Hawk Talk

[PMarshall]

Anybody have any idea what is the most efficient rpm to run a 3 blade 72 inch Warp Drive prop at. The only information I can find is the tip speed should not be higher than mach 0.92 as this will creat a lot of noise. I have a 503 with ebox attached and the 3.47 reduction gear fitted. I want to fit this combo to a CGS Hawk and want to get the best performance out of the setup. Any ideas please.

[Abe]

Hi PMarshall! (Which SA county are you residing?
Rainier Lamers (quiet lately?) posted an excellent post a year ago saying we are revving our props too slow for efficiency. With the 1:3.47 you will not have to worry about tip speed. Warp is indestructible but not the most efficient, and the 72" 3-blade is methinks far too much prop for the 503. It will give a very narrow speed range. The Hawk would do better on a 62 to 64" 3-blade NC/Powerfin/Kiev or 2-blade 70" GSC.
FlySafe!
Abe.

[jpage]

Hi PMarshal. I am also having a CGS Hawk built but with a Jab2200. As I understand it the most efficient will be as close to the Mach 0.92. See this link http://www.pponk.com/HTML%20PAGES/propcalc.html. Are you in the Stanford area?

[PMarshall]

Thanks for the advice. We have a farm between Hermanus and Stanford where we have a short runway and quite a large flying community of about 8 aircraft in total. We are replacing our trike with the hawk as the trike is no fun in the wind next to the mountain.

It seams that most props on microlights run at around mach 0.6 tip speed. I have not found any articles or manufactures spec to say what the most efficient prop rpm is only the max speed is stated. Thanks I will have a look for Raniers post.

Hi JPage I have heard from Dave that he is building the jab version for you and will be interested to see how it performs. We also considered this option but it pushes the cost up significantly for what we intend using the hawk for, a cabbage patch plane to replace the trike.

I have flown the hawk 2 up in 503, 582 and 912 versions and it fly’s well with all the engines. The 912 in my opinion is too much for the hawk it fly’s the best with the 503 but the extra power of the 582 is very useful on short strips and sink. The hawk has excellent flying characteristics and is very easy to fly. Just one warning keep your eye on the airspeed it can loose speed quickly and mush. Keep your eye on the airspeed and she is capable of flying in almost all weather conditions. One of the best value for money aircraft money can buy. The hawk is also in my opinion the best flying light microlight aircraft around.

[jpage]

As you can see I've lurked for about a year, trying to decide which plane to buy. Microlighters and Avcom have been incredibly helpful in finally making a decision, even though the Hawk wasn't mentioned much. Went for a flight in the 582 powered Hawk, and new immediately that the Hawk was the right plane for me. I just wanted 4 stoke, but couldn't aford a 912. Hoping for the performance of a 582 in cruise, but not too sure of the take off and climb. In a months time we should find out.

[Hawk]

Hi JPage Where are you based?

[jpage]

Cape Town

[PMarshall]

The Jab combo should be good. Prop diam might be a issue. I would expect you would get similar performance as the 582. I would guess a better choice than the 912 as this engine is a bit of an overkill for the hawk, a bit heavy and overpowerd.

JPage where are you based in cape town? Would love to see the Jab version when it arrives.

[jpage]

I'm in Rondebosch, but will probably keep the Hawk down near Arniston where I go on weekends. Will you be going to the TFD fly-in in October? Maybe we should try to get some of the Hawks together down there for a formo with the airforce Hawks :D. As for the prop diameter, I've learnt a lot about these things in the last few weeks although I must admit that I'm still pretty clueless. We've settled on a 65 inch ground adustable, which should give about 2800 RPM static thrust(I think) The Ecoprop is limited to 3000 RPM , although the Jab motor makes full power at 3300 RPM. Max. Torque(210 Nm) is at 2500 RPM. Can't wait to see what happens, and whether all the predictions about engine overheating on the ground take place. I'm installing the Enigma from Rainier to do all of the engine monitoring with 4 CHT's and EGT's. It really seems like a fantastic piece of kit, and I still can't believe that they are built here in the Cape. Spend hours late at night playing with the simulator much to the wifes annoyance.

When will your Hawk be ready? Hopefully for TFDC

[PMarshall]

TFD? When and where?

We have the hawk in our hanger already and we are busy test flying. We are trying to finalise the engine prop gearbox story. At the moment we have a 503 fitted but we are going to change this for a 582.

Will you be opperating from andrews field or Bredasdorp.

[Griffin]

..and I still can't believe that they are built here in the Cape.

There are a lot of interesting thing being built in the Cape. We just hide them when the folks from the big smoke come and visit.

TFDC is from the 9th to 11th November
http://www.flyin.org.za/index.htm

Are there any other Hawkes in the Cape apart from the Austin's?

[jpage]

Thanks for the link. Was only out by a month.

As far as I know there is John's one at Bot River, Dave has a few obviously, PMarshall busy test flying and mine almost complete. I think that there is one at Greyton as well. Could be a nice fly in to TFDC.

[PMarshall]

Here in an extract from an email from chuck about the correct prop and gearbox ratio's for the 582 hawk fitted with 68" 3 blade warp drive


If you use a Warp drive prop then you will need the C gear box because the Warp is much heavier and exceeds the inertia limits for the B box. Frankly I'm not too keen on the Warp drive prop my experience with it was not as good as with a Powerfin or Ivo..It seemed if I pitched it for good take off performance then it over reved in the air .Then if I set it for good cruise it was doggy on Take off ,I couldn't get a happy medium that was as good as the other two. Also because of the heavier weight when power was applied the engine would spool up instead of having an instant response to the throttle. As far as using a 2.58 vs 2.62 with an IVO or Powerfin prop the ratios are so close I never really noticed a difference.

With a fixed pitch prop I usually set the ground rpm at about 6200 revs and it will unload a bit to about 6400 WOT. In the air I cruise at 5300 - 5800 rpm depending what cruise speed I desire and if the need to get there is more important then the fuel burn. Some guys fly slower then that but I'm always in a hurry