- Joined
- Jan 4, 2007
- Messages
- 1,081
I have made a couple "false starts" on building a Hummel Ultracruiser, but have somehow switched to building something else on a couple occasions. Though the first couple starts I have actually built a fair number of parts including formed bulkheads, control surface ribs, nearly all the parts to build the "truss" style ribs, and numerous other parts. I'm seriously considering re-starting where I've left off and have one big consideration I'd like informed input on to make one big decision about how to proceed.
Originally, the Ultracruiser plans showed building to a 25' wingspan (It was actually a couple inches short of 25', but lets call it 25'). Years ago some builders started leaving one bay off of each outer wing panel and built to a 22.5' wingspan (Again, it was a couple inches short of 22.5', but again let's call it 22.5'). Hummel's testing actually showed that the UC was still within the 103 regs for stall speed with a slight tweak to the recommended setting of the ailerons. That's great, since I want a legal ultralight 103 Ultracruiser.
My indecision is this, do I build to the 25' span or go the clipped wing 22.5' route? I'm convinced I can build either to the 254# limit. I visited a gentleman who's UC came in with 1/4# to spare with the long wing, and got a lot of lightweight building tips from him. I'd prefer the more compact short wing version, but where's the trade-off or "balance" (for lack of a better term) when comparing cruise speed of the long vs short wings? In my mind I can see a conflict with the shorter wing having to fly at a slightly higher angle of attack, which would increase drag slowing the plane down a tiny bit at cruise power...correct? But, then again the long wing, at the same power and gross weight, would fly at a lower angle of attack which should reduce some drag, but would also have more wetted surface area and frontal area. So, how would one determine a preferred route to the least drag and best cruise speed at identical power/thrust? The short wing apparently saves about 7# on the weight of the plane, so that's also a tiny consideration.
All other considerations like exceeding 103 legal top speed, whether or not it can be built to under 254#, etc. aside, what would be the suggested direction based on the short wing/long wing drag consideration? Just to add a bit more info, the long wing comes in at 112.5 Sq. Ft. wing area compared to 101.25 Sq. Ft. with the short wing. I already have the 1/2 VW I would use on the Ultracruiser, so no matter what wingspan I would build, the power available would be the same for either.
If I have missed supplying any info needed to give an informed answer please let me know.
Thanks, in advance.
Lynn
Originally, the Ultracruiser plans showed building to a 25' wingspan (It was actually a couple inches short of 25', but lets call it 25'). Years ago some builders started leaving one bay off of each outer wing panel and built to a 22.5' wingspan (Again, it was a couple inches short of 22.5', but again let's call it 22.5'). Hummel's testing actually showed that the UC was still within the 103 regs for stall speed with a slight tweak to the recommended setting of the ailerons. That's great, since I want a legal ultralight 103 Ultracruiser.
My indecision is this, do I build to the 25' span or go the clipped wing 22.5' route? I'm convinced I can build either to the 254# limit. I visited a gentleman who's UC came in with 1/4# to spare with the long wing, and got a lot of lightweight building tips from him. I'd prefer the more compact short wing version, but where's the trade-off or "balance" (for lack of a better term) when comparing cruise speed of the long vs short wings? In my mind I can see a conflict with the shorter wing having to fly at a slightly higher angle of attack, which would increase drag slowing the plane down a tiny bit at cruise power...correct? But, then again the long wing, at the same power and gross weight, would fly at a lower angle of attack which should reduce some drag, but would also have more wetted surface area and frontal area. So, how would one determine a preferred route to the least drag and best cruise speed at identical power/thrust? The short wing apparently saves about 7# on the weight of the plane, so that's also a tiny consideration.
All other considerations like exceeding 103 legal top speed, whether or not it can be built to under 254#, etc. aside, what would be the suggested direction based on the short wing/long wing drag consideration? Just to add a bit more info, the long wing comes in at 112.5 Sq. Ft. wing area compared to 101.25 Sq. Ft. with the short wing. I already have the 1/2 VW I would use on the Ultracruiser, so no matter what wingspan I would build, the power available would be the same for either.
If I have missed supplying any info needed to give an informed answer please let me know.
Thanks, in advance.
Lynn
