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Sport Planes (Formerly I/C & Gas Conversion) Discuss I/C or Gas Conversions, Aerobatic Planes and Sport Aircraft

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Old 11-16-2005, 05:09 AM   #1
manga
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Default Great Planes Seawind conversion

Hi

I am new to electrics but this plane has me very interested. I think it can be a challenge to convert to electric. It is a flying hull. The specs are as follows:

"Wingspan: 71 in (1805 mm)
Wing Area: 676 sq in (43.6 dm2)
Weight: 10.25-12.25 lb (4.6-5.5kg)
Wing Loading: 35-41 oz/sq ft (106-127 g/dm2)
Length: 56 in (1410 mm)
Requires: 2-stroke .60 cu in (10 cc) or 4-stroke .70-.91 cu in (11.5-15 cc) engine, 5-7 channel radio w/7-9 servos"

The main problem I foresee is the available prop clearance. According to other forums the limit is 13". Great Planes recommends a 3 blade prop for the glow engines. I guess a 4 blade prop could also be used.

Any ideas what kind of set up (motor, gear, prop, battery, ESC) would work for this plane? Specially in light of the fact that prop size is limited by the design of the plane.

Thanks
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Old 11-16-2005, 03:50 PM   #2
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I'm not going to be of much help here as far as recommendations go. I looked at this plane as a conversion candidate myself and decided against it. That plane has some pretty hefty wing loading (35-45 oz/sq ft). If it flies glow it'll fly electric but it'd take an outrunner brushless with a lipo pack fer sure and lipo's and water don't mix very well.

Good luck in your quest! I'll be very interested to see what suggestions you get.

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Old 11-16-2005, 04:21 PM   #3
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I'm thinking 6S LiPoly battery for power, or 20-cell NiMH, but the LiPoly will be about half as heavy...

For motor on a .60-size sport plane conversion, I would normally recommend the AXi 4130/16 or the new Eflite 60 outrunner. What I'm worried about is being able to get enough propeller on either of these so there's enough power available to fly the plane. A motor with a slightly higher Kv rating than either of these would be a better choice on 20 cells.

Actually, I just got to thinking, and why not use more cells? A 7S LiPoly or 24 cell NiMH would allow these motors to spin a smaller prop faster. The AXi is rated for up to 8S, so that may even be an option....

Going with an 8S LiPoly, I estimate that you could run a 12x8 3-bladed prop on the AXi 4130/16 and be right in the ballpark.
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Old 11-17-2005, 03:12 AM   #4
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Originally Posted by Warden View Post
If it flies glow it'll fly electric but it'd take an outrunner brushless with a lipo pack fer sure and lipo's and water don't mix very well.
What is the concern with lipos and water? Tab corrosion?

Bill
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Old 11-17-2005, 10:34 PM   #5
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Thanks all for the imput. If you have more suggestions it would be appreciated.

Any thoughts on using the Kontronik Tango 45 motors for this application?
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Old 11-18-2005, 12:13 AM   #6
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Use a Vario adjustable pitch prop. 13" dia and dial in a pitch of 14" to 16". That should load the motor up and work fine. I did this to my 88" Skymaster.
Bob
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Old 11-18-2005, 12:39 AM   #7
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I too have looked the Sea Wind (@ 6S & mulitblade); specifically for flying off snow.

A friend at my club has flown his with a .90FS and say its not “heavy”, maybe 8 pounds w/retracts.

He says its quite fast in the air yet is very docile on landing; and tracks very nicely.

And, he too is looking forward to flying it off snow.
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Old 11-18-2005, 01:04 PM   #8
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Default Lipos and water.

BillB, This is taken from "Answers.com".

The lithium in a Li-Poly cell is hazardous and will react violently with water.

Obviously, this would take a cell puncture for the lithium and water to mix but that scenario would be far from out of the question in a seaplane crash.

Answers.com isn't where I got the initial info. It may have been on this board that someone was thinking of putting lipos in an RC boat and the lipo/water hazard was mentioned.

It's kind of odd, too but recommended methods of disposal of Lipos involves puncturing a hole in the case and soaking in salt water. The kicker is that the cell is completely discharged before immersion.

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Old 11-19-2005, 07:53 AM   #9
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Originally Posted by Warden View Post
BillB, This is taken from "Answers.com".

The lithium in a Li-Poly cell is hazardous and will react violently with water.

Obviously, this would take a cell puncture for the lithium and water to mix but that scenario would be far from out of the question in a seaplane crash.

Answers.com isn't where I got the initial info. It may have been on this board that someone was thinking of putting lipos in an RC boat and the lipo/water hazard was mentioned.

It's kind of odd, too but recommended methods of disposal of Lipos involves puncturing a hole in the case and soaking in salt water. The kicker is that the cell is completely discharged before immersion.
Warden - Thanks for your response. I have just become painfully aware of another concern with LiPos and water.

Not too long ago, I flipped a floatplane in fresh water. No damage, but the 5S2P 5000 mah pack got wet. The pack has balance taps. I just recently noticed that one pair of parallel cells is always out of balance - charges higher and discharges lower than the other pairs. I suspect that an aluminum tab has corroded and that only one cell of the 2 cell pair is in the circuit.

The manufacturer agrees that corrosion might be the problem. Rather then open the pack myself, I have elected to send it to him to see if it is salvageable, but I am afraid that there may be other corrosion and the pack is toast.

Sorry to take the thread off topic - I am seriously considering the Sea Wind conversion.

Bill
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Old 11-19-2005, 06:48 PM   #10
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It seems that Lipos and water require extra precautions. Has anyone tried covering the conections with heat resistant silicone compund? Would that be detrimental to the battery pack? Sorry if the question sounds naive, but I am new to electrics, let alone Lipo technology.

What do R/C boat hobbists use to protect their battery packs?
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Old 11-21-2005, 01:26 AM   #11
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Originally Posted by bruff View Post
Use a Vario adjustable pitch prop. 13" dia and dial in a pitch of 14" to 16". That should load the motor up and work fine. I did this to my 88" Skymaster.
Bob
buff,

Did you mean 2 or 3-blade prop? I noted that they also make 4-blade hubs. Nice product!

May be a 11- 12" dia 4-blade prop with 14-16" pitch would work for this plane.
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Old 11-21-2005, 01:56 AM   #12
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There is NO metallic Lithium in a LiPoly cell.

Here's some myth buster literature.

http://www.hardingenergy.com/pdfs/LiPolymer.pdf

http://americansolarchallenge.org/te...iumcontrol.pdf

http://www.ulbi.com/documents/msdshe...14-Polymer.pdf
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Old 11-21-2005, 02:02 AM   #13
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SeaWInd conversion thread
http://www.rcuniverse.com/forum/m_3378048/tm.htm

You might also check these conversions for a similar sized plane conversion-
http://www.hobby-lobby.com/glow2econ.htm
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