Landing speed increase with weight increase?
08-30-2017 | 01:21 PM
#26
On my current build with a forecast weight of 15.5 lbs, it was noted when removing the tail planes from the box that they were unusually heavy (totaling 15+ ounces). A decision was made to build all else and asses the tail planes before mounting. It was found that with the furnished tail planes, 12.5 oz of nose weight was needed to balance.
I determined that if 5oz of tail weight was saved by making replacement tail planes, doing so would eliminated any requirement for nose weight, thus saving 17.5 oz of aircraft weight. In fact, enough was saved to allow bolt on stabs rather than fixed glued stabs and still obtain the 5oz tail diet and the goal.
This proved to have a double benefit because the wing foil uses a Clark Y foil and because of the lift of such a foil, it needs a positive stab to control pitch and such positive angles are a bit hard to estimate... so it helps to have either an adjustable stab or bolt on that can be shimmed. A positive stab is a big plus for such a plane because it then becomes a lifting surface or lifting stab and thus lightens wing loading. .
At any rate, saving weight is a good thing and worthwhile when it can be done. If you can save 1.5 lbs... I'd say that it is worth doing and will yield a reward of better performance and flight.
I determined that if 5oz of tail weight was saved by making replacement tail planes, doing so would eliminated any requirement for nose weight, thus saving 17.5 oz of aircraft weight. In fact, enough was saved to allow bolt on stabs rather than fixed glued stabs and still obtain the 5oz tail diet and the goal.
This proved to have a double benefit because the wing foil uses a Clark Y foil and because of the lift of such a foil, it needs a positive stab to control pitch and such positive angles are a bit hard to estimate... so it helps to have either an adjustable stab or bolt on that can be shimmed. A positive stab is a big plus for such a plane because it then becomes a lifting surface or lifting stab and thus lightens wing loading. .
At any rate, saving weight is a good thing and worthwhile when it can be done. If you can save 1.5 lbs... I'd say that it is worth doing and will yield a reward of better performance and flight.
10-02-2017 | 01:21 PM
#27
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From: Fort Smith,
AR
With all things equal, except weight and velocity, weight is equal to the square of velocity. Then the square 21 minus the square root of 20 divided by the square root of 20 times 100 gives the percentage of velocity increase, which appears to be 2.4695. The landing speed in this case should be 1.024695 times 40 or 40.9878. Now 41 is close enough to this. The key thing here is the square root of the weight determines the velocity.
10-03-2017 | 06:35 AM
#30
Is not the issue that although the reduction in the stall speed may be small it does mean you now have a bigger 'safety margin' using the same landing speed?
The other aspect is the power required to fly which for the same air frame is directly proportional to weight. A !0% reduction means you have 10% more spare power!
The other aspect is the power required to fly which for the same air frame is directly proportional to weight. A !0% reduction means you have 10% more spare power!
