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Old Aug 26, 2008, 10:15 PM
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Al
Actually, yeah, it was the never extend motor to ESC thing I heard, not the other, and yep, that all makes sense

Kendall

I did not weigh anything before building, but I don't see how it could come in at 3kgs. My battery is only 4s 4000mah and I have it pretty far up the front of the fuse to balance, and I have added no lead or anything for balancing. I havent really done anything to add extra weight, well except for running a lot of CA and then epoxy around the joins of the pylon mount (but then I'v put holes in that to for airflow so its probably no different). I have a seperate receiver battery, but its a super light NiMh job. Mine came in at almost 3400 grams in the end I think. I havent actually put my setup on the wattsup meter yet, but going on some other figures from the net, on 4 cells I get 2700 grams of thrust, so I think your setup should be just fine.

If you want to save some bucks, the Tower Pro 3520-7 option with 14x7 prop on your 5 cell battery would give you buckets of thrust to clear the water nice and fast.

Although mines pretty much ready for flight testing again, I unfortunately still havent got round to it.

Paul
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Old Aug 26, 2008, 11:48 PM
Postcards From The Purple Edge
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United States, OK, Sand Springs
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3400g--that's more like what I was expecting. I figure if I go with the 12x6/1000W+ setup I could even throw another 500g 5s/4000mAh battery into the nose and still come off the water with 125W/lb.

How did you work out the battery tray in the nose? Did you do anything to waterproof the battery hatch?
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Old Aug 27, 2008, 02:16 AM
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Yeah I think you will come out to at least the weight I have, although I'm sure I read somewhere that there might be a few hundred grams difference in the weight of the airframes, so maybe yours is a little lighter than mine (or heavier).

I just cut a hole and made a hatch out of ply. I covered the hatch, and to waterproof, I put some kitchen plastic wrap over the bottom of the ply hatch, and then put a layer of bathroom silicon around where the hatch screws on, then screwed it down, wiped away the excess, and let it dry overnight. Then unscrewed it and peeled the plastic away. I then screwed it down and using my finger (with a surgical glove on), and rubbed a light layer of silicon along the edge all around where the hatch sits. I don't know if this is 100 per cent waterproof, but it would be pretty close, and I didnt see water going up there at anytime while on the water anyway, so think it is good enough. In fact, initially, I just used some foam tape on the hatch like I did on the rear hatch, except that the piece of ply I used for the front one, was a little warped, so ended up doing this. You might be able to just use some of the supplied foam tape.

I just made a simple battery tray from ply with a couple of bits of balsa down the sides,and use a piece of hook and loop velcro to hold the battery down. If using a bigger battery like you are going to use, it probably will end up a bit nose heavy if you put the tray in the same place. If I were you, I would cut the hatch out back from where I did, starting from where the cabin is, which will give you more room to get your hand in, plus you can then cut away the ply cross internal brace further back from the one I did, which will give you more chance of getting the balance right.

In fact, dont do the hatch and battery tray until last. Get everything else in there and the plane finished first, so you can work out about where the battery will need to go to get the right balance.

Cheers,
Paul
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Old Sep 01, 2008, 01:03 PM
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Joined Feb 2005
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On the subject of extending ESC wiring, you may want to take a look at the July 08 issue of Model Aviation, page 104, Battery Clinic column.

It clearly states that the ESC to battery wires should not be extended beyond 12" max. ESC to motor wires can be as long as needed. These comments are made by Patrick del Castillo of Castle Creations and Bob Boucher of AstroFlight. It also mentions where to find info on adding capacitors so the battery wiring could be longer.

Joe
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Old Sep 02, 2008, 04:29 AM
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Thanks Joe, okay thats interesting. Did it give any reason for not extending them?

Also, what are other guys doing with pylon mounted planes then? I know that others who have done the Neptune have done it this way. There isnt really any other way to get Airflow to the ESC than have it in the Pod, and run the battery leads down, and there was certainly no way I could have balanced mine if I'd put the battery right near the Pylon. I'd have had to add a LOT of lead in the nose to do that.

I deffinately had no problems in the 4 short flights I did. In two weeks I'm hoping to take it out for a longer flight so I guess I'll see if there are any problems then.

Cheers,
Paul
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Old Sep 02, 2008, 05:29 AM
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Paul,
As for what some others are doing, my flying buddy just did a Seamaster with the ESC behind the motor and the batteries under the wing. Flys great! No issues with bench testing and three flights from water so far. He used a Turnigy motor and ESC.

I am doing mine now with the ESC in the forward area under the wing and the batteries accessed thru a hatch in front so the wing doesn't have to come off for battery changes. Seems to balance just fine. I am using a Rimfire motor and CC Phoenix 60 ESC with a TP 5S2P 4400mah Lipo.

As for cooling the ESC, I always oversize the ESC and enclose them in the hull. I depend on the volume of air in the hull and the fact I never stress my components to their limits. Been flying a Drake II seaplane for three years now with no issues. Also an Aventura Twin and a Aquastar. Built two more depron Drakes this year and did the same with no issues.

As for why it might damage components, it seems like after ESC pulses the motor, little current is needed from the battery and the field collapses around the wire generating "ringing" (a spike in voltage) on the battery wire which can destroy the ESC if large enough. This is not uncommon in electronics and you would be able to see it if you had an oscilloscope. I would think the issue would be more common with large cell counts. These are my words, not from the article, and I take no responsibility for them!!

Joe
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Old Sep 02, 2008, 07:35 PM
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Okay, thanks Joe, well those guys would know alot more about this stuff than me, so I guess it must be right.
Still, I do know of some guys who have done it this way, and me being too lazy to start rearranging everything, and not having much spare time, I reckon I will just see how things go. I'm running a receiver battery, so at least I should be able to get it down if the ESC dies


The thing I guess I'm a bit worried about, is if the extended leads can somehow cause interference. With the Ultrafly Hawk, you have to run extended battery wires down the fuse, and I know a guy who got one and after a few flights, he mysteriously seemed to loose all control, and still cant work out why it happened - could it be something to do with the extended power leads???

Paul
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Old Sep 03, 2008, 06:22 AM
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Paul,
I've not heard of any interference issues using brushless motor systems. The frequencies used are far below the 72mhz or other similar radio systems.

As you mentioned, go out and fly it. When you range test it, run the motor.

My flying buddy may get another chance with his this weekend. I doubt he will have any problems if his previous flights are any indication.

I hope to fly mine in about two weeks.

Good luck,
Joe
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Old Sep 04, 2008, 02:10 AM
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Good luck with the Maiden Joe, let us know how it goes
Cheers,
Paul
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Old Nov 11, 2009, 12:55 PM
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Bump for ancient history.

I posted on SCALEFAN's thread in the glow-to-electric conversions forum, but it doesn't look like anybody's watching...or cares.

I'm finally putting mine together after letting it sit in the basement for a year. The last thing I need to do is order my servos and I'll be all set.

I wanted to post up a quick question for anyone who's built/flown this bird. The manual says the CG is 108mm from the LE but that seems a fairly far aft starting point given a 310mm cord. I'm inclined to go with more like 75-80mm or just over 25% cord, especially for the maiden. What did you guys do with the CG?

kendall
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Old Nov 11, 2009, 02:58 PM
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Quote:
Originally Posted by tuppertn View Post
Bump for ancient history.

I posted on SCALEFAN's thread in the glow-to-electric conversions forum, but it doesn't look like anybody's watching...or cares.

I'm finally putting mine together after letting it sit in the basement for a year. The last thing I need to do is order my servos and I'll be all set.

I wanted to post up a quick question for anyone who's built/flown this bird. The manual says the CG is 108mm from the LE but that seems a fairly far aft starting point given a 310mm cord. I'm inclined to go with more like 75-80mm or just over 25% cord, especially for the maiden. What did you guys do with the CG?

kendall
Hey I care! In fact I've been reading as much on the Neptune as I can as I just received mine day before yesterday! I'd like to go electric, but it looks like it would cost about another $225- compared to glow to which will cost nothing extra as I have extra engines etc. I have been inquiring about building tips and ideas for this plane as I might as well try to avoid any previous problems that may have occured, but it sounds like this is a great plane. I think I read the C of G was from 3- 3 1/2 inches from the leading edge (mine didnt come with a manual) but on the maxford sites downloadable manual it shows C of G at 102 mm or 4 inches. Rule of thumb I heard is 1/3 the wing width from leading edge- Anyway keep posting because I'll be watching
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Old Nov 11, 2009, 06:22 PM
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Well, groovy, Fariplay. In that case I'll post up on a couple of things I encountered in the build.

My motor weighs 10.5oz and right now I'm balancing with 22.3oz of batteries in the fuse pretty much right under the prop. With a .46 weighing in at 17-18oz with muffler you'll probably have to add some nose ballast to balance. If you've got a .60 or .75 laying around it might work better (might as well make the weight usable right?) although it would make the plane more top heavy and I'm not sure how well it would fit the cowl. One of the nice things about going electric with this plane is that you get to weight the keel with the batteries.

I had two issues with the emmenage assembly. These may be difficult to describe, but hopfully either they'll make sense when you start building or maybe you won't have the issues at all.

1) Assembled per the manual the bottom of the rudder stuck out below the keel fin. I wanted to keep the rudder protected by that fin but positioning it high enough on the fin to protect the lower edge had it interfering with the elevator travel at the upper edge.

2) With the stab positioned on the fin so that the elevator hinge line was even with the back of the fin there's a large area of bare wood exposed on the LE of the fin. This is visible on nearly every picture I found of the thing online.

So far I've tried adding a shim of lightened 1/4" ply under the stab. That raised the elevator hinge line out of the rudder's way. Then I shaped the shim to blend the exposed wood area into the stab. I just need a scrap of matched covering to finish the job. Another option would have been to cut down the rudder to allow for elevator travel. Hmmm, now that I look at the pictures again I may do that instead if I can find a good match for the covering.

If anybody has a better idea before I make it all permanent I'm open to suggestions.

kendall
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Old Nov 12, 2009, 07:32 AM
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[QUOTE=fairplane I think I read the C of G was from 3- 3 1/2 inches from the leading edge (mine didnt come with a manual) but on the maxford sites downloadable manual it shows C of G at 102 mm or 4 inches. Rule of thumb I heard is 1/3 the wing width from leading edge- Anyway keep posting because I'll be watching[/QUOTE]

I don't have a Neptune but do have a Seamaster and the Neptune seems to be just a Seamaster knockoff. The CG on a Seamaster is 3- 3 1/2 inches from the leading edge and it flies fine when set there. I have done two glow ARFs and my latest is an electric. All went well at that setting.

The specs on my electric Seamaster are as follows:
Wing span: 59.5" Area: 725 sq.in. Wing loading: 24.9 oz/sqft. Wing Cube Loading: 11.11 AUW is 125.5 ozs. Powered by a Rimfire 42-60-600 Brushless, a MA 13x8.5 prop, a CC Phoenix 60, 2 x TP 5S1P 2200 mah Extreme Lipos in parallel and a CC BEC set for 5.5 volts. Max current is 46.25 amps and 807 watts (actual flight data - eLogger). 6.43 watts/oz - 102.88 watts/lb. AR7000 receiver is used in this plane. HS-475HB servos are used for the rudder and elevator and a HS-325HB servo for the ailerons. JR X9303 radio for control.

tuppertn said.....
Another option would have been to cut down the rudder to allow for elevator travel. Hmmm, now that I look at the pictures again I may do that instead if I can find a good match for the covering.

Well, I would consider making the skeg a bit larger and that would protect the rudder where it extends below the present skeg.

I attached a Photo of a buddy's new Neptune flying at Lily Pond this past fall. Very nice performer.

Joe
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Old Nov 12, 2009, 08:34 AM
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Cool. Thanks, Joe. I knew the Neptune was a Seamaster copy but I wasn't sure if the dimensions were exactly the same. Looks like they are though. Looks like it's a faithful copy at least.

That looks like a nice setup. Pretty close to what I'm doing. The MAS 13x8.5 is my prop of choice too. My motor is a slightly higher kV, I think, so on 5S it draws just over 1000W.
Quote:
Originally Posted by jpgilbert View Post
Well, I would consider making the skeg a bit larger and that would protect the rudder where it extends below the present skeg.
Another good idea. "Skeg"...I like that word.

I see from the pics that your FB braced the t-tail. I thought about doing that with some aluminum tubing, but I don't recall anyone else mentioning that it may be necessary. More to think about I guess.

kendall
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Old Nov 12, 2009, 08:03 PM
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I gave up on the shim idea. The more I looked at it the dumber it looked. I open the covering on the top edge of the rudder, cut it down by about 1/2" and ironed the covering back in place. Looks fine and did the job well enough.

kendall
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