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Joined: 2/1/2002 From: Middletown,
NJ, USA Status: offline
quote:
ORIGINAL: Kmot
That does indeed look very interesting!
But slow! The prop's going to be in the wake of the fuse, not many prop choices, lots of intersections to make drag.
Will it be faster with the gear up? Most likely, but I bet it's because the wheel wells will cause less drag when full, clean fixed gear might be as fast.
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Joined: 4/9/2002 From: Cleveland,
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One thing that strikes me in these designs, is that they really do not give any consideration on how to accomodate a muffler or tuned exhaust on the engine. Disappointing.
I was pleased to see someone finally using a 90deg rotating nose gear. (Btw F-20 ARF folks - that is the way to go on a retrofit - need not even be steerable)
< Message edited by bob27s -- 10/23/2006 3:33:40 PM >
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Bob Brassell Jett Engineering - Engine Mfg Support Forum Host
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Joined: 12/11/2001 From: South Plainfield, NJ, USA Status: offline
Bob,
I sent an email to Jett Eng. this morning asking for a tuned muffler for this type of application. I figure the normal Jett-Stream built to point straight down will be good enough. I'm actually quite surprised nobody has made a pusher muffler before. I guess many use the Pitts style.
I was looking for an R/C car or Heli header/pipe to fit my YS 45 for my Nitro Bobcat. I may be better off getting this plane and using the YS 61 with the Heli tuned pipe.
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Joined: 4/9/2002 From: Cleveland,
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Hi Mark,
Dub is out of the office for a couple more days. I saw the email too.
Im not sure the jett-stream can be modified or built differently for these applications. There is a reason it looks like it does So building one with an exhaust exiting somewhere else might not be possible - but may be worth looking at.
On the keecat, a turbo-jett would probably be the way to go. With that side mount installation, it would not look too bad back there.
Quite a few folks flying the Bobcat simply installed a diverter tube off of the muffler. One guy ran the exhaust down through a hole in the wing to allow it to exit below the plane. One bent up a horse-shoe shapped aluminum tube, and affiexed that (no photos). Sounds like that guy does tube bending for a living - it is think wall, and a tight radius bend (frozen/ice, sand inside?)
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Bob Brassell Jett Engineering - Engine Mfg Support Forum Host
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Joined: 12/11/2001 From: South Plainfield, NJ, USA Status: offline
Don't bends like that create backpressure? Diverters facing into the wind could be pushed back at speed. Changing the exit on the tuned pipe shouldn't change too much. Look at all of the reversed ducted fan props for the larger engines.
I would rather have a better engineered solution. For now, I will fly the plane with the YS 45 using a Pitts style just to get the test flights over with. Hopefully Dub will be able to create the ultimate solution.
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quote:
ORIGINAL: MMallory
Don't bends like that create backpressure? Diverters facing into the wind could be pushed back at speed. Mark
Not when done properly... turning is not a big issue. The key is the inside diameter of the extention tube. It has to be larger than the ID of the exhaust outlet. Too many folks use a diverter with a tiny inside diameter, and yes, that will affect performance. On the Jett engines, if you size the diverter so it fits "loosely' over the OD of the exhaust stinger, and then snug it in place with a clamp or tie-wraps, and keep it to a reasonable length - performance is not affected.
Dynamic pressure from facing into the wind might be a little bit of a problem, but due to the muffler angle, it does not face 100% parallel to the flight path - so the effect is not huge.
Biggest issue - is its hard to make something that does not look goofy.
< Message edited by bob27s -- 10/23/2006 7:06:02 PM >
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Bob Brassell Jett Engineering - Engine Mfg Support Forum Host
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Joined: 2/2/2004 From: Rio Piedras, PUERTO RICO (USA) Status: offline
Bob this the Setup that you talking?
see this setup
I'm not a good picture taker, but here's my Bobcat. I've been flying the crap out of this plane so much that the cheap blue plastic film on the top wing has pealed off in little small sections. Great flying plane. Everyone comments at the field how well it flares and lands. Out of a dive, its got to be doing at least 125 easy.
MY SETUP: YS 61-AR engine w/10x8 APC Macs pipe. 4 -3421 JR in empenage, 2 - JR 4131 in wing, 2 Futaba thro/steering PPG clear coated two tanks, 16oz & 8 oz Hayes Bolt on wings ( interior 8-32 / blind nut 2" from LE) old P&E functional struts from 1989 sitting around wait for a home. Tetra wheels 6V 2000 mah NiH 8.5 lbs
I cut open the main gear support structure and reinforced the gear block and capped the cutout area with 1/8 ply. Stripped off that ugly green anti glare and repainted it black. Looks much better, at least to me!
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Joined: 2/21/2002 From: SOBIESKI, WI, USA Status: offline
Here's a thought...Davis Diesel Products (the boys who those diesel conversion heads for glow engines) also make a strap on pusher type pipe with the outlet facing to the back of the plane. I used one of those on my YS 45 on a Combat Models F16 and it worked great. May have lost a of bit rpm not using a conventional tuned pipe but it worked great.
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All Forums >> RC Airplanes >> Extreme Speed Prop Planes >> rich model keecat.60 size kingcat with retracts 
rich model keecat.60 size kingcat with retracts - 
So building one with an exhaust exiting somewhere else might not be possible - but may be worth looking at. 
