22" Ultimate Biplane for IPS Power - RC Groups
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Oct 27, 2004, 12:07 PM
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P. Tritle's Avatar

22" Ultimate Biplane for IPS Power

I've been looking at my 20" FF Ultimate Biplane for awhile with thoughts of R/C conversion. The original rubber design was published in Model Builder magazine several years ago. It looked like it might be a bit small, and since it needed the R/C mods anyway, I decided redraw the plans to 22". Going up 10% isn't a tremendouse increase in size, but added just enough to make the design "feel" right for a park flyer.
The model has wing area of 165 sq. in, and should build up at 5 oz or less, for a wing loading under 4.5 oz/ sq. ft. It should work good. The p-type will be built for 3 ch. R/C using a 4:1 IPS drive and a 700 2C Lipo.
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Oct 27, 2004, 12:33 PM
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The Tail Section

The tail section is framed using 3/32 sq. balsa. As with the full scale, the tail will be double braced, using fine kevlar thread.
Oct 27, 2004, 12:36 PM
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Fuselage Assembly

The basic fuselage frame is done in 3/32 sq. balsa. The formers are 1/16 sheet with 1/16 sq. stringers.
Last edited by P. Tritle; Oct 27, 2004 at 12:41 PM.
Oct 27, 2004, 12:40 PM
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Motor Mount

The motor mount is a simple 1/16 sheet balsa plate with the motor glued in place using Household Goop.
Oct 27, 2004, 12:43 PM
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I like your craftsmanship! Your build looks very clean and I wish you the best of luck with the project.

I think if it were me I might reconsider gluing the engine. Maybe you could extend the more typical square dowling for the motor mount? I would be afraid that the 'household goop' might give way under flight conditions?

I'd like to see more! Post the plans!

Oct 27, 2004, 12:45 PM
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Finishing the Basic Fuselage Frame

Once the motor is mounted, the stringers on glued in place on the forward bottom. To keep the weight down, no hatch will be added to the front end, rendering the motor inaccessable.
Oct 27, 2004, 12:50 PM
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Ben, I usually glue the motor in using silicone, and so far haven't had any problem, but for this one I decided on Goop because it's much stronger then silicone. The downside with Goop is that you CAN"T get it off, no matter how hard you try. Again, it's a matter of simplicity and weight saving. To use the more conventional motor stick, the second former would have to be solid, as well as a back-up former to support the rear end of the stick.
Oct 27, 2004, 12:52 PM
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Well, you bit the bullet, huh? Just had to have another looper after the Dr1 flight Looks really nice so far. Can hardly wait to see it fly.

Does this mean the YMF5 is on the back burner? Gotta keep you motivated.

Ben, the goop holds very well for these little motors. I wouldn't use it for sp400 stuff, but sp280 and smaller are OK. Not that much thrust. And, with Pat's landings, the props never come near the ground anyway

Oct 27, 2004, 12:53 PM
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The Plans

Ben, Here's a shot of the plans.
Oct 27, 2004, 12:56 PM
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Charlie, The Waco is still very much on the front burner. I'll need to finish up the Porter plans though and get the instructions written before I get too much farther into it though. But that's OK, just keep cranking down the thumbscrews, you just gotta' keep the heat on to keep some guys going! LOL!!!
Oct 27, 2004, 01:01 PM
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Servo Mounting

The Cirruss 4.4 servos are mounted on 3/32 X 1/4 balsa beams supported by 1/8 sq. balsa rails on the fuse sides. The elevator pushrod is a Sullivan #507 tube with a .020 wire pushrod. The rudder will use kevlar thread pul/pull cables.
Hope to get started on the wings today. Will post up the progress as it happens.
Oct 28, 2004, 12:51 AM
Fly it like you stole it..
Tram's Avatar
Oh wow.
Oct 28, 2004, 10:05 AM
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Great bird Pat!

How much dihedral are you using?


Oct 28, 2004, 10:23 AM
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Building the Wings

On these lightweigh models, sanding the trailing edges can be quite a chore, so, before the wings are framed, the trailing edges are pre-sanded. Here's a trick I use that works great. For those of you who already know about this, bare with me, for the rest, I hope this helps.

To make the jig, warm up the Hot Glue gun and glue a piece of .046 wire to the edge of a piece of scrap pine, plywood or particle board. Use some king of straight-edge to insure it stays straight. Using the trailing edge stick as a spacer, align a piece of 3/32 wire at the front edge and glue it to the board. Once the glue hardens, sand the taper into the T.E. stick with a sanding block. Sand all the way down to the wire, which serves as a stop to keep all the T.E. pieces nice and consistant.
Oct 28, 2004, 10:32 AM
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Now We Can Build The Wing

Framing the wing is a simple matter of pinning the spars to the plan, gluing the ribs in place and then adding the leading edge and pre-shaped trailing edges. I didn't glue the ribs at the dihedral breaks until the dihedral was blocked up.
To get the proper dihedral, the lower wing tips were propped up 5/8". The top wing tips were blocked up 3/4". With the tips at the proper hiegth, the remaining ribs were glue in place.
Once the glue has dried completely the wings were removed from the board and sanded to shape.

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