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PS: What is that?

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PS: What is that?

Post  flyjsh on Tue Oct 21, 2014 1:51 pm

Is it a cricket bat?


Perhaps a mock up of for a new submarine....



Ooops, upside down, Embarassed errr ummm, the view from below



Maybe an airplane? (Flying inverted) Embarassed




Yes, indeed, it is an airplane:  the P.S. aka The Prop Saver.  I found the plans on Outerzone http://www.outerzone.co.uk/plan_details.asp?ID=2713

I made a few changes.  First off, being a solo flyer, I added tundra tires.  Wanting to make it easier to store, I used rubber band mounting for the wings, and pegged the vertical stab.  If the plane flies well, I can make additional stabs and mounts that I can swap in the field and voilà!, a flying test bed!  




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Re: PS: What is that?

Post  pkrankow on Tue Oct 21, 2014 2:07 pm

So....how well does it fly?

Phil
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Re: PS: What is that?

Post  flyjsh on Tue Oct 21, 2014 2:24 pm

I don't know yet, but I am betting better than I do Very Happy I need to get some lead under the canopy: with the engine placement, it builds tail heavy.

FYI, the canopy is cut from the "shoulder" of a Sea Breeze bottle http://www.seabreezeclean.com/
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Re: PS: What is that?

Post  flyjsh on Tue Oct 21, 2014 7:27 pm

So much for the flying testbed idea. DAMMIT! An unproven plane, unproven engine, and a marginal pilot: me trying to find level, engine hiccups, power on smash and go, and the stab rips out. The small area of the two dowels I used was insufficient, and they ripped clean out the bottom of the stab. Only cosmetic and field reparable damage otherwise.

The article sad it would be heavy and slow, and from that short flight I agree.
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Re: PS: What is that?

Post  Cribbs74 on Tue Oct 21, 2014 7:43 pm

If at first you don't succeed...

Hey, at least you tried. Glue it up, fix the problems and go again!

Ron
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Re: PS: What is that?

Post  roddie on Tue Oct 21, 2014 8:11 pm

That's a radical engine mount! I like the 45 degree "diamond" look. Fairing that back; as geometrically neat as it looks, must have taken some time. Does the plan specify this?

IMHO... that vertical-stab/engine pylon.. needs to have some "integrity". Maybe glassing would help.. but that fin needs to be mounted rigidly to the fuse. The weight of the engine dictates the strength of the mount. Maybe 1/8" birch-ply epoxied into a fuse-slot.. and/or gluing-in square-stock rails either-side of the joint for support would help prevent separation when stressed.

Did the model seem "controllable" at any point? Could the wing saddle be moved back any.. With that fuse.. you have a lot of options/area to try to incorporate "rails" into the wing-attachment.. and hook & loop mating-surfaces, to lock any lateral movement for dialing-in the ultimate CG. The rubber-band attachment-system is still desirable. With the aid of rails.. and the hook & loop's ability to "hold" a linear position.. it takes some of the stress off a "rubber-band only" style of mount.
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Re: PS: What is that?

Post  flyjsh on Tue Oct 21, 2014 10:15 pm

roddie wrote:That's a radical engine mount! I like the 45 degree "diamond" look. Fairing that back; as geometrically neat as it looks, must have taken some time. Does the plan specify this?

IMHO... that vertical-stab/engine pylon.. needs to have some "integrity". Maybe glassing would help.. but that fin needs to be mounted rigidly to the fuse. The weight of the engine dictates the strength of the mount. Maybe 1/8" birch-ply epoxied into a fuse-slot.. and/or gluing-in square-stock rails either-side of the joint for support would help prevent separation when stressed.  

Did the model seem "controllable" at any point? Could the wing saddle be moved back any.. With that fuse.. you have a lot of options/area to try to incorporate "rails" into the wing-attachment.. and hook & loop mating-surfaces, to lock any lateral movement for dialing-in the ultimate CG. The rubber-band attachment-system is still desirable. With the aid of rails.. and the hook & loop's ability to "hold" a linear position.. it takes some of the stress off a "rubber-band only" style of mount.

Yes, the plan uses that mount. I initially thought of scraping it, notching the stab, and mounting a TD, but I thought the model needed that visual element. As to its neatness.... black hides imperfections. I tried to do it exactly as the plans had described, but ended up just eyeballing and sanding.

The fuse is slotted all the way through and the stab inserted. Since I am going to glue it in, I probably will add gussets.

It seemed very nose heavy, but the cg was pretty much spot on. It seemed to have more down authority than up (to be safe, I'll add a guide for the push rod to reduce any flexing). I like the idea of velcro attachment! Never thought of that. Aside from moving the cg (or reducing the amount of ballast), how will shortening the distance between the wing and elevator affect handling? On one hand, it shortens the arm of the elevator giving it less authority. On the other, it seems like it could make it twitchier Huh...
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Re: PS: What is that?

Post  flyjsh on Tue Oct 21, 2014 10:17 pm

Cribbs74 wrote:If at first you don't succeed...

Hey, at least you tried. Glue it up, fix the problems and go again!

Ron

Oh, she'll fly again. Except for the stab, I could have field repaired her.
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Re: PS: What is that?

Post  RknRusty on Tue Oct 21, 2014 10:23 pm

1959, eh. There wasn't so much of a box to think outside of back then, so anything could be tried without so many naysayers. Looks aerodynamically feasible to me. If you can get a steady run out of that cantankerous Bee.
Rusty

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Re: PS: What is that?

Post  roddie on Tue Oct 21, 2014 11:07 pm

I thought that being able to adjust the wing fore/aft would allow you to play with the CG without adding weight. This isn't an option with a conventional fixed-saddle/mounting. Yes.. it will change your moment-arm.. but that could be advantageous.
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Re: PS: What is that?

Post  pkrankow on Wed Oct 22, 2014 7:23 am

Is the bell crank in the wing or fuse? If it is in the removable wing I see a few problems if locating pins or some other solid attachment is not used. If it is in the fuse, then an adjustable tip guide might be in order, but the lines should be in the same place with respect to CG so the tip guide is less needed.

Nose heavy models fly poorly, tail heavy models fly once. Start nose heavy.

Phil

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Re: PS: What is that?

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