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Old Mar 08, 2008, 01:02 PM
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Florence, Al
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rcnewb - are you running the arrow shaft through the entire fuselage?

Jeff
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Old Mar 08, 2008, 10:26 PM
Gone Flying.
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Western NY
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Hey Jeff -

Not through the entire fuselage, that would make fitting the battery in there nearly impossible. The arrow shaft will be secured with epoxy and kevlar thread, perhaps with some aluminum mounting brackets. It's still a work in progress though...
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Old Mar 10, 2008, 05:18 PM
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this sounds like it should be alot of fun. But why are you guys hand launching your projeti's? rog man, rog !! mine take off grass in about 3 feet or so.... ask tram.
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Old Mar 11, 2008, 06:18 AM
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Quote:
Originally Posted by kissfan
this sounds like it should be alot of fun. But why are you guys hand launching your projeti's? rog man, rog !! mine take off grass in about 3 feet or so.... ask tram.
I was actually considering building a small ramp for take off, should be fairly simply to build. It would require enough clearance for the prop and somehow be able to keep the wings straight to account for a torque roll.
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Old Nov 10, 2008, 09:56 AM
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Pilipinas
Joined Mar 2005
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Quote:
Originally Posted by rcnewb
The 10mm arrow shaft arrived (finally!). Here are some photos of what I will be using to mount the motor. Should be fairly simple. I'll fill the void in the circular arrow shaft with epoxy and will wrap with kevlar string for extra strength...
Hi. Where did you get the red motor mount?
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Old Nov 10, 2008, 03:45 PM
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bolkow -

I bought the red motor mount (designed for a 10mm stick) from http://www.radicalrc.com/shop/?cat=9...s=98%3A2136694

However, I don't see that specific mount sold there any more, but they do have a fairly large selection of other stick mounts to choose from. I'm fairly certain that red mount is made by GWS, you might be able to find it online from another vendor if you're looking for that specific mount. It is made of aluminum.
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Old Nov 11, 2008, 05:51 PM
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Pilipinas
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GWS mount

Tnx rcnewb,

I have this GWS mount on my Projeti. It's made from piece of sheet aluminum, cut and bent to shape, unlike the one you have which is machined. At 430 watts, the mount seems to be doing fine. I plan to crank it up to 600 watts with 4s lipo and worry the mount won't hold up. Bent aluminum has the inherent weakness along the stress areas corner of the bend.

I have a clubmate with a 900+ watt (4s with bigger motor) Funjet. At straight lines, my Projeti on 3s is just as fast as the Funjet, but the Projeti can do tighter turns. That Funjet's going to eat dust when I go 600 watts. I just hope the mount won't rip off at WOT.
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Old Nov 11, 2008, 08:24 PM
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One of the first tests I ran after mounting the motor to the c/f arrow shaft was to run the motor at full throttle in bursts (with motor attached via kevlar/epoxy) -- the carbon fiber arrow shaft was secured in a vise to make sure the mount held up to the ~5 lbs. of thrust at WOT. After testing, I am certain the mount will not be the weak spot. It takes a lot of force (far greater than 5 lbs.) to bend aluminum that is more than a few mm thick.

The biggest challenge is mounting the arrow shaft securely to the Projeti in a manner that will distribute stress on the frame as evenly as possible.

You should have no problem dusting that FunJet at 600W. The Projeti is a much lower-drag airframe, at 500W it should almost be able to keep up with a 900W FunJet.

Are you using a 10mm balsa stick with that GWS mount, or did you use carbon fiber? No matter what you used, if you want to err on the safe side, wrap the area where the mount contacts the stick/carbon fiber shaft with thread (preferably kevlar) and use epoxy liberally around the mount to really lock it in place.
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Old Nov 12, 2008, 08:40 AM
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Pilipinas
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Quote:
Originally Posted by rcnewb
Are you using a 10mm balsa stick with that GWS mount, or did you use carbon fiber? No matter what you used, if you want to err on the safe side, wrap the area where the mount contacts the stick/carbon fiber shaft with thread (preferably kevlar) and use epoxy liberally around the mount to really lock it in place.
My LHS ran out of 10mm basswood and I don't trust the integrity of hard balsa 10mm stick. The end where the mount is attached weakens considerably when drilled with 2x 3mm holes for the screws. There's this clubmate who had the same mount with a 220-watt motor on a balsa stick in a tractor configuration. Less than a minute into the maiden, the motor (with prop) shot out of the nose of the plane. Good news is, it was over at least 8-foot tall grass, no damage to the plane. Bad news is, the same grass made it impossible to find the motor.

I stacked 5 popsicle sticks then CA'd them together. Wrapped 1 and a half inches from both ends with two layers of ordinary thread and soaked it in thin CA. Screwed the aluminum mount on one end and buried the other end (at least 3 inches) in foam and epoxy. The structure feels solid and looks like it can take at least 7 kilos of longitudinal force. The lateral strength of course is only as good as the foam it is buried into.
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Last edited by bolkow; Nov 12, 2008 at 08:48 AM.
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Old May 14, 2009, 11:00 PM
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Columbus, OH
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So....what happened?
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