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Old May 05, 2007, 12:32 PM
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United States, MN, Shakopee
Joined Nov 2006
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cool! i wish i could do that
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Old May 06, 2007, 09:53 PM
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Tango Juliet's Avatar
Mobile, AL
Joined Aug 2006
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WOW That's fast compared to mine. I did end up putting the OS 25FX on it and I'm pleased with it. I need to get just a little more RPM out of it, nothing a little needle valve adjustment can't cure. I've probably run 12-14 four ounce tanks through it now so it should be good and broke in. It's really the only airplane I have right now that flies, and I just love it! Speed isn't really an advantage in combat, manueverability is, and I can turn inside of almost anybody.
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Old May 07, 2007, 07:39 AM
Lower??
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Tucson, AZ and Abroad...
Joined Jun 2003
184 Posts
Yes, but at only 3oz lighter than my Norvel 40, I doubt you can turn that much tighter... :-) And the Norvel .40 is the SAME price as the .25FX

-Matt
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Old May 07, 2007, 10:47 AM
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Maybe I should clarify my response... Almost anybody at my field.
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Old Sep 14, 2007, 09:09 AM
Learning More Every Day...
Cincinnati, Ohio
Joined Aug 2007
24 Posts
Gremlin Plans

OK Guys,
I was sent this from the guys at RA Cores. It was set up by someones club - photos and advice. http://www.snhflyingeagles.org/pdf_f...tionPhotos.pdf
Hope it helps...

Mike
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Old Apr 16, 2008, 12:35 PM
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Joined Nov 2007
42 Posts
Streamer paper...

Okay, so no problems on the leader line, but how do you attach
the line itself to the streamer paper so that it stays on without
ripping right off?
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Old Aug 07, 2011, 07:22 AM
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United States, MA, Southbridge
Joined Feb 2010
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Quote:
Originally Posted by ERJ_Pilot View Post
Streamer paper...

Okay, so no problems on the leader line, but how do you attach
the line itself to the streamer paper so that it stays on without
ripping right off?
The way we have been doing it for the contests is to roll the ended down 3-4 times and then fold it sideways into thirds and wrap the string around a few times and knot it. The other thing is not to try to keep crepe paper intact at Mach 3 I'm very happy with the speed on my OS .32ABC powered Gremlin with unlimited vertical BUT, I use an 11x4 prop so I get torque instead of raw speed and it gives me nice smooth speed through all the maneuvers

Still selling them at the 1992 prices, just had to bump shipping and we have PayPal now for instant gratification http://www.racores.com/
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Old Sep 05, 2011, 03:15 AM
Geppetto
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United States, CA, San Francisco
Joined Dec 2005
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I built this one for a friend some time back.
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Old Feb 12, 2012, 05:24 PM
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United States, MA, Southbridge
Joined Feb 2010
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I will be posting an HTML version of the new instructions with clickable pictures in the next couple of weeks. Stay tuned here. The downspout is still available at Aubuchon's Hardware

We currently have 10 New England contests scheduled for 2012. You can see various Gremlin related videos on my YouTube channel Forgive the indoor stuff posted most recently, it is indoor (or build) season in New England. There is a Gremlin product playlist and a combat footage playlist on there.

Jim - RA Cores
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Old Mar 04, 2012, 04:50 PM
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Mt Tamborine, Queensland, Australia
Joined May 2008
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A friend and I both bought gremlins, he's managed to get his in the air but had a crash that destroyed his wing due to elevon flutter. He built it according to the plan with the end of the elevon trimmed back. He did have a bit of a gap between the wing and elevon and didn't fit any wing hinge tape or anything else to eliminate any effect from the gap.

His gremlin is powered by a .46 AX OS Max. It flew well and fast for several minutes at half throttle, but when it got opened up to wide open throttle, the flutter happened pretty quickly and he lost about 80% of one of the elevons due to the flutter (which was also loud).

He suspects the wood in his elevon may have been a bit soft. He covered his elevons with a film similar to solarfilm.

Given that I'm building a very similar gremlin, I'm keen to understand what has to be done to minimize the risk of flutter. Considering it only happened at WOT, I suspect overpowering the plane as we are doing requires extra effort? In the alternate build notes available on the gremlin site, I notice that David Beach trims his elevons even further.

Thanks
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Old Mar 04, 2012, 05:09 PM
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United States, MA, Southbridge
Joined Feb 2010
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Quote:
Originally Posted by tobermei View Post
A friend and I both bought gremlins, he's managed to get his in the air but had a crash that destroyed his wing due to elevon flutter. He built it according to the plan with the end of the elevon trimmed back. He did have a bit of a gap between the wing and elevon and didn't fit any wing hinge tape or anything else to eliminate any effect from the gap.

His gremlin is powered by a .46 AX OS Max. It flew well and fast for several minutes at half throttle, but when it got opened up to wide open throttle, the flutter happened pretty quickly and he lost about 80% of one of the elevons due to the flutter (which was also loud).

He suspects the wood in his elevon may have been a bit soft. He covered his elevons with a film similar to solarfilm.

Given that I'm building a very similar gremlin, I'm keen to understand what has to be done to minimize the risk of flutter. Considering it only happened at WOT, I suspect overpowering the plane as we are doing requires extra effort? In the alternate build notes available on the gremlin site, I notice that David Beach trims his elevons even further.

Thanks
hi Tony. Sorry to hear about your buddy's crash. The 46ax is way too much engine for the Standard Gremlin and things are going to happen fast at those speeds. When you get to anything over a .32 you really have to seal the elevon gaps as they are going to cause a lot of turbulence. You also need to look into possibly going to 4-40 pushrods and links for the Elevons. You want to make sure there is as little slop in the linkage as possible because going that fast, you are going to find some harmonic that will just get things vibrating and as your buddy found out, things break quickly. The other piece than can be done is to fix the outer 2" of elevon to the wing to reduce the turbulence factor at the tips. but even with all that done, I'm not sure the airframe is going to stand up to those speeds. to recap:

most important is sealing the hinge gaps.
second is to trim the outer portion of the elevons down (which you said he did)
next is to beef up the control linkage and get your connections as tight as possible. I have gone to these Dubro 4-40 ball links
use a heavy duty servo as you will lose the teeth if you get any flutter (by the time you hear it, the game is over except for the crying)
Fix the outer 2" of the elevon to the wing

They were really only meant for .25-.40 sized engines. Guys have used .46s but the AX is more like the power of a .60. Even when I use my .32ABC I down prop it to an 11x4 to get the torque but not the speed
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Old Mar 04, 2012, 07:27 PM
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Mt Tamborine, Queensland, Australia
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Thanks
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Old Mar 04, 2012, 07:40 PM
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USA, MA, Townsend
Joined Jan 2008
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Hi Tobermei ,
Coreman has some great info there and I would like to add my 2 cents worth. I build Gremlins for combat not for high speed but I do push the what I call " limits" of a good combat plane. I use a Thunder Tiger 36 Pro with a 10 x 5 APC prop for my open class and get awesome results although I believe the OS 32 is the best for a combat Gremlin. I use the Thunder Tiger because it is cheaper and feel I can compete with the OS. I use the stock 2 inch elevon with the end tapered down to 1 inch starting from about 12 inches in from the end. I attach the elevon with 4 ca type hinges with them at 1 inch from each end and the others spaced between. Leading edge of elevon should be beveled so you can get the gap tight and still have deflection. Then just seal the gap with tape of your choice.
But if you just want fast and not for combat I would just cut the whole elevon down to
1 - 1/2 inches or less and seal the hinge gap. I have seen Gremlins with a 46 and they do scream ! but in combat I can get the advantage with the lighter 36 most of the time. Like Coreman said, tight linkage and good servo's are going to help. Let us know how your flights go !
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Old Mar 04, 2012, 08:02 PM
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Mt Tamborine, Queensland, Australia
Joined May 2008
757 Posts
Thank Teambarger.

We've got quite an interest in the Gremlins at my local club ever since I ordered mine. We've got a total of six either being built or in transit to us.

I always wanted the gremlins to be a smaller motor, like a .25 or .32 but other's in the club said we should all use .46 as it's the most common motor likely to be laying around.

After the problem my friend had with his using a .46 AX and yours and Coreman's comments, I'm now looking for a smaller motor. I did as you suggested, beveled the elevon so I could get full throw with a small gap, but will now also tape the gap regardless of whether I use a smaller motor or not.

My own view is I want slower speed, not screaming fast. I may try it though, with the larger motor but with a slow fly prop. I use one of those on a .40 sized profile plane to good effect.

Good to hear you've used the CA hinges to good effect. I wanted to use them but avoided after reading the instructions.

I've finished the wing and was read to set the CG but now will wait till I see what other motor I can find.

Are normal sized servos with karbonite gears good enough?
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Old Mar 04, 2012, 09:00 PM
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USA, MA, Townsend
Joined Jan 2008
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Keep in mind that I build mine for Gremlin contest and I fly very aggressive so I don't build them to last a long time. If you don't use foam safe thin CA it will melt some foam on the wing if you use to much. I don't worry about it myself. I also just use standard servo's with plastic gears. I have never stripped gears or had a servo fail on me during combat.
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