Large scale ultralights
 

I am building a 1/3 scale ultralight scratch build as there are no kits available, i decided to build an air bike, open frame and something that would fly realy slow.

RE: Large scale ultralights
 

That looks interesting! How big & what engine?

Thanks!

RE: Large scale ultralights
 

What material did you use on the frame?

RE: Large scale ultralights
 

OK some more details on this bird. I iriginally had a spair Honda 22cc 4 stroke engine not doing anything and thought a ultalight wood be good for it but the engine had no where near enough power when i did taxi tests on the fraim so i bought a new engine for it.
The plane is 1/3 scale of a real ultra light called an (air bike) there is quit a bit of info on the internet for this plane and there is a couple of small basic outline drawings of it and the wingspan for the 1 seat version is 26' so that would make my 1/3 scale wingspan at 104" and i just used the small drawing to measure up the other parts. there is a tandom version as well. There is also some info here on rcuniverse about this plane with scetches that i used. My wingspan is now 110" with the winglets added. The pilot figure is 1/3 scale.
cord 18", and i used Clark y for airfoil, it has flaps, costom suspension, the engine is a DZY twin cylinder 48cc 4.2hp engine looks good and it will have plenty of power with this engine. The airfraim is all STEEL and i used car brake line tubing which they some times call bundy tubing, it is lite wall with a copper coating on it and very easy to work with and not to heavy, I used 3/8" die for main runners and 1/4" for all diagonals and other bites, and used 68% silver solder and oxy asetaline to weld joints, this stuff melts as easy as normal solder at low temp but is much stronger, but more exspensive, just file ends of tube to get good fit so you start with not much gaps. using steel looks fantastic the joins are so neat and it is so easy to add strong brackets for anything such as wing stuts.

RE: Large scale ultralights
 

Thanks for the added information. The tubing structure looks great and that is interesting how you did it. I have used some high silver solder on aircraft chrome molly tubing and it makes a good strong joint but you have to have the tubing red hot to get a good joint. Jerry Nelson is using an epoxy called 'MetalWeld' that he says he is having good results with so I have some of that ordered for testing. I am looking at 1/3 scale WW1 & Golden Era planes with tube fuselage structures so that is why I am looking at different ways of joining the tubing. Your structure looks great and the plane should be fun to fly.

Did you use standard balsa construction on the wings? I have looked at ribs of 1/8 inch door skin (like lite ply) and added wholes for lightening and they work pretty good.

Cliff

RE: Large scale ultralights
 

Hi Cliff the silver solder that i use has a very low melting point and the steel no were near gets red hot, the silver solder is in rod form with a flux coating, you can get different silver content rods and i have used several including 48% and 68%, the higher the silver content the stronger but the cost goes up also, for low strenght joints i us the lower content to save cost but i use the higher content for the stronger joints, 1 rod here costs me A$20 and i can get maybe 5 - 10 joints out of 1 rod. it flows realy easy and does not leave lumps or a messy weld, i have my oxy flame turned down as low as it will go and just a very narow flaim is good to direct the heat, to much heat and all the silver solder will disapair. My be you were refering to brasing rod which is totaly diferent and yes that does take a lot of heat and would not be sutable for this. I have made my wing out of foam but the way i do it it looks like it is built up bolsa becouse of the bolsa strips to keep weight down and becouse i cover it in plastic so not to melt the foam, do not put the plastic covering direct on the foam if you use this method. to give you an idea of wight for this method of wing construction it is 110" X 18" so that is (1980" sq) and weighs 2.75 kgs or 6 lbs. the totel weight for this plane with the all steel fraim is 9.5kgs or21lbs and the wing loading is 24.37 oz per foot sq so that isnt to bad for a all steel plane, i think using molly steel would weigh more but the thin wall brake tube is very light . The small tube i use the 1/4" or 6.39mm outside die has a wall thickness of .7mm and the 3/8"or 9.5mm outside die is also .7mm wall thickness. When the frame was finished i got it grit blasted and powder coated. I am just puting the finishing touches on the plane now and plane to maiden fly it maybe within the next week so i will keep you posted and some more pictures.
STEW

RE: Large scale ultralights
 

I have been thinking about this thread and i dont want to mislead anyone that i am an exspert on steel and welding, i have no background in engineering but have just tryed things through exsperimentation. so what i am saying is that this method has no garintees that it wont fail, i wouldnt want peoples planes falling out of the sky on my account. May be if there is some quolified enginerring type out there that can coment on this method of fraim building as i am sure that steel in model airplanes is a much underused resouse, it is very easy to work with and all those atachment points are so easy to make and sould be very strong. I will keep you posted as to how my plane stands up to the real test - of flying it.

STEW

RE: Large scale ultralights
 

Nice job!!!!!!!!!!!I thought I was the only nut. Ha Here is my birdman tl1a, which is an ultralight I build and converted to an rc 34 ws and 168lb, finish but not flown yet. I really like you project

RE: Large scale ultralights
 

Hi Gizmos thats a big machine when you say converted to rc 34 you didnt mean that it is remote control did you? looks like a full size mokeup man in frount?. I will finish this plane today and on saturday take it out to the feild for testing, i may not fly it on that day as i have to get it inspected , over 7kgs and i had some radio twitching to sort out, am thinking of puting a whip aerial on it to get it away from the steel fraim and may have to earth my radio gear to the steel fraim and have a common earth.

RE: Large scale ultralights
 

I have finished the air bike now and am waiting for some real carm weather to test fly it, the finished photos at the air feild can be seen by cliking on (my GALLERY). there is a little bit of radio interferance i suspect due to the steel frame so i have a frend building a full lenth tuned wip aerial for it and i may try earthing the radio gear to the steel frame. This bird does not like any cross wind due to the high lift wing, i taxied it in windy conditions with flaps down and it wanted to lift off at walking speed but i think not enough air speed for full control, it was better with flaps up. More flight tests to come stay tuned. Stew.

RE: Large scale ultralights
 

That is some fantastic craftmanship in the fuselage structure, thanks for trying something different and sharing it.

RE: Large scale ultralights
 

The steel frame is not hard to build and does not take long, no waiting for glue to dry and the atachment points are so easy and strong
i took the frame to powder coaters so all the hard work is taken out of it. I have put 6 flights on it so fare and it flys good. I solved the radio interferance by grounding the receiver negative to the steel frame just like a car chassie and then put on a whip earial and this plane now has the best range performance of any of my planes. It weighs 9.5 kgs . i started out by adding 2.1 kgs of lead to the frount becouse someone said i must have a c of g of 25% -wrong- and it even flue good with all this extra weight in the frount. It is a clark y and i have removed all the weight and c of g is now 31% . No need for flaps as it flys very slow without them and lands at walking speed. the engine is just perfect the plane flys on about 1/3 throtle but there is plenty of power to pull up after a slow pass down the strip.

RE: Large scale ultralights
 

Hi Stew,

I was very interested in the idea of using Bundy Tubing for a fuselage structure. I shall purchase some and test it for strength, I've never thought of using brake line, BRILLIANT!
I have the drawings of a 1/3 scale Cub and looking at the cabin structure realised that I might as well make the whole fuselage of steel tubing.
I also think that you've made a very interesting model, nearly as mad as flying an ultralight by radio. This is a really wierd thread.

The higher silver content of silver solder the lower the melting temperature, I am a bit vague at this length of time about the exact composition, I think the 60% silver is the lowest melting temperature silver solder. If you're interested I will look up the figures. Of course the higher the silver content the more expensive it will be.

The material must be really clean of oxide to make a joint. After mechanical abrasion I normally use separate powdered flux rather than coated rod, that way the flux can be applied before the heat reaches the steel. If the steel is heated without flux, oxides form which stop proper bonding. The powder flux is usually applied as a paste, the powder is mixed with alcohol (recommended) or water (nearly as good)

I use a srtictly neutral oxy-acetylene flame and keep the flame moving while avoiding touching the inner cone on the work or solder.

For small joints I used a rod of silver solder hammered flat to make a 3/32" rod about 3/8" wide and then sheared to make a narrow strip. This way a number of different size of silver solder can be produced for different sized jobs. You can use all of the silver rod by silver soldering the short end to a steel rod to give you something to hold.



old git - - - - - - aka John L.

RE: Large scale ultralights
 

Hi John , yes you can do a lot with brake tubing, i first got the idea in 1988 when i got the contract to build a 32' long scale static model of the NASA space station for world EXPO 88 in Brisbane Australia. I needed a building method that was strong, light weight and easy to work with as i literally had thousands of joints to make. although you will be corect in the method of making a perfect joint , I never had the time in that project to prepare perfect welds so i just used flux coated silver solder of about 60 - 70% , bevaled all the jounts to iliminate gapes as best i could and wasnt to particular with the oxy acetaline acept to say that i kept the flame to a minimum - not much heat is reqired but it must be a pin point heat ie dont use a propane torch - use the smallest tip on the oxy and turn it down so the flame is only about 1/2 " long. I used the very same method to build my AIR BIKE and i have never had one joint fale in the thousands that i have done so i guess is what i am saying is that this is not complicated i have no background in welding what so ever so if you can do as John has sujested that is good for best results, if however you are like me and a master of no particular trade then dont get to hung up on finess, you can make a reasonably good weld without to much prep work or skill. Just make a weld and try to brake it, if the pipe bends first then it will be OK. Just remember silver solder runs very easly once up to melting temp so be carful with the flame, dont hold the flame on the job for to long at a time or the silver solder just runs away.

RE: Large scale ultralights
 

HI and WOW
I am looking at the same project and here you are just up the road and already built one!
Do you still have it, did you make any plans?
I was thinking crome molly tube but I like the brake line idea!
I am thinking a 31cc Ryobi for power as I have several of these engines and love them. Do you think it's enough to pull 104 inck airbike around?
Any thoughts on my project would be great.
Thanks
Rob

RE: Large scale ultralights
 

That's a really interesting project! I actually thought of doing a similar project last year. I bought a set of plans for the Afford-A-Plane ultralight intending to build the full size. I never went through with it because I couldn't find much info as to the air-worthiness of it and didn't want to risk my life on an unproven design! But I had thought of building a 1/4 or 1/3 scale model of it. A model of the A-Plane would be very easy to build since the full scale is built up of square aluminum tubing and plate aluminum, all bolted together. Should be very easy to duplicate.



Mike

RE: Large scale ultralights
 

I wonder what ever happened with the airbike???[sm=72_72.gif]

RE: Large scale ultralights
 

My Airbike is still in one peice . I do not fly it that often but have maybe put 20 flights on it. It is not a windy day flyer as it has tremedous lift and a small amount of wind will lift it up when I am trying to land. It flys very slow and it does not like flying above half throtle, I have the 48cc twin petrol engine in it, about 4.2hp I beleive. I have flaps but have never used them. It reqires constant atension on the elevator and alerons as the tail moment is very short, but it flys very realistically and every body enjoys seing it fly. I only used very basic plans that are free on the internet but they showed no measurments so I had to just use a scale rule to get all the measurments as I new the actual wing span so you can work out a figure for scaling. Hope that helps some.

RE: Large scale ultralights
 

I know this is an old thread but it's of great interest to me. InoticedChopperMike mentioned the Affordaplane. I built a 1/4 scale model of one and have been flying it since 2009 (aluminum fuselage, Ryobi 31cc conversion). It won "Pilot Project of the Month" in Model Airplane News in November of 2009 and Flying Models did a four page story on the build in December of 2009. It's been the absolute MOSTFUN I've ever had with an RC project of any kind and it always attracts attention at the flying field. I find stewaustralia's use of steel tubing particularly interesting'cause I have thought about building anRC model of theLegal Eagle ultralight as well and that has a steel tubing fuselage. Maybe it'stime to break down and order the plans. I'll post acouple pictures of my Affordaplane here and a link to aflying video I made last year as well. I'm really a fan of the ultralights...

www.youtube.com/watch

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RE: Large scale ultralights
 

Amazing workmanship, and inspirational, on both birds!!

RE: Large scale ultralights
 

Hi Stew,

I was wondering how the silver soldered joints held up long-term. Did everything hold together well? I'm looking into building a steel tubing fuselage and yours really turned out great. If the strength and durability is adequate I may go with your building technique. The solder rod is pretty pricey but the results look fantastic...

Pete

This plane first flew last year in May. She has many flights on her now and still going strong. One of my favorites for sure. It's my own design based on planes like the Legal Eagle XL, Airbike, etc. Gets lots of attention and positive feedback at the flying field... :-)

Very nice aircraft!! What size/type of engine? Wingspan? Weight?

Thank you!... :-)

Wingspan: 126"
All-Up Weight: 35 lbs.
Engine: DLE 40 Twin

Amazing that a 35# plane can be pulled around by a 40 cc engine!