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Old May 19, 2009, 06:14 AM
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GOK
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GOK
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Turkey, Izmir
Joined Aug 2005
1,302 Posts
Well, I finally ordered the electronics for the P51 - they should arrive late this week. I am going to try and fly this model with 4s lipos and a relatively small motor. The motor I ordered is the sk3548 900kv, I gave a link to in my previous posts. This is in the range of a power 32 or an axi 2826-12 I believe.

I know people are usually flying these 40-50 size warbirds on 5-6s and axi 4120s or eflite power46 motor but I didn't want to move up to 5 or 6s lipos just yet - particularly since I already have a few 4s packs. I thought if I could keep the model light (under 90 oz or at around 5.5lb) this motor should fly the model decently on 4s- this way, the retracts may lso hold up much better hopefully.

With 4s lipos and 12x6 - 12x8 props the motor should produce around 700-800 watts and 55-65 mph pitch speed at 45-55 amps. 60 mph is not a speed demon but with 125-135 watts per pound and 1.1 weight to thrust ration the P51 should fly quite scale - and a bit extra. This ofcourse is considering that I can end up with an AUW of 5.5lb MAX.

Anyways, the motor weighs 6oz so I realized that I had to place my batteries inside the cowl as far forward as possible. With this in mind, I completely ditched the pack placement idea in my previous post and started cutting and bashing the firewall to make space for the batteries inside the cowl. Now this is where I was really surprised. I am not familiar with these large glow models so I don't know if this is common but I found inside the firewall two huge leads pre installed (4.6 oz total) . By getting rid of them, and a few other bits and pieces, I shaved off 4.75 oz (mostly from the nose unfortunately).

Since my pack will be pushed all the way into the cowl (its a huge cowling with plenty of space) and since the pack weighs 18.5 oz, I think I will be able to compensate for that weight loss from the nose. I am feeling a bit more confident that I might be able to finish this model with an AUW of up to 5.5lbs, if I can get her to balance without any dead weight.

Oh, the access to batteries will be through a hatch at the underside of the cowl. I hate the idea of cutting into a beautiful cowl but I don't think I have choice here. Besides, I don't think it will even be noticed in flight. This method worked a treat in my 1/5 cub - only I couldn't think of making a hatch there I just cut a hole under the cowl

Here are a few pics.
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Last edited by GOK; May 19, 2009 at 07:08 AM.
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