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Author Topic: Design by Committee  (Read 1771 times)

Offline Jim Pollock

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Design by Committee
« on: February 11, 2006, 01:36:27 PM »
Ted, and Everyone else too

Here is what I propose.  I have a basic sheeted SV-22 foam wing, with 4 inch bellcrank assembled with 1" flat tips, like Brett's Infinity.  Let's design the rest of the plane  including the flaps with the following basic information.  Power system is a rebuilt PA-61 RE with a Hi-Tourque pipe.  The wing does not have gear blocks installed. The airplane will probably utilize a Carbon Fibre Landing Gear.    ???'
 

Questions.  Percentage of flap to that of the rest of the wing?
                   Acceptable nose and tail moment arms?
                   Percentage of Stab/Elevator area to wing + flap area?
                   Percentage of Elevator to total Stab/Elevator area?
                   Fuselage ease of construction and asthetics(sp?)
                   Target design weight?

Alright let's begin..... The rest of you on the forum are the design committee!
Ted is the committee chairman.

Lastly,  Ted, are there any other questions that you would like to add to the basic premise?

Jim Pollock,
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« Last Edit: February 11, 2006, 11:52:45 PM by RC Storick »


Offline Ted Fancher

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Re: Design by Committee
« Reply #1 on: February 12, 2006, 06:20:30 PM »
Hi Jim,

Cool idea.  I'm going to be monitoring the input and will try to keep from throwing too much in right away.  I think that will generate a lot more input than the other way.  Right or wrong (and believe me, I'm not any rocket scientist on this stuff) when somebody with a bit of a record of success expresses a point of view on this subject it tends to get accepted as gospel and discussion breaks down.  Ergo, I'll keep a bit quiet until there's been some discussion already. 

What I will promise to do is to step in with an opinion if I see something gaining momentum which is out of step with my understanding of how these things work.

My only comment at this point would be to start with a realistice assessment of what weight you're likely to be able to build this critter.  Everything else has to pretty much evolve from that prediction.  Be really critical and honest about past performance (your own at the building bench) and work from that premise.

The other thing you need to do once that is determined is figure out how much area you've got in the existing unflapped wing so you can make a determination of what you'll need to do in terms of flap area and movement to handle the weight.

One final clue, you've probably read enough of my ramblings to realize that, while I think stunt ships should be as light as you can reasonably make them, I'm not one that thinks missing a target weight is an automatic disqualifier for a good airplane (Lord knows, I've played that game over the last fifty years!)

Ted

Offline Bill Little

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Re: Design by Committee
« Reply #2 on: February 12, 2006, 08:40:36 PM »
Hi Jim, Ted,
I would expect you can easily build a plane this size at 62oz, Jim.  If you agree, that gives you a point to start from.

 
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Offline Randy Powell

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Re: Design by Committee
« Reply #3 on: February 12, 2006, 11:27:28 PM »
>>Be really critical and honest about past performance (your own at the building bench) and work from that premise.<<

Wish I had some sort of consistent benchmark to draw from. I seem to build an insanely light plane followed by an unacceptably heavy plane, followed by a very light one...ad nausium.

The Cobra I'm building looks to come in under 40oz. The new PA plane (at 740 squre inches) also looks to be quite light, coming in at under 55oz. But the plane I built last winter was a real pig. And the one before that was no lightweight. I don't see that my building practice is much different from plane to plane.

Hmmm...Maybe it's those helium tanks I just had refilled... :-X
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Offline dirty dan

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Re: Design by Committee
« Reply #4 on: February 13, 2006, 02:19:17 PM »
If you are going to key off Brett's Infinity, calculate the fuselage side area he used and increase it at least by 25%.

Other than the above piece of advice shrewdly arrived at, I'll be merely following along. My only claim to fame when it comes to "design" is that I have not yet thoroughly ruined Mikey's SIG Skyray 35 design, although the second of three models built might still prove me wrong.

Dan
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Offline Ted Fancher

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Re: Design by Committee
« Reply #5 on: February 14, 2006, 03:55:08 PM »
Well, your moderator just spent a couple of days in heated discussion with medical professionals.  The occasion for which was to study the affects on the human body of crashing one's bicycle at about 10 or 12 knots.  I believe the Brits would term the ultimate maneuver a "bunt".

Suffice to say, the bicycle fared better than did the bicycle rider.  Seriously dislocated left shoulder (posteriorly which is,  I'm lead to believe, much rarer that the garden variety anterior dislocation suffered by mere mortals).  In addition, the knobby end of the bone (the humerus) suffered a break although they expect that to heal on its own assuming the life support system for it remains intact and functional.

Other than that, a very stiff neck (ya ought'a see the funny looking bicycle helmet now!  It doesn't look so funny after performing its magic, I'll tell you).  A very funny red ring all the way around my nose, a fat lip which makes me lisp even more than usual and a knee that looks like a fat toddlers after falling out of the tree house.

Four to six weeks for recovery assuming something more insidious doesn't sneak into the picture during physical therapy and then I'll be as good as new.  The doctor said there should be no reason I won't be able to win the US Open once I'm cured.  Which is good news inasmuch as I have a hard time winning the Fancher Open on even my best golf days prior to the spill.

Probably make completing the Jamison for VSC OTC out of the question.  I should be able to finish up the detail items on the Ruffy with no problem once I get out of the sling though.  Probably show up at VSC once again hoping to get in a maiden flight before officials start.

So, Jim, if you leave off the wingtips what's the span going to be?  How about the aspect ratio?  (I'd assume the flaps will be somewhere between 22 to 25% of the chord at all stations and probably full span).  Anyone want to discuss why that is of interest?

Ted

Offline Randy Powell

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Re: Design by Committee
« Reply #6 on: February 14, 2006, 04:35:51 PM »
>>Probably show up at VSC once again hoping to get in a maiden flight before officials start.<<

Join the club. My first VSC and it starting to look like the clear will be drying on the way to Tucson.

Sorry to hear about the shoulder. More practice doing shoulder rolls? Had a motorcycle wreak once. After seeing my helmet after the crash (I came out of it with just a few bumps and bruises) , I would never, ever ride a motorcycle again without a noggin cover.
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Offline Larry Cunningham

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Re: Design by Committee
« Reply #7 on: February 14, 2006, 04:57:00 PM »
Randy,

You COULD pull a Tony Lang and paint your ship at the
contest! No kidding, he actually built a model at the site,
painted and finished it. The Arizona sand kept him from
a 20-point finish.. ;->

Ted, I'm wishing you well on the injuries. Take care of yourself,
things don't heal like they did when we were 25 years old.

Best,

L.
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Offline Jim Pollock

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Re: Design by Committee
« Reply #8 on: February 14, 2006, 06:57:24 PM »
Ted,

Sorry to hear about you recent unfortunate encouter with an unyielding ground!

I weighed the wing and it is a whopping 12 ounces without benefit of helium.  Well, I will check on the span, area and aspect ratio in a few minutes and report back probably tomorrow.  Adding the flaps, horn and hinges will undoubtedly add close to if not more than 4 more ounces - - WOW a pounder of a wing!  Guess we'll need to keep the fuselage and empanage fairly light in order to keep this thing at least in the 4 pound range (64 ounces that is).  Does anyone have any great ideas on lightening up the rest of this plane??

Thanks all,

Jim Pollock

Offline Jim Pollock

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Re: Design by Committee
« Reply #9 on: February 15, 2006, 06:58:24 AM »
Ted, all

Wing Span is 59" with the tips
Root Chord is 10"
Tip Chord is 8 and 3/16"
Aspect Ratio is appx 6.4 without the flaps

Yes Ted, please enlighten the rest of us about the 20-25% full span flaps?

I'm guessing that about 23% will give a total wing area in the 663 sq in range.

Jim Pollock   ???

Offline ash

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Re: Design by Committee
« Reply #10 on: February 16, 2006, 01:38:48 AM »
While you're still in the boundary setting mode, consider a few things like:

Overall Style: How it will look etc. Sleek and long like a Trivial Pursuit or fat like a Jug or Bearcat? Modern or classic lines?

Material Limits: Can you deal with composites, carbon veil, tow etc or strictly balsa/ply? Glass or silkspan? Moulded shells or carved?

Special features: Take-apart, adjustability, how many appearance points to aim for etc.

Your Flying Style: What are you comfortable with (we mostly don't know) in terms of lap time, smooth or hard cornering, any part of the pattern that troubles you?

I got a bit carried away there, but I guess some of those things can help formulate the design.

Adrian Hamilton - Auckland, NZ.

Offline Jim Pollock

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Re: Design by Committee
« Reply #11 on: February 20, 2006, 04:51:36 PM »
Ted, All

Well, it's time to decide on moments and stab/elevator area and ratio.

From general convention, I would expect 9.5 inches of nose from the leading edge of the wing to be about right and maybe 17.25 inches from the trailing edge of the wing to the trailing edge of the stab.  I know that's not the aeronautical engineering way of figuring things but, modelers use it pretty often.  So, I will too!
I expect the wing to be 663 Sq. In. with the flaps, so we need to develop a stab/elevator combination that will easily change the direction of this thing.  Oh, yeah, just one more thing, this thing's name is going to be Excelsior, that's a sister ship to the Enterprise - sorry Randy!  I just like the always higher aspect to the meaning of the name. 

I guess I'll need to go back over to the SSW forum and look up Brett's formula for determining an appropriate area for the stab/elevator, I think a final product over .56 is desired?

Jim Pollock   ::)

Offline Ted Fancher

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Re: Design by Committee
« Reply #12 on: February 20, 2006, 07:20:08 PM »
Randy,

You COULD pull a Tony Lang and paint your ship at the
contest! No kidding, he actually built a model at the site,
painted and finished it. The Arizona sand kept him from
a 20-point finish.. ;->

Ted, I'm wishing you well on the injuries. Take care of yourself,
things don't heal like they did when we were 25 years old.

Best,

L.


Thanks, Larry.  You are exactly right (and we haven't agreed all that much the last couple of years!  ::) )

Started P.T. today and it looks like everything will probably work out OK eventually.
 
Ted


Offline Jim Pollock

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Re: Design by Committee
« Reply #13 on: March 10, 2006, 07:41:00 PM »
Designers,

     Thanks to Brett I now am armed with the tail area ration formula it is.

             Tail Area X Tail Moment / Wing area X Wing Chord  (at root I suppose?)

             Where Tail Moment = CG to the 1/4 Chord of the tail group
             (ie, Stab and Elevator) actually CG should also be the wing 1/4 Chord
              I believe, but Brett uses CG for simplicity.

             Lets see:   My Stab/Elevator combo as I have laid it out on paper has
            a root total chord of 6.75 inches and a tip chord of 5.0 inches.  The span
            totals 26 inches.  so the tail group area = 6.75 + 5.0 / 2 X 26
             which is; 152.75 sq in.  My wing area will be 663 sq inches and the
            chord flaps included is 12.75 inches the moment arm from the quarter
            chord of the wing will be 25 inches.  Lets plug these figures into the
            formula and see if we can get something over .4 for an answer.

                                      152.75 X 25  /  663 X 12.75  =  .4517493

             Yes that gives some over the .4 goal!  I suppose we can add a little
              more area or moment arm if we can balance it with the engine and
              other items in the nose! 

              Thanks for all the suggestions so far.  Now we need to come up with
               what the fuselage and vertical stabilizer will look like.  I already
              know that DD suggested determining the side area of the Infinity
             then squaring it?   Naw, I don't think so.  Maybe just a little less than
             the Infinity.  Too much side area can be as bad as, or worse than
             too little I would think!  Ted, what do you think regarding side area?

             Jim Pollock javascript:replaceText(' :P', document.postmodify.message);
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Offline Jim Pollock

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Re: Design by Committee
« Reply #14 on: April 09, 2006, 06:07:47 PM »
Well, Golly y'all,

Looks like the committee decided to resign?  Hope the moderator didn't?

As far as the fuselage design of the Excelsior, I think the aft side view of
a Trivial Pursuit is very good.  Just some changes so it doesn't look exactly
like a TP and were in business with the final part of the excelsior design.
I hope we all have had fun with this? 


Jim Pollock

Offline Bill Little

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Re: Design by Committee
« Reply #15 on: April 09, 2006, 06:17:59 PM »
Hi Jim,
The "design" sounds good!  The Excelsior  should have all the right numbers.  My first post on this was my thinking that about 62 oz. might be a good weight.  And I wouldn't be afraid of it in the mid 60s. How does it look so far, weight wise?
I missed the power train you are planning to use. ??
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Offline Jim Pollock

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Re: Design by Committee
« Reply #16 on: April 10, 2006, 05:49:11 AM »
Bill,

The power train is a PA .61 with the hi-tourque pipe.

Jim

Offline Bill Little

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Re: Design by Committee
« Reply #17 on: April 10, 2006, 06:41:54 AM »
Bill,

The power train is a PA .61 with the hi-tourque pipe.

Jim

I don't know how I missed that, Jim!  I just went back to your original message and saw it!  :o :-[
Thanks!
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Offline Jim Pollock

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Re: Design by Committee
« Reply #18 on: April 11, 2006, 05:14:26 AM »
Bill, Robert

Why is every post I make numbered post #19?????

Just curious.  Do I need to change something somewhere?
also, it seems now when I try to pull one of the smily faces
into my text the entire text of the script is displayed...... minor
I know, but still a bit annoying.  Well gosh, I couldn't even get
one to pull into this post as evidence...aaaggghhhh - oh well..

Jim Pollock

Offline Bill Little

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Re: Design by Committee
« Reply #19 on: April 11, 2006, 09:42:05 AM »
Bill, Robert

Why is every post I make numbered post #19?????

Just curious.  Do I need to change something somewhere?
also, it seems now when I try to pull one of the smily faces
into my text the entire text of the script is displayed...... minor
I know, but still a bit annoying.  Well gosh, I couldn't even get
one to pull into this post as evidence...aaaggghhhh - oh well..

Jim Pollock

Hi Jim,
The ??? smiley is there as I red your reply, but I don't follow the "post #19" part. (??)
Bill <><
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Offline Jim Pollock

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Re: Design by Committee
« Reply #20 on: April 16, 2006, 04:18:02 PM »
Bill,

I thought the board was numbering each separate post.  Now I see that the
board is only keeping track of the total number of post made.


Jim Pollock, The dummy   ''

Offline Steve Helmick

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Re: Design by Committee
« Reply #21 on: April 16, 2006, 06:10:27 PM »
I'll vote for a 2" Randy Aero Needle Nose Spinner, Randy Aero Carbon LG and a painted canopy. Oh, and red, white and blue, with lots of stars, please. y1  Steve
In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.

In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

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Offline Jim Pollock

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Re: Design by Committee
« Reply #22 on: April 17, 2006, 05:54:40 AM »
Steve,

Yes to all except the red, white and blue with lots of starts, I've already done that too many times!

This one gets yellow, orange, black and and white with a goodly number of checkerboards - I havn't done checkerboards yet!  Probably something like
Dale Barry's Tempest II

Jim Pollock    ;D

Online RC Storick

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Re: Design by Committee
« Reply #23 on: April 17, 2006, 08:58:39 AM »
Bill, Robert

Why is every post I make numbered post #19??

Just curious.  Do I need to change something somewhere?
also, it seems now when I try to pull one of the smily faces
into my text the entire text of the script is displayed...... minor
I know, but still a bit annoying.  Well gosh, I couldn't even get
one to pull into this post as evidence...aaaggghhhh - oh well..

Jim Pollock

Well I am not sure what you are doing? But I did go in and look at your settings. Let me know if it is working now. >:D x: ^-^ b1 j1 n1 y1 <= '' %^
AMA 12366

Offline Jim Pollock

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Re: Design by Committee
« Reply #24 on: April 17, 2006, 01:24:48 PM »
Hi Robert,

I finally figured out that the board was keeping track of total number of posts, not numbering each separate post.  I hope you do well at the Nats this year!
Hopefully you will have enough time practicing with a coach.

Jim Pollock    ;D  ::)  y1

Offline Jim Pollock

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Re: Design by Committee
« Reply #25 on: May 05, 2006, 06:18:02 AM »
Well for now anyway,

I need to lay of from building this airplane until I get relocated to Anniston, AL
It's time to start packing boxes ect,  Ugh!  :P

Jim Pollock 


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