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Old Mar 26, 2014, 08:26 AM
F2D Pilot/Mechanic
Bob Mears's Avatar
United States, TX, Lubbock
Joined Dec 2011
307 Posts
One other thing I havent seen mentioned yet, and came to light when you said it didnt have much line tension when flying...make sure you have some lead out sweep. If the lines exit forward of the CG it will create all the problems you have been having. The line exit should be about 1" behind the high point of your airfoil.
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Old Mar 26, 2014, 03:03 PM
Registered User
Joined Jan 2008
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I always wondered about leadout position in combat airplanes, as it was way back from where I would put it in a stunt ship. I built one of Bear's monoboom airplanes just for fun, With ST G21-35 on case pressure. I put in adjustable leadouts. First flight with leadouts slightly behind CG, as in a stunt airplane. It was wild. Second and subsequent flights with leadouts back in the usual combat airplane position. I suppose line drag on 018 lines at 100+ MPH is much greater than on a stunt airplane.
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Old Mar 26, 2014, 04:28 PM
gizzo don't tweet
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Adelaide, Australia
Joined Jan 2008
2,953 Posts
Thanks Junkstar! .
Bob and Jim, I had no idea about how leadout placement affected the way a plane flew (other than that they obviously did )so I just built it per the plan expecting success. More fool me... Mr. Arnold sent me a few articles which helped clear up that mystery, but I still have a lot to learn. Thanks for sharing the info about the combat planes, that's interesting. I built a coreflute combat a couple years ago that's a lot of fun. Doesn't turn very tight but otherwise its ugly but fun. It has an adjustable leadout made from a bent wire shoved into the flutes on the tip of the wing. How does a proper adjustable one work?
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Old Mar 26, 2014, 06:54 PM
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Joined Feb 2009
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That's good advice about the leadouts, but looking at the photos of your model, I don't think they were the problem. The centre point of them was well and truly behind where your CG should hopefully have been, so they shouldn't have caused the model to fly in. (Leadout position on these old designs was often very conservative.)

If the model is straight, has a bit of outthrust and right rudder, and sensible leadout position, there isn't much left to make it come in at you on takeoff. Grass stalks and seed heads can certainly do it, but otherwise, I'd be suspicious of your tip weight and lines. It sounds like you probably had 52' of Laystrate (heavy gauge perhaps?) and that may have been simply too much for this size model and the amount of tip weight in it. I know you said it was a big washer, but it'd probably want to weigh at least 25 or 30g.

Steve

(PS a proper adjustable leadout guide is usually a length of ply with a slot cut in it. The leadouts go through a slider which can move back and forth in the slot, and is clamped with a bolt & blind nut. A Vulcan shouldn't need one, though!)
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Old Mar 26, 2014, 09:28 PM
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downunder's Avatar
Adelaide, South Australia
Joined Sep 2003
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Here's a very simple adjustable lead out guide I used on a flat wing stunt trainer I built for my son. The guide is just a piece of 1/8" ply recessed into the top of the wing. Same principle applies if it's fitted inside a wing tip. The brass bushing in the alloy slider extends through the ply slot to keep the slider straight.
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Old Mar 26, 2014, 10:34 PM
gizzo don't tweet
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Adelaide, Australia
Joined Jan 2008
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Thanks guys. That leadout looks pretty simple. Learn something every day . Steve, the lines are set up for 2.5cc rat race so possible are too heavy for this model. Weirdly, the flat wing thing (it's a very old Aeroflyte Cherokee without the canopy) I'm flying manages ok on the same lines with no fin at all and about 75 watts of power with about 5' of line wound back onto the handle. Only in a flat circle though. Any climb and the lines sag and pull it in. downunder, thanks for the pic. Do you mind if I ask details of the son's stunter and whether a plan is available?
Cheers
s
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Old Mar 28, 2014, 02:07 AM
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Adelaide, South Australia
Joined Sep 2003
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Quote:
Originally Posted by gizzo View Post
Do you mind if I ask details of the son's stunter and whether a plan is available?
There aren't any plans because I just made it up as I went along . However the wing is made from 2 lengths of 1.2 metre by 12mm sheets butt glued together and tips added for an overall span of 1.4metres. And flaps. I've covered the wing with doped on nylon for extra strength. Fus length is .9m to the firewall with an RC type mount for the engine bolted on. Tailplane is 60cms x 15cms with (like the wing) a bit of taper front and back for appearance ( ) sake. Original engine, as in the photo, was a Magnum 53 but that was a POS so I ended up using a Stas's 42 RE with a pipe which worked brilliantly. Of course, later I found out there were only 50 of these engines ever made!

For a stunt trainer it flies rather well considering the flat wing but I can do the full pattern with it although squares don't look too square . For learning round manoeuvres it's not bad at all.
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Old Mar 28, 2014, 03:12 AM
Diesel Danny
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Australia, VIC, Bellbridge
Joined Nov 2013
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G'day.

Looking at your original photo's it appears that you used a 4" pitch prop. This is a little low compared with what the original I.C. engines would have utilised. Most .15's would have used something like a 7x6 at about 13,000 rpm+. With an I.C. engine this at the low torque end of the power curve. The pitch is required to get the airspeed up.

Regards * Danny *

ps. Failing that, maybe the original designer is rolling in his grave because you put an electric motor in his design and he's hexing the model ;-)
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Old Mar 28, 2014, 06:53 AM
gizzo don't tweet
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Adelaide, Australia
Joined Jan 2008
2,953 Posts
Thanks downunder.
Danny, that's funny Good one!
You're right, it's an 8x4. I couldn't remember if my Enya 15 ran an 8x4 or 8x6. Anyway, seems to be no shortage of power.
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