FWIW My latest design.

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deskpilot

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Hi folks. A couple of weeks ago, I received a pm from Billyvray asking for more info on my staggered biplane design. He suggested that I might publish details for all forumites to ponder, criticise or just get a good laugh. :mad2: No, really, he didn't say that. Just joking.:roll:

Anyway, this is the tale so far.

I have designed a few planes before and they always got too complex eg,

Bolt_1st_mockup_front_quarter.jpgBolt_1st_mockup_rear_quarter.jpg The DeMansfield Bolt with it's prop rotating around the tail boom (still love this design but it isn't easy to acheive a safe, un-stayed version.
Twin-boom pusher2.jpg An Unnamed and unfinished single seat pusher
VT-ICE iso.jpg VT-ICE a 'way out there' Vectored Thrust-Inverted Channel Experimental
As now.jpg EagleRay, a 'double delta' or truncated taper fighter look alike based on the John Dykes JD-1 Delta.

At that point, I decided that if I'm going to fly my own aircraft, I needed to get back to basics and aim for something that fits our 95-10 category (very similar to your 103) Not exactly cheap and nasty, but hell,.......... cheap. Now I've always wanted something out of the box. Not some clone of a clone of a clone, so I started to work on a simple version of Andre Stark's AS-37. A close spaced, staggered biplane with ailerons on the 45degree end planes. The wings were spaced and staggered a 2/3's cord and the plane was powered by a Citroen flat four boxer engine driving contra-rotating props. He had 2 seats and the aircraft proved to be flyable but was under powered so he later changed the engine for some thing more powerful.

Construction-rear quarter [800x600].jpg Initially I was going for very light and simple but, after some research and advice from Pylon500, I started to redesign it to have cantilevered wings using ali for spars and ribs. Nothing wrong with that but the part count went up horrendously and I became very aware that I was going to exceed our 300 Kg MTOW. Consequently, I've now changed to a simple single wing variation but kept the same power configuration. As yet unnamed here id my latest rendering.

Front quarter single wing.jpg rear quarter single wing.jpg Single wing in need of an engine.jpgMy next job is to model the engine, a borrowed Rotax 508, 4 stroke that is apparently based on the 503 2 stroke. Whatever, should be powerful enough at about 45hp (hope my memory hasn't let me down here)

Bill was interested in my method of achieving a light weight contra drive system so here it is. Simplicity itself.

Contra-rotating props drive system.jpg I hope you can see my intent. The main drive chain goes over and under and over again so the any 2 adjacent gears are rotating in opposite directions. Secondary chains feed out to the props. Feel free to copy or modify for yourselves.
I have designed a simple differential braking system using bicycle disc brakes. Unfortunately I haven't be able to get it to be proportional as well. On the control stick, you simply twist the bake lever left or right then squeeze the lever for left or right brake only application. Keeping the lever centralised, applies both brakes together.

Brake lever assembly [800x600].jpgBrake lever assembly underside [800x600].jpg If the weight gets out of hand, this will be the first deletion in the design.

I am still working on the side mounted control stick (makes it easier for an old phart like me to climb aboard or fall out of when dismounting :roll:)
I'm also still figuring out a simple but strong, method to attach the outer wing panels. I don't want to spend half an hour rigging and de-rigging every time I fly. Got me some ideas but need to sleep on them some more. The centre section of the wing is approx 7.5ft, just inside our max width for towing.

Well that's it for now. Would you believe it, the wife wants to go shopping........again.

By all means ponder and criticise. If you feel you need laugh, just don't tell me. OK?
 

DaveD

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Perth, Western Australia
Hi Doug,

I like it, the contra drive system looks nice and simple, especially if you use the idler gear to provide the chain tension.

What's your thinking behind the cruciform tail. Are you aiming to keep it out of the wing downwash and propwash, or is it for ground clearance on the elevators? It looks to me like it might be in the shadow of the main wing at stalling angle of attack (may just be the perspective view).

Which CAD system do you use? Solidworks?

Cheers

Dave
 

deskpilot

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Morphett Vale, South Australia. Just south of Adel
Hi Doug,

I like it, the contra drive system looks nice and simple, especially if you use the idler gear to provide the chain tension.

What's your thinking behind the cruciform tail. Are you aiming to keep it out of the wing downwash and propwash, or is it for ground clearance on the elevators? It looks to me like it might be in the shadow of the main wing at stalling angle of attack (may just be the perspective view).

Which CAD system do you use? Solidworks?

Cheers

Dave
Hi Dave, easy answer first, I'm using Google SketchUp, free download. Takes a bit of playing around with and experimentation but it will do most things I want. There must be easier ways to do things for some one who is an 'expert' or at least, has had some training.
Re primary chain Idler, yes. I'm actually thinking of using 2. A strong one on the drive side to isolate any engine pulsing and then a light one on the return side to take up any slack. Hmmmm, more weight.
Not sure how the tail design came about. Sort of evolved. Certainly didn't think about blanking from the main wing in stall attitude. Can't be all that bad though as I'm Sure Pylo500 would have already pointed it out. He has been my mentor throughout this project. Oh, forgot you're in the States. Pylon500 is a well respected builder here in Oz. Not shown yet are the flying wires that help support the tailplane. Still got to work out the control system for the elevator. There won't be any wires or struts to the main wing.

Another forumite has asked why I deviated from the original biplane design. Here's why. Just looks heavy.

Contruction with outer panels [800x600].jpg
 

Jay Kempf

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I have designed a simple differential braking system using bicycle disc brakes. Unfortunately I haven't be able to get it to be proportional as well. On the control stick, you simply twist the bake lever left or right then squeeze the lever for left or right brake only application. Keeping the lever centralised, applies both brakes together.

View attachment 20504View attachment 20505 If the weight gets out of hand, this will be the first deletion in the design.
Cool idea. I see a fatal flaw. Your are in an emergency landing scenario panicking (I don't mean that personally I was thinking me), and you are death grip on the stick and you already committed to the brakes and you then need to move from a left to a right or the reverse brake application to stop a turn or skid on the ground. If you already have the both brakes mode on there is friction to override and go left or right so you would have to let go of the brakes and then reapply after rotating. If you had a death grip on one side the different height of your little paddles will block changing left to right or the reverse. So you would have to process all that in your brain in a panick.

My solution... instead of rotating the lever tilt it somehow or tilt the orange/gray paddles and make them one and put a roller or some non friction device at the bottom of the lever so that it can roll side to side under load. Another dumb idea would be to link the brake application to the lever but put the differential on the rudder pedals.
 

bmcj

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My solution... instead of rotating the lever tilt it somehow or tilt the orange/gray paddles and make them one and put a roller or some non friction device at the bottom of the lever so that it can roll side to side under load. Another dumb idea would be to link the brake application to the lever but put the differential on the rudder pedals.

Or control the differential with side to side motion of the stick (aileron input).
 

deskpilot

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Morphett Vale, South Australia. Just south of Adel
Jay, care to send me a sketch of your ideas. I've had similar comments from another builder but I can't get his idea of tilting the lever for differential braking to work in my head. Linking the brakes to the pedals would be too complex I think even though that is the most obvious and intuitive way to do it.
FWIW, I really try to avoid 'death grip' situations :gig:
Suddenly had an idea based on your description. Will ponder it a bit more and remodel.
 

DaveD

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Perth, Western Australia
Not sure if this is totally correct but looking at the blanketing of the tail plane at stall angle(16 degrees), It seems I'm sorta in the clear.

View attachment 20532
You're well in the clear there, the perspective view lead me astray!! The danger area is diagonally above and behind the main wing; draw a ~45deg line up and back from the leading edge and a ~30deg line up and back from the trailing edge and that's the boundarys of the blanketing effect from a stalled main wing. It's sometimes an issue with T-tails. I was going to suggest that a lower horizontal stab would be a bit more structurally efficient, but with wire bracing I doubt that's true either!

BTW I'm not in the 'states! I'm just over the bight in WA... but I am a Pom! :)

Cheers

Dave
 

Dana

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I like the design... kinda puts me in the mind of an Aircam crossed with a PDQ-2. Why the T-tail, though? Looks like it would be simpler and stronger if the stabilizer was at the base of the fin.

For the drive, why conterrotating props? No torque, I know, but it's really not an issue. I would also rethink chain drive; there are many reasons why it's problematic. It doesn't absorb power pulses (I know you mentioned idlers, but that adds weight) and the need for lubrication means you'll have oil or grease on your plane in line with the chains.

Re [differential] brakes, what's the matter with heel brakes? Simple and no complicated linkages.

-Dana

Of all the forces in the world, only the Federal Government has enough power left to destroy America.
 

Jay Kempf

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Jay, care to send me a sketch of your ideas. I've had similar comments from another builder but I can't get his idea of tilting the lever for differential braking to work in my head. Linking the brakes to the pedals would be too complex I think even though that is the most obvious and intuitive way to do it.
FWIW, I really try to avoid 'death grip' situations :gig:
Suddenly had an idea based on your description. Will ponder it a bit more and remodel.
OK, I'll wait to see your new sketch and then I'll grab a screen grab and mark it up.

Meanwhile, here's dumb idea number 2, or is it 3? If the deathgrip thing is going to give fits on the stick how about putting the brake handle on the throttle stick instead. That could have a heavy spring left and right tilt just like the main stick but it wouldn't get in the way of the flight controls. All your ground handling axis would be on one stick that way. Land normally and then drive it around like a powered wheel chair using the other stick push to go, squeeze to stop, lean (or twist) for differential. I'm not helping at this point, I know that.... :)
 

deskpilot

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OK, I'll wait to see your new sketch and then I'll grab a screen grab and mark it up.

Meanwhile, here's dumb idea number 2, or is it 3? If the deathgrip thing is going to give fits on the stick how about putting the brake handle on the throttle stick instead. That could have a heavy spring left and right tilt just like the main stick but it wouldn't get in the way of the flight controls. All your ground handling axis would be on one stick that way. Land normally and then drive it around like a powered wheel chair using the other stick push to go, squeeze to stop, lean (or twist) for differential. I'm not helping at this point, I know that.... :)
What a brilliant idea. An ultralight with a HOTAS system. Only problem is, one would need to be ambidextrous. My initial concern would be inadvertent throttle changes. Imagine powering up when you in a skid to the left or right, you're way behind the plane and ****ting yourself at the same time. :roll:
Having done the 'pondering' bit, training and intuition does point to bakes being coupled to rudder peddles, so I'm off to ponder some more.
As for the rocking the brake lever, I can't get passed the fact that the fulcrum will always have to push one cable down as it pulls the other up. Pushing a cable does not apply brakes and I can't see a way to maintain tension in the pushed side.
 

cluttonfred

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I find your design elegantly simple and attractive in a "21st century Demoiselle" kind of way and would really love to see it fly. My suggestion on both the contrarotating props and the differential braking system is simply, don't bother.

With the tail outside of the prop wash there will be very little "torque effect" so you could simplify and lighten your power installation by having both props turn the same way. You also would be able to use two identical props and not need one clockwise and one counterclockwise.

A steerable and perhaps slightly larger tailwheel would be more than adequate for a slow and simple design. Most of my limited flying has been in European factory-built microlights and none had differential braking. I would also suggest an off-the-shelf ultralight hydraulic brake system or adapted mountain bike hydraulic brake system operating from a single cylinder as far more effective for very little additional weight.

P.S.--It also occurs to me that you would have much shorter prop shafts and perhaps some low-speed control benefits from propwash over the ailerons if you used tractor rather than pusher props. You could also then have full-span ailerons or flaperons. The downside, of course, would be the safety issue of the props in the same plane as the pilot and not too far away. Ouch!
 
Last edited:

bradyaero

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Hi Deskpilot,

Great concept, you have some nice lines in your design. I'd suggest sketching a front mounted engine version for comparison sake.

Keep up the good work, Greg
 

Jay Kempf

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Think of this as providing a brake bias system if you had the two brake cables in your hands it would be intuitive to pull on either one simultaneously for total brake force and to bias the tension for steering. So then you need a mechanism to provide that. One lever can tension both cables but you then need a way to bias between the two cables. That can be done by twisting or tilting the lever. Have you ever seen a tiller on a large airplane for ground handling? The best ones I have seen are a small steering wheel that you grab with your fingers. Your palm rests on a button in the middle. The wheel steers while the palm button brakes. Very intuitive. Your brake lever could be the same. If the top of the throttle stick grip and brake lever rotated on the bottom of the throttle lever you would twist left or right for bias while squeezing the lever for braking. That is done just by routing the cables to the lever straight down to two pulleys below or near the throttle stick base pivot. When you twist you add tension to one side and remove it from the other while you are providing a stable tension feel that doesn't change at the lever. I have mountain bikes with those sorts of brakes. The lever feel is actually quite light. And you could always go hydraulic.
 

deskpilot

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I really like the 2nd aircraft. As for the braking; 2 brake levers parallel to each other works fine :)
Hi. Don't know why I didn't pursue that pusher design, is kinda neat isn't! Re brakes , I think this might be the way to, especially as I've also got a steerable tail wheel now. Wasn't in the original design.

Jay, your system sounds good but I'm still not imagining it correctly. Just in case I, or some-one else might still consider it, would you sketch it, scan it and post it. I'm intrigued whether I use it or not.
 

Aircar

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DP - your configuration reminds me a bit of the SV 10 Tardis(2) that Sander Ve Enstra designed and built -- I helped a bit on it and by chance ended up doing the first flight in it with him -there is a photo on "Australian Opal and other" thread . We had two 250cc Fuji Robins and direct drive pushers and it flew well enough although on our third landing we managed to crack a prop from debris thrown up (on his gravel strip next to the main Tocumwal strip from where our first two circuits were done ) I'd look at a simple tubular rear fuse for simplicity and maybe consider the suggestion for tractor props --in which case the Lazair configuration is pretty good as a basis . If the props were far enough inboard you could avoid having to couple them (and the dynamics of power pulses or harmonics in the chains etc ) and if the tail was a H type with the fins in the propwash you get good power out (single engine) behaviour (a Lockheed trademark)

BTW have you ever run across Dave Beteridge ? (was at 'the levels' tech park with Australian flight test company last I heard ) -designer of the Hornet flying wing and first president of the AUF..
 
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