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Old May 01, 2012, 02:08 PM
Former B52H Crew Chief
aerofly0610's Avatar
Green Bay WI
Joined Feb 2009
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Ambitious project, I look forward to seeing your results... Please by all means show us pictures and videos (successes and failures!).
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Old May 01, 2012, 02:20 PM
pd1
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United States, MA, Haverhill
Joined Jun 2006
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Just a thought, my Sparky came out nose heavy. I had to add weight to the tail to make it fly well. Also I think the rudder area should be increased. I have to add power to make mine turn.
It does fly well and it is relaxing to fly.
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Old May 01, 2012, 03:50 PM
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United States, MD, Elkton
Joined Oct 2011
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Quote:
Originally Posted by pd1 View Post
Just a thought, my Sparky came out nose heavy. I had to add weight to the tail to make it fly well. Also I think the rudder area should be increased. I have to add power to make mine turn.
It does fly well and it is relaxing to fly.
Pd-1 As weird as it sounds,that's why we're investigating this drive system...I won't shorten Sparky's nose,although it's nose heavy....By my convoluted thinking,with the engine at the cabin end of a long shaft,the drive system can be lighter from the windshield forward,(half an engine,hollow shaft) than the full engine at the nose...Overall weight will be up,of course,but the wing and stab are both lifting surfaces,able to support the increased heft.
Doubling the size of the stab should increase it's weight to balance the plane easily.
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Old May 01, 2012, 03:56 PM
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Looking at the rudder size,and with input from Pd-1 (thank you) ,I'm going to increase the size of the rudder twofold,the elevator one and one half again.

I don't always obey wind warnings,so a little additional control will be a comfort.

I'm going to Toy-r us, to look for 5" wooden wheels on a kid's pull toy or such for Sparky.
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Old May 02, 2012, 08:48 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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If you make it a little bigger, the view while flying it will improve immensely

The mid-mounted engine, plus extension shaft, is a fascinating idea. Looking forwards to seeing how it comes along.

D
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Old May 02, 2012, 09:39 AM
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I will share success and failures-FAILURES? HA!, as we move along.

If I can prevent one person from the heartbreak of failure,I will have been successful.

We spoke of a gear reduction at one point.Keep that in the back of your mind.....way back....but retain it.,just in case.

The original Sparky has 1/8" MW single landing gear struts..Knowing full well that won't be adequate for "Sparky too",I designed a double wire gear,with the Classic curved rear leg.I also like the 'arch' I see on some models from one wheel to the other,as a spreader...Functional or not,I'm adding it.

We're 'improving' the basic design as we progress...strong and light.
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Old May 03, 2012, 02:07 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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For this size of model your doubled and "arched" 1/8 wire gear is more than appropriate. In fact if you'd done the main legs in 5/32 it may have been better considering your planned overall weight.

My 84 inch 5.5 lb old timer uses the same doubled and "arched" setup as you've done all in 1/8 wire. It's stiff as a board for that weight and more than enough. With double the weight I'm sure it'll be fine but you can likely expect a trifle more "jello" wobbling as it flexes.

The frame work pictures are looking great! I also see that you haven't shifted the engine back to the cabin yet.
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Old May 03, 2012, 04:15 PM
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Our engine drive system is mocked up on a separate platform,duplicating the 1/4 A/C plate shown in the photos.
Each system will be tested to exhaustion,and will be interchangable for demonstration purposes.
If unforseen problems arise,I'd rather they appear in the garage,than in the air.
Once adequate testing is done,the airframe should act as a "glider', if engine failure occurs,unless the failure takes some structure with it.
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Old May 03, 2012, 10:07 PM
B for Bruce
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The 'Wack, BC, Canada
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Certainly a wise way to proceed. I'm looking forward to hearing about how it works out.

Just out of curiousity are you going to use the suggested helicopter fan and shroud to cool the engine? Or have you got some other idea?
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Old May 04, 2012, 06:50 AM
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The way the nose is designed lends it's self to a partially hidden,large air scoop on the bottom...actually not a scoop,but an open area which doesn't alter the plan view lines.An area appro.3" x 7" can be left open,and with a bit of 1/32" balsa, incoming air can be directed to the helicopter type fan.
Similarly,an area in the aft fuse will be used to exhaust the heated air.
I had done a Topflite P-39 ,many years ago,with a marine head on the engine,and a miniature radiator for cooling.With my limited knowledge and experience at that time,"unsuccessful"didn't accurately describe the failure.
30 years later,large- finned gas engines,and a willingness to add non-scale openings for cooling air,may enable success this time around.
I'm willing to experiment again,but this time with a secondary,back-up ,standard drive system,if the trials fail.Hence the 'bolt-in' replacement.
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Old May 04, 2012, 02:01 PM
Laser Cutter Guy
United States, PA, Greensburg
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Old May 04, 2012, 02:17 PM
My hangar is,... "almost" full
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Old May 04, 2012, 08:33 PM
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United States, MD, Elkton
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I posted a Classified ad for some 5, to 5-1/2" wooden wheels for Sparky..A Gentleman with Laser and CNC as new toys offered to build a pair,enlarged copies of the wheels commonly supplied with Comet kits from by-gone days.His PDF file is at the classifieds site.Nice looking wheel.
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Last edited by epoxyearl; May 04, 2012 at 08:38 PM.
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Old May 04, 2012, 11:49 PM
B for Bruce
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The 'Wack, BC, Canada
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I remember reading about a remote enclosed engine setup for an airplane which used the marine head and some copper tube wrapped around the upper cylinder. It connected to a remote radiator located in the scale position. To pump the liquid a Robart (?) vibratory fuel pump was used. These pumps were mounted to the engine bearers and used the waste energy from the engine vibration to move the liquid.

In a model boat no such pump is required since a simple angled end tube situated to scoop up water from below using the forward speed is all that is needed to move a good volume.
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Old May 05, 2012, 04:47 AM
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United States, MD, Elkton
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Yes- I used that as a 'crutch' for defending my desire to do this experiment.I remember it was on a glow engine.
My major concern is attempting to cool a 50 cc Gas engine with air.in A P-39
I firmly believe,at the expense of scale fidelity,enough cooling air can be routed through the area at the nose wheel doors,back through the fuselage,and around a closely ducted engine.
This 'air tunnel'equates to a jet fuselage in my mind.
Scale prohibits any cooling air exhaust area in the rear,but I'm not a fanatic.....the bottom of the fuselage could be opened enough to allow heated air to escape....A 1" wide slot 10-12" long would certainly suffice,and not be too noticable,except from the bottom.The nose gear area exists already....
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Last edited by epoxyearl; May 05, 2012 at 12:12 PM. Reason: Describe proper aircraft
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