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Author Topic: Mark Drela Corsair  (Read 4051 times)
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dwidrick
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« Reply #50 on: June 12, 2018, 11:27:25 AM »

Cant wait to see more of your fine work! Looking good!
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David
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« Reply #51 on: June 13, 2018, 01:42:59 PM »

First time building a radial engine...0.413g.

Regards
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_shadow_
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« Reply #52 on: June 18, 2018, 12:24:58 PM »

Wings done, the sliced rib will be added later.

Regards
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dwidrick
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« Reply #53 on: June 18, 2018, 07:13:23 PM »

Looking good Shadow!
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David
Alan Mkitarian
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« Reply #54 on: June 18, 2018, 08:14:26 PM »

Shadow,

      I first saw Mark as a 13 year old when he flew this model at the Bridesburg gym in Phila. where I still fly.

  It had retracts on it and as it rose off of the deck the gear tucked up in the wing.  He would not show us how they

worked.  Shame and because of that I never tried a peanut...  Alan
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_shadow_
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« Reply #55 on: June 19, 2018, 01:16:48 AM »

Alan,

He teases with the word 'retracted' in his article. I'm considering making removable landing gear.

David, is F9 a joke? Can't find it anywhere in the plans.

Also, i have installed the scoops a bit pre-maturely, will need some adjustments later.

Regards
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dwidrick
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« Reply #56 on: June 19, 2018, 06:11:38 AM »

I Cant say i ever found F9 either! I didn't bother with W9, just made sure tissue was glued to ribs about were W9 would have been. It flows in nicely! Got to say Shadow, yours looks a lot better than mine at this stage and am sure it gonna fly good!
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David
dwidrick
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« Reply #57 on: June 19, 2018, 06:18:08 AM »

I have built Marks Bubble Dancer,Apogee,and both flew great. His builds are not for the hurry up and fly type but more to detail and good workmanship. Would and will build more of his designs in the future!
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David
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« Reply #58 on: June 19, 2018, 06:47:31 AM »

I Cant say i ever found F9 either! I didn't bother with W9, just made sure tissue was glued to ribs about were W9 would have been. It flows in nicely! Got to say Shadow, yours looks a lot better than mine at this stage and am sure it gonna fly good!

David,

There is provision on the article/plan  to add a piece of 1/16 x 1/32 strip at the bottom center of the wing for tissue attachement, this strip glues over W9, which is kinda weird. Maybe i'll leave out W9 as well.
Also was thinking of making W7 inline with the LE.

Thanks for the kinds words Smiley

Regards
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« Reply #59 on: June 19, 2018, 11:41:07 AM »

David,

Here is where I am right now, tack glued the wings.

Seems like i would need to move the wings (at the spar/LE) further up. Somehow the spar ended up right below F3, it should just behind it.

Should the air-scoop / LE touch the wing saddle?

Rough check shows maybe 1 -1.5 deg of positive incidence at thw wings.

Regards
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dwidrick
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« Reply #60 on: June 19, 2018, 06:19:11 PM »

The 1/32x1/16 strip goes under W9 and spar leading edge goes behind F3 and the scoop does touch wing saddle! From looks of it you are close with air scoops. Don't know if you can see clear but hopes this helps!
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David
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« Reply #61 on: June 19, 2018, 08:38:37 PM »

The 1/32x1/16 strip goes under W9 and spar leading edge goes behind F3 and the scoop does touch wing saddle! From looks of it you are close with air scoops. Don't know if you can see clear but hopes this helps!

Thank you very much!

Alan, I got a reply from Mark Drela re the retractable landing gear.

"It was kind of a Rube Goldberg system.  The rear rubber hook was on a coil spring on the rear peg, which also had two thin threads attached to it.  When the rubber was wound the spring would put slack in the threads.  The threads ran to two 0.005" wire spring clips which when slack would retain the sprung LG struts in the retracted position.  When the rubber was nearly unwound, the threads would tighten, pull on the clips, and thus release the LG struts.
It sorta worked OK, but required lots of adjustment.  Cool, but a lot of work and trouble.
MD"

I need to decipher this ( or someone else?) , a diagram would have been easier  Grin

Regards
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« Reply #62 on: June 20, 2018, 05:40:14 AM »

My interpretation of Mark's description is:

The rear rubber anchor peg was tensioned by a coil spring pulling it back to wards the tail. As the spring moves the peg backwards - it pulls on 2 lines attached to release clips on the  UC legs, releasing them and allowing their own light springs to lower them and lock them down.

When the motor is fully wound - it pulls the rear peg forward - causing the 2 lines to stay slack and thus for the UC to stay retracted, maintained there by the clips.

Thus the model would be launched, wheels up and at a particular point on the motor run down, the spring on the rear peg would over ride the rubber tension, and release the UC clips allowing the legs to drop for landing.

It would take considerable adjustment to get the legs to come down at the right time (before landing preferably Smiley) and this could only be done after the model had been trimmed and the final rubber size determined.

As Mark mentioned - lots of work and more weight as well.

Hope this is accurate and that it helps. I can't imagine too many 13yr olds doing this today.

It's a nice model BTW

John
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dwidrick
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« Reply #63 on: June 20, 2018, 06:42:19 AM »

I don't know about you but to me it was a challenge just to build the plane let alone putting on retractable gear! Smiley
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David
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« Reply #64 on: June 20, 2018, 09:20:45 AM »

My interpretation of Mark's description is:

The rear rubber anchor peg was tensioned by a coil spring pulling it back to wards the tail. As the spring moves the peg backwards - it pulls on 2 lines attached to release clips on the  UC legs, releasing them and allowing their own light springs to lower them and lock them down.

When the motor is fully wound - it pulls the rear peg forward - causing the 2 lines to stay slack and thus for the UC to stay retracted, maintained there by the clips.

Thus the model would be launched, wheels up and at a particular point on the motor run down, the spring on the rear peg would over ride the rubber tension, and release the UC clips allowing the legs to drop for landing.

It would take considerable adjustment to get the legs to come down at the right time (before landing preferably Smiley) and this could only be done after the model had been trimmed and the final rubber size determined.

As Mark mentioned - lots of work and more weight as well.

Hope this is accurate and that it helps. I can't imagine too many 13yr olds doing this today.

It's a nice model BTW

John

That makes more sense..but there is still the other half of the
mystery, the rotation of the struts.

Regards
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Hepcat
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« Reply #65 on: June 20, 2018, 05:50:06 PM »

In #54 Alan said he remembered seeing the ‘Corsair ‘ taking off and then the wheels retracting. In #61 Alan mentioned further information which said the flight started with wheels up and they lowered for landing and this was achieved by attaching the motor hook to the motor peg with a spring so that as the motor ran down the hook would be pulled backwards and then lines attached to the hook could release the undercarriage. 
As Shadow had said he would like a sketch to make things clear I started doodling away last night as I read what was said and the result was the horrible scribble below. Immediately below the horrible scribble is another one I started this morning intending to draw something sensible but I realized immediately that it was hopeless.  How would the tension spring be fitted safely and accurately to the motor peg. How would a tension spring resist the torque of a wound motor and ‘thrashing’ of the unwinding motor. I have left the sketches to amuse you and to wonder if anyone else admits to doing such scribbles.
A long time ago it was quite common to see drawings of moving motor pegs operating things like incidence changers.  IIRC the motor peg was ‘hinged’ in one fuselage side and moved in a fore and aft slot on the other side, with a spring pulling the motor peg back in the slot as the motor ran down. Obviously one can run a line from the moving end of the peg to operate other things.
John
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« Reply #66 on: June 20, 2018, 06:59:05 PM »

I must admit John(Hepcat) by Alan's remembering the ROG, but Mark appeared to imply the reverse. However I wouldn't be too surprised if Mark had come up with a system to raise and lower the UC!

I think I would use the spring to pull the peg back in slot, to avoid problems with the thrashing rubber motor?
There could then be a small(very) light screw adjustment at the fuselage anchor for the spring perhaps.

All more than a challenge for a 13" WS Peanut.

Shadow - I think I would be flying it wheels up if I were you.

Rotation of the UC struts? You're pulling my leg?

John

John
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flydean1
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« Reply #67 on: June 20, 2018, 10:40:15 PM »

On the Corsair the main gear rotated 90 degrees to lie flat in recesses in the wing.  Similar to F6F Hellcat and P40.
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« Reply #68 on: June 21, 2018, 04:19:15 AM »

A challenge and a half on a peanut Corsair though FD. Smiley

John

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« Reply #69 on: June 21, 2018, 05:05:11 AM »

4.1g as of now, hope the end up between 9-10g.

Regards
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Snaky Stringer
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« Reply #70 on: August 11, 2018, 07:03:59 PM »

The gear retracting or lowering system described sounds very like that on the Sterling P47 I built a long time ago. On that model the gear was sprung and released by a T-shaped wire attached by thread to a sprung rear motor hook.There was a sliding carrier for the thread on the centre section of the wing. As the motor ran down the wire T was pulled back and released the gear, which then snapped down. It didn't look very convincing but worked. I believe the plan is available in the gallery. Sterling models also dropped bombs and fired rockets.  Obviously it would be more complicated with Corsair gear, which would also have to rotate as it swung back into the well. I have considered having a go, but perhaps not at Peanut scale.
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« Reply #71 on: August 11, 2018, 07:08:00 PM »

The Sterling P-47 in question is Kit A4 and is in the gallery.
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OZPAF
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« Reply #72 on: August 11, 2018, 07:43:27 PM »

That nice shot of your bones really emphasises how light Drela's structure is. Not much there for the tail plane.

John
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« Reply #73 on: August 12, 2018, 01:52:47 AM »

The gear retracting or lowering system described sounds very like that on the Sterling P47 I built a long time ago. On that model the gear was sprung and released by a T-shaped wire attached by thread to a sprung rear motor hook.There was a sliding carrier for the thread on the centre section of the wing. As the motor ran down the wire T was pulled back and released the gear, which then snapped down. It didn't look very convincing but worked. I believe the plan is available in the gallery. Sterling models also dropped bombs and fired rockets.  Obviously it would be more complicated with Corsair gear, which would also have to rotate as it swung back into the well. I have considered having a go, but perhaps not at Peanut scale.

Thank you...it's so much easier to understand the mechanism now.
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« Reply #74 on: August 12, 2018, 01:54:26 AM »

That nice shot of your bones really emphasises how light Drela's structure is. Not much there for the tail plane.

John

Thanks...i dread covering it, although it turned out pretty strong ...will continue soon to complete it.

Regards
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