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Old Sep 08, 2012, 03:27 PM
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Quote:
Originally Posted by Bugman Jeff View Post
Just a side note for you guys, the square tubes are aluminum, not steel. While they look like steel, they aren't magnetic(and non-magnetic stainless would be way to expensive for what this plane costs).
Jeff,

They must have sent me the LX version by mistake; even the pushrods are austenitic stainless steel.

Barry

BTW - For Jack and others, here's some more photos of the wing assembly fitup pieces...

After very light sanding to remove factory surface glue, still measures about 2.0mm thick with my caliper's depth gage.



fitup with carbon rod (same outside diameter as aluminum pipe)



fitup showing fitment with factory bevel edges



again, fitup from other side, similar factory bevel edges



coming together



other side view



then together. You can see the foam step up where they meet



again, leading edge. Foam steps down where they meet.



fuselage opening, looking rearward, no steps in foam



another view looking forward, again no steps in foam.



A solution might be to replace the 2mm thick plywood with 1mm carbon sheet or 1/32" (0.79mm) thick plywood. The carbon would remove 2mm of step from where the foam meets up. Removing the factory plywood without damaging the foam could be a chore, and cutting carbon is pretty messy. You'd also need a 10mm hole cutter (pins measure 9.78mm diameter). Sheet carbon available from many sources, including HK...

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Old Sep 09, 2012, 07:50 PM
I'm a Registered User
Evansville, WI
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I stand corrected about the tubes. Stainless seems like an odd choice though.

As for your fitment issue, you might be able to use the back of a spoon to compress the foam and get rid of the step. EPO foam is pretty good about staying put after it's been compressed into shape.
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Old Sep 09, 2012, 10:07 PM
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Quote:
Originally Posted by Bugman Jeff View Post
I stand corrected about the tubes. Stainless seems like an odd choice though.

As for your fitment issue, you might be able to use the back of a spoon to compress the foam and get rid of the step. EPO foam is pretty good about staying put after it's been compressed into shape.
Jeff,

That might not be a bad idea, but after looking at the photos a second time, I now see the biggest problem is the airfoil 'angle of attach' is not the same between the two wing halves. So I'll eventually remove the plywood and install a thinner replacement to correct the factory defect.

Barry
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Old Sep 15, 2012, 01:58 PM
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Wing Fitment Update

I managed to shave off the plywood from the wings and the fitment is great with the plywood removed from one side.

Removed the plywood with a safety razor blade and a pair of vise grips. The safety razor is just long enough to reach between the plywood and foam, but not long enough to handle with my fingers. So the vise grips were used to grip the edge of the handle. The razor was used to cut the adhesive from the plywood, taking care to avoid cutting into the foam. Once the end is cut, I used my fingernail to lift the plywood enough to further insert the razor. In some spots, the glue lifted without requiring the razor, but most of adhesive required cutting to free the plywood.

Used my calipers and measured the thickness of each piece of plywood; they measured to be about or slightly less than 2mm. The small square was less than that, maybe 1.79mm. Anyway, based on the my measurements, it looks like 2mm of stack up is what’s needed to correct the factory defect.

As a fix, I could shave the foam on one side by 2mm, then reattach the plywood with glue, but I really don’t think I could do that with much accuracy. So I’ll likely replace the plywood with 1mm thick carbon sheet.

Here’s some photos showing the fitment with the plywood removed on one side…





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Old Sep 15, 2012, 03:09 PM
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Art-Tech 60A ESC Load Testing Results

This is the 60A ESC that came with my D2500...



It was provided without any specifications. Itís labeled 60A, but thatís just the motor controller output, not the built-in BEC. So, with no specs, I wanted to see how it handles a current load.

What I found from my testing, was that itís probably good enough for a 3A rating, but the voltage drops pretty rapidly after that. So, I donít think this ESC is good for aerobatic maneuvers on D2500ís equipped with flap servos.

These controllers usually also come labeled with some specifications for the BEC. The BECís typically come as 2A, 3A, or even 4A at usually 5V. They typically round off the rating to single digit, so a 3A rating is likely putting out better than only 2.5A @ 4.5V. Not what youíd like to see.

To run a load test, I purchased 10 inexpensive, ten ohm, 3 watt, resistors on eBay from a seller in China ($2.97USD with S&H). For each load, I soldered additional resistors in parallel to act as a load, until I had ten data points.



Hereís the results for the resistors in parallel (RIP) test..



As you can see by the chart, the voltage drops as the load current increases. In flight, as your wing loads increase, such as pulling out of a dive, the wing servos can approach their stall current. This current load causes the BECís output voltage to drop. Any voltage drop below the range of voltages that the Rx can handle; creates a undesirable brownout condition for the receiver.

Iím going to test some other ESCs and maybe a separate UBEC to see how well they perform, but on to other things for now.
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Old Sep 15, 2012, 03:33 PM
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Just add in a plug in capacitor to empty slot in your receiver. It will cure the brownouts
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Old Sep 15, 2012, 08:39 PM
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Quote:
Originally Posted by geives1 View Post
Just add in a plug in capacitor to empty slot in your receiver. It will cure the brownouts
Yea.... Knocking on wood works too.

The capacitor idea could provide some reserve voltage potential for borderline conditions, but these big birds react slowly course corrections, so any capacitor reserve would be likely used up too quickly.
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Old Sep 16, 2012, 07:53 AM
.: Looking for Thermals :.
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Chile, Quinta Regiůn de ValparaŪso, Los Andes
Joined Jun 2002
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I bought an UBEC rated for 3 amps and, as I have a Aurora 9, I plugged the 4S Lipo to the SPC port in order to monitor it's voltage. Today I'll try to fly her.
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Old Sep 16, 2012, 03:19 PM
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It lives....

After my crash detailed in post 1003 It's almost back in one piece.
I managed to find my missing wing pieces and the undercarriage wheel in the farmers field after he'd used the combine.

A few hours fixing the left wing wing and it looks good to go.


Chunks out of LE.
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Root detached. gorilla glued back on then two lengths of 5mm carbon tube inserted from root end for strength.
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Two black smudges are end of carbon rod.
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Gorilla glued back together
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Wing snapped outboard of aileron
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Missing chunk on LE after tip glued back on. Spare bit of foam was fitted in and three lengths of 2mm carbon rod fitted across the break.
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Result...
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Seems plenty stiff enough and only 4g heavier than the right wing after the fix. The leading edge of both wings are now covered with Crossweave tape for a bit of extra strength/protection (not to mention covering a few dings...)
After touching up the decals with permanent marker pen the result is below:-
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The wing-joining tube was also cut in half as it was bent - a carbon tube was inserted through the middle in order that the aluminium tube locates across the centre of the wing-join.
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Just need to re-attch the wheel and fit a couple more 2mm carbon rods across the fuselage break.

With a bit of luck should have it ready for Tuesday's session. It's by no means perfect but hopefully should be up to the job..
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Old Sep 16, 2012, 03:46 PM
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Looks good
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Old Sep 16, 2012, 05:12 PM
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Motor Details

For reference, here’s some photos of the motor that came with my D2500, along with some basic dimensions..









Sourcing a replacement motor might be difficult. Art-Tech sells replacement motor, but finding a dealer with a spare may be a problem.

Apparently the motor is used by other models. I found this 3720 motor is used on a Dynam Peaks DY8947 42" Bi-Plane sold by Nitroplanes.com, but expensive, Part # 60P-BM3720A-KV650...

http://www.nitroplanes.com/60p-bm3720a-kv650.html

Nitroplanes.com also sell an inexpensive replacement motor shaft for this motor....

http://www.nitroplanes.com/60p-bm3720a-kv650-shaft.html
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Last edited by Barry2020; Sep 29, 2012 at 12:08 PM.
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Old Sep 16, 2012, 11:40 PM
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Thanks for all the in depth info Barry. The BEC data is especially nice to have.
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Old Sep 17, 2012, 02:37 PM
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It was spectacular last saturday!

Doing a power loop and the elevator hinge failed on the back side and it dove straight into the ground! I had planned to remove the weights from the wings, but not in this manner (they flew out). Spinner and cowl buried about 4 inches into the ground. Wing tip broke off, boom snapped just forward of the aluminum tubing in the fuse. All hinges (EPO Foam) were fatiqued and/or broken. Fuse completely severed just forward of the leading edges of the wing, mostly pieces. Canopy broken in places, fair amount of damage to the motor mounting, horizontal stab bent and stiffening on top lost.

Good news is that the motor was not damaged, nor any of the electronics or servos, wing rods and tubing also OK. In spite of all that I think it will repair pretty well. Biggest challenge is to get the correct alignment of the motor and shaft.

Considered buying new fuse or just trashing the whole thing, but after assembling all the pieces I think it can be repaired and will fly again.

Since the stiffening piece on top of the stab was lost can anyone tell me if it was carbon or what? The bottom of the stab has a piece of (?) or plywood and am wondering if the lost piece was the same.

Dr. Jack will be in the operating room shortly after the Foam-tac arrives.

Advice to all; replace all the foam hinges! This thread has a few posts on doing that.

I have several other gliders to fly so shouldn't miss any opportunities to fly during the repairs.

More later on the reconstruction,

Jack
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Old Sep 17, 2012, 07:45 PM
I'm a Registered User
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Joined Dec 2006
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Sorry to hear that Jack The spar on top of the stab is a square carbon rod(square is stiffer than round). One of the nice things about this plane is it's repairability. Coming from a guy who's smashed his plane to bits more than once, I can tell you that it glues back together pretty well. You'll be up and flying again in no time
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Old Sep 17, 2012, 09:10 PM
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Thank you Jeff!
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