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Skymaster Gripen ARF Engine Selection

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Skymaster Gripen ARF Engine Selection

Old 08-07-2008, 06:46 AM
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MattyC-130
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Default Skymaster Gripen ARF Engine Selection

I have a Skymaster Gripen ARF and deciding on an engine for it.
Possible choices
JetJoe 1800
Jetcat 70
Jetcat 80
RAM 750
I think an 18LB thrust engine should be perfect for this jet.
Any inputs woud be greatly appreciated
Thanks
Matty
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Old 08-07-2008, 06:59 AM
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Default RE: Skymaster Gripen ARF Engine Selection

Matty,
You can also look at the new Jet Central Rabbit or the trusty Falcon and dial it down.

Regards,
Rob
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Old 08-07-2008, 09:05 AM
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Default RE: Skymaster Gripen ARF Engine Selection

Matty,

I've got a SM Gripen too and went through the same dilemma of choosing an engine. I also have a RAM750 but figured that, while it would fly the Gripen, it likely didn't have the power (19lbs) thrust to get out of high alpha maneuvers since it's a delta wing (high drag). The Gripen will likely weight about 23-25 pounds (the old non-ARF plus versions came in as high as 30 pounds) unless you keep it bare bones mininum of equipment and put the turbine all the way in the tail to eliminate the exhaust pipe. I wanted to put in a smoke system, regulator, lights, etc so I wanted a bit more power.

Regarding your list (plus a couple more)
Joe Jet - hmmm, I've heard good things and bad about quality,reliability, fit, etc. I bought a starter bullet from them to fit on the RAM. I wasn't impressed with the quality.
JetCentral Falcon - a good engine from what I hear though not quite as fuel efficient. When SM went to the ARF Plus and moved the gear forward 1-1/2" they had to make the main tanks 1-1/2" shorter/smaller (and also made the forward tank smaller though I'm not sure why - possibly because of the bulkhead at the fuselage joint.
Jetcat 70 & Jetcat 80 - likely good choices if you keep the plane light. However, these are not SE (fast throttle response engines). The 80, 120, and Titan are all the same size though there is a slight increase in weight for each
Wren and Behotec - Good products from what I hear but nobody has one locally and it's alway nice to have some local knowledge/experience in case you have problems.

Jetcat 120SE - I decided on this one. Bob Wilcox trained me on my first turbine (GWM) and I've always found him professional, helpful, and responsive. There are many Jetcats in the Southwest. This engine is an SE with the faster throttle, and I can always just turn down the max RPM if the 120 has too much thrust for the Gripen.

Good luck with your Gripen,

Jim

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Old 08-07-2008, 06:30 PM
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Default RE: Skymaster Gripen ARF Engine Selection

One point to remember is that you dont just fly flat out on the falcon or even the eagle.
With the throttle response on these engines, you fly the throttle as well..
The fuel consumtion per the factory is..

Falcon Fuel Consumption: 0.27 Lt/min (9.1 Oz/min. avg.)
Super Eagle Fuel Consumption: 0.2 - 0.35 Lt/min (7- 12 Oz/min. avg.)

Jet Cat P-120SE Fuel Consumption: 12oz/min at full power

Regards,
Rob
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Old 08-07-2008, 07:13 PM
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Default RE: Skymaster Gripen ARF Engine Selection

Jetcat 120SE, hands down.
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Old 08-07-2008, 08:43 PM
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Default RE: Skymaster Gripen ARF Engine Selection

My Gripen came out about 22 lbs. with a Jet Central Falcon. I would recommend an engine of at least 20 # thrust. Powerwise the Falcon is ideal. I like everything about the engine except the fuel consumption. I fly it half throttle most of the time, and open it up a couple of times during a flight. Maybe there is something wrong with my engine but my average fuel consumption is about 12 oz. per minute.

The three tanks that come with the ARF+ hold a total of 72 oz. (I measured them). I added an extra 15 oz. tank to bring the total capacity to 87 oz. I use a taxi tank and still can't plan more than a 6 minute flight. Last week I put on a 6 minute flight and had one aborted landing approach, so I was in the air about 7 minutes. After taxiing back to the pits I had only a few ounces of fuel left.

My buddy had a Gripen with a Jet Central Eagle (30#) in it. It was overpowered in my opinion. Interestingly his flight times were the same as mine and he very agressive with the throttle.

Of course it depends on what level of performance you are looking for. I've seen videos of Gripens with a 14# turbine in the tail and with a P-70 in the conventional location and wasn't impressed with the performance. The new Jet Central Rabbit or Merlin 90 might be a good match if you keep it light.

Joe
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Old 08-07-2008, 08:53 PM
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Default RE: Skymaster Gripen ARF Engine Selection

A customer of mine, Brian Kenton currently runs 87oz in his Falcon powered ASM Panther (wet weight 10.5kg).. 6 mins run time(1 min ground, 5 mins flight) uses only 54oz.
This meets the average of 9oz per min, his full power run temp is 500deg.. Can you tell me what yours is, as i think it maybe burning too much fuel.
Does your Falcon splutter when accelerating from Idle.. We tune this out of all engines we deliver..

Regards,
Rob
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Old 08-07-2008, 10:10 PM
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Default RE: Skymaster Gripen ARF Engine Selection

Rob,

The ECU shows 544 C as the max. temperature during my last run. I plan on flying it this weekend so I will double check it. The engine runs very smoothly, no sputter.

It's not due for scheduled maintenance for a while, but I was planning on having the fuel consumption checked into the next time I have to send it in.

Joe
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Old 08-07-2008, 11:28 PM
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Default RE: Skymaster Gripen ARF Engine Selection

Interesting as SM states, between 12-20lb
There goes my idea for my next jet,[&o] I was hoping to run my P70 (17.5lb) in the Gripens tail-

Ants
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Old 08-20-2008, 07:01 AM
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Default RE: Skymaster Gripen ARF Engine Selection

I don't know if this is going to help you but I have just flown my gripen with a jetcat P-120SE. It's the old heavy gripen and weight's in a 10kg exactly.
I think power levels is a very personal thing and my thing is POWER.
I have flown a Eurosport with a P80 in it and I was dissapointed, this is why I bought the Gripen as it was smaller that the euro and why I bought the more powerful 120SE.
Having said that I also think a rookie II with a p160 is underpowered as well. (I know it's a sickness)

To sport fly the gripen and use the canards to full effect you want the extra power. (O.K I wanted the extra power) I still need more flights to make a final decision.
The full size Gripen is a short take off and landing type aircraft, shouldn't ours be as well??

What I really want to know is can we use full canrad for landing like you can on a rookie?
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