Design and build an 'Ultralight'

[AusFlyer]

Jeez, you guys - looks like time to ramp up modelling skills so I can keep up. Last serious drawing for me was 2D AUTOCAD last century! And you don't want to know how long ago IGDS was.

 

Great concept, good idea with the crown and pinion.

 

 

[onetrack]

Not sure if you've seen this, Deskpilot - but it appears someone has actually produced your propellor-around-a-tailboom idea - not in an ultralight, but in a gyrocopter.

 

Lightning Autogyro | Helicopters International, LLC

 

The website is a little short on detail as to how it all actually works, but they've obviously got it to work.

 

To me, the design appears to be a little flimsy, but hey, I guess someone with a degree of competence did the calculations.

 

 

[Deskpilot]

Not sure if you've seen this, Deskpilot - but it appears someone has actually produced your propellor-around-a-tailboom idea - not in an ultralight, but in a gyrocopter.To me, the design appears to be a little flimsy, but hey, I guess someone with a degree of competence did the calculations.

Onetrack, I agree with you, it does look flimsy. That thin tube holding the tail assembly might be steel of course. Others have done the same on aircraft but they usually have a support beam going under the prop and then up to join the main boom.

 

Pylon500, nice to see you posting again. You seem to have been away for a long time, or I haven't been reading threads on which you have posted. Anyway, thanks for the drawing, very simple, very neat. Somehow, I doubt that it could be kept to 95:10 specs though.

 

 

[pylon500]

Pylon500, nice to see you posting again. You seem to have been away for a long time

Um, yes, well I've been away for quite a while...

I've wandered over into a different realm, and dabbling as an amateaur writer!

 

Was just having a bit of a break and came back here to see what's happening.

 

I'm probably not very good, as a writer, so will probably come back eventually.

 

The differential system is typically being used on all these small contra-rotating helicopters.

 

 

[BillSF9c]

On catch-up mode. Read Vol 1 &7 and will read up. Did expect to begin w basic specs, such as wing loading, span, chord depth, landing speed. 80knots? As do not exceed, fine. If wing is high you can run an axle for pusher and tractor, but no counter rotating. Some advantages. Flex locates eng position along the shaft, but adds cost of 2nd prop. Allows front eng, push prop. Low wing better for ground effect, slow landings but high lends a dihedral-like balance. Pilot etc weight all hangs in tension - easier? New at this - forgive me. Might like larger dia (bike) wheels. Not always a landing strip. Fairings? Motorcycles are slow due to being aerodynamically dirty despite small frontal area. A half-fairing add-on is a nice option for speed or distance. BillSF9c

 

 

[BillSF9c]

Ok! Pusher has some efficiency advantages! Maybe hurts the "cheap" aspect which was to be 1 hallmark. Yes, thrust is behind drag. True. Tractor seems obvious. But front wheel drive cars are more or less recent. Rear wheel thrust causes rare instability, "spun-out." V few boats use tractor. It IS behind you if you go down, so land on the tail in event of a mishap. Shocked at how few posts over several years, but they were good! I did designs when I was 11 in '61. Cardboard for fabric. Ha! Time to reinvent the wheel.

 

 

[turboplanner]

Compression is engineering term a tube in compression is one where the ends are being pushed towards their midpoint. The opposite is “tension” where the ends are being pulled away from their midpoint.

 

You could call something a compression tube in a building where the load only applies one way, but I wouldn’t use it on a wing, because, while it might be true on a wing in level flight, it may not be while taxying or flying upside down or during wing flutter, and you might accidentally only calculate the compression forces, amd forget the tension forces which may be greater.

 

 

[Deskpilot]

Well I'll be. What a turn up. I thought this subject was long dead and buried but I'm sure happy to see it resurrected.

 

Greeting Bill, new members always welcome, as is your input. Might I suggest you do read all the thread and don't go off at tangents as I originally asked.(not that you have.....so far)

 

 

[BillSF9c]

Yes, Turbo... I was thinking of the entire project. Sitting atop a "fuselage member" would be fine, esp w a midwing. A topwing with bodyweight suspended, (how is optional) takes less material in tension.

 

I like how you managed the eventual prop around fuselage, Desk... kept "cheap" relatively in the game. Optional 7/8 duct in the works? This is like the wingtip, adds efficiency! Maybe clear Lexan?

 

I'm most sad more material.was not covered... yet grateful of only 7 pages to follow. Guess I am on my own. After decades on motorcycles, was (very)surprised about the chain heating and failing, issue. I wonder if wind, side-deflecing the plates, is why.

 

 

[Deskpilot]

Bill, what are you referring to.I can't make out your connection to earlier posts. Please clarify.

 

 

[BillSF9c]

Well, I guess I have an advantage, having read the adventure (all of the posts, over just a day or so, so they all are 1story, conjoined, story.

 

First, I did not quite get how/why the decision to go midwing was chosen. Perhaps just preference. High-wing seemed to me to less.costly, a main thrust of the project initially, (as I took it, anyway.) And simpler for the less skilled. Maybe it was an issue of 'public' perception. "No way... I'd be hanging, ready to fall, if I didn't ____ tight/well enough."

 

Secondly, a pusher prop on fuselage spar was chosen. Many issues were raised. They were admirabley circumvented!!!

 

Lastly, chains versus pullies fir said prop drive was raised and being a bike repair type I had to notice how chains were disfavored. Apparently they get very very hot in this configuration..I have not had time to mentally addtess the issue, yet. I first thought that chains are not usually subjected to a lateral wind. This would cause plate friction which is unusual. It now occurs to me that the speed of the chain might be greater than on a motorcycle.

 

All moot points... Just things I noticed. I checked all links during the story. I could not get the results to open when it got the final approval PJK (or something)-1... nor did I see any final DNE or cruise or fuel data. Just curious.

 

I have not engaged in UL craft recently, but got the bug again. I come from R&D and enjoy design, but am not to proud to borrow ideas. It was a grand read... sorry it ended. Maybe an epilog?

 

Thanks, one and all!!!

 

BillSF9c

 

Near San Francisco CA USoA

 

 

[Deskpilot]

OK. First point, why mid wing? I can't remember my reasoning then but now....mid wing gives one the ability to see over and under the wing when in a steepish turn (coming onto base leg for instance)

 

Why a co-axial pusher prop.........just to be different perhaps Given to choise, I would have gone for 2 contra-rotating props for a less swirled airflow over the tail feathers.

 

ICE instead of electric for longer flight times and ability to go X country. Not all airfield would be able to recharge batteries.

 

Yes, chains get hot, are noisey and if one should break, that a lot os metal flailing around to do untold damage around and behind it (tail feathers)

 

This was just a design for design purposes really so no actual flight data was included. I would have been happy with about 90 knots cruise @ 13 lpm fuel burn.

 

If I were to take this up again, I'd also include morphing control surfaces to make it really a one off special.

 

 

[Blackhawk]

Hi Deskpilot,

 

Been following your design from the start, where are you up to with it.

 

I've had a passion for the tailboom propeller aircraft because of the protection given to the prop and the better efficiency. 

 

Counter rotating props could be done without being complicated.

 

I've been tinkering with a boom prop design myself.

 

 

[rotax618]

Good grief, the secret to success in aircraft design is finding what you can eliminate, a lightweight aircraft flies best. A prop around the boom adds enormous structural complexity and introduces vibration into the slender boom and tail structure for no real gain excepting maybe asthetics. Contra rotating propellers adds more complexity and weight as well as unknown torsional vibrations to the drive system. 

 

Contra-rotating propellers are rarely use except when connected to turbine engines because of destructive torsional vibrations, they certainly have no place on ultralight aircraft.

 

 

[Blackhawk]

REALLY ?

 

 

[rotax618]

YEP

 

 

[Deskpilot]

Ha Ha, I'm so pleased, and surprised, that this design of mine keeps getting resurrected.  I have to admit that I haven't done anything (had to read the whole thread to re-acquaint myself) with it for a long time due to my wife's health, and mine. Had a mini stroke a month ago. All's well though, no lasting effects except for the fear of another, more dangerous one. I am still trying to complete my Thruster restoration albeit VERY slowly due to lack of funds. (penny-less pensioner)

 

So, Blackhawk, Tell me more about your view on this design,.

 

Rotax, "the secret to success in aircraft design is finding what you can eliminate" Really, I think you should take up ballooning. The success of aircraft design is in creating something that meets ones needs for a given objective. ie, for me, something totally different to the usual clone of clones of clones. something that challenges usual standards, something that might leave my mark in aviation history. If that means making something a little heavier than usual, so be it. Now, what's your contribution to aviation?

 

To other readers, sorry for the rant. I'm still interested in having a discussion even though I'm not building. A few of you have asked about specifics like flight characteristics and detailed design specs, well I'm not into math's at my age so basically, the answer is I don't know. Obviously, if I was going to take it further, I'd have to have that done by some-one in the know.

 

Have you seen this other tread on my design, www.recreationalflying.com/topic/25072-my-latest-want-to-build/

 

Just found these images of some-one elses take on the idea.

 

 

 

 

 

[Blackhawk]

The HM-1000 (which is a Flying Flea design) in the above photos has a Rotax 582 engine.

 

Now watch the video and see how well it performs.

 

 

 

 

 

[Blackhawk]

This is my concept mid boom propeller aircraft; a bit heavier the yours at 600kg MTOW and the boom has more support from below.

 

It should have very good handling characteristics and light on fuel. 

 

Unfortunately no folding wings.

 

 

 

[Blackhawk]

This is another brilliant mid tailboom propeller aircraft; the HB-204 Tornado tandem seat trainer.

 

 

 

 

 

 

[rotax618]

If you wish to register your amateur built grand design in Australia it has to be less than 560kg TOW. There isnt a lot of wriggle room if you dream includes a couple of 100-150mm dia high speed bearings and a bevel gear system with torsional vibration dampening - I dont want to appear to be a troll or naysayer, I know how difficult it is to design and build an aircraft within the RAA regs.

 

I wish you all the best and look forward to hearing of your design processes.

 

 

[Blackhawk]

There isnt a lot of wriggle room if you dream includes a couple of 100-150mm dia high speed bearings and a bevel gear system with torsional vibration dampening - I dont want to appear to be a troll or naysayer, I know how difficult it is to design and build an aircraft within the RAA regs.

Well; all I can say is I'm glad your not designing my concept aircraft.

 

I don't know where you got 100-150mm high speed bearings and especially a bevel gear system.

 

If you look closely at the HM1000 photo you will see the tube that has the prop hub is about 44mm so the solid bearing shaft would be 38mm, so the bearings would be 38mm ID x 63mm OD x 4 off (2 at the front of the hub and 2 at the hub. This is a proven system and has been operating for nearly 20 years.

 

Being a belt drive it gives you the required reduction and would be turning the prop at about 2700rpm max. and using belts, torsional vibrations are almost nil.

 

The top support for the rear fuselage is that thin solid round bar (about 20mm OD) that connects to the 38mm solid bar at the front of the prop.

 

Haven't got a clue where your bevel gear system would go.

 

 

 

[rotax618]

The bevel gears was in reference to contra-rotating props. If you are considering an arrangement like the HM100, all well and good, I retract my concerns, I erroneously thought that the boom was to be cantilever. Perhaps a sketch of your design might help.

 

 

[Blackhawk]

Just go up 4 posts; the 3 view drawing is there; it's fully enclosed so you can't see the internal tube frame but basically the same setup as the HM-1000

 

But not a flying flea design; it's a boxwing.

 

 

[Blackhawk]

Bevel gears in a counter rotating gearbox makes it too complicated and heavy; it can be done with spur gears only and will run smoother an quieter.