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Old Jul 20, 2011, 01:46 PM
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It wasn't me...
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I read on another forum that the crash was because the owner (name unknown) put the receiver under a metalized plastic cover of some sort. Others recommended against it, but after a successful range check, the owner decided to fly.
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Old Jul 22, 2011, 05:28 PM
Larry Dudeck is offline
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Then there were three...


The F4 has always surprised me every time I tried to launch. She never did what I expected her to do. Finally I figured I had the correct combination of tension and thrust, perfectly dry grass and a slight breeze out of the south.

22 paces, full throttle, step on the pedal...

I don't think the F4 got more than 6" off the ground, rolled left, cartwheeled, losing the left wing in the process. Bouncing to a stop, the front end broke off at the air inlets...

Picked up the pieces and went home. She is now in a big box, buried behind some of my adult children's belongings (they leave home, their junk doesn't).

I will not even attempt a repair, just let her sit until I need the hardware...
Old Jul 22, 2011, 05:37 PM
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Hi Larry,
Bummer to hear that. Best thing to do is what you did and walk away from the plane for a while. Doesn't make ya feel any better though.

Dan Eaton
Old Jul 22, 2011, 07:20 PM
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Hi Larry,

I'm sorry to read that your F-4 didn't go as planned. Sometimes models just don't last as long as we'd like them to, do they?.

Some of my favorite models had lasted only a few flights and then they're banished to the boneyard or trashcan.

Dan
Old Jul 22, 2011, 07:37 PM
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As an old friend used to say, that's a big dragstrip. I'm sorry to hear the flight didn't fare better. It always hurts to lose one, especially when it's so new.

Daren
Old Jul 23, 2011, 11:00 AM
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Sorry for your loss, Larry.

Fuzz
Old Aug 09, 2011, 08:34 AM
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Thanks for the condolences...

I guess I'm over the loss and looking forward to my next build.

The Piperjet Altair has a lot of appeal to me. Using a single MF480 as a standard unit of measure, the Altair will have a 66" wing span, about 365 sq.inch usable wing. The fuse will be about 7" wide at its widest point.

Have the initial outline drawn and need to get into the details but my summer is disappearing much too fast so I will spend as little time indoors as possible for the immediate future. It'll be a winter project for sure.
Old Aug 09, 2011, 05:32 PM
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I saw your thread in the scratch build forum, Larry. Very sporty!

Fuzz
Old Aug 27, 2011, 10:01 PM
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Quote:
Originally Posted by Larry Dudeck View Post
My spread sheet converges at 64.5 mph, based upon a frontal area of 119.4 sq.inch (my F4 has a frontal area of 126 sq.inch, the difference due to the three tanks hanging from the bottom), 92 oz AUW, 44 oz. of static thrust and a Cd=0.225 The value of the Cd is the big unknown but I'm guessing it is 10% lower than that of my F4 due to the iron-on covering.

The Cd plays a major role in all of this. For example, if the Cd was 0.15, the program would converge at 75 mph. If the actual Cd was 0.3, the program converges at 58 mph.
Hi Larry,

I was able to get my F-4 shot by the radar gun today at the Big Jolt. At 104F+ the density altitude was pretty high.

Most of my passes were upwind at 89mph with a headwind of about 5mph or so. Toward the end of the flight I did one downwind pass, but that was 88mph.

This pretty much agrees with my estimation. The measured efflux on my F-4 is 105mph. So, subtract 15mph and that works out to ~90mph.

Dan
Old Sep 06, 2011, 09:34 AM
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Dan,

Good info. Based on a density altitude of 1775 ft (104 F @ sea level), the drag coefficient calculates at .051. From various on-line sources, this is not unusual.
Old Sep 07, 2011, 02:08 AM
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Hi Dan, how many watts is your current set up?...I think I need to pic up a F4 when I get home....Umm love balsa...
Old Sep 07, 2011, 02:24 AM
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I think Dan's midi is running approx 900W. I'm running 1100W but only with a 70mm, in a lightened version.

Fuzz
Old Sep 07, 2011, 08:04 AM
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sounds like a 2kw 90 would work nice!
Old Sep 07, 2011, 10:30 AM
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Yep. Daren is flying his on a midi pulling 2kW (in thick air) and his flies great!
Old Sep 17, 2011, 12:54 PM
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Without going through 60 pages of threads... what retracts are people using/have been used in this bird?


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