Photos of 90% Ultimate for IPS Dual - RC Groups
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Nov 14, 2003, 05:08 PM
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Photos of 90% Ultimate for IPS Dual

Hi Foamies,

Here's my latest effort on the Foamie front. It's loosely based on Tim Hart's Ultimate Bipe, scaled to 90% to better suit the IPS Dual drive. At this scale the wing chord looked worryingly small, so I increased it to 160mm (6 1/4"). It's all 3mm Depron, coloured with Sharpie pens.

I wanted someting that would hide the gear and look a little better than a profile model, so I simply cut two fuse sides and spaced them one E-Tec width apart with Depron bulkheads. A bit more work, but worth it for the better looks. I used 0.4 x 2mm carbon flat top and bottom of both wings.

690mm (27") span
160mm (6 1/4") chord
30mm (1 1/4") aileron chord
IPS Dual B, 1180 GWS prop
2 x 1200 E-Tecs
3 x no name 5g servos.
Jeti Rex 5 RX
247g (8.7 oz) AUW

On this set up it will hover for most of the pack. It flies really nice indoors, the transition in and out of hover is particularly smooth and drama free. It does nice tight loops and rolls, and flies inverted with almost no down elevator required.

The big surprise is how well it flies outdoors. For it's size it eats up sky, doing big tumbling stuff, but can also be flown right up close. I test flew it on a very windy day (20 mph +), but whilst not much fun it was always in control.

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Nov 14, 2003, 05:12 PM
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I increased the tail areas a bit, to match the wing chord increase.
Nov 14, 2003, 05:15 PM
Registered User
The "canopy" area has 6mm depron bent to the side profile, glued between the 3mm sides, then sanded to a rounded shape. The fuse top in front of the canopy was done by bending 3mm Depron around a broom handle.
Nov 14, 2003, 05:33 PM
Trapped in California
foamflyer's Avatar
Hey Salto, great looking plane! What do you mean by IPS Dual? Is it dual ball bearing? Which drive is it (the A, or B, etc)? Good thinking on the use of Sharpie pens. I recently found a silver Sharpie and want to use it to try to simulate panel lines.

Nov 14, 2003, 05:40 PM
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Ralph A. D'Amelio's Avatar
I believe he means dual motor ips....flies the TM great with lopos.
Nov 14, 2003, 05:47 PM
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I used the IPS dual RXC (7.2V) motors mounted on a B gearbox. See

I used this motor/gearbox/prop combination to keep the current down and the flight time up. The motors draw about 3.4 Amps (total) on 7 Volts so the power is about 24 Watts. I get bored before the pack runs down, and the motors should last forever.

Nov 14, 2003, 05:51 PM
Registered User
Some more figures on this model.

Wing loading: 3.7 oz/sq ft. - nice, slow stall
Power loading: 44 Watts/pound - could be better, but still hovers!!
Energy loading: 15.45 Wh/lb - flies forever!!

Nov 14, 2003, 06:17 PM
GenesisCreation's Avatar
Congratulations on a great looking plane Salto!
Nov 14, 2003, 06:54 PM
RCGroups Author
SoarNeck's Avatar
Hey Salto, great looking model! I've been tempted to build something like this for our upcoming winter season, and was wondering if you would be able to give me some more measurements. I know next to nothing about designing biplanes, so I'd like to get some details from a model that clearly works well.

Could you tell me:

- distance from the LE of the bottom wing to the backplate of the spinner
- distance from the TE of the bottom wing to the LE of the horizontal stab
- stab root chord, tip chord, span
- fin root chord, tip chord, span
- sweep of the wings
- separation distance of the wings.

If you wouldn't mind, I'd be really grateful!
Nov 14, 2003, 07:15 PM
Registered User

Have a look at this link, and download Tim's plans for the Ultimate Bipe

I simply printed this plan out at 90% scale. I added 10mm on the LE and TE of both wings, made the aileron chord 30mm, and kept everything else important pretty much the same except the stab and rudder/fin which I scaled up about 20%. I also dropped the balanced tail surfaces because I thought they would be too susceptible to damage. And of course, I made two 3mm fuse sides instead of the single 6mm profile on Tim's plan.

Next build I will take out most, if not all of the sweepback to get rid of the strong yaw to roll coupling, and adjust the wing position to keep the balance right. I guess I'm waiting to see what Tim is doing about this before proceeding. I'd also do balanced tail control surfaces and increase the elevator area some more to get better elevator authority in high alpha manoeuvres.

I hope the above link, plus these comments answer your questions. If you want more info just ask.

Nov 14, 2003, 08:27 PM
RCGroups Author
SoarNeck's Avatar
Thanks for the reply - I didn't realize that this was based on an available design. Too much time in the sailplane and High-Performance forums...or is it that RCGroups has too much interesting info on it?
Nov 28, 2003, 10:53 PM
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poobs's Avatar
Feb 10, 2004, 06:35 PM
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Hey Graham.

How does it knife at that weight ?

Feb 10, 2004, 07:35 PM
Registered User
Hi Michael,

It knife edges well, I guess because there is plenty of rudder authority and side area (and power). Plus with the biplane configuration and central, zero Deg. thrust line all the thrust and drag forces are nicely aligned.

In level flight the swept back wings produce a strong yaw to roll coupling - the model can be flown on rudder only (no aileron) quite easily. At zero angle of attack on the wings, as in knife edge, this coupling will drop to zero, but the entry to knife edge can be a bit tricky. I usally lift the nose a bit first, then drop in a bit of down elevator as I roll over and enter knife edge. If I don't get it right, the yaw to roll coupling will slowly screw the plane out of knife edge.


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