Sounds to me like a really fun project.  I would suggest you make provisions to ad throttle later just in case you want to have even more fun with it.  Touch and go's are lots of fun.  Three line is simple to do and enjoyable.

I don't believe I'd couple the throttle and flaps.  When you drop the flaps, sometimes you need to feed in some throttle to stay ahead of the power curve and if they're coupled together, I think you might start a mad cycle of need for power and flaps? less power! less flaps! more power! less flaps! .....weeeell, I think you get the idea.
I seriously think they need to be separate operations.

I suggest you go read the rules for scale at the AMA site.   Most options like flaps, bomb bay doors, lights and retracts had to be separate from the throttle or even the elevation lines.   

Just do it!  Would love to see pic's of the final product.

Many a NATS winner has flown with flaps connected to, or controlled from, the throttle of a 3-line system.  I personally used such a method, first in a Zlin Akrobat (my first one; the second one had digital controls down the lines - in 1975!), and a Fairchild PT-19 (1st place NATS winner in Sport Scale).  But there were countless others before me who controlled their flaps with the throttle. 

I wrote about my method in the May 1980 issue of Model Aviation.  Basically the flaps would come up at complete full throttle; and they would come down at approximately 1/3 throttle.  It worked with an old "Digipace" dc servo and 2 micro-switches positioned on the throttle pushrod (the article shows a drawing). 

When sitting on the runway at idle ready for takeoff the flaps were down.  Advance the throttle to almost full throttle to takeoff with the flaps down.  At cruise altitude a momentary blip of full throttle would trigger the servo to lift the flaps.  Then throttle back to cruise speed with the flaps up.  The flaps would stay up until the engine was throttled back to a speed that I thought would simulate the downwind leg of a full-scale landing pattern, approx. 1/3 throttle.  At that point the flaps came full down and stayed there as long as I didn't go back to full throttle.  I could adjust the throttle setting during landing without affecting the position of the flaps.

It all worked quite well actually, although a proportional digital system is of course way better.

Mike

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Mike
Thank you so much for your posting. I truly appreciate your input. I am not planning to compete, just want to have fun and be able to do Touch and Gos. I don't plan any other functions beyond throttle and flaps.

Bill
The way Homer built his original Sharp Shooter he used 3/8 sheets for the sides plus a lot of blocks. He also had the radiator scoops operational and the tail group was made from 1/2 thick sheets. I do not know what was his reasoning but it flew well enough at 8-1/2 lbs to capture 3rd place. On a 46-1/2 inches wingspan, I would think that one would have to be extremely careful if keeping the weight down is a priority. I assume that scale models do not have the severe weight restrictions necessary for stunt. If you basically fly straight and level plus touch and go, well - the wing loading could go much higher. I plan on Very Much lighter model.
Joshua

Marcus
Thanks for sharing and kudos to your friend, very, very nice model. Looks like coupling the flaps and throttle works great.
Joshua

I'm not saying the coupled flaps would "wrong", it's just that with the throttle at idle with the added drag of full flaps, you can get so far behind the power curve that you might drop like a rock.  Power controls decent, attitude regulates speed on an approach.

Unless you're making an instrument approach...



 

One reason heavy scale models do OK is the ability to land, dead stop, and do the taxi lap without having the engine throttle down close to quitting.

Lighter models that do proper high flight and maybe even a loop or wingover often have trouble throttling down low enough to land and do the taxi lap without accidentally taking off.

Flaps sort of work against good touch-and-goes and taxi laps.  They force you to slow down even more to get the model to land and stay down.

Interesting. How would you control your descent rate in sailplane? 

Not being a smarty pants. The premise of the conversation is about tying flaps and power together.

Flaps control the approach angle... That's what they do. They change the aircraft's configuration. They are also draggy, so yep, you need to add power to maintain the same descent rate.

Like yourself, Chuck, I'm not trying to be a smarty pants, but I would never make an instrument approach in a sailplane.  I always wanted go up in one, never got to because I allowed me to be way too busy.  I feel I missed a great opportunity by not going.
Yeah, I know it's not too late, but, well, still busy ya know.
You're spot on about the flaps and the rate/angle of descent and power, and truthfully, this discussion has been going on for as long as I can remember being a pilot.  There are two camps, and the interesting thing is, at least in my opinion, neither camp is wrong because both approaches, (ooo, baaaad pun!) work.  The examiner I mentioned chuckled and finally closed out his comments with, "Whatever works."

Thanks to all who offered advice and opinions. Since my intial posting I received much valuable input and guidance from Clancy Arnold and based on what I have learned, I revised my plans. As it stands right now I am finishing a special handle with 4 control functions: Throttle, Flaps, Retracts, and, Rudder/Tail Wheel steering. I am painting the handle right now and by this weekend hope to complete the UTronics installation. Due to availability of fiberglass components, scale spinner, and canopy - I have ordered the plans and parts for Brian Taylor's 69" P-51D. They are without a doubt the most accurate scale plans for a P-51D ever. I have a Saito 82a engine and will most likely start building next month. I expect it to be quiet long term project, probably around 2 years to completion.
Joshua

Thanks Will.
The attached picture of Brian Taylor's prototype will give a good idea of the scale fidelity potential of this P-51D.

You have quite an undertaking there.  I remember a couple of scale modellers out in western KANSAS that said scale models are never complete.   Jeff Perez was one of them and Bob Simmons was the other one.

Update:

Before starting to cut parts, I wanted to have all the necessary hardware in hand. Obviously - the engine is a critical part. I did a lot of research and it is obvious that for the most part a 90 size four stroke is about as large as most would go. I envision the finished model will probably weigh in the range of 8-10 lbs, so, I had to decide between a Saito 90 and the new OS FS-95V. I hate noise so this is also a prime factor for me. I read whatever I could find on the new OS FS-95V (not a whole lot out there), and what got my attention was the fact that the engine is a real torquer and has a muffler designed for low noise. I decided to invest in one, and broke it in yesterday and this morning. I tend to run my engines slightly rich so, I broke it in with a Master Airscrew 14-6 on Omega 5% Nitro Castor/Synthetic mix. Here is what I found out:
At full throttle with the 14-6 the engine can turn in excess of 10,000 rpm.
Idle can get down reliably to around 2200 rpm.
Vibration level is extremely low.
Deep growling sound - even at wide open sound. None of the obnoxious shrill of 2 strokers or even high performance screaming 4 strokers.
I than switched to a Master Airscrew 15-8 which is the largest recommended by OS for Scale Models using this engine - 7500 rpm wide open.
I have seen a test on youtube where this engine spun a 14-6 prop at around 11,000 rpm and produced 9 lbs of static thrust.
To sum up my experience so far: Absolutely Fabulous little gem! The easiest to tune engine I ever ran, noise friendly, extremely powerful and steady runner.
In addition to the engine I just finished building a handle with 4 control functions.
Time to start cutting wood:)

Thanks Will

Glenn
I would encourage you to look into a Brian Taylor Spitfire. Start by finding a build thread for one here: http://www.rcscalebuilder.com/forum/forum_topics.asp?FID=4, this will give you a very good idea what it takes to build one. Parts and plans are available here: http://www.bhplans.com/BTPlansPg1.html and here: http://www.trapletshop.com/gb/c/1168/modelling_plans_and_parts
Joshua

Joshua:

That is a really great job on that handle! What is the black device on the extreme left of the handle assembly? Also, what is the yellow material that you have finished the control panel with? Is that just paint?

Jim Fruit

Throttle idle trim pot.

I want to know if this beautiful piece of equipment will be for sale some day?

Blessings
Allen

In reference to reply #20 by Fred Cronenwett:
Fred wisely suggested getting an ARF and converting it to CL to serve as a test bed, back-up and a trainer. Well, the opportunity presented itself today on RCGroups in the form of a Top Flite Gold Edition P-51 "Big Beautiful Doll", 65" wingspan airframe. The asking price was less than half that of the kit, and, this is a complete airframe that has been flown as RC before and the builder moved on to other planes and gave it to a friend who is into foammies and is not interested in putting the P-51 back in the air. I will head to Atlanta, GA Friday to pick it up. I plan to convert it to CL rather quickly since I already have the engine, retracts and servos. I anticipate that it will be very close in performance to my intended scratch built P-51D model while serving as good practice and intro to CL Scale. Pictures can be found here.
http://www.rcgroups.com/forums/showthread.php?t=1813802
What do you guys think?
Joshua

Fred
Thanks for the input and encouragement. I have a PDF copy of your book on CL Scale. Shall I follow the recommendations for bell crank installation per the book? Does the bell crank go on the horizontal center line of the plane (engine thrust line)? Any other practical advice you can offer is most welcome.
Joshua

"On the P-51 you will want the bellcrank just above the wing in the fuselage, don't put it too high becase the vertical location also matters."
Questions:
When you say "Just above the wing in the fuselage" do you mean just above the wing cradle in the fuselage? (since this is a removable wing).
Also, the fuselage is probably about 4" wide, why would there not be enough room for the bellcrank to swivell around even if mounted on the center line? I plan on using a 3-1/2" - 4" bellcrank.

Thanks

Joshua

Keith
Thanks for your contribution. Does this mean that I can literally place the bellcrank in the wing? I don't recall ever seeing a picture of a low wing WWII plane where the leadouts did not come out the side of the fuselage. I hate those and would much rather have the bellcrank in the wing where the only portrusions are the ends of the leadouts coming out at the wing tip.
Please elaborate some more.
Joshua