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- Jan 4, 2007
- Messages
- 1,076
I'm currently back "ON" with my on-again/off-again Hummel Ultracruiser project. I'm about to start assembling wing ribs and have to decide whether to build the original 25' wingspan or the short-wing and probably more popular 22.5' wingspan. Both wingspans are "approved" by Hummel.
My question is what effect will the short vs longer wingspan have on cruise speed? I see drag reduced by having less wing leading edge frontal area with the short wing, but I can also see drag added since it would be flying at a slightly higher angle of attack at a given speed (let's say 60 MPH) Would the opposite effects pretty much cancel out one another, or would there be an appreciable benefit in going "long" vs "short". To me, even a couple MPH difference would help me make up my mind since picking up 2 MPH from 60 MPH would be a 3.3% increase.
My preference, for cosmetic reasons mostly, would be the short wing, but if there's enough reason I'd build the longer version. OK, I'll also admit there would be 2 fewer ribs to build too!
Here are some specs on the plane using my weight and 5 Gal of fuel. I've used the Pt. 103 empty weight of 254 for the long wing, and deducted the reported 7# weight saving realized when building with the short wing.
Long wing - 25' wingspan - 434# Gross Weight - 3.86#/Sq. Ft. wing loading
Short wing -22.5' wingspan - 427# Gross Weight - 4.22#/Sq. Ft. wing loading
Short wing is 90% of the long wing's span
Short wing has a .36#/Sq. Ft. higher loading, which is ~9% higher
FWIW, the Ultracruiser has a very thick main spar; almost 10" tall. Chord is 54".
I would expect the stall to be a couple MPH lower with the long wing which I would expect it to make the plane slightly more docile on takeoff and landing. Hummel does maintain that 28 MPH stall can still be achieved with proper rigging of the ailerons with even the short wing.
If I left out information needed to give a educated opinion, please let me know.
As always....Thanks, in advance!
Lynn
My question is what effect will the short vs longer wingspan have on cruise speed? I see drag reduced by having less wing leading edge frontal area with the short wing, but I can also see drag added since it would be flying at a slightly higher angle of attack at a given speed (let's say 60 MPH) Would the opposite effects pretty much cancel out one another, or would there be an appreciable benefit in going "long" vs "short". To me, even a couple MPH difference would help me make up my mind since picking up 2 MPH from 60 MPH would be a 3.3% increase.
My preference, for cosmetic reasons mostly, would be the short wing, but if there's enough reason I'd build the longer version. OK, I'll also admit there would be 2 fewer ribs to build too!
Here are some specs on the plane using my weight and 5 Gal of fuel. I've used the Pt. 103 empty weight of 254 for the long wing, and deducted the reported 7# weight saving realized when building with the short wing.
Long wing - 25' wingspan - 434# Gross Weight - 3.86#/Sq. Ft. wing loading
Short wing -22.5' wingspan - 427# Gross Weight - 4.22#/Sq. Ft. wing loading
Short wing is 90% of the long wing's span
Short wing has a .36#/Sq. Ft. higher loading, which is ~9% higher
FWIW, the Ultracruiser has a very thick main spar; almost 10" tall. Chord is 54".
I would expect the stall to be a couple MPH lower with the long wing which I would expect it to make the plane slightly more docile on takeoff and landing. Hummel does maintain that 28 MPH stall can still be achieved with proper rigging of the ailerons with even the short wing.
If I left out information needed to give a educated opinion, please let me know.
As always....Thanks, in advance!
Lynn
