Gary
From what others have told me, Bernie's program was pretty specific for 65cm F1D. I still use it to compare the effects of changes to a design. I figure if a change produces a positive result in the program it might be beneficial in real life. When it tells me that my PP will do 25 minutes I don't necessarily put much stock in that.
The program is a pretty good tool for predicting stability. A big negative number for the static stability margin can mean the model will be difficult to trim.
Bill Gowen
Decatur, GA USA
----- Original Message -----
From: Warthodson_at_aol.com
To: Indoor_Construction_at_yahoogroups.com
Sent: Saturday, March 18, 2006 4:17 PM
Subject: Re: [Indoor_Construction] A-6 design variables
Don,
I have had the best results from stabs of 50% to 42%. I have tried larger
stabs up to 70%. They seemed to work well at lower torque levels, but I couldn't
get them trimmed to handle the high torque levels required at Johnson City &
Kibbie dome. Maybe the tail booms were too floppy or too long, but I never
pursued it further. My CG is approx. 1.25" behind the wing trailing edge. My tail
booms range from 8.5" to 9.5" long. Within these ranges I have not been able
to measure any difference. It sounds like you need a better motor/prop
combination. What were the specifications of your motor & prop?
Even with repeated 1/4 motor tests, I find it difficult to measure
differences between two models because each wind of the motor produces different results
on the same model. For example, I have tried to winding a quarter motor to
80% of max winds & each flight produces a different time on the same plane.
Going from memory, the variation is 5 to 10 seconds. that is 20 to 40 seconds on a
full motor. I have also tried winding to the same torque each time with
similar results. This variation masks any difference between two similar models
with only slight design differences. I would love to hear how others try to sort
out the differences between two designs.
To add one more thought. I have used Bernie Hunts program to simulate &
compare designs. It has pointed me in the right direction, but at some point I
cannot duplicate the results it suggests.
Gary Hodson
In a message dated 3/18/2006 2:34:55 PM Central Standard Time,
ddeloach_at_adelphia.net writes:
What you think the optimum TMA and tail area are for A-6? I have only built
one and it has a 50% stab, appx 130% CG and did 8:52 at ETSU. Dead sticked
from 50 ft too. I am wondering what I can do to improve it.may shorten TMA
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Received on Sat Mar 18 2006 - 13:58:25 CET
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