we shouldn't fly, or drive a car, which is far more likely to harm others. Other conditions that might cause us to fail a Class 3, like Heart Disease or Diabetes, require personal, individual, judgment calls.

My OPINION is that if, for example, your condition is controlled, so you are unlikely to pass out, go comatose unexpectedly, then go have fun. You might die of a Heart Attack? Lots of people will. With no warning. So ask yourself, is that a possibility? Or a certainty? ( don't respond with answers! These are semi-rhetorical questions to ask yourself ) My call is to stay within my Real physical limitations. Not feared ones.

I spent a few years on blood thinners, and the prescribing Doctor warned about bruising and bleeding issues. He didn't want me to continue doing full contact martial arts. ( SCA armored historical combat ) That made sense. He also didn't want me to ride a motorcycle, or bicycle. I might fall down! That is excessive caution IMHO, YMMV.

I don't need to know your medical history. Use your own informed judgment. You may be just fine flying Light Sport where your medical history isn't anyone 's business, unless you crash.

keep on dreaming.
Was messing around for a couple minutes with your idea of Mustang shaped outline on Hummel wings. Looks promising, thanks! 1617232880298.png
 
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Tangoavenger

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3-way comparison:
Ultracruiser
shortened 65% P-51 caricature
65% P-51


Now, the caricature I've been trying to work at, to cut weight, has the same wing and tailplane as the 65% scale P-51, both of which have significantly greater tailplane area than the Ultracruiser.
I have a deposit on a Hummelbird, which is only 46 pounds over FAR103 with an 86 pound VW engine, so I'm thinking about an engine swap and going ultralight. I've been toying with some paint ideas and thought of you: 1618557166282.png
 

MadProfessor8138

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I have a deposit on a Hummelbird, which is only 46 pounds over FAR103 with an 86 pound VW engine, so I'm thinking about an engine swap and going ultralight.
A Hummelbird will not make Part 103 for a few reasons.......ask me how I know.
1. Too heavy
2. Too fast
3. Stalls too fast
4. Fuel.....you can work around that.

There are other Hummel designs that will meet Part 103......but not the Hummelbird.
Been there and gave up on that after a few years and many different components & engines later.

Kevin
 

Tangoavenger

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A Hummelbird will not make Part 103 for a few reasons.......ask me how I know.
1. Too heavy
2. Too fast
3. Stalls too fast
4. Fuel.....you can work around that.

There are other Hummel designs that will meet Part 103......but not the Hummelbird.
Been there and gave up on that after a few years and many different components & engines later.

Kevin
Thank you Kevin. I was thinking I would swap in Ultracruiser wings, maybe redo just the fuselage skins in lighter aluminum like the ultracruiser, and with a 30lb 2 stroke engine (ZDZ500), I think I'd be okay, but it's a lot of work/changes
 

Bigshu

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Thank you Kevin. I was thinking I would swap in Ultracruiser wings, maybe redo just the fuselage skins in lighter aluminum like the ultracruiser, and with a 30lb 2 stroke engine (ZDZ500), I think I'd be okay, but it's a lot of work/changes
I mentioned a similar idea to Terry Hallett, but with H5 getting lightened up. He said that there are enough changes that his suggestion was just pick up UC plans. Discount for repeat customer?
 

Tiger Tim

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Using the Hummel Ultracruiser as a start, would it be feasible to leave the lion’s share of the wing alone but make tapered ailerons/flaps? That way the spars and ribs stay unchanged (and un-tapered for simplicity) but the wing planform is a little more Mustang-y than the Hummel’s Hershey bar wing.
 

karmarepair

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Using the Hummel Ultracruiser as a start, would it be feasible to leave the lion’s share of the wing alone but make tapered ailerons/flaps? That way the spars and ribs stay unchanged (and un-tapered for simplicity) but the wing planform is a little more Mustang-y than the Hummel’s Hershey bar wing.
Your reward will be TERRIBLE aileron response. You want you ailerons big at the wingtips, to maximize their moment arm on the roll axis.

The Thatcher CX-4 tapers the ailerons like this, and the Only Fair aileron effectiveness is one of the few complaints about this airframe.
 

Riggerrob

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Colin Thatcher designed CX wings for his favorite style of flying: docile. Since he wanted to make the airplane easy to fly - for low-time pilots - so Colin designed for a slow roll rate.
Pilot reports also concur that CX-4 is one of the most docile tail-draggers.
In conclusion, Thatcher's CX-4, -6 and -7 series do exactly what they are designed to do.
 

Marc W

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The Thatcher CX-4 tapers the ailerons like this, and the Only Fair aileron effectiveness is one of the few complaints about this airframe.
The "Only Fair" aileron response is not because the ailerons are tapered. It is because the inboard end of the aileron matches the airfoil contour, which is fine as far as it goes. However on the shortened outboard end of the aileron, the top surface follows the line of the airfoil contour and the bottom surface is angled upward, away from the airfoil contour. This is a recipe for flow separation on the bottom of the aileron. When deflected downward, the outboard end of the aileron is ineffective as it travels through the dead air behind the rear spar until it reaches clean air along the bottom line of the wing.

I fixed that problem on my CX4. I made new ailerons with a longer chord. I made the outboard end of the aileron to fit the airfoil contour and lengthened the chord of the inner end of the aileron. My ailerons are crisp and light. Instant response!

The Thatcher roll response has nothing to do with the taper. It has everything to do with the detail design of the taper.

Colin Thatcher
is really Dave Thatcher.

Edited to add that I also made my new ailerons thicker than the wing at the rear spar to try to keep the flow attached. Something worked because they work great!
 
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