RE: P-39 "where to find"   
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RE: P-39 "where to find" - 2/7/2006 3:03 PM   
oliveDrab


 

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From: Christoval, TX, USA
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Some questions:

1. Would the motor/speed control/ and batteries you described be the right size for a P39 with an 80" wingspan? I'm really
new to electric flying and don't have the expertise to know what size electric stuff to put into an airplane. The plane would
have retracts.

2. I was going to build my P39 (or P63) from the Pepino plans. I assume the plans call for a fully sheeted wing and fuselage.
Don't want to end up with a really heavy plane so I would cover the plane with monokote. Currently I'm building a T34 B Mentor and
am glassing the surfaces with oil-based polyurethane and .5 ounce fiberglass cloth. It's turning out very well but I don't believe
I should do that for my electric P39 / P63.

3. I'll use a Hitec radio receiver like I always do, but what about servo's for this electric P39 with an 80" wingspan? What's your
preference?

4. Would you recommend powering the radio receiver off of it's own dedicated battery, or power it off the same battery as the
electric motor?

5. Are the batteries you're recommending LiPo's? I've got a couple of Kontronic motors that run off of NimH. They've got lots
of power but seem to be large and heavy.

I saw a video of one of the astronauts who happens to own a P51 and a P63 Kingcobra. The video showed the P63 in flight - I kept
rewinding the tape and replayed it over and over. I wanna sit in it and pretend...zoom zoom.

Thanks in advance
-oliveDrab

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RE: P-39 "where to find" - 2/7/2006 3:23 PM   
Darrell B.



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Status: offline 		oliveDrab,

Here are my thoughts on this project and your questions.
-the motor that you choose will be determined by your final flying weight of the airplane. In all of my cases I look at how many watts I will need to have at least 100watts per pound.
-I'm going off of my TopFlits Giant Mustang and how it performes at 23#. It flies great, but I'm hoping to increase the prop pitch on this one for a much faster ariplane. I will still sheet the wing, and fuselage, but not glass it. Pepino calls for glassing the entire airplane, but I'm choosing to use Sig coverings, and coverite trim sheets for the numbers and graphics.
- I think that a lighter ariplane would fly well on the AXI 5330 outrunner or the Actro 60, but both of these have a lower Kv than the T-Rex that I choose to use. My preferance for motors is to use outrunners without a gear box. I think that the Hacker Acro 50XL using a 14 turn would work well also. It flies the Hanger 9 77" Mustang very nicely at 16#
-I'm using the Futaba 9001 servos with a 5 cell onboard flight pack made of Eveready 2500mAh NiMh cells for a 6+ volt pack. You will find that as you go to the larger speed controllers that they don't have the BEC on them, and from what I have read you are better off without it on these big power systems.
_ I always use Lipo batteries, in this case a 10s4p pack of 2100mAh cells from MaxAmps. In reality I have been able to pull over 9000 mAh from these without any problems! WOW....
-The way that Pepino joins the wing panels together I think that I"m going to build an extra joiner for the secondairy spar to help with flight loads. I like to fly agressively....
-Retracts are a nobrainer, except that you will need to special order them. I'm using Robarts that they helped my design for this exact plane. Well see in a couple of weeks now how they are going to work. Use what you like best.

If I missed anything, feel free to ask.
Good Luck,

Darrell

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RE: P-39 "where to find" - 2/8/2006 9:55 PM   
oliveDrab


 

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I'm having a hard time comprehending these "outrunner" motors. The motor is bolted to the firewall and the whole case spins, right? So the whole case is enclosed in the fuselage and the whole thing spins. Does this create any special problems?

This is reminiscent of a WW I plane, that used a motor called a Gnome rotary (?). The motor was bolted to the plane and the cylinder heads actually rotated with the prop.

oliveDrab.

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RE: P-39 "where to find" - 2/9/2006 2:28 AM   
Darrell B.



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Status: offline 		That is a fairly good way to look at it. The magnets are glued into the bell of the motor. The wiring go into slots on the part of the motor that gets bolted to the firewall. The prop is attached to the bell and it spins around the stators with the wiring. Here are a couple of pictures of the one in my Mustang. What you don't see in the last picture is that behind the spinner is the front of the bell of the motor.

Darrell

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RE: P-39 "where to find" - 2/9/2006 4:28 AM   
oliveDrab


 

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In the middle picture, what's the white cylinder behind the motor?



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RE: P-39 "where to find" - 2/9/2006 1:03 PM   
Darrell B.



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Status: offline 		It is a PVC Pipe fitting that I used as a stand off, to help save weight. In comparison to the weight of wood or other materials it is very light and just as strong. It is also very straight, and square. I wanted to use the origional engine mounting system to maintain the built-in offset that the firewall had so I needed something true. It is a little trick I learned from Greg Covey, and it is working fantastic. If I were to use any other method of mounting a motor, I would build the traditional box that extends through the fire wall.

Darrell

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RE: P-39 "where to find" - 2/22/2006 6:44 PM   
oliveDrab


 

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Hey Darrell -

What charger do you use to charge your 10s4p 9000 MaH battery?

Thanks
oliveDrab

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RE: P-39 "where to find" - 2/22/2006 7:54 PM   
Darrell B.



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Status: offline 		My battery is divided into two packs of 5s4p 9000mAh. I bought two of the Astro 109s on sale, and use them to charge my packs. I charge one off of the truck battery, and the other one off my battery that I bought for just running chargers on my bench. With a 5s pack the Astro will only safely charge at about 6.5amps, so it takes about 1.5 hours to charge when my batteries are really low. If I go over this charge rate the charger gets really HOT! I looked at the instructions that came with the charger, and they recommend the highest charge rate for 3s or maybe 4s applications. After that it steps down considerably. If you look around you can find the Astro 109 for $114 on sale usually all of the time. I got mine at Southeast RC in Florida. There are also several new chargers comming out that are capable of charging this size of packs. At the time the Schulze for around $500 was the only other one capable of charging my packs. Oh what a difference a year makes....

Best Regards,
Darrell

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RE: P-39 "where to find" - 3/7/2006 3:29 AM   
oliveDrab


 

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Darrell -

I converted my Hobbistar 60 to electric power. Put a Kontronic Fun480-33 into the plane with a Jazz 40-6-18 ESC. I've got a 4 cell 14.8Volt 4000 MaH Lipo to provide power, and I bought the Astro 109 to charge the LiPo.

You said you charge your Lipo's using your truck battery and another battery you use for charging your batteries on your workbench. So I assume you pop the hood on your truck and connect the Astro 109 to your truck battery.

Can you plug your Astro 109 into a 12V receptacle inside your truck? I've got such a receptacle inside my truck. But I'd need some sort of plug to fit into the receptacle and would then connect the plug to + and - on the Astro 109.

What about the battery on your workbench? What type/brand is that? I heard one guy say he uses a deep-cycle RV battery.

Geez, I hate to ask stupid questions. But I'm a little leary of Lipo's...I've heard opposing views....some say nothing to worry about, others say store them and charge them in a metal ammo box!!

Thanks in advance!

-oliveDrab

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RE: P-39 "where to find" - 3/7/2006 2:36 PM   
Darrell B.



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Status: offline 		oliveDrab,

You said you charge your Lipo's using your truck battery and another battery you use for charging your batteries on your workbench. So I assume you pop the hood on your truck and connect the Astro 109 to your truck battery.
Yes I just connect right to the battery in my truck.

Can you plug your Astro 109 into a 12V receptacle inside your truck? I've got such a receptacle inside my truck. But I'd need some sort of plug to fit into the receptacle and would then connect the plug to + and - on the Astro 109.
I have tried using the accessory plug in my truck also, but found that it won't deliver enough power when I'm charging a large battery, and the charger says low battery voltage. If it was a heavy duty outlet it might work.

What about the battery on your workbench? What type/brand is that? I heard one guy say he uses a deep-cycle RV battery.
Nothing special, I just use a regular 675Amp/hr battery I picked up at Wall-Mart. I think that my next one might be a deed cycle, but this one works fine. I find that in a days flying at the field it never goes down, and at home I connect my trickle charger to it to keep it topped off all the time.

Geez, I hate to ask stupid questions. But I'm a little leary of Lipo's...I've heard opposing views....some say nothing to worry about, others say store them and charge them in a metal ammo box!!
Lipos are all that I have used. They provide excellent power to weight, and if you use a little common sense, and respect them they won't cause you any problems.

Good Luck,
Darrell

< Message edited by Darrell B. -- 3/7/2006 2:38 PM >

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RE: P-39 "where to find" - 6/11/2006 10:52 PM   
oliveDrab


 

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Yo Darrell -

Did you ever start or finish your electric P39? Did you decide to glass it or Monokote?

-oliveDrab



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RE: P-39 "where to find" - 6/11/2006 11:46 PM   
Darrell B.



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Status: offline 		That is a big yes on the P-39. Here are a couple of pictures of my progress to date. I'm shooting for an early fall maiden.


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RE: P-39 "where to find" - 6/12/2006 3:58 AM   
oliveDrab


 

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I assume you went with the TRex 40 and the batteries/speed controller you used on your P51. What brand retracts did you use and are you glassing or Monokoting? What's your color scheme going to look like?

Looks like your nose is plastic with bondo on the seams.

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RE: P-39 "where to find" - 6/18/2006 8:18 PM   
Darrell B.



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Status: offline 		Yes,
I used the same power system I used on the P-51, I used some Robart gear that I worked with them to design for me. We used their P-39 struts, and the retract mechanisms from the Midwest AT6. You mount them so that the angle goes backward, and that gives you the scale location and angle that the real plane had. The nose is just a mockup that I made out of foam. The real one is going to be fiberglass, that I will make after I get the plug all sanded, and a mold made around it. This is my first attempt at making cowls, and it may take me a couple of tries, so please be patient with me. The finish is going to be Sig covering. Here is a picture of my paint scheme.
Good luck to all,
Darrell

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RE: P-39 "where to find" - 6/18/2006 8:43 PM   
oliveDrab


 

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Olive Drab with stars-and-bars is so awesome. I assume it'll be a flat or satin finish. Is SIG Covering like Monokote?

Since I'll be building the same P39, I'll need to have Robart make the same landing gear for me. I assume they'll know what I'm talking about when I mention your P39 project. Maybe this is something they should add to their product line.

I'm sitting here trying to envision how you're going to make the mold for the nose. Can you simply make a wooden nose (slightly undersized), cover it with fiberglass cloth / resin, let it dry, then remove the wooden plug, and viola... you're left with a fiberglass nose. As you can tell - I've never done this either.

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RE: P-39 "where to find" - 6/19/2006 1:06 AM   
Darrell B.



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Status: offline 		Most times, the cowl is molded out of a negative cast of the origional plug or piece. You cast the mold out of some material that will retain its shape when you are using it. The cowl is layed up inside the mold and allowed to cure. It is then removed from the mold and you have your piece. There are several threads that outline and give a blow by blow description of the process. If I can ever get it to work for me, I might be persuaded to make a few extras for those others that might want to model this airplane. My current concern with my plug is that the spinner ring has gotten larger than the 5" that was called for in the plans by about 1/16 inch. This does depend on the fact that there is a variation on all of the views of the plans in this measurement already. None of the views match exactly in their measurements of the size of the spinner diameter. I am also attempting to create a scale spinner for the plane as well. If I'm successfull it will be fiberglass and perfectly ballanced. It should weigh half what an aluminum spinner would which should help me to not have to add weight to the tail of the plane for balance. If the landing gear on my plane work well, then it should be no problem to get Robart to make another set. Thanks for the interest in my project. I'll keep everyone updated as to my progress. I have the tail assembly covered with the white. I'll try to get a picture of it up this evening.

Darrell

< Message edited by Darrell B. -- 6/19/2006 1:09 AM >

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RE: P-39 "where to find" - 6/19/2006 10:26 PM   
Darrell B.



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Status: offline 		Here are some pictures of the covered tail...

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