Design and build an 'Ultralight'

[Tomo]

1, thrust is still side on to the bearing, not good in my opinion.

You can get thrust bearings, so the bearing part is actually designed to handle the side load... Like a throw-out bearing on your clutch...

 

If you are going to make another bit for your two bearings, that would make it a lot better, at first I thought you may have to nearly weld something onto the tail boom...or drill a hole through it, which isn't a real good idea...

 

 

[Deskpilot]

Tomo, I guess we need to leave this to a more qualified engineer. It's certainly outside my area of expertize. My last thought on the subject is that it would probably be best to have it down in the hub, and right in front the prop, before the first support bearing. I'm not sure if the current bearings are designed for the side load.

 

 

[Tomo]

I've quickly made up a bit of a hub assy on the lathe, using wood so I don't waste any steel...

 

I don't really know why I did it exactly, but thought you might want to have a look anyway. I haven't bored out the middle on the (will be tail boom sleeve) section, that's why it's still solid...;)

 

Also I made a bit of a recess for the bearing to rest against on the sleeve section, that's why on the photo where it's standing by it self, the bearing is staying there, it's sitting on the ledge. Also the bearings are just old wheel bearings, that's why there the tapered type with, cup and cone... they would be an ideal bearing to use, except they have got to run in either grease or oil.

 

The groove in the big bit is just where I put a smooth V belt groove in, just for the heck of it:big_grin:

 

Anyway, Hope I don't annoy you to much...

 

 

 

 

 

 

 

[Deskpilot]

Good one mate. the big difference is the size off the main bearings. don't know if there are suitable ones with a 150mm i.d.

 

Seems like you and me are the only ones left in this thread. Come on guys/gals, surely you've got something to say

 

 

[Tomo]

don't know if there are suitable ones with a 150mm i.d.

Went around to one of our suppliers this morning and the 150mm I.d x 210mm O.D, ball bearings are around the $370 dollar mark for a non sealed bearing, sealed is a bit more on top of that I presume... they also have thrust bearings of that size as well, but would be pretty exy also, I would think....

 

I didn't price any taper roller bearings, but I would think they would be very similar in price...

 

Anyway there's a few statistics to play around with, you can pretty much get what ever size bearing you want, you pay for it that's all... At the moment where doing a final drive, and the I.D of two of the bearings in it are about 12", 300mm...!

 

Like Doug said, C'mon fella's let's get some feed back from you...:thumb_up:

 

 

[Guest drizzt1978]

I spoke to my friend, who is in his final year as a engineer, with lots of focus in Aerodynamics, he toped the University in fluid dynamics...

 

Please use this information as constructive criticism... NOT a put down

 

I think the centre of drag would be in front of the centre of thrust and

 

it would be unstable, and the propeller would try to overtake the pilot

 

and flip the plane.

 

 

 

also I would be a little concerned (but not as much) of where the centre

 

of lift was relative to the centre of weight, normally a wing tries to

 

"push the front of the aircraft down" due to the moment it has, and

 

hence the elevators to push the tail down .

 

In short I reckon it would get out of shape and not be able to be caught, if more thought was

 

put into the aerodynamic moments, the position of the propeller around

 

the fuselage would not be a problem.

 

 

 

normally the engines are low slung to counter the moment from the wing,

 

without wing profile data, weight distribution and stiffness (which

 

effects the damping of the plane movement) it is very hard to say with

 

certainty that it'd be ok

 

 

 

hope that doesn't leave you with more questions than u started with

 

 

 

catchya

 

So there it is...more confusion!!!

 

Im not sure If he wants to get involved in this thread, because he has a lot on his plate at the moment, and he is recovering from a Motor Bike accident...

 

 

 

 

 

[eastmeg2]

There are aircraft out the which prove that you can pretty much place the propellor anywhere along the centreline of an aircraft provided that the thrust line is aligned correctly. Just look at the Sapphire, Vampire, or any trike for that matter. I'm pretty sure I've even seen a picture from the USA of a plane in flight with the prop positioned at the very rear of the aircraft behin the horizontal stabiliser.

 

 

[Deskpilot]

Been there to Eastmeg2. Toyed with this some time ago. Looks like I went for 2 seats initially then changed my mind. Long drive shafts are the main problem I think, but an interesting concept all the same.

 

'78, I'm not going to argue this your friend, it's way above my head at this time. I understand where he's coming from and agree, weights and balances need to be carefully planned. I'll get more involved in this area when I have decided on wing section, size and so on. Still revising my knowledge on basic design at the moment. Please pass my thanks to your yank(s) Hope he recovers well, and soon. Dem bikes are soooo dangerous.

 

 

 

[Galpin]

Deskpilot,

 

Your drawing has a similarity to Molt Taylor's Mini-imp. I used to have the plans, but they were discarded when we last moved. If anyone is thinking about following-up this design there will be a site on the net that will answer some of your questions.

 

 

[Guest ozzie]

I think the centre of drag would be in front of the centre of thrust and

it would be unstable, and the propeller would try to overtake the pilot

 

and flip the plane.

Not quite sure what your mate is on about here.

i think the only way you can have that problem is if the thrust line is to low and the drag to high or vice a versa, high thrust line power up goes nose down ect if the thrust and drag lines act close together then isn't this the whole concept of placing the prop on the boom. for stability and efficiency you have to have the 4 forces all acting as close together as possible.

 

 

[Guest drizzt1978]

Those engineers complicate everythinh aye!!!

 

 

[farri]

G`Day Deskpilot,

 

Are you seriously,serious?.

 

I got into flying by building my own, very similar, 2 seat tandum UL aircraft,25 years ago.

 

I had very little spare money and only a few basic cane farmers tools,it was a pusher, powered with a Robin 440 engine and a timing belt reduction drive, turning a 3 blade 60 inch Ultra prop,it flew briliantly and was registered with the AUF,flew it saftely for many years,the same design would suite a single seat version.

 

Your not sugesting we start the whole Ultralight concept over again are you?.

 

Regards,

 

Frank.

 

Ps, The aircraft is still around but I redesigned the engine mount and fitted a Rotax 582 engine, it`s registered under catogary 19

 

 

[Guest Maj Millard]

G'day Frank, Hey going around a second time wouldn't be a bad idea would it ?. I could probabily handle the fun, and I know you could. Hey pulling on all those starter ropes again, just the way to go. It should be safer this time also.

 

The first real UL movement was at the beginning of flight, we are really the second time around. If they keep over-regulating it, or make it too expensive, I have no doubt we will see a third time around one day. That is of course if the current generation ever gets off it's Arxx, and actually builds something !..................

 

 

[Guest Maj Millard]

Hey I don't have any probs with the design. Granted the prop on the boom is a little different, but certainly do-able I think, with what's available today. Just a matter of digging up the bits, and doing some proof testing on a static stand.

 

The only (minor ) problems I see with prop placement would be stones from the main gear, and ease of prop replacement/refitting. The boom/tail would need to be easily/quickly removed and replaced, and would need to be foolproof.

 

The control linkages for the tail, which I am assuming would run inside the boom /prop hub, would need to be very well covered at that point.

 

As far as flying goes, I see no reason why it wouldn't, thrust line is perfect, it's a midwinger with everything going through the center pivot point. There would be great airflow over the tail surfaces so they would be very responsive.

 

My only suggestion would be to maybe consider an inverted V tail. As Lazair pilots like myself and Ozzie will tell you, they work fine. It might also simplify the linkages in the boom ?.

 

The big problem of course in going away from convention with aircraft design (boom prop, Vtail) is to convince Joe average that it is safe, and that he should have one, if you are thinking sales later down the line.

 

Unfortunatly aviation history is littered with great designs, that just didn't make it for the above reasons, not because they wern't good concepts.

 

You really need to be a bit like Bert Rutan who simply said "to hell with the doubters, I'm doing it anyway !" How many people actually know that one of Berts first design successes was the anhedraled V type stabilator on the McDonnell F4 Phantom, whilst he was a test engineer in the US Airforce ?.

 

If you want to look at a real minimum, easy and cheap to build, and successfull aircraft, you can't really go beyond the single seat Kolb design................

 

 

[Deskpilot]

G'day Frank, Hey going around a second time wouldn't be a bad idea would it ?. I could probabily handle the fun, and I know you could. Hey pulling on all those starter ropes again, just the way to go. It should be safer this time also.The first real UL movement was at the beginning of flight, we are really the second time around. If they keep over-regulating it, or make it too expensive, I have no doubt we will see a third time around one day. That is of course if the current generation ever gets off it's Arxx, and actually builds something !..................

Well said Maj.

 

Frank, I'm not re-inventing anything, just updating and, hopefully, improving on what was once a 'penniless flyers' project. Using todays knowledge to be able to build a fast(er), safer plane than those of the 70/80's. It's getting a bit out of hand I know but, most of us can't afford plastic fantastics, see all metal as a long and daunting trial/trail and yet still want to fly around this wonderful country of ours. How far can you comfortably fly something like a Drifter or Thruster. Great craft that they may be but an all enclosed cockpit, sleek lines and a bit of sexiness that makes people(well some of them at least) say 'Wow, look at that. I want one' My hand drawn shetch is somewhat bulbus but I'm in the early stages yet. In actuallity, it will be more angular as I'm avoiding the use of Fibreglass.

 

Rather than taking the negative view, which BTW, I requested right at the begining of the thread (did you read that bit?) how about posting some info on your attempt, perhaps a 'proof of the pudding' photo or two.

 

As a general update, I'm still working on the wing profile and structual design. I've recently got in touch with a guy in America who is at the same stage, doing the same thing although, being an areo engineer, his will be what a lot of you would call 'the real thing'.

 

 

[Deskpilot]

Maj, just seen you last post. Thanks for you support. You put it very well and have covered the important point, ie, non flyers conception of what a plane should look like. With the inverted V tail I'd be remaking the Mini-imp but with a revised prop position. Must say I like that plane but. Vertical fins and horizontal stabilizers are conventional for conventional people, and they're the ones I'm aiming to 'convert'.

 

 

[Guest Maj Millard]

Yes Deskpilot I see your point in keeping it simple, and understand you urge to do something a little new or different also, that's how we evolve I reckon. I don't think Frank was suggesting you are re-inventing the wheel, maybe just playing Devils' advocate. After all he is from Turin, and maybe has a shroud hidden somewhere in his house.

 

On a serious note, Frank has been flying and building ULs since day one, and I would welcome his suggestions or input anytime..................

 

 

[Guest drizzt1978]

.......it will be more angular as I'm avoiding the use of Fiberglass.

 

Just wondered why? And what will you be using?? Isn't fiberglass the wopty do and can be repaired...

 

As for angles are you going stealth style. Lots of angles to swoop into controlled airspace. ;););)

 

 

[farri]

Well said Maj. Frank, I'm not re-inventing anything, just updating and, hopefully, improving on what was once a 'penniless flyers' project. quote]

 

Doug,

 

I`m not sugesting anything,I simply wanted to know if you were fairdinkum.

 

I agree with you completely, understand the situation fully and by no means want to be negitave on the issue because I and a couple of others were responsible for making it all happen up here, way back then.

 

I was determined to make it happen and wasn`t going to let anyone one, or thing, stop me,had I been negitave, it would not have happened,however,it`s a different world we live in today and the system has become even more of a challenge.

 

Let`s just get away from the actual design of the aircraft for a moment and look at the legal aspect of it.

 

Who takes ultimate liability for the the design and construction,every individual contributing has a duty of care,where does duty of care begin or end,even if an independent person or company put it togeather,where do those submiting the details stand, legaly, anyone working on the project would be liable,it becomes a nightmare in reality.

 

I`m quite happy to contribute for the fun of it, however, I`m not so sure that we could put the aircraft, on the ground,ready to fly,as you describe it, at a total cost that would be much different than most of what we already have.

 

Keep,keeping the dream alive.

 

Regards,

 

Frank.

[Guest ozzie]

For your 'pod' have you considered a tube frame and cover with coloured sailcloth ala CGS Hawk. simple cheap lightweight and easy to repair.

 

Ozzie

 

 

[Deskpilot]

No offense taken Farri. This is my dream of course, but not necessarily to go as far as actually marketing.

 

Re the 'pod', keeping in mind people with no particular skills, I was thinking in terms of stitching thin ply panels together. Something like the stitch and glue boat build method. Being as they'd be curved, they'd end up quite rigid, particularly if you wanted to get your hands, and everything else, sticky by applying a coat of f/glass over the whole thing. I want to avoid making molds etc for a full pod. There will be a tubular frame inside but this will be quite light.

 

 

[Deskpilot]

A quick update. Been playing with wing structure design. Still thinking foam sandwich for ribs but that's not set in stone. Ref attached image, my basic idea, compression tubes are a bit on the thick side I think, trailing edges are plywood. Haven't included the ply leading edge 'cause I can't model it as yet. There would be a 'lightening' slot in the ribs through which the compression tube will run. End treatment and riveting not included. At present this model represents a 20ft span and 4ft cord, or there abouts. The tube look a bit oval 'cause I had to scale the cord, not thinking straight when I set the spar spacings.

 

In reality, I want the main spars to go full width of the cockpit/pod. Damned if I can think of a way to do that without cutting or somehow re-sizing one or both tubes. Any ideas or pointers guys? Have tried looking up glider methods without success. Any site worth visiting please? Need pictures, so much easier to understand.

 

Still haven't settled on what airfoil I'll use nor the final size of the wings.

 

 

 

[Deskpilot]

Hi Harris (formerly known as Harwis, renamed by his work mates) Good to see you back on line. Why the difference, because I want to be different. Why Not? Yes, there is some expense involved but I'm not thinking about that at the moment. Got to get the overall design finished and then I'll look into reducing cost and weight if necessary.

 

I'm currently working on the wing profile. I'm starting with a basic Clark Y with a modified 2 stage Youngmans flap. If anybody has a better idea and would like to share their thoughts, I'll be happy to receive advice.

 

 

[Deskpilot]

Oh, before any one asks 'Why flaps', cause, hopefully this will be a slippery little critta.

 

 

[Guest ozzie]

Boom drive props

 

here are some photos of props rotating around the fuse tube. two different aircraft here.

 

thanks goes to Scott Perkins who runs the www.vula.org site for going thru his vast collection to find these photos

 

Ozzie