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Old Apr 12, 2011, 07:41 AM
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Originally Posted by I R Irv View Post
That's the Didel 4.5 Ohm motor, I thought it was the strongest on the market until I saw a 3 Ohm motor at Skyhooks just recently. How knows what the Cubs is could be even lower.
TODD
Possibly. Anyway, this is an interesting discussion that could probably be saved for another thread...

Back to some NB goodness.

I had a few more flights with NB #3 last weekend. This version has the reduced dihedral of ~15 deg, 20" dia and slightly reduced AUW as compared to #2. The reduced dihedral is noticeable, but when combined with more rudder throw, I like it!

My Motrolfly DM2203-1600 should be arriving this week. That'll take another 10g of weight off along with another 5g savings by swapping in a smaller ESC.

I had a bit of scare though... one of my other planes threw a prop blade on a GWS 7x3.5 HD as I was bench testing it. Keep an eye on those GWS props! If you see white 'stress' marks at the blade root, change the prop!

I then checked over the NB and tossed the 9x4.7 GWS SF prop I was using... the blade root was visibly weakened. I installed the new prop saver #PS3B I got from Don @ StrongRC. (Thumbs up to Don, quick service and good product!) The 7mm pilot on these adapters fits the GWS HD props perfectly. However I had to ream it out a bit to fit the shaft. Once installed, I put on a new GWS 9x5 HD which should be a lot stronger. No more props coming apart... I hope!
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Old Apr 12, 2011, 10:23 AM
flyin' fool
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Vancouver Island, Canada
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Quote:
Originally Posted by rcrich View Post
building a new nutball. were should i put the cg on a 34 inch plane?thanks rich
Start of with 25% or 8 1/2" at the wing cord and adjust from there to suit you flying style.
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Old Apr 12, 2011, 10:42 AM
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Weakened props and wobblies need lots of care and attention. I've seen lots of scary close calls over the years. Attaching a prop with an 'O' ring, no matter what the material is it's made from, is not really safe to begin with. Keep it to 70 watts max, do lots of inspections and use surgical tubing 'O' rings if possibe. Neoprene 'O' rings are meant to be compressed, not stretched and rubber bands arn't made from rubber.

I've had all three materials fail from old age and the props drop off on models just hanging from my shop ceiling. I no longer leave props on my models in storage mode just to make sure when the get do used they get a fresh attachment.
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Old Apr 12, 2011, 10:47 AM
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Good points goldguy.

I periodically inspect my props and o-rings. In this case, I simply forgot to give the model a pre-flight check. At least I had enough common sense to stay out of the line of fire when throttling up.
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Old Apr 12, 2011, 11:01 AM
When pigs fly rc
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Thanks GOLDGUY for the cg info. Now I have to come up with some kind of landing gear set up. Im torn between trying to enlarge the original one that my 17 inch had or come up with something new. I was tossing around the idea of something close to the bugs landing gear from light flite. Any one try something other then mounting to the motor mount plywood.
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Old Apr 12, 2011, 11:27 AM
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Hi Rich,
Lightweight RC Plane Landing Gear Tutorial (9 min 43 sec)

this is what im using for my 3rd NB. I designed my NB so it looks like a fat p51d mustang now. The landing gear really makes it look like one. I guess it's a bit heavy for NB standard, but it's really strong.
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Old Apr 12, 2011, 11:47 AM
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I've used Dave Reap's two-wheel LG described in pictures 1 and 2 here on my Nutballs.

Built with one continuous piece of .032 music wire (for small size NBs, e.g. 17" dia) and with the wheels at front as shown, it can spring back like the Bug's landing gear does on heavy landings. It's easy to make and uses no carbon fiber. Mine's held on with a piece of skewer at the apex.

If you decide you want the wheels further back for better ground handling and/or if you want to stiffen up the LG a bit, simply mount it with the wheels at the back instead of at the front. Works just as well that way.

BTW, I found the tripled foam at the front of the NB's spine is strong enough, without adding the plywood reinforcement shown, particularly if you go over the tripled foam area with some packing tape.

I don't have a very good picture handy, but you might get the idea from this one borrowed from another of my posts: link
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Old Apr 12, 2011, 11:53 AM
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Did I mention it's removable too?
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Old Apr 12, 2011, 12:13 PM
When pigs fly rc
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I like the idea that its removable. I Dont know if .032 will be strong enough on a 34 inch nutball. I will have to look in the shop and see what I have.
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Old Apr 12, 2011, 12:18 PM
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Right, I'd guess you'd be looking at 1/16 or so. It'll be a bit more of a job to bend it into shape, but it should work just the same.
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Old Apr 12, 2011, 01:07 PM
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I'm using 1/8" MW on my 26", so that or 5/32 for a 34 incher. With a NB that size, the weight of the LG is not going to be a big deal.
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Old Apr 12, 2011, 01:10 PM
When pigs fly rc
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Do you guys think a 34 can fly slower then the 17 "?
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Old Apr 12, 2011, 01:29 PM
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Canada, ON, Ottawa
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Where this particular LG design is concerned, flimsier is better in terms of springing back from the apex attachment point. 1/8" might be too stiff, I don't know. Go with TLAR method.

"It don't mean a thing if it ain't got that spring"

P.S. Rich, for bigger Nutballs like you're building, I would go with the plywood reinforcements as originally described by Dave R. Sorry, I didn't see what size you were building before I posted about omitting those.
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Old Apr 12, 2011, 01:37 PM
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Absolutely, smaller always flys faster, no matter the design. A 34" span is 6.3 sq. ft. and even if you built it at two pounds RTF, the wing loading is only 5 oz. per sq. ft. and that's nothing for a wing that size. If you check out Dave's big ones, he get that size down to under 3 oz. per sq. ft., then you've really got something.

A word of caution here, pick the right servo for the right job at hand. I'm using GWS 19g Park servos on my 17 ounce 26" because the 9 grams Naros were not powerful enough or have strong enough gears. I realized that after three failures, once stripped gears and twice I ran out of control movement because the servos lacked the power.
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Old Apr 12, 2011, 01:44 PM
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If your running a big prop and have long landing gear legs on a 34", even 1/8" MW is probably marginal, it does have to hold up the plane to start with. That's why my 26" uses 1/8" and it's plenty springy.
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