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P-51 Mustang engine cooling


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Hello Guys,

I am half way through assembling an ARTF World Models Mustang P-51 60. I decided on it after reading a good review by Alex Whittaker, he used an RCV 91 engine as it could be totally enclosed without cutting the cowl.  This sounded like a great idea, so I got the same engine, but I have been worrying about the lack of cooling. There is a fairly large hole behind the prop' but no exit for the hot air. I was thinking of drilling out the dummy exhaust pipes, but I have a feeling that this won't be nearly enough. Has anyone had any ideas about cooling the motor without doing to much cowl bashing? I don't fancy seizing the engine on its first outing.

Cheers,

Cliff

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Hi Eric,

Many thanks for that, I suppose I could drill a series of holes at the bottom rear of the cowl where you suggest. The engine will be inverted, and the cooling intake at the front is at the bottom and quite wide, so the air should flow around the cylinder and exit at the holes with a bit of luck.

I will hang on in case someone has already done one as you say - there's not any immediate rush to do the cowl. I've got a few other things I can be getting on with, (and it's not exactly good flying weather is it?) Can't see the windsock anymore, it just blew away......... 

Best regards,

Cliff

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Thanks Bruce,

A few other people have mentioned that it flys really well - can't wait!

The RCV 91 will fit inside the cowl, so I am worried about the hot waste air getting out - I might have to get the drill out. BTW Has your son had any problems with the retrac's? The article that I read mentioned a potential problem with them.

Cheers,

Cliff

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I have built and flown the World Models Mustang 60 with an RCV 91CD in what can be said to be quite extremes of temperatures, from a "freezing" 10° to the early 40's°C here in Dubai. A great combination.

I have only enlarged the exit to an acceptable level on the bottom of the cowl.  Eric was correct in saying the hot air is larger by volume and needs to get out of the cowl quickly.  The general rule is the exit should be 3 times the intake volume, not sure if I have got that but the engine still ticks over nicely and has "oodles" of power for fast low, very low, passes up our runway.

 I will be flying the plane again tomorrow morning but as we are heading into winter will have to endure a  minimum temp of about 21 in the morning and low 30's by the time we leave the field at lunchtime.  I will take some photos of the opening I have, this should help and hope the photos will help you.  Of course, I realise that you may have flown the plane already, if so, hope all went well.

The undercart is fairly "wobbly" but has held up well.  We do have 300m of tarmac to aim at but you know the misjudged occasional flare can catch you out and it is still in one piece. Use half flaps on the base leg to slow things down a bit.  When turning onto finals dial / switch in full flap and keep a few clicks of throttle to settle into the correct glideslope, flare, and just as the main wheels touchdown chop the throttle completely.  Let her run on the mains and watch the tail slowly descend as speed decays.  This is one plane that will give you goosebumps on the low passes and when you get the landing right, enjoy.

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Hi Roger,

Many thanks for the reply, very useful information indeed, particularly the landing info'.  I haven't flown the beast yet, I'm not in any rush to finish it because the weather has been, how can I put this, "less kind" than the type that you are enjoying in Dubai

The pictures will be much appreciated as well, I was actually hoping that someone might have pictures of one already completed and tested as Eric suggested earlier in the thread. I hope that you had a good day flying today.  

Thanks again and best regards,

Cliff

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Hi Cliff

 Once again, enjoyed the flying and took a few photos.  I will attempt to create a "Photobucket" account and get them posted.  If you prefer, send me a PM and I will send directly to you.

 We flew out at our new flying field, it is about 35kms from the centre of Dubai and still being developed.  However, we have a 200m tarmac runway, a large pit area and and taxiways, also tarmac.  Grass is still to be planted and other facilities include a clubhouse, storage room and toilet blocks (all air conditioned of course).  Most importantly we have shade for the planes in the form of a large area adjacent to the pit area for the planes and us to relax under.

Regards

 Roger

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Hi Roger,

Many thanks for the photos and other information, very useful stuff. I will probably start off trying the slot idea first, I can't see it getting quite as hot in Cheshire as Dubai!

I will route take the crankcase breather tube out one of the slots as you suggest, it will save gunking up the cowl. I mamaged to get the flaps and ailerons set up last night, so it just leaves the retrac' servo - I saved the tricky one until last. The cowl is all ready apart from the cooling vents so that shouldn't take too long now.

I hope that the club BBQ goes well, just don't burn the sausages! 

Thanks once again for all your help.

Best regards,

Cliff

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