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Old Jun 26, 2012, 06:56 AM
RFJ
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Build Log
BritKit Build Off 2012 - Mercury Crusader

Time to start a second model in the BritKit build off but this time something completely different from the Veron Phoenix.

A friend of mine is a top class control line stunt pilot who has competed successfully in many national and international events. When watching him fly his FAI class models I had often wondered how they would go without the lines. Only one way to find out

I looked at the KK Spectre and Mercury Monarch but I really wanted a "full size" F2B class model and was too lazy to scale them up. This limited the choice to a Mercury Crusader or a Performance Kits Pinnacle although there may have been other kits available back then that I am not aware of. Anyway, I chose the Mercury Crusader and managed to get an excellent full size plan from Derick at Model Plans.which has all the parts traced and drawn from an original kit.

One or two minor fuselage modifications will be needed to produce a practical electric powered R/C model.

July is a holiday month in this part of the world (Battle of the Boyne and all that) so there may well be some short interruptions to this build log but we will no doubt get there in the end

Ray
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Old Jun 26, 2012, 07:37 AM
Blueplaidcanard flyer
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Nice,plenty of wing area and the tail looks to be a good size.
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Old Jun 26, 2012, 07:53 AM
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Good choice Ray; if I remember rightly from reading the (I Think) M.A. review the Pinnacle was a bit of a dog!

Watching with interest as always. I've added your link to the build off thread.
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Old Jun 28, 2012, 07:38 AM
RFJ
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Quote:
the Pinnacle was a bit of a dog
Didn't know that so it seems I have, fortuitously, made the right choice

Of course control line stunters have been flown successfully before with R/C eg. Nobler, Thunderbird, Peacemaker, Squaw and probably many others. The general layout is not dissimilar to early FAI pylon racers like Frank Van den Bergh's Phaeton. I had one of these back in the early 70s and it flew beautifully.

Looking at the plan I thought the nose too long and the tail moment too short so I reduced the former by 1" and increased the latter by 2". I also increased the fin/rudder area very slightly. Everything else is as per the original.

Weight is shown as 3lbs which will also be my target for the R/C version.

Structure will use my own preferred methods and wood sizes and yes I'm afraid this one will also use a foam wing and plastic covering.

I have cut a complete kit of all the major parts and collected all the hardware I will need so construction can now start.

Ray
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Old Jun 28, 2012, 08:43 AM
Blueplaidcanard flyer
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On my nobler I left the nose and tail moments as drawn and should have done what you did,as pitch was a bit twichy.One of the guys bought the nobler and still flys it but he put a glow engine in it and the covering is starting to lift.
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Old Jun 28, 2012, 10:06 AM
RFJ
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I think it's all a matter of compromise. We want to try and preserve the essential character of the model without inhibiting it's potential flying characteristics. I have been told that even back then a standard mod to the Crusader kit was to add at least 1" to the moment arm.

These designs have a sharp pitch response to enable them to fly very tight corners. I wish to emulate this to some degree but pulling a sharp 90 degree turn at full throttle one and a half meters above the ground from a vertical dive is not my idea of fun

If the basic handling is OK I will try the coupled elevator/flaps used on these designs. The balance point for the standard control line Crusader is shown as 20% MAC. . Exponential could be useful on the elevator although it is not something I normally like to use - we shall see

Ray
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Old Jun 28, 2012, 10:32 AM
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With the standard tail moment on the nobler it took about 60% expo on the elevator to tame the beast,had it been 2" longer I'm sure it would have better.The nobler with full span flaperons had a nasty tip stall that took about 1/4" of washout to tame,it would snap with next to no warning either way it felt like going.
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Old Jun 28, 2012, 11:08 AM
RFJ
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Interesting. Not so worried about tip stall. The Nobler has a large piece of aileron moving about at the tip whereas the Crusader's blends to a point. Also looks like there is a bit less overall taper on the Crusader wing.

Can you recall your R/C Nobler's weight and balance point..

Ray
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Old Jun 28, 2012, 01:03 PM
Blueplaidcanard flyer
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Just a bit over 3lb by an oz or2 and I think about 28% mac for the c/g but if Ed has it out this weekend I can check as the strips on the fuse change from yellow to red at the c/g point I used.
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Old Jun 28, 2012, 02:33 PM
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Ray
From the more basic side of airy-dynamics - the rule of 'been there, done that, won't do it again'.

Like all CL stunters, it has no dihedral. That and the lower wing position will tend to make the rudder roll the model in opposition to the yaw induced - left rudder will cause a right roll, and vice-versa. I've designed and built two models with that set up, and won't make that mistake again. The second had its wing very little below the thrustline, but still had that adverse yaw-roll coupling.

On the moment arm, etc, I'd suggesst you figure out the wing and tailplane areas and do a few basic sums on them and the CG. Regardless of your good intentions to stick to the design of the original, it will now be flying around without the benefit of being anchored to a pilot who is only concentrating on one single matter.

I too would put a 90 degree pullout from a vertical dive at five feet above ground into the 'emergency manuevre' bracket for an RC model

D
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Old Jun 28, 2012, 04:33 PM
I like real wooden aeroplanes!
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Ray

I too would put a 90 degree pullout from a vertical dive at five feet above ground into the 'emergency manuevre' bracket for an RC model

D
The F3P guys do it all the time Dereck! Often at 5 inches rather than 5 feet! Mind you, they are flying a bit slower than our usual outdoor R/C models. What really bugs me though are the guys with the VP props who stop short of the ground and reverse back up! That's against nature
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Old Jun 28, 2012, 06:00 PM
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The F3P guys do it all the time Dereck! Often at 5 inches rather than 5 feet! Mind you, they are flying a bit slower than our usual outdoor R/C models. What really bugs me though are the guys with the VP props who stop short of the ground and reverse back up! That's against nature
Very true, but there's a slight difference between an F3P model and a converted CL stunt model, if I'm not wrong

'Guys'? Most of the F3P pilots I've seen appear to be children whose parents have bought them a new and possibly more exciting toy. At least they aren't sitting in front of a screen, though the reset button in the event of a crash is more likely to be a parent with a credit card...

Backing up an aircraft is not that odd. Once watched a C130 do it quite nicely, though it was on the ground and getting out of a parking bay...

Actually, F3P is pretty refined compared to the true floppydoppy world of '3D' - which we all know all aircraft flew in, until the marketing division appeared over the horizon. F3P is like FAI shot in slow motion, and indoors.

No-one, I trust, can object to indoor flying. I mean, no wind, no need for sunscreen/snowshoes, night flying almost 'on demand' and, if lucky, a very handy coffee bar steps from the pits. My spousal unit often wonders if I aren't joking - I've said the first thing I'm buying when we win the lottery is a gymnasium!

Still, compared to the 'musical jelliwobblers' I saw fly at the E Fest this year, F3P is somewhat, well, boring. Fortunately, state registered old ph*rts are not allowed to buy such devices, so mostly we're okay.

Back to normal programming...

D
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Old Jun 29, 2012, 06:08 AM
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.........Most of the F3P pilots I've seen appear to be children whose parents have bought them a new and possibly more exciting toy. At least they aren't sitting in front of a screen, though the reset button in the event of a crash is more likely to be a parent with a credit card.............
I don't know if they're all children, but the 'youngins' appear to be the best at it. They've honed their hand-eye coordination by sitting in front of a screen. Yeah, watching a compulsory round is a little like watching paint dry. Just ask Ray. I think he's judged some F3P contests.
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Old Jul 01, 2012, 06:39 AM
RFJ
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F3P, F3A and judging...... a big subject and perhaps this is neither the time nor the place for a long discussion. What I will say is that as a judge I always try to remember that all the guys (young and old) have put a lot of time and effort into their building and practice flying and deserve my best attention no matter how "boring" and repetitive the flights become. Don't really enjoy it though - "judge not lest you be judged" keeps coming into my mind

Enough talk - time for some building.

Tailplane first as usual. I like the center core method rather than an open frame for tailplanes of this size and section. Draw the structure on a 1/16" sheet outline, add all the bits (twice - top & bottom) then carve and sand to section.

The lightening holes probably don't save much weight but show willing

My deliberate mistake was the V cut out in the elevators for rudder clearance. I just followed the plan and then it dawned on me that this was a control line model with a fixed rudder so the size shown would not allow for enough rudder throw. Easily corrected before covering. Finished weight covered with Oracover is 2.9 ounces.

There you go - model 1/3 finished already

Ray
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Old Jul 01, 2012, 08:55 AM
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There you go - model 1/3 finished already

Ray
By my reckoning you should be flying it by Wednesday then! Gary
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