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Old Yesterday, 02:41 PM
altitude adjustment
thumbhead's Avatar
USA, CA, Irvine
Joined Mar 2005
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Pull/Spring on 2.5m

I've had a pull/spring setup for rudder and elevator control on a few DLGs and was wondering if anyone has used this setup on something larger.

I have a Pulsar Pro 2.5 RES that I plan on building without a motor and was thinking pull/spring would save a good amount of weight. I was thinking of using a pair of HS65 MGs and should be able to use a pretty beefy spring compared to what is usually used in DLGs.


Mark
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Last edited by thumbhead; Yesterday at 04:48 PM.
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Old Yesterday, 02:59 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
21,859 Posts
Yes.
Bob McGowan used to do that on his lightest Supras, with a built up custom rudder before the non molded ones were out.
Another thought is spring/pushrod assist.
A spring in the surface, but then use a very light CF rod in place of the string. Sort of a bit of insurance and able to push if needed. A .040 cf rod with bondable teflon tube doesn't weigh much.

R,
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Old Yesterday, 03:27 PM
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Mark:

I built a 2-meter Pures ("Pure RES") and used pull/spring for the V-tail. Between removing push rods, and having to remove ballast to maintain CG, I saved almost an exact ounce. I had originally installed the manufacturer's push rods in plastic tubes. I simply used the existing tubes as string guides, but still saved an ounce. A second Pures got pull/springs right off the bat, also using the plastic tubes.

I also use pull/spring as you do, on DLGs. I will be using it on more larger airplanes.

Yours, Greg
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Old Yesterday, 03:36 PM
altitude adjustment
thumbhead's Avatar
USA, CA, Irvine
Joined Mar 2005
518 Posts
Exactly the responses I was hoping for. Thanks guys.

Mark
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Old Yesterday, 03:37 PM
Detail Freak
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Its been my experience that the tubes also weigh quite a bit, depending on what ones they are...
That is why I am a fan of the bondable teflon. Its very light.

R,
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Old Yesterday, 03:41 PM
altitude adjustment
thumbhead's Avatar
USA, CA, Irvine
Joined Mar 2005
518 Posts
I plan on using glass beads at the exit holes with no tubes.

Mark
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Old Yesterday, 03:55 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
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Obviously that will be very light.
The only issue, if it is one, is getting the pull string threaded down the fuselage, and making sure they aren't rubbing or somehow twisted....
That's where having the tubing is an advantage, even if only the ends are secured. Makes a handy guide.
Once it's installed though, I think you are home free.
I'm looking at Beadalon wire for dlg's and other pull string installs. They have differing sizes.
R
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Old Yesterday, 06:43 PM
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Quote:
Originally Posted by thumbhead View Post
I plan on using glass beads at the exit holes with no tubes.

Mark
Hey, did you get that idea from me?

My Art Hobby Sky-V 2-meter has a V-tail with string/spring. In my build thread I show the installation with the glass beads and small pieces of teflon tubing at the fuse exit near the tail.

I had no problems at all with the performance. The plane has good control even at high speeds.
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Old Yesterday, 06:50 PM
altitude adjustment
thumbhead's Avatar
USA, CA, Irvine
Joined Mar 2005
518 Posts
I did Drew. Glad to hear it works well.

Mark
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