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Rabbit vs. Cheetah for the C-ARF Flash

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Old 11-13-2010, 11:48 PM
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Default Rabbit vs. Cheetah for the C-ARF Flash


Greetings Mr. Clapp and anyone else who can enlighten me,

I have shortlisted these two turbines for my soon to be delivered (classic) c-arf Flash. Of course, they are in very different thrust classes. However, as one would expect, their fuel consumption rates are also significantly different. Please correct me if I'm wrong, but I understand that the Flash can be flown with the Rabbit without the optional wing tank for about 8-9 min., whereas with the Cheetah one would need the wing tank - i.e. more weight, plus the little extra weight from the actual turbine install. How do all these (and probably other) variables balance each other out on this plane? I would be particularly interested in more specific data, such as WOT speed, take-off and landing behavior, aerobatics, overall "feel", flight time, etc., when comparing the Rabbit with no wing tank vs. the Cheetah with wing tank on the Flash.

Thank you in advance.

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Old 11-15-2010, 10:17 AM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Beavis:

You will enjoy your classic Flash regardless of which turbine you select.

My Flash was originally powered with our Falcon and subsequently with our Super Eagle. Super Eagle dialed down to 24 lb of thrust, produced longer flight times using less fuel.

Many customers are using the Flash/Rabbit combination and sing its praises ! Cheetah weighs 1 lb more, produces 31lb of thrust but uses more fuel. While I have not tested the Cheetah / Flash combinaton, you will not be disappointed with either choice.

The Flash is fast. . .but again, I have no airspeed figures. Our state of the art ECU has a built in airspeed port for those who wish to check this out. Eagle Tree makes a great telemetry unit which as well provides some serious data for those who like to follow this.

Rabbit and Cheetah are presently on 7 - 10 day delivery schedules.

Best regards,
Eric
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Old 11-16-2010, 10:57 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Can't address the Flash/Cheetah combination, though I do have a Cheetah which I thought about putting in the flash, but just like it too much with the Rabbit.

My Standard Flash is powered with a Ribbit on a Tamjet pipe. Dry weight of this setup is between 21-22 lbs. Like Eric said, it is a great combination. Speed is right around 170-180 just straight and level on a 90 degree day, and around 700 altitude readings taken on a good radar gun. You can push more out if it from a dive and on a cool day the speed is better. Vertical in same conditions is very good but not unlimited. However I flew two days ago with the temp at 52 degrees and vertical was unlimited, at least unlimited as far as I cared to go. I fly out of a 400ft strip and takeoff role is around 120 ft with no headwind and 20 degrees of flap. I do not fly with the wing tank bit did add a sump to my main tank just because I did not like the idea of the flat bottom tank. Anyway that gives me about 95 ounces of fuel plus the header tank. I set my timer at 8 minutes and do not start it till my takeoff roll. I go gear down at 8 minutes or so and usually am on the ground by 9 minutes. I almost always have around 20 ounces of fuel left and have never been into UAT. My plane is set up with 45 degees of flap and about 6mm of crowe which makes the plane totally nuteral on approach. With this setup it pretty much lands itself, acts pretty much like a trainer. As to overall feel of the plane, to me it flys pretty much like a really fast pattern plane. Does the best point rolls I have ever seen.

Hope that helps.
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Old 11-17-2010, 11:28 AM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash


Yes, that helps a lot! Thank you and Mr. Clapp very much.

Sailing1, could you please give the specifics of the sump system you've installed (brand and install diagram, or alike). I've never installed one.

Thank you again.
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Old 11-17-2010, 03:20 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Beavis,
There isn't a brand, we just modified the stock main tank adding a sump to the bottom rear of the tank. This means you cannot use the full bypass but you really don't need it with the Rabbit and probably not with other turbines either. There are some pictures of a couple of different tank modification on the Flash Build threads. I will see if I can find a picture of my tank and the install in my Flash and post in the next day or so.
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Old 11-17-2010, 07:06 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Here are some pics of Sandor's Flash tank mod, before and after:
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Old 11-17-2010, 09:22 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

I can't comment on the flash, however I have owned both engines and I now own the cheetah and a rhino. The cheetah is about 3/4 lb heavier (I weighed this against my rabbit when I had it). One thing to consider is this: If you decide to change airframes, you will have a much larger choice to choose from using the cheetah than the rabbit. Both turbines are awesome, but for the 3/4 lb weight different, to me it's a no brainer. If you already own the rabbit, than go with that. But if each turbine is within your price range, I would go with the cheetah. You can always dial the engine thrust back which will save fuel and go easier on the turbine. I missed my rabbit, but the cheetah can fit so many more airframes that are better suited to the additional thrust. Hope this helps.
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Old 11-17-2010, 09:56 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash


Thank you both for the new additional info and insights.

As to the pictures of the sump, is it Hysol (Aeropoxy) gluing the sump to the tank? Was the sump itself made with fiberglass and finishing resin?

Best,
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Old 11-17-2010, 10:12 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Here is a picture of the tank in my Flash. The sump is 7 inches long and just over 1 1/2 inches deep and the width of the standard tank. The construction was pretty simple - we made the sump portion by laying up glass over a male plug and then cut the bottom of the main tank out and glassed the two pieces together. The entire sump section is behind the baffle in the main tank. The simple rear support screws off which allows the tank to be removed from the rear. I finished it off with a Dreamworks heavy duty clunk. Have never had a problem with fuel starving or any air in the UAT.
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Old 11-17-2010, 10:31 PM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash


Sailing1,

It looks great, very robust. You also gain sizeable additional fuel storage capacity of course, as you had mentioned. I assume that, because of that extra capacity, the fact that the sump also has a flat bottom is not an issue (?).

Thank you for sharing the picture and all the very helpful info,
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Old 11-18-2010, 07:48 AM
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Default RE: Rabbit vs. Cheetah for the C-ARF Flash

Flat bottom of the sump is not an issure as it is now 1 1/2 inches lower than the rest of the tank. I have never really measured the new capacity of the tank but think it is around 95-100 ounces.
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