Changing the clothes on the mannequin

That is a phrase Mr. Robin Hunt has used when talking to me before.
It applies to the change of appearance of a design. Much like all the "Noblers" of the '60s.
My current PAMPA plane is a Geo Juno. It is really a Saturn (geo wing) redrawn with a turtle deck to the Juno look. A rudder change, 1/2" added to tail moment, slight things here or there, but a Saturn in disguise.
What are the feelings about these sorts of ships? From a performance stand point that is. Mine has been an exceptional flier, but is there certain things to watch out for when redoing an existing design?
Changing from a bubble canopy to a turtle deck, vice versa, etc..(??)
I like a certain "look", but I can't always get that "look" except to change an existing proven design.
Thanks
Bill <><

LAST EDITED ON Nov-24-04 AT 10:10 AM (CST)
 
Bill,

Well, using an existing, proven design then modifying it to suit your tastes is safer than entirely freelancing. An Impact, by any other name, would smell as sweet. As long as you stay within certain parameters, it should fly much the same.

Thanks Randy,
What are those parameters, though? I think several others would like to know how much liberty can be taken.
I'm in it for the women and money like Larry C.
Bill <><

>That is a phrase Mr. Robin Hunt has used when talking to me
>before.
>It applies to the change of appearance of a design. Much
>like all the "Noblers" of the '60s.
>My current PAMPA plane is a Geo Juno. It is really a Saturn
>(geo wing) redrawn with a turtle deck to the Juno look. A
>rudder change, 1/2" added to tail moment, slight things here
>or there, but a Saturn in disguise.
>What are the feelings about these sorts of ships? From a
>performance stand point that is. Mine has been an
>exceptional flier, but is there certain things to watch out
>for when redoing an existing design?
>Changing from a bubble canopy to a turtle deck, vice versa,
>etc..(??)
>I like a certain "look", but I can't always get that "look"
>except to change an existing proven design.
>Thanks
>Bill <><
>
>When the character of a man is not clear to you, look at his
>friends.
>Japanese Proverb

Hello Bill; Airfoils, moment arms, balance points, the basic "numbers" of a particular design, should be kept to in your redesign. If you change the location of the landing gear, it will affect balance in some way, for example. Going from a bubble top to a turtle deck fuselage will add side area and influence handling in the wind, either to the good or bad, and put a little more weight towards the tail. It's the little things that add up to big things sometimes. I think really good designs can stand a little cosmetic massaging and not change the way it handles greatly, just might take a little more trimming. Nothing wrong with adding your own personal flair to a design,though. Otherwise, we might all be flying green box Noblers! Not really a bad thing, but a little mundane in the long run
Have fun and a great Holiday,
Dan McEntee

Bill,

What Dan said!

Here's a good example. My original elliptical plane, Tango Red, flew pretty well overall, but I felt it needed a bit more flap. I didn't want to change the planform of the wing, so in the second version of the plane, I swept the trailing edge of the wing forward slightly on the same planform basically trading a small bit of wing area for flap area.

On one hand, this worked quite well. The wing developed a good deal more lift (most of the flap area was added to the tip chord) and the slight of mushing I got in hard corners in the original design went away completely. Tango II will turn a very hard, clean corner. But there was an unintended consequence to the design change.

The new plane had a wicked yaw problem, especially on hard corners at 45 degrees and at the top of the hourglass. Worse on outsides than insides but evident on both. This was partially attributable to a slight misalignment of the fin and rudder (hey, nobody's perfect), but mostly due to the swept forward trailing edge. The fix for Tango II was to cut off the fin and straighten it out (Duh!) and add a "Rabe" style articulated rudder to help offset the yaw. It's quite a bit better now but not "right". The ultimate fix will be to substantially increase the side area aft of the CG in the next iteration to dampen the yaw. Probably keep the wiggly rudder too.

The point is, you change something, even if it's to fix a problem, you may unintentionally be introducing a new problem that will need fixing. Ad nausium, if you're not careful and carefully consider the changes you plan.

that sounds like a very good example of prop gyroscopic precession Randy. When you increase the turn rate, it makes the problem more noticeable. Al's rudder is currently the best solution for that problem. Using the wiggly rudder gives you a lot more freedom in the profile of the fuse. It doesn't have to have a deep rear body to help damp out the yaw.

HI Bill. "Variation on a theme" I belive is the musical version of this. In 1998 when I got back into cl, I decided for better or worse to design my own stunter. I took the "numbers" from the top ten planes and came to the conclusion that the plane would have to be called the "consensus" as there was so little difference. The biggest area that seemed to be different was the side area and the "modern" very thick air foil ala Big Jim. Seems a lot of planes are diguised Noblers, Genesis's, Patternmasters, etc.
So, I decided to build a kit! LOL

In a sense the question can't be answered because only you when you are satisfied!!
Paul Walker's Impact is a modified Patternmaster. My guess is at sometime in the past, he flew a Patternmaster and the wheels started turning (as they tend to do with stunt flyers),and presto. Windy based most of his career successfully around modified Patternmasters. Tom Dixon's Time Machine is a modified Patternmaster. Experimentation is a form of intelligence. The fact that you are trying different things means that you have come to a point in your development whereby, you can start to branch out and try different things. Your only obligation at this point is to supply us with a suffcient quantity of pics!!!

"I don't know about this tuned pipe business. I practiced on that thing until my lips turned blue, and I still can't play a stinkin note."
"Homer J. Simpson"