Basic Modern Ultralight, BMU

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Protech Racing

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Jul 10, 2020
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Today I made the wing attachments and hope to glue up the bottom flat foam to the spars . I also moved to conventional ailerons to bank a little weight .
I will need to draw up a bellcrank to make the up 2 xs the down next.
 

Victor Bravo

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Lol, everything is relative. I've tested them to over 300# the axle starts to bend before the wheel breaks.
The engineer I consulted with on a landing gear project said that in very rough terms, you drop tested to a 45 degree 2G arrival at gross weight. The actual deceleration was a lot higher, but you walk that back quite a ways because the wing is still producing half of it's lift even at and beyond stall.

So assuming this is close to being accurate, a 600 pound gross airplane would result in each wheel seeing 2G X 600lb. or 1200 pounds, divided by 2 wheels, or 600 pounds each wheel.
 

rv7charlie

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I'm not sure it's even valid to split the gross between the wheels. Landing on one gear is a normal thing in crosswinds, and if you happen to stall while attempting that...
 

kubark42

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Oct 19, 2020
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I'm not sure it's even valid to split the gross between the wheels. Landing on one gear is a normal thing in crosswinds, and if you happen to stall while attempting that...
This only follows somewhat. If you stall and land hard on one wheel, the gear will compress and the plane will be on two wheels very rapidly. Or you'll be dragging a wing tip. Either way, the odds of a single wheel taking the full brunt is marginally marginal.

That being said, it's still fair to say that in a hard landing the distribution will never be equal. However, since the test cited by the engineer is a 45-degree 2G drop test, this implies that the design load is equally spread across the wheels (or else they would have specified the bank angle in addition to pitch).
 
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Hephaestus

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Jun 25, 2014
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YMM
The engineer I consulted with on a landing gear project said that in very rough terms, you drop tested to a 45 degree 2G arrival at gross weight. The actual deceleration was a lot higher, but you walk that back quite a ways because the wing is still producing half of it's lift even at and beyond stall.

So assuming this is close to being accurate, a 600 pound gross airplane would result in each wheel seeing 2G X 600lb. or 1200 pounds, divided by 2 wheels, or 600 pounds each wheel.
I was working to convince myself those particular burley 16x3 wheels weren't going to obliterate themselves with anything approaching the kind of weights/loads we're talking about. I mean they're meant for a 2 kid stroller/trailer - maybe 50-60lbs not an airplane ;)

Axle would be the weak point and could be upgraded from the ones I had. But didn't pursue it further.
 

Hot Wings

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Nov 14, 2009
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Like your substitution for traditional bar clamps in post #50. I'll try to remember it..........just a little trig needed to adjust the load.
 

Protech Racing

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Jul 10, 2020
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412
The wing design is still in flux. I think that I can hot wire the TE ,by moving the foil foreword 2 in .
Then I will look at fitting the main ribs with a little geodetic angle to reduce twist.
 

Protech Racing

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Jul 10, 2020
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412
I decided that if o pay attention, I can cut the trailing edge stock with the 12 ft straight edges , also known as spars.
Thinking ahead , I should cut the stock for both wings before I glue up the spars.
This foam is scored at 12 and 24 in . Thus, my center bottom foam is 24 in.
I also took some advice and will use the 5200 and Loctite max for the small surface area joints. IE the spars but and TE joint.
the large flat joints will be GG .
 

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