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Old Jan 14, 2009, 09:01 PM
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sammy's Avatar
United States, SC, Okatie
Joined Jan 2002
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Jim or Mark- any estimate yet on the all-up weight and loading? For the amount of power you are talking, I would guess a load of 10-12 oz./ft sq., which would mean a weight of 40-50 ounces, assuming a wing area of around 4 sq. ft.
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Old Jan 14, 2009, 09:51 PM
Flying electric since 1986
Mark Wolf's Avatar
USA, IN, Brownsburg
Joined Oct 2000
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553 sq. in. Estimated weight 60 ounces for 15-16 ounces per sq. ft.
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Last edited by Mark Wolf; Jan 15, 2009 at 06:56 AM.
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Old Jan 14, 2009, 09:56 PM
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Jim Young's Avatar
Brighton, MI USA
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I estimate the AUW closer to 60oz. on the high end based on my other designs similar in size. With ~3.8 ft^2, the wing loading should be around 15oz/ft^2 which is right in the ballpark for a bipe. Anything lighter and it would be a real kite.

Power should be more than sufficient. The Scorpion 3020-14 should draw around 30 to 35A at 10V. That's 80 to 90W/lb! I remember when we only dreamed of such power loadings!

-Jim
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Old Jan 15, 2009, 06:54 AM
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Mark Wolf's Avatar
USA, IN, Brownsburg
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Only 90 watts per pound? Don't you know planes can't fly with so little power? How am I supposed to hover?
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Old Jan 15, 2009, 08:40 AM
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Ken Myers's Avatar
Commerce Township, MI
Joined Aug 2001
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I'll hold your plane vertically for you while you make zoom, zoom, swish sounds. I'll even run up and down the flight line right in front of the other pilots for you. We wouldn't want to miss a chance to annoy them.
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Old Jan 15, 2009, 09:54 AM
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Mark Wolf's Avatar
USA, IN, Brownsburg
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See you in July!
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Old Jan 15, 2009, 04:22 PM
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USA, MA, Longmeadow
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Quote:
Originally Posted by Mark Wolf
Horizontal stab and elevators ready for hinging. Once I finish the hinges, I'll cut the elevators free and then cut both the elevators and stab in half at the center. The halves will plug into tubes fixed in the vertical stabilizer.
Based on the above, am I correct in assuming that the design requires two elevator servos?

Mark
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Old Jan 15, 2009, 05:11 PM
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Mark Wolf's Avatar
USA, IN, Brownsburg
Joined Oct 2000
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Quote:
Originally Posted by buzzltyr
Based on the above, am I correct in assuming that the design requires two elevator servos?

Mark
Using two servos isn't required, but that is my plan. One could use a single servo with a split pushrod arrangement or join the elevator halves through the vertical stab and use a more traditional set-up.
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Old Jan 16, 2009, 11:18 AM
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Jim Young's Avatar
Brighton, MI USA
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I recommend one HS-65 for the elevator and rudder.

-Jim
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Old Jan 16, 2009, 11:52 AM
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Thanks Jim and Mark for the insight. But wouldn't some additional hingeing be required, beyond capturing the elevator dowel in the fuselage somehow? Just curious!
As shown in the pics, the only hinge seems to be the strap at the outside corners of the elevator.

Mark
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Old Jan 16, 2009, 12:33 PM
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Mark Wolf's Avatar
USA, IN, Brownsburg
Joined Oct 2000
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Quote:
Originally Posted by buzzltyr
Thanks Jim and Mark for the insight. But wouldn't some additional hingeing be required, beyond capturing the elevator dowel in the fuselage somehow? Just curious!
As shown in the pics, the only hinge seems to be the strap at the outside corners of the elevator.

Mark
The vertical stab and elevator joiner tube is the center hinge point.
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Old Jan 16, 2009, 06:14 PM
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USA, IN, Brownsburg
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Rear fuselage construction begins with the crutch, which as I've posted before is two pieces of 1/16 balsa laminated with some scrap stick to provide some additional stiffness.



The crutch slides into the fuselage in place of the battery tray. The steps on the crutch locate the rear fuselage formers. The formers are only dry fit to the crutch. Do not glue them! The crutch is only there to hold the formers in place and add support until the the stringers are in place. Once that is done, it will be pulled out through the front of the fuselage.



3/32 balsa braces help hold the formers square to the crutch during assembly:





I blocked up the fuselage so that the crutch was true to the table, then dry fit the vertical stab in place. Once I verified that the stab was square I glued it in place.

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Last edited by Mark Wolf; Aug 03, 2011 at 10:26 AM.
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Old Jan 19, 2009, 04:43 PM
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Mark Wolf's Avatar
USA, IN, Brownsburg
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She's slowly looking like a Waco! I apologize for the slow progress.

After blocking the fuselage up and squaring everything as best I could to the table I began putting the stringers on the fuselage. At this point all the stringers are in place except a few small ones at the top of the fuselage. I wanted to leave myself some access to the rear fuselage until I get the elevator linkage in place.

There are a few places where the stringers go under the fuselage sheeting. In those areas the stringers should be notched to allow the sheeting to contact the formers. I used some scrap ply to make a simple sanding jig. This made the job quick and uniform. Just set the stringer in the slot and sand down to the ply.



Forward fuselage with notched stringers:



I used a few squares and a bunch of magnets to hold the vertical true while the stringers where installed. Did I mention how much I like using magnets instead of pins? When the stringers where in place I pulled the rear fuselage crutch out of the assembly. It worked perfectly! I can even slide the crutch back into the fuselage without difficulty.



Fuselage:





Now for the really cool part of this airplane! On the smaller Waco, Jim used a wooden latch mechanism activated by pulling an eyelet in the cowling. While the sliding tray of the smaller model was replicated in this larger version, Jim decided not to use the same latch and suggested screws. I wanted to come up with a way of securing the tray that was easy to operate and preferably didn't require the use of tools. What I settled on was set of spring loaded pins that are released by pulling the pilot up ~1/2". I drew up some rough sketches first, but most of this was done on the fly and so doesn't have the finished look of Jim's laser cut parts. It does work smoothly though and I think is a neat feature.

I started by making two supports from 1/16 ply, which are attached to the existing fuselage structure. I also incorporated the servo rail mount into these supports. This places the servos higher and further forward in the fuselage than shown on the plans. I did this for better access to the servos and also to put the rudder and elevator linkages more inline with the servos.



An inverted "U" shaped plywood arch is holds the 1/16 steel retaining pins. Some triangle stock helps support the pilot mounting plate on top. The pilot is then screwed to the arch. A small spring from the hardware store holds the latch closed. This arch piece slides in rails glued to the support pieces shown in the previous picture.



Latch in place:



The bottom end of the spring is captured by a piece of 1/8" dowel slipped through the eyelet of the spring. The dowel is held in place by the forward crutch and a few bits of scrap balsa.



To access the power tray just pull the pilot up a bit and hold, slide the tray out the nose and release the pilot. The latch mechanism weighs less than half an ounce (not including the pilot).

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Last edited by Mark Wolf; Aug 03, 2011 at 10:29 AM.
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Old Jan 19, 2009, 08:03 PM
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Dave Grife's Avatar
Coldwater, Mi. USA
Joined Jul 2000
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Hi Mark,

Very cool

-DG
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Old Jan 20, 2009, 05:33 AM
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Jim Young's Avatar
Brighton, MI USA
Joined Jun 2000
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Very Ingenious, Mark! You'd make a good model designer!

-Jim
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