"Little Go Bipe" - 5-6 oz foam biplane; new design, free plans! - Page 2 - RC Groups
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Dec 08, 2006, 12:26 PM
magic612's Avatar
Incidentally, I've noticed quite a few threads about not only biplanes but other foam planes that have a full fuselage. I think this plane could be easily modified to have a more "full" fuselage put on it - it would really just be a matter of adding some formers and some 2mm foam skin. I haven't designed that into the plane, but adding it should be a snap for those with the skills to do so. (And anyone that does, please share pics and/or plans to add it!)
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Dec 08, 2006, 11:53 PM
magic612's Avatar

Landing gear

I was disappointed to discover that the .032" wire I had intended to use as landing gear was not strong enough to support the plane. So, I had to go with the .047" wire I used for the prior design. I was hoping to save a couple grams of weight, especially since it's up front, but I realized that my AUW with a 200 mAh battery was still only 5.25 oz, which is right where I wanted to be anyway.

To attach the landing gear, I first CA'd a small strip of 1/32" plywood to the bottom of the fuse, about an inch or so back from the nose. I then CA'd two small pieces of 1/32" at the aft section of that larger piece of ply. Then I took another longer piece of ply, and made an "open" slot (soon to become a closed slot for the gear wire). I added two pieces of ply along the sides, making sure to CA them to the sides of the fuse as well. Then the pre-bent wire slides right into the slot.

BTW - If anyone has a better and easier way of making landing gear for small planes - LET ME KNOW! This is the one part I seem to have trouble doing - BUT - I also really like having landing gear on my planes whenever possible.

Hopefully the two pics show enough detail that what I did makes sense!!!
Dec 09, 2006, 12:03 AM
magic612's Avatar

Motor mount

This will really depend on what motor you use. If using a brushless setup with a .375" square mount, you're golden and this will be a snap. If, on the other hand, you're using a GWS IPS drive like me, it's a bit more complicated, but not terribly so.

First, using an X-Acto knife, I shaved down a larger piece of balsa to fit inside the IPS gearbox. Leaving a similar length available on the outside, I cut this piece (approx 2" total length). Another piece of balsa was shaved to a 3 degree angle, and the gearbox piece of balsa was CA'd to that. A third piece (about 1/4" x 1/2") is used to keep the gearbox high enough so that the motor fits neatly between the gearbox and the fuselage spar.

If the motor is set so that it sits in front of the end of the fuse spar, the plane's CG would be too far off to balance with just the battery. So be sure to keep the motor over the fuse spar, and the prop no more than about an inch in front of the end of the fuse.

Pic should clear this one up, I hope.
Dec 09, 2006, 12:11 AM
magic612's Avatar


And basically, that's about it. I came in at the weight I intended, and even slightly larger packs shouldn't be much of a problem for it considering the wing area. Here's what I've figured (assuming Common Sense R/C LiPo's):

- With 200 mAh pack / AUW of plane = 5.25 oz, Wing area to weight ratio is 2.8 oz per sq. ft.

- With 350 mAh pack / AUW of plane = 5.50 oz, Wing area to weight ratio is 2.92 oz per sq. ft.

A WOT, the 200 mAh pack should easily provide 6 minute flights (and much longer with less than WOT), and the 350 mAh packs should give approx 10 min flights at WOT. I would imagine 500 mAh packs could be used too, as that would only weigh in AUW's of around 5.75 oz, and approx 3 oz or so per sq. ft. weight ratios.

If I've left anything out of this, please let me know, I'll go back and edit or correct anything necessary. I'm not sure if I'll get a chance in the next few days to maiden this particular version, as winds are suposed to be 15 mph for the next few days, but two prior versions of this have flow successfully, at higher AUW's of about 6.5 oz, so I'm looking forward to improved performance from the lighter frame of this version, as well as the benefits of using Lipo packs.

Any upgrades or modifications that anyone wants to do - go for it! Post 'em here; I'd love to see what others come up with to improve on this plane.
Last edited by magic612; Dec 09, 2006 at 12:21 AM. Reason: spelling errors
Dec 11, 2006, 12:11 PM
magic612's Avatar
Well, the wind didn't cooperate over the weekend for the maiden, and I don't have a place to fly indoors (yet...). Maybe I'll bring it to work with me this week and see if I can give it a spin at lunch. If not, I'll have to wait for next weekend, and hope the weather isn't too terrible then.
Dec 11, 2006, 10:29 PM
Registered User
Patiently awaits news of flight good luck !
Dec 12, 2006, 08:04 PM
Registered User

fuse spar

How long is the Fuse spar ?
Dec 13, 2006, 08:58 AM
magic612's Avatar
Originally Posted by korgroth
How long is the Fuse spar ?
Fuse spar is 18" in length, 3/8" square. (I think the full size plans note this.)
Dec 13, 2006, 03:32 PM
John Cock...tos...ton
Stephan8's Avatar

Too Heavy?

I just started building one last night. All I have is pink fff. I built and assembled the wings, fus and tail. I have not assed rudder, ellevator or any other parts. It weighs now at 2 oz. Will I go over weight. I am ordering a 480 Lipo and have gws brushless.

I will post apic soon but am wondering If I am already too heavy.

Dec 13, 2006, 04:27 PM
magic612's Avatar
That depends on the rest of your gear (radio, motor, servos, battery, etc.). Here's what my "other" gear weighs, assuming my lightest LiPo is used:

Motor/gearbox: 1.06 oz
Lipo (200 mAh): 0.53 oz
Radio gear: 1.15 oz

My plane's AUW is 5.25 oz, so the plane itself weighs in at 2.51 oz. I think you're probably right on target for now. I know this design will fly even at the relatively heavy weight of 6.5 oz (my previous designs used a 1.4 oz NiMh battery pack!!).

Sounds like you'll be okay, especially if you're going brushless. I intentionally designed it to fly with a relatively weak geared/brushed set up. Of course, if you can use a lighter LiPo and lightweight radio gear, that will only serve to help the plane's performance.
Dec 13, 2006, 05:21 PM
John Cock...tos...ton
Stephan8's Avatar
Thanks magic,
I plan on going light as i can with servos, reciever and control linkage. But motor and battery might be a little bigger than you used. But...It does sound promising if yours weighed 2.5. Again...thanks
Dec 13, 2006, 05:33 PM
magic612's Avatar
Anytime - let me know how if flies for you!!
Dec 15, 2006, 09:10 AM
John Cock...tos...ton
Stephan8's Avatar

My Bipe

Well, here are the pics so far. I am awaiting a shipment of esc, servos, small reciever and 350 2s battery. From my calcs so far I should come in at 5.5 oz. But things never finish the way they shold so maybe closer to 5.75 oz.

Anyway, it's been fun so far and I can't wait to maiden in the front yard! Maybe this weekend if stuff comes by Saturday.

Until then I am stuck.

Dec 15, 2006, 09:16 AM
The RC Repairman
amitysanimal's Avatar
Does that pink FFF work as well as the blue? I saw some at my HD and it looked pretty thick to me, probably 3/8" thick. Is that the same as what you used?
Dec 15, 2006, 10:45 AM
magic612's Avatar
Stephan8 - Nice job! Looks great - wow, I must say I'm quite humbled that you liked my design enough to make it yourself.

I noticed that you cut some foam out of the wing supports (to save weight, I assume?). I've never used the pink (or blue) foam before - do you find that with the cuts, the wings still hold the airfoil shape sufficiently? The Depron I used really needed the entire wing support to be glued to the wing to keep it's shape - I'm just curious how the FFF works at holding it's shape with less surface area to adhere to on the supports.

Let me know how it flies for you when you get your radio / battery equipment. In the meantime, you can do some glide tests - CG You should be fine even at 5.75 oz, I would think. That'd be a wing ratio of 3.125 oz / square foot.

On another note, I found some cheapie $0.75 DC motors yesterday, and was thinking of making a version of this plane that's scaled down 70% - those little motors produce 15W of power, so I thought if I used 2mm Depron, I might be able to make a version as light as 3 oz or so, assuming I only used two servos in the 4 gram range (aileron and elevator only - no rudder), and do away with the landing gear, since it'd be so darn light. Plus, I'd be using a 3x3 prop (direct drive) on the motor anyway, so wouldn't need to worry about much prop clearance. AND, as if that weren't enough, I also got a new brushless motor last week, so I considered making a much larger version too.

Too many options, too little time!!!!

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