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Author Topic: George Perryman's "Whistler"  (Read 6048 times)
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Peter Hess
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« on: May 03, 2014, 01:28:28 PM »

I am about to start on a pair of Whistlers.  ("Model Airplane News", January, 1965)  The only thing that suggests this design to me is that it is a little funky and should look neat flying.  I have some nice wing blanks cut but before I start hacking away at them I have some questions about the airfoil.  The plan shows an airfoil with a very blunt entry and a shape that looks like an arc with the high point at about 50%.  I don't know a whole lot about HLGs but I do know that this is far from current design criteria.  Other than fidelity to plan, is there anything that would be gained or lost by using an airfoil with a sharp entry, a high point at 25% - 30%, and flat from the high point to the trailing edge.  Perhaps I should make one to plan and the other with a more modern airfoil?  Any comments or suggestions would be much appreciated.
Peter Hess
Canton, CT
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« Reply #1 on: May 03, 2014, 09:33:14 PM »

Perhaps I should make one to plan and the other with a more modern airfoil?  Any comments or suggestions would be much appreciated.
Peter Hess
Canton, CT
I like that idea, and it would be interesting to know if there's a difference in performance between the two.
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« Reply #2 on: May 04, 2014, 07:40:46 AM »

Peter,
Leaving aside any possible aerodynamic arguments the flat rear top side from the 25% point is easier to make, and get both wing panels the same and, more importantly, removes a lot of wood and therefore weight.  That must be good.  As far as a sharper leading edge is concerned I would bet money (well a little bit anyway) that the air molecules would give it a friendly glance and it would remove a little more wood as well.  Just get out the paring knife and get moving.
John
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« Reply #3 on: May 04, 2014, 09:51:28 AM »

From a weight saving and ease of build standpoint I agree with John. Also, the sharp LE/straight from high point to TE airfoil isn't so modern. It was shown in one of the 50s/early 60s Zaic Aeronautic yearbooks and probably pre-dates the Whistler design. Although there have been some later refinements, the original foil still works well.

Peter
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Peter Hess
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« Reply #4 on: May 04, 2014, 07:57:14 PM »

Thanks, folks, for your comments.  And, Peter, you proved the accuracy of my comment that I do not know a whole lot about CLGs.  I appreciate the information.
Any further comments or suggestions would be greatly appreciated.
Peter Hess
Canton, CT
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« Reply #5 on: May 04, 2014, 08:57:31 PM »

Peter,

If you decide to go with two wings, one original and one modern, I would like to see the comparison. I have long felt that until CAD and laser cutting came along, we could only approximate airfoils making all of the subtle variants of little consequence. I even remember reading in a biography of a famous modeler/designer how he would only plot a couple of points of the airfoil and fill in the shape using his size 9 Florsheim shoe as a curve. To me, it seems that major changes in airfoil shape would of course make a difference but subtle changes would have little or no effect. The sharper entry should be less drag and therefore more speed. This is a topic I know very little about but interests me none the less. I look forward to your findings and possibly learning more about this from this thread.

Mike
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sweepettelee
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« Reply #6 on: May 04, 2014, 10:09:18 PM »

Peter,
I agree with the early responders, re airfoil changes, but two points come to mind.
Firstly, airfoils accuracy of early plan drawings was notoriously inaccurate. 
In fact, I think it was Prof George who famously said some of his airfoils were traced from his size 10 boots!
Secondly, my 'HLG historian spies' :-) have said the OCD (Oakland Cloud Dusters) started the trend of 25-30% HP in conjunction with flat angled front &
flat from HP to TE. With some variation, most HLG/TLG/CLG models today fit that general set of airfoil parameters.

Current trend is for a bit more upsweep(aka, Philips Entry) & carrying it out more toward tips combined with generous tip washout.

Leeper
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« Reply #7 on: May 04, 2014, 11:35:25 PM »

Thanks for the history "tid-bit" there Lee. It's quite interesting. I wonder, was Joe Foster using any Phillips entry on his indoor HLG's during the 1950's?
The sharp LE, sharp HP, flat bottomed, flat backed airfoil is still an enigma for me; but it seems to work well for indoor especially.
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sweepettelee
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« Reply #8 on: May 05, 2014, 12:34:18 AM »

John, etal,
Joe Foster's 52 Nats winning IHLG had a moderate
LE radius to the best of my knowledge, but no Philips
entry per se.
I have always wished I could have spent more time
learning @ Joe's elbow. He was my mentor & taught
me so much in a short time.
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Peter Hess
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« Reply #9 on: May 05, 2014, 04:20:24 PM »

Leeper:
Thank you for the information.  The last sentence of your message of yesterday notes the use of "generous tip washout" and that leads me to ask the following:  Is the washout generally achieved by sanding it into the tip or by skewing the dihedral joint?  Or, is it a some folks build it in and some folks skew the dihedral joint kind of thing?
Thanks in advance for your input.
Peter Hess
Canton, CT
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sweepettelee
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« Reply #10 on: May 05, 2014, 06:47:36 PM »

Well Peter, this is my third attempt at answering your query! It seems HPA went dark for reboot in middle of my postings...

Where was I?...Oh yes, Peter, I use each method in moderation, to paraphrase Confucious.
Recently, We/I are using more LE upsweep out closer to tips.
This demands sanding more from the TE @ tips to be able to achieve true washout.  Tips now take on the 'Tater chip look', since by definition,
washout means the TE must be at higher angle relative to LE of adjacent panel. 
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« Reply #11 on: May 06, 2014, 09:47:18 AM »

Just as a general remark, I've flown the Whistler in several sizes, and it's a nice forgiving airplane. Start with a little incidence, say .25 deg differential between wing underside and stab, and add small gurney flaps to the stab TE as needed for further incidence adjustments (or use a modern fuse with carbon boom so you can adjust with screws, which is much better). Mine flew left-left very reliably. They did not like a reversal of direction between climb and glide (meaning right-left), perhaps a function of the large tail volume. I'm told that similarly proportioned gas models are known to do the same thing (think Civy Boy, as well as high-thrustline designs). Might also be a function of the low-mounted rudder.
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Peter Hess
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« Reply #12 on: May 06, 2014, 10:03:28 AM »

Lee:
Thank you for your persistence in getting your last message posted.  Your information was very helpful.
After reading the message it dawned on me that lurking in a box of "stuff" that came to me through several intermediate owners was a copy of the plan for your Sweepette 19 that I had "filed" for future reference.  Studying your plan in conjunction with your posts above was very informative.  If my renewed fascination with HLGs persists it will all be very useful as I build up my glider chops to the point at which building a Sweepette with an  expectation of some degree of success will not be unreasonable.
Thanks, again, for your help.
Peter Hess
Canton, CT
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« Reply #13 on: May 10, 2014, 02:59:50 PM »

I just stumbled on this thread and I'm building a couple Whistlers I started yesterday. I plan on trying to make them catapult jobs using the notch on the fuse.  I don't fly competition, just sport fly and my throwing arm is shot.  The plans don't show a balance point.  Any suggestions to a starting point for balance?.
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« Reply #14 on: May 16, 2014, 06:45:31 PM »

I guess George wantedus to figure it out ourselves. He would say "you never know for sure how the model will fly until you get it outside and put it into the Laboratory". My wood might be very different from yours and so different results are very likely. He was always trying new ideas. After all he built models and also did the same when the models for the Lockheed wind tunnel over in Georgia. He was amazing.He solved a very serious problem when the C-130 was first being flown. He told them to adjust the trailing edge of the wing and when the suggestion worked out he told them it was just an old free flight model trick. Ever hear of washout?

NASA told George his wingtip design was far more efficient than theirs. He had some of the Reno Air Racers convinced to use the tips on their aircraft but he passed away before I got his report.
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« Reply #15 on: May 17, 2014, 06:41:53 PM »

Thanks Flyace for the response.  I haven't fooled around much with HLG or CAT gliders (or FF for that matter!). I made a lead nose weight for the first Whistler and the CG is around 50%.  I'll do some glide tests and adjust with some clay.
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« Reply #16 on: May 18, 2014, 06:44:53 PM »

Well, I took my first Whistler out today for some glide tests and a couple cat shots.  It needed a little nose weight and i started tweaking the trim to get a left glide.  I was trying to get a R launch and a L glide. My launches were kind of a big loop and then transition to a L glide.  My big mistake was being too anxious to get it in the air.  I had a couple test launches and was getting close to feeling like i almost knew what I was doing, when on the last launch, it caught a little lift, the wind took it a couple hundred yards directly into the trees and tall blackberrys.  Gone...the next one I'll wait for more favorable conditions.  I had fun tho, and that's what it's all about! Smiley
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« Reply #17 on: May 18, 2014, 10:24:40 PM »

I sure am glad you had fun with your Whistler. If you would like to try another ff from his glory days I would look for a kit from Sig that was named Mini Maxer. He was happy to recomend the kit for me back in 1993. He designed  a P-30 that was lazer cut and I think  BMJR kits and sells it. The MiniMax is smaller and is not lazer cut. He designed models and they always looked very different from anybody elses.

I hope your Second Whistler sticks around for many more flights.
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« Reply #18 on: May 27, 2014, 05:11:42 PM »

Here is Whistler Take 2.  She weighs 25.1grams with fluorescent paint on the tips and stab and clear dope sprayed over everything.
Finished it this weekend and haven't test flown yet.  I added a hook for cat launches.
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Re: George Perryman's "Whistler"
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« Reply #19 on: May 27, 2014, 05:29:00 PM »

Glad to see the finished Whistler. Do you have the tips painted also on the bottom?

This design just screams for others to make it happen.
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« Reply #20 on: May 27, 2014, 06:26:14 PM »

I just painted the tops. Hopefully to help find it in the tall grass.  It's a cool design.  I am putting the Speckled Bird on my bucket list, i love George's designs.
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« Reply #21 on: May 27, 2014, 06:47:27 PM »

Here is Whistler Take 2.  She weighs 25.1grams with fluorescent paint on the tips and stab and clear dope sprayed over everything.
Finished it this weekend and haven't test flown yet.  I added a hook for cat launches.

Nice, but I hate to tell U that U can expect the fin to be knocked off when it flies past your fingers at launch...
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« Reply #22 on: May 27, 2014, 08:59:31 PM »

I kind of figured that.  I slit the center of the fuse with a dremel slitting saw blade in my drill press and CA'ed a strip of .014 unidirectional carbon fiber that extends about a 1/2" past the stab.  I hold on there for launch so I'm behind the fin when I let go.  Maybe don't get all the available stretch out of the rubber but it worked on Whistler #1.
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« Reply #23 on: May 27, 2014, 09:27:53 PM »

here is a pic of the tail with the CF insert
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« Reply #24 on: May 27, 2014, 09:45:08 PM »

My bad, I forgot about using a stinger grip...hmmm, that carbon bit is skinny, so I hope you have strong gripping fingers.
Of course U might glue some 100 grit sandpaper to the stinger sides...so u can expect to sand a slot in your fingers as U let go...a joke, kinda...
Stan uses grippy gloves sometimes for TLG, so there's an idea.
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