LE XL hopes

[Memberberries]

Hello, I have been lurking on here for a while and dreaming up a build the whole time. I have had an obsession with bush planes for some time and hope to end up to something like a Just Aircraft Superstol or Kitfox STI after a few years. 

For now I need a way to get lots of taildragger hours for cheap and have fun in the process, which led me to the XL. I have plenty of places to fly locally in northeast OK but many of them will tend to have taller grass ie pastures. 

this leads me to my thoughts on setup, I have seen many people run 20" tuffy wheels but after seeing the overweight just 103 solo with 29" bush tires I keep wondering if fat bike wheels and tires would work on the XL, might be a custom hub but that should be simple enough with 180mm disc brakes. The only other thing I would be wanting to do not completely by the book is the engine, I have a thing for radials and the Verner 3vw has me captivated. This engine wants a bigger prop so the taller wheels and tires seem to make sense and other birds flying with this engine seem to have an abundance of top speed so I am led to believe the drag would not be a problem either.

After those two things the rest of my plans would be as it was designed and attempting to bleed all the weight possible in the process to keep it within the limits of 103 and every pound saved would allow for potential to have some basic instruments.

any input on the wheels and engine choices?

[scottiniowa]

 
 , I have a thing for radials and the Verner 3vw has me captivated. This engine wants a bigger prop so the taller wheels and tires seem to make sense and other birds flying with this engine seem to have an abundance of top speed so I am led to believe the drag would not be a problem either.

After those two things the rest of my plans would be as it was designed and attempting to bleed all the weight possible in the process to keep it within the limits of 103 and every pound saved would allow for potential to have some basic instruments.

any input on the wheels and engine choices?

The best thing about starting now, is that at least 3 and maybe more will be flying with the Verner engine before you get to that stage...things should really be ironed out on them in just the next few months.

As far as the wheels go, much comes down to load ratings, and building in strength where you need it.
Best of success and welcome!

[stevejahr]

Re: wheels

Fat bike wheels would probably work very well on a LE. They could be very draggy but then so is the rest of the airframe.

One aspect of tire design is load rating and a major factor here is area of the contact patch. The wider tire has a wider patch and this contributes quickly to increased load capability. Fat bikes use this for low air pressures and buoyancy and suspension, but it would also work for increasing weight capacity. And even a part 103 ultralight is heavier than a bicycle so increased weight capacity is something to account for.

The next thing you need to account for is that bikes do not have the lateral loading that an ultralight will have in a sideways landing. A bicycle will have some lateral loading as the body works the pedals from side to side but not anything like the initial contact on an asphalt runway. This is the only part that requires alternate hubs and the main thing here is to use a wider hub to provide better load distribution (do the math on spoke angles in the lateral direction). Look at hubs for recumbent trikes and you can get larger axle diameters and integrated disk mounts. Then hack it into two parts to elongate the center cylinder and buy spokes of the length required to match (there are online calculators for this).

So I guess it comes down to how comfortable you are with building your own wheels

[Dan_]

There are plenty of these birds including the prototype flying with the plastic Tuffy wheels.  The landing gear tubing will fail before even the plastic wheel will.  There is a fellow back in 2012 that did an empirical test of the side load limits of the "as drawn" wheels and landing gear, and the gear failed with the side load and he is still using the Tuff wheel as far as I know.


https://www.youtube.com/watch?v=VIIRW8u8nB8&list=UUopLDNHH_5BR8eBpJgrJfAA


There are also many flying with "stock" mountain bike wheels which I will lay odds are multiple times stronger in side load capability over the tuffies.  With this taildragger, you will learn to land straight, or your will get real good replacing landing gear tubing.

Remember bikes put side loads on the wheels too, especially the front one and especially on mountain trails when making turns.  The forces acting on the wheel are trying to pull the tire off the rim (at the contact patch) toward the inside of the turn, and are trying to push the axle out of the spokes to the outside of the turn.


If Mtn bike wheels still don't seem strong enough for you, read about making your own hubs without a lathe here...

If you want to beat that dead horse into oblivion read about making Pietenpol hubs here...

[Memberberries]

Thanks for all the input, I've rode mountain bikes quite a bit and I would be comfortable using their wheels, I've done some pretty rough things and good wheels have never been what broke, I plan to stick to downhill wheels rather than lightweight wheels because they will only be grams apart but I think the strength will be worth it. I expect that landings will not be too violent without consequences to the gear and airframe. The pastures around me are pretty flat and smooth but some might need mowed more often if they are going to be used as small strips.

One thing that I'm not too sure on is whether the le or lexl would be better for short takeoff and landings in rougher terrain. I was assuming the xl because it has a lower wing loading and with some vg's I might be able to give it some more flexibility but I realize that a smaller plane at the same weight means that it might be a stronger design and maybe more forgiving to a greener pilots learning curve?

I'm not worried about top end speed so the extra drag of the tires and any other add-ons is going to be OK with me.