Heavy Gyro flying but not climbing.

[AirCommandPilot]

I fly an Air Command Elite single that weighs in at a hefty 631 lbs. (831 lbs all up flying weight with pilot) Most of the extra weight is due to the 90 hp Subaru EA82 and PSRU. I'm flying under 25' SkyWheels. The engine produces 450 lbs of thrust with a 68" 4 blade Warp Drive.
During the winter months, I didn't have a VSI, but it took off nicely with lots of lift. Now that the heat and humidity has set in, I'm not getting any where near the climb rate I expect or need. It seems to get a small "bump" of lift right when I leave the runway, but as I try to climb out, I'm only getting up to 50-100 fpm if I'm lucky. Occasionally I'll get under a cloud and get 400-500 fpm for a few seconds. The density altitude last Saturday was only around 2300'.
What types of improvements can I do to the machine to get the lift I need?

Lift--- Take off at 10:00

No Lift--- Take off at 3:30

 

[eddie]

Bobby 2,300' elevation is nothing,your problem could be several things rotor rpm,engine rpm,prop pitch.

Usually increased HP will solve a lot of problems,but check everything else first.

 

[AirCommandPilot]

I'm getting right at 5200-5400 RPM out of the engine at max throttle and the rotor flys around 355 to 390 rpm.
Could I be using too much thrust on the drag? Nothing physical has changed on the machine since last winter.

 

[eddie]

The number sound good Bobby,with that much weight you might have been right on the edge with the colder days and the

hotter days push you over the edge on HP.

When my RAF first flew with the 2.2 Subaru as 4850 elevation,it would fly with one, but the extra weight with 2 made it where

it would get off the ground about 3' and that was it. engine rpm and rotor speed was ok just not enough HP.

A 2.2 Subaru would probably make a really good performer out of it.

 

[scottessex]

Sounds to me like your rotors are too small diameter for the weight.

 

[AirCommandPilot]

I'm guessing a Yamaha RX1 would solve the HP problem..........

It defiantly would, but I'm not ready to spend the money yet.

 

[AirCommandPilot]

Sounds to me like your rotors are too small diameter for the weight.

Does anyone know what the "suggested rotor rpm" should be for SkyWheels?

 

[AirCommandPilot]

The number sound good Bobby,with that much weight you might have been right on the edge with the colder days and the

hotter days push you over the edge on HP.

When my RAF first flew with the 2.2 Subaru as 4850 elevation,it would fly with one, but the extra weight with 2 made it where

it would get off the ground about 3' and that was it. engine rpm and rotor speed was ok just not enough HP.

A 2.2 Subaru would probably make a really good performer out of it.

I do have a few 2.2 s at the house that need to be rebuilt. As well as a micro squirt controller to wire the ignition and fuel injection. I just hate to spend the money, and still have all that weight. Yamaha is looking nicer everyday.
My Rotax 532 would fly it, but I had to stay at full throttle to maintain altitude. That's when I went with the Subaru. Too bad it weighs so much.

 

[scottessex]

No Title

Hmmmm I have a dominator (open without pod) 65hp Rotax 582, 23ft dragon wings, 60" prop, empty weight 300lbs. all up weight full fuel 525lbs.
I can climb in the summer @ 6-700 fpm, 900fpm+ in winter @ 800ft evevation. rotor RPM 340-365 depending on temp etc.

What is your rotor Rpm?

rotor size by weight, also go up in size for higher elevations.

R squared x Pi = Square feet of disk.
Divide total weight by square feet of disk.
1.3 to 1.8 lbs per sq ft. safe range.
I like 1.5 for all gyroplane blades.

 

[scottessex]

I forgot to mention, the rotax makes 350lb thrust static.
Yes the whole thrust to weight ratio is a big deal.

 

[AirCommandPilot]

I was discussing trying a longer rotor with one of our club members and he said I didn't have enough reserve power due to too much drag and that the rotor will just speed up to make up for the weight.
I'm not sure if that's the whole story.
With mild temps outside I have about 30 lbs less thrust than one of our machines with a 100hp Rotax 912. (488 lbs vs 455 lbs). They use a 27' rotor on a machine that weighs less than mine with a 25' rotor.
He says I need to reduce the drag, or add power, but the rotor diameter won't make a difference.
Does this sound right? According to the chart Scott added, I should have a 26' to 27' rotor.

 

[scottessex]

Yes He is correct on one count, the rotor will speed up because of the extra weight, If your smaller rotors are turning faster to lift the weight they will create much more drag than a larger rotor turning slower.
You can reduce drag with a larger rotor and a larger rotor will create more lift since it has a larger surface area, (think larger wing)
With the weight of your machine you are approaching light 2 place weight, most 2 place gyros use 27-29 ft rotors.

What is you observed rotor RPM?? it should be in the 350 range. + or - a few.

Or you could just ditch the subaru and loose the extra engine weight and replace it with a yamaha.and gain more power .but that gets kind of pricey too.

Can you borrow a set of blades to test the theory? then you can determine which way to go.
By the way some of the best bang for the buck rotors are the Tango rotors Available from Tango in Atlanta Georgia.

 

[AirCommandPilot]

I'll have to look around the hangar. We've got a half a dozen or so rotors on a rack. I'll have to measure and see if any are 27' and find out who they belong to.

 

[Gyro28866]

On my Tandem Dominator, I have a set of 27' Dragon Wings. My fueled up all up weight is normally about 710 pounds, and gets lighter as I burn fuel. So, my rotor loading is approx. 1.25 and my RRPM is approx. 304 (depends on DA).
Yes, loading is light and RRPM is at a minimum; Ernie has told me to maintain a minimum of 310 RRPM. When I really slow fly, the RRPM will decrease in to the low 290's. All that said, I think the reduction of Induced Drag on the rotor because of significantly lower RRPM is a plus. There is a down side to this, I have less "Beam Strength" in the rotor because of a decrease in centripetal forces; and I fly accordingly. ( Yeah right? )
However, when I put someone in my rear seat. The numbers change and are between 350 and 365ish; depending upon the weight back there.
With a 100 hp engine and a 3 blade 74" Warp Drive pitched to limit static engine rpm to a couple hundred rpm below redline; she is a home sick angel. When the Density isn't kickin my butt, I have seen her maintain 2000 rate of climb. 15 seconds from ground effect to 500' and 30 seconds to 1000' agl. She will slow fly, no really slow fly. I can maintain S&L at 15mph IAS. Let your Buddies try to slow down and stay with you. hahahaha. ,Ok, enough about mine.
Point is, flying over rotored is like putting glider wings on your bird. There are advantages and also disadvantage's. Before you consider a longer rotor, make double sure that at full stick back and rocked back on the tailwheel, that you will not have a rotor strike into the ground. Cross wind landings really unnerve me on this machine. She is real tall and has a loosy goosy nitrogen strut main gear shock system and feels bad on the ground. And I do not do cross wind landings.

 

[AirCommandPilot]

On my Tandem Dominator, I have a set of 27' Dragon Wings. ......

Some if not most of the issue was found that the lash adjusters were not playing well with the Delta grind on the cams. I swapped the cams back to stock as well as some OEM lash adjusters and I get 465 lbs of thrust at around 5500 rpm. It flys/climbs well now, but the rotor speed at cruise is right at 365 rpm. Not horrible, but about 40 rpm higher than most of the modern two place machines around here. (mine is a single).
I'm going to hold off on the 27 footers for now. It climbs out here in this humid summer heat at around 500 fpm. I just don't yank and bank on it, due to the heavy weight hanging from a light design.

 

[NoWingsAttached]

I solved the problem you are experiencing on an Air Command single CLT with a Soobie, quite well. Drop me a line when you want to get serious about flying and replace that engine with a Yamaha which puts out 150 HP and weighs 1/2 as much as the Soob: [email protected]

 

[AirCommandPilot]

I solved the problem you are experiencing on an Air Command single CLT with a Soobie, quite well. Drop me a line when you want to get serious about flying and replace that engine with a Yamaha which puts out 150 HP and weighs 1/2 as much as the Soob: [email protected]

If I had the money, I would do it in a heartbeat. What would I be looking at (ballpark) for engine and adapter plate?

 

[NoWingsAttached]

Ya know, the Yamaha 4-stroke conversion engine kit price has remained the same since 2007: figure $7000-$8000 as your budget to get it in the air.