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Old May 05, 2014, 02:07 PM
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New Zealand, Wellington, Paraparaumu
Joined May 2007
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Chevrons tend to flutter like that - at the root, and at the TE. Noticed that before I started building with EPP in the late 90's, all we had was DOW type foam, and flutter used to be quite destructive, as you've found, and at much lower speeds. After that always fitted a short straight carbon tube spar as close as possible to the TE as you've done in your repair. If that spar is stiff enough it should hold. I do suspect that one could design the planform, washout, wing section etc (i.e. the 'system') to not flutter in this way, but that part I've not been able to figure out yet... So in the meantime, just run a spar through there in all chevron builds
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Old May 05, 2014, 10:58 PM
Where's the wind?
the_canuck's Avatar
United States, CO, Denver
Joined Jun 2004
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How much Strapping tape was used before the NS covering? I couldn't tell in the pictures.

My 72" personal LJ has seen speeds over 150mph with no issues. I used about 1 layer all over of strapping tape top and bottom doubled up in the center section, 2 full length standard ribbon spars top and bottom, and 2 layers of 10mil NS. (It's harder to get the 72 strong due to the larger size). Oh, and I also gooped the foam before covering. Its flying weight is 60oz as it sits right now.

I'm Rick James back in the day clocked the single spar, 1.5lb black foam at 148 mph before his folded with a ribbon spar failure.

A larger tail will help slow speed performance but not really needed if DSing.

I hope to have the Lumberjacks back in production soon. They do fly nice! The airframe can be built fairly light but for DS you need to add some beef to the build. The plane flies even better when built heavy!

Andrew

www.canuckengineering.com
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Old May 06, 2014, 12:10 AM
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Christchurch, New Zealand
Joined Jul 2005
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Nice work getting it re-built! Easier than building a new one thats for sure. Giving me more motivation to finish my big EPP Chevron
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Old May 06, 2014, 11:14 AM
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screamin' eagle's Avatar
Pacific Palisades, CA
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Quote:
Originally Posted by the_canuck View Post
How much Strapping tape was used before the NS covering? I couldn't tell in the pictures.

My 72" personal LJ has seen speeds over 150mph with no issues. I used about 1 layer all over of strapping tape top and bottom doubled up in the center section, 2 full length standard ribbon spars top and bottom, and 2 layers of 10mil NS. (It's harder to get the 72 strong due to the larger size). Oh, and I also gooped the foam before covering. Its flying weight is 60oz as it sits right now.

I'm Rick James back in the day clocked the single spar, 1.5lb black foam at 148 mph before his folded with a ribbon spar failure.

A larger tail will help slow speed performance but not really needed if DSing.

I hope to have the Lumberjacks back in production soon. They do fly nice! The airframe can be built fairly light but for DS you need to add some beef to the build. The plane flies even better when built heavy!

Andrew

www.canuckengineering.com

Hi Andrew,

No strapping tape used in the build, but I added a 24" carbon tube trailing spar and covered the entire plane with 2-3 layers of 10 mil laminating film. I did not have the benefit of the instructions and could not find them on line, so I just went with what I knew. Just looking at it, using only ribbon spars on a plane that size didn't seem like it would hold up.

After handing around the transmitter at Parker, there was lots of interest in the plane and where to get a kit. My buddy (Chronic DS'er) and I agreed the LJ was the most fun to DS of all the foamies we brought along for his visit to the mainland (which included a lot of laps at Weldon with the plane). I think a new run of kits would do very well. I'd be keenly interested in a black EPP version too.

With the added spars, and even before re-covering, the plane feels very, very stiff in the center. I did replace the stock fin (which was getting batted around badly in the DS) and the gooped on center fin made a noticeable difference in DS. It's probably a bit oversized, but boy was it stable frontside and back.

Dominic
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Old May 06, 2014, 12:01 PM
Where's the wind?
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United States, CO, Denver
Joined Jun 2004
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It's pretty amazing how stable it gets at speed. Other designs tend to do the opposite. It can handle ratty turbulent grooves easier than some other designs I've messed with.

Maybe in a month or so I'll have my Hot Wire machine up again so I can cut some cores for kits.

Strapping tape does add quite a bit of rigidity to the plane.

Oh, and the Black EPP is not great. The white 1.9# is much better to build with. I gave the last of my black EPP to a local modern art sculptor here in Denver, John Mcenroe. I'm sure it's unrecognizable now, knowing his 'strange' ideas of art. It's better than using it for kits that for sure.

http://www.johnmcenroeart.com

Andrew
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Old May 06, 2014, 03:27 PM
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Pacific Palisades, CA
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Interesting re the black EPP. By the way, are you getting any BeEvos in soon?

Dominic
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Old May 06, 2014, 04:57 PM
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USA, NV, Reno
Joined May 2003
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I'd be interested in a Lumberjack but I'm not sure if I would go 48" or 60"

If you already have a Bee a BeEvo is cool but I think Bee>BeEvo .
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Old May 06, 2014, 06:07 PM
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Pacific Palisades, CA
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Quote:
Originally Posted by 1000MPH View Post
I'd be interested in a Lumberjack but I'm not sure if I would go 48" or 60"

If you already have a Bee a BeEvo is cool but I think Bee>BeEvo .
Stu,

My Bee is a really light build, about 20 oz. Flew a buddy's 30 oz BeEvo a bit and found it much more fun to DS, even in relatively light air. I know you love your Bees and have some heavy ones. Why less love for the BeEvo?

D
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Old May 06, 2014, 08:37 PM
Where's the wind?
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United States, CO, Denver
Joined Jun 2004
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Bee Evo doesn't handle rough air very well. It's pretty much all we have in Colordo to fly. Bee is better all round for flying in Colorado.
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Old May 07, 2014, 08:21 AM
Objects in mirror are losing
1000MPH's Avatar
USA, NV, Reno
Joined May 2003
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They don't turn as hard. A little bit harder to find a good CG for DS.
Still a very good wing but when I fly it back to back vs my 2 other heavy Bees I find it not as good.
You can try them for yourself at the end of the month if you like.
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Old May 07, 2014, 12:51 PM
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Cool, thanks Stu.
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Old May 07, 2014, 08:46 PM
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malad, idaho
Joined Dec 2004
2,436 Posts
good to hear from andrew!
here is my V2 LJ. i added a 10mm carbon tube spar and a short 8mm tube. just routered it out and glued them in with gorilla glue.
it will fly again soon.
i have an extra j-dub fin i'm going to use. it'll be a little more than necessary, but i think it'll perfect!

marty
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Old May 08, 2014, 05:01 PM
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Looks good Marty. Can't wait to get mine in the air again too.
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Old May 08, 2014, 05:04 PM
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Can you fit full-sized servos in the LJ 60?
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Old May 08, 2014, 07:37 PM
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Yes, they fit easily.
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