Hurricane Mk103

Help Support HomeBuiltAirplanes.com:

pictsidhe

Well-Known Member
I picked up two tins of Sherwin Williams 'vinylsafe' paint yesterday. I have only got as far as selecting and cleaning a test piece of coro. Apart from painting that and leaving it on the roof, I want to paint some 6" square pieces of flashing and measure stasis temperature in bright sun. Compare them to black, white and non vinylsafe paint. I have a thermocouple meter to do that. I have found an exact non safe paint sample for one of them, the other one is going to have to be something close-ish as I'm not buying a gallon...
Thanks for the dragon weights

mm4440

Well-Known Member
I saw your project post today, but can't reply there. You state that the wing area is 114 sq. ft. and the weight should be 454 lbs (254 plane, 170 pilot, 30 fuel) for a wing loading of 3.98 lb/sq. ft. How do you plan to achieve legal UL stall speed of 24 knots? The usual way to establish UL stall speed is through the nomogram in AC 103-7. Using that the calculated stall speed will be in excess of 24 knots.

This is an academic question only, since no one including the FAA will ever know the difference.

pictsidhe

Flaps.

Well-Known Member
If your wing has flaps for more than 50 % of the span the AC 103-7 nomogram gives you a CL of 2.0....which is the highest CL allowed. That still puts the stall speed over 24 knots. If your flaps are less than 50% of span the allowed CL is 1.8, which puts the stall speed slightly higher.

I guess my point is that every "UL" that I'm familiar with that only has 114 sq. ft. of area lands over 30 mph (in the real world).

HBA Supporter
helium

BBerson

Light Plane Philosopher
HBA Supporter
If the ultralight weighs less than 254 pounds empty, it can qualify by calculation with less than 114 sq,ft.
Checking calibrated weight is rare, I think.

pictsidhe

Well-Known Member
I have a tapered wing. That means that I can't use the appendix for stall speed. I will have to measure it. A thick tapered wing with split flaps can generate a lot of lift. Have a look in TOWS if you don't believe me.
If I fail to hit 24, the plan is to add a flaperon feature. I am fairly confident that I won't need to, though. You are not required to demonstrate stall speed in every flight...
There are a lot of 103s out there with similar wing area to mine and no flaps.

Well-Known Member
There are a lot of 103s out there with similar wing area to mine and no flaps.
Absolutely! And none of them meet the legal requrements exactly...but they're close enough.