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Questions about CG Electra fuselage

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Old 05-20-2005, 09:41 PM
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monty_11
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Default Questions about CG Electra fuselage

Hi,

My son & I have just about finished the construction phase of building our Electra, but before putting the skin on it I thought I'd ask people's opinion on a few questions that I've been wondering about.
1) I've read a couple comments about the fuselage of the Electra being weak behind the wings. Is this anything to be very worried about? This plane will be used for very gentle soaring and basic glider training - no hard flying expected.
2) I'm a bit concerned that the tail may be susceptible to damage on landings. Since there is no tail gear and the stabilizer is basically on the ground am I likely to lose it when landing in long grass? Has anyone ever tried to velcro the stab on?
3) What about landing gear? Worth it or not? Single wheel, dual wheel, retract, no retract? Any opinions?
4) This one gives me the most worry. The battery compartment is only held closed by a single small screw (which holds the battery comp. clasp). With the weight of the battery sitting directly on this screw, and with movement in flight, what are the chances that my glider will drop the battery pack and attached electronics in mid-air? I'm thinking that maybe I should glue a locknut on the inside and replace the screw with a bolt.

Thanks for any feedback,

Peter.
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Old 01-28-2006, 03:11 AM
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sy5nak
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Default RE: Questions about CG Electra fuselage

Hi, it's been a while since you posted, and it looks like no one else bothered to reply.

By now you've probably found out a few things, but let me throw in my two cents.

I think that the single wheel under the CofG is good for a couple reasons. If you are landing on a flat and somewhat hard surface, this will keep the prop from digging in and causing damage to your engine.

On the same note, may I also recommend a collapsable prop?

Locknut sounds like a good idea.. let me know how that went.

Velcro also sounds interesting... let me know how that went as well.

In closing, my dad bought me my first electra in '92. I should have let him fly it first!

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Old 01-28-2006, 12:45 PM
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monty_11
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Default RE: Questions about CG Electra fuselage

Hi sy5nak,

Thanks for the reply
In the end here's what I did ..... and what happened

I glued the stabilizer on as per the plans and I haven't had any problems with it being pulled off on landings, although the grass on our flying field is kept relatively short. Bushes however tend to hang onto the stabilizer quite well. I've only had one seriously bad landing due to the Electra gliding so well, that I ran out of field - and height - and had to put it down in some bushes and gravel off the end of the field.

I'm getting a bit ahead of myself though. Back to the first flight and my biggest concern over the battery compartment. In addition to the small clasp included in the kit, I installed a small block of balsa at the end of the battery compartment under where the post for the clasp was mounted. I put a strip of velco on this block and the back of the battery comp. door. to give it extra strength. After this mod, I balanced everything up, charged up the batteries and headed for the field early on a Saturday morning. No one was at the field when I got there, which is probably a good thing, so I headed over to the long grass on the far side of the field to launch. With no small amount of concern I set the throttle to half, gave it a chuck and it flew - for about 20 feet - before a wing tip caught a small bush and it cartwheeled into the grass. Checked it out and found I had pulled a couple of the cowling screws loose and cracked the thin plastic canopy, but other than this there was no serious damage. By this time our senior instructor had arrived and this time he launched it for me and I manned the radio. No problems this time.... lots of power from the cobalt 05 and up it went... and went... did I mention there was a nice wind blowing? Well, the instructor says ' better not let it get too high being the first flight and all' so I put the nose down and dropped 50' or so, went into a nice right bank off the end of the field and promptly launched my battery door, battery and who knew what else, into the pond.
After a couple seconds of trying to pull out of the bank, I realized that without the battery in the plane I had no control and stood there watching many hours of effort slowly spiralling down over the trees .... remember the wind I mentioned? Well, to give the Electra credit, it continued to fly, porpoising up and down because the CG was now off, and spiralling further off the field. The instructor, having been through several lost planes and subsequent recovery operations, starting marking the probable point it would contact the trees - triangulating on several landmarks. We finally lost sight of it when it hit the trees and off we went to track it down. Long story short - we found it right along the path the instructor had plotted after about 15 minutes of searching. To my amazement, it had fallen through the only hole in the tree canopy, bounced of a nice leafy bush and hit the ground without a single tear in the covering. The only real damage was a crack in the cowling former. I guess you don't get much luckier than this.
Back to the shop..... this time I put a heavier ply batttery door on, installed a single foam wheel under the CG, and put two 4-40 screws through the door into blind nuts in the balsa block that had originally held the velcro strip. Oh... luckily I didn't loose any of my electronics - the deans connector on the battery pulled out of the ESC before it could tear all the electronics out of the plane.
Since making these mods, I have put probably a couple dozen flights on the Electra and it flies very well. I need to get a new battery this year since my backup to the one I lost was only a 6 cell instead of a 7 cell, but it still pulls into the air well with the 6cell. Flight times are averaging around 15-20 minutes with no thermalling so far.
The one thing I wish I'd done differently with the mods is to have used a heavier guage wire for the landing gear. On heavy landings it will bend the wire and push the wheel up against the bottom of the battery door. This is a good thing in a way, because I can tell if I've made a good landing by looking at how bent the gear is

Anyways, I'm pretty happy with how it's worked out and I'm looking forward to this year's season. Have a couple new planes to try this year as well, so I should keep myself busy.
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Old 01-28-2006, 01:32 PM
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sy5nak
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Default RE: Questions about CG Electra fuselage

Thanks for the info.

I will be building my new electra shortly, and these are some good suggestions.

I'll post a website here soon, where you can watch my building strategies. I'll also be modifying the wings with the removable wing-tip option, as well as some ailerons. This should prove interesting...



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Old 01-29-2006, 06:44 PM
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Default RE: Questions about CG Electra fuselage

The electra is a tough plane. I have one that is over 15 years old and still flying. I've had to reapird the wing over the years and the fuse needed a little TLC here and there.
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