BalsaBob

My Feedback: (24)

Wondering what the best engine/fan combination is for the Red Arrows Hawk ARF (by AMD). I believe they suggest an OS 46 VXDF (with the Turbax Fan), or with slight modifications, an OS 91 (with a Dynamax unit). It appears to be a fairly large plane (53" wingspan) .... is the OS 46 VXDF/Turbax combination powerful enough ? ? Thanks. Bob

tomcatman

My Feedback: (2)

What is the AUW of this model? With a 53" wingspan, i'm guessing somewhere in the neighborhood of 9 to 12lbs, depending on how it's built. I would certainly consider the OS 91/Dynamax combo. For the performance, I think it's one of the more reasonably priced packages out there without breaking the bank. I have many videos of ducted fan meets throughout the country from back when turbines were only starting to come out into the market and this is the combo most of the big names used...from from small single engine models to the big twins, and they flew with great authority!!! JMO

vinnyjet

My Feedback: (39)

i have seen 2 hawks fly with the os 46/turbax combo
both flew nice/ what is the weight difference between
os 91 dynamax and the os 46/turbax combo
this was off concrete runway
hope this helps
vinny

jetflyr

As Vinny asked: What is the weight difference in adding a Dynamax and .91. Another pound or so?
Larry Wolfe (the US importer through JHH) flew his routinely on a .46/Turbax reliably and fast! and I had the oportunity to fly his original one with zero complaints on power!
Oh...this was also seen in Denver, at 5400ft.
Save the weight, go with the .46/Turbax.
(my 2 cents)

Greg

tomcatman

My Feedback: (2)

Sounds very good. We should also ask ourselves however, does the difference in power given almost twice the size in displacement, justify the extra pound or so? Believe me guys, i'm a FIRM believer in "IF IT AIN'T BROKE, DON'T FIX IT" LOL!! I for one, just truly love what i've seen in the OS 91/Dynamax combo. I can also truthfully say, i've never seen a Turbax powered model. I'm not for knocking what I haven't tried. I guess it comes down to what it always does....personal preference. Bob, at this point I think it's safe to say, with this particular model, whatever you choose will do just fine. Knock em dead!!!

growingupisoptional

G'day, also looking at this combination of aircraft and engine.
Will stick with the OS 46 and turbax fan and one day in will go the WREN 54 or similar power plant.
I'm going to use the ducted fan as a stepping stone, don't have the cash to throw a turbine in the air for a test flight. Bummer. So will get it all up and running on the ducted motor and then when I'm dead confident. Maybe ??? MMMmmmm Turbine.

Quick questions are; is is a stable airframe? If I'm going to put a turbine in it I want stable. My Extra is for aerobatics.
Also what fuel does an OS DF motor require? Is it fine of 5%nitro or does it need more?
Will this combination get off a grass strips?

You thoughts appreciated.




Wanna be turbine pilot

BalsaBob

My Feedback: (24)

Thanks for the input/comments. The weight difference between the OS91 and the OS46 is 8 ounces. Overall weight difference might be about 12 ounces (a slightly smaller pipe and a bit less fuel). From what I have read about the OS46 VXDF, it is quite a good engine .... and much improved over the 46 that OS had a few years ago.

As far as putting a turbine in this Hawk .... on the box it says 'Not suitable for turbine installations'. Thanks. Bob

1Eye

My Feedback: (2)

growingupisoptional wrote ...
Heh, heh ... depends on who you talk to and which model of the Hawk they've flown. Too much yank on the elevator and some I've seen are prone to depart controlled flight in a heartbeat [] I'm not an aerohead but I think the short tail moment/small tail volume has something to do with it. Yup, I had one ...

Mike

MiragePilot

My Feedback: (6)

I think that once you combine the weight differences between the engines, fan units, tuned pipes and increased fuel volume, the net weight difference between a .46 DF and .91 DF installation is closer to 2lbs.

Peter

tomcatman

My Feedback: (2)

Does anyone know what is the difference in THRUST between the two systems?

AAbdu

My Feedback: (18)

From what I've heard, the power difference is not proportional to the weight difference. The OS .46 combo puts out great power for its weight. Another consideration is the fuel capacity and flight times. The OS .91 drinks fuel like a thirsty sailor and you would be hard pressed to get much more than 4 minutes of flight time on the fuel that it is designed to hold. That plane was designed for a .46 and the weight, wear and tear from increased vibration, flight loads, and limited fuel capacity might not be worth the extra performance of the larger engine. I try to stay close to the manufacturers suggestions as it is in their best interest that we succeed. All this is not to say that a little planning and re-engineering can't make it work like a dream, but is it worth it? That is where your personal preference comes in. What others have done and experienced is a good barometer of what you can expect.

Good luck on your decision, let us know how it turns out.
Anthony

Dave03B

I have the PJP Hawk, slightly smaller than the AMD. 46vx/Thorjet fan/JMP pipe. Havent had the chance to fly it yet. Will be able to get a weight est. soon if anyone's interested.

razorice79

My Feedback: (1)

I changed out a k&b45 fire/turbax 1 out of my jhh mirage with a os91/dynamax, i gained 2 pounds+, but i also had to add 1 servo, 1 flight mixture, 1 fuel regulator, and hopper tank. ohh and upgraded the two 8oz main tanks to 11oz tanks.. I like the more POWER[:@]
but dont like the lump in my engine hatch cover from the size differents in engine/fan combo..

[sm=lol.gif]RaZoR

razorice79

My Feedback: (1)

I believe that the os46/turbax puts out 7-8 pounds of thrust and the os91/dynamax puts out like 11-12+? i could be wrong, but I know theres a large difference between the two. PROPER/CLEAN FLOW PATHS (ie., thrust tube diameter,inlets,etc) also will change how much thrust you get.. ? Im somewhat new to rc jets, but thats what ive learned through research & experience.. could be wrong![sm=lol.gif]
RaZoR

tomcatman

My Feedback: (2)

Ok, so we're looking at an average of about 4lbs of add'l thrust with the OS 91/Dynamax combo. You gain approx. 2 add'l pounds of weight with this setup, but I think it's worth it. That extra 2lbs or so of thrust leftover might be the difference between 120mph and 150!!!! Know what I mean? On the long run of course, it all boils down to personal preference. I say, "BE ALL YOU CAN BE!!"