le fou

My Feedback: (12)

Hello,

I am thinking of getting into ducted fan. I have a K&B 7.5 and I am planning to use a dynamax unit. What aiframe would be the best for this combo? I was thinking about the Hawk or the A4-Skyhawk but they seem to be slow with the K&B 7.5. Any recommenations?

Thanks,

Le fou

L Turner

My Feedback: (3)

I believe the 45 sized DF engines are undersized for the Dynamax fan. You should probably contact Jet Hangar Hobbies for a Turbax I DF unit and the available OS ducted fan engines, since it would be near impossible to get parts for K&Bs. A lightly built JHH Sabre is a good starting point, could later be converted turbinized.

Adil Nasim

My Feedback: (61)

I agree,

The .45 size K&B will NOT work with a Dynamax. It is best used with a Turbax-1 fan unit. As far as airframes, JHH has a good line-up. My personal favorites are the F-86 as well as the Mig-15 from JetMart USA. Plenty of speed if built right.

You can't go wrong with either airframe.

Adil

A7Bldr

My Feedback: (40)

Which K&B .45 do you have? Carb in the rear??
The old version may not be worth messing with....

Jim

le fou

My Feedback: (12)

Thank you for your replies. I have a K&B 7.5 with the carburator on the front (by the crankshaft) and a perry pump on the back, am I in troubles?

Thanks,

Le fou

A7Bldr

My Feedback: (40)

Although I've never operated an older one like that, I've heard they are a pain.

The OS 46 VX is the best engine out there in this class.
Jim

MMallory

My Feedback: (1)

Le fou,

Yes, you are in trouble. That engine is not well suited for reliable ducted fan use. I have one on a Diamond Dust prop plane and it does ok by bypassing the pump. The K&B 7.5 with the rear carb is a much better choice for a ducted fan. Personally, I didn't have the greatest luck with the OS VX. It ran fine for a couple of runs and lost peak RPM. The K&B 7.5's seem to get better the more you run them.

Mark

le fou

My Feedback: (12)

What about the K&B 82 or the OS 91 VR-DF - Are those any good?

Thanks,

Le fou

Adil Nasim

My Feedback: (61)

K&B 82 is a decent engine although a little heavy and not as powerful.

The OS 91 is/was the industry standard !! You can not go wrong with that as long as you don't over-lean it too much. Get the right pipe, a mixture control, use quality fuel and you will have a very user-friendly engine with great longevity.

This class of engines (.82-.91) also opens up the airframe possiblilities endlessly

Adil

le fou

My Feedback: (12)

Thank you for your inputs. Would you consider a ROSSI 105 to be as reliable and powerful than a OS 91?

Thanks,

Le fou

Terry Holston

My Feedback: (1)

No....................Carb is too finicky, and the Rossi runs too hot. Will melt tuned pipes!