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Converting C/L model to RC


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there's a KK Spectre thread on here which triggered a couple of memories of my C/L days. I started to wonder if the Spectre could be scaled up to about 60" span and converted to R/C and if so is there anything I'd need to change?

my initial thought is the fuselage would need to have the distance from wing to tail increased. Is there a formula for this or do I just make it look right?

id be interested in any thoughts or opinions

thanks

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There have been pull-out plans for a few conversions, the Marquis, Skystreak and Firebird come to mind. For the Spectre I think you could stretch the fuselage slightly, if I remember rightly you would be looking to make the tail moment at least 1 1/2 times the wing chord. Or build as is and use very small elevator movements.

I thought about the Mercury stunter, was it the Crusader? That probably wouldn't need scaling. Google tells me it was the Crusader and it had a 56" wingspan. That would make a nice sized model. Or what about a Spacehound? That was a stylish looking model.

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There's a whole load of C/L stunt classics with really nice lines ..... no pun intended, that look like they'd adapt to a nice sport RC model. Another one I was always going to build and never quite got round to it is the Comodore ( plans on outerzone) it might even lend its self to EDF power who knows.

Anyways, thanks for all the excellent suggestions, looks like I've a lot of pondering to do

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This is a scaled down conversion of a Nobler original by Georg Aldrich.

Why scaled down, because at the time of building there were limited range and numbers of brushless motors.

Some aspects were redesigned by necessity.

A major fault is the rudder is pretty useless.

Could do with UC, there is not enough room for UC, mostly down to size of model and the Lipo.

Another limitation is that the fuz is highly tapered, which means that apart from right at the front, there is little room.

If I were to make another it would be much bigger, to free up space, for equipment.

Apart from the negatives, it still is flown, handles generally well, no real stall. You just have to accept it originally was designed to go round in circles. Not designed to specifically roll, knife edge, nor necessarily go fast (more a single speed, what ever it was doing).

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I have a Spectre, which I had thought of refurbishing.

The more I looked at it, the more it became apparent, I would have to start from scratch. The panels are odd lengths. One side is full of Plasticine. The body would have to be opened up to get rid of the coupled elevator and flaps. The fuel tank is built in of wedge type. Plus the model is in a sorry state. Apart from these issues, I have lost the drawing.

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The Spectre had a horribly weak spot where tehflap connector caame through the fuselage sides just below the rear of the open cockpit.

I have even seen one snap in mid air,

WE learned to put a ply doubler in that area,

Not so much a problem with a radio version but I would have a doubler from the firewall back to behind the wing anyway

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A typical type of design limitation with respect to RC use is the flap, which we would want as an aileron. Outboard they often are quite narrow, compared to the root. This reflects that the actuation is a one piece torque rod type of wire, actuating at the root. The arrangement is the opposite of having the principal area at the tip for an aileron.

The body tends to narrow in the middle as there is only the bell crank there, it does not need to be wider. The narrowness helps with the tracking, in conjunction with a rudder often set to turn the model out of the circle, to help in maintaining line tension in the cross wind part of the circle.

Possibly team racers offer a better CL to RC model, as the rules as I remember them had a minium cross section. Although the latter mono wheel types look nothing like a full size racing plane.

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I converted a Crusader to R/C sometime in the 1980s. Modified the flaps from being coupled with elevator to make them act as ailerons. Initially they weren't very good being very narrow near the tips. Added extensions at the tips to make them wider ad this improved things enormously. Also had to remove part of the inboard C/L wing to even things as far as the wings were concerned. Flew well and could turn very tight loops as I found on one flight when it was coming towards me and getting a bit low. Somehow I had managed to get it inverted without realising and was very surprised when on pulling a lot of up elevator it did a half loop downwards before flying away from me - a bicycle clips moment.

Sadly it was among other models, engines and radio gear which were stolen from my shed.

Malcolm

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Posted by Andy Stephenson on 04/04/2020 16:47:02:

CL models usually have zero dihedral to allow the control wires a straight run to the elevator bell-crank. If converting to one to R/C you might find significant adverse roll on application of rudder without adding a commensurate amount of dihedral to the wing.

A.

Care to explain why ?

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With the benefit of hindsight, I now favour the PM approach, rather than the path I choose.

PM seems to take the spirit of the earlier model, drawing/building a model which provides the facilities for the servos, cable runs, Lipo and so on, in conjunction with the constructional practices, and access to the interior, which are typical of this era, to achieve the functionality of take off, landing a level of stability needed as a RC model.

My mistake has been to adhere as closely to the original concept as is possible, only very reluctantly deviating from the original design.

I have also built another CL stunter by KK I cannot quite remember the name, other than the wing was a near triangle, in that case enlarged a lot. No pictures or model any more.

I would be perhaps tempted to go for an enlarged Team Racer now, the type that were almost semi scale such as the Mercury Mac or outlandish design such as the MAP Jabberwocky etc.

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For the last few years, I have a partly finished CL Peacemaker that I now intend to finish as an RC version. The wing structure is finished, but not covered and with no bellcrank mount bits.

"One day", when I'm feeling brave, I shall finish it with the profile fuselage, and cutouts for he Rx and elevator servo.
Mounting aileron servos in the thick wing will be dead easy of course and no rudder will be needed.

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Posted by PatMc on 04/04/2020 22:56:38:
Posted by Andy Stephenson on 04/04/2020 16:47:02:

CL models usually have zero dihedral to allow the control wires a straight run to the elevator bell-crank. If converting to one to R/C you might find significant adverse roll on application of rudder without adding a commensurate amount of dihedral to the wing.

A.

Care to explain why ?

If the vertical C of G is above the wing, as it will be on a low winger, then right yaw will induce left roll which is (to say the least) not expected behaviour for the pilot. For example, using rudder to counter adverse yaw from the ailerons would actually more than counter the ailerons instead and result in an opposite roll. A small amount of dihedral will cancel that out.
A good example, (which does look somewhat like a scaled up control line plane) is the Pete Tindals Excitation. Which had a massive wing cord and no dihedral. It flew very well and for years was very much my “go to” plane. But the lack of dihedral did make it very different to fly - it needed arm fulls of (say) left aileron when left knife edging or flat turning and vice versa when to the right.

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