New RAF 2000 build

Greg Vos

Active Member
Joined
May 26, 2019
Messages
379
Location
Cape Town
Aircraft
R44/22 H269/300 MD 500 Magni (all); Xenon RST; DTA; ELA; MTO Trojan
Total Flight Time
Stoped counting at 2000
Loving this thread 👌 when a man builds and works on his gyro I enjoy training him 🍺 will be checking in here regularly, loving the enthusiasm and support
if it was SA the guys would be moaning and bad mouthing the project ….as we know locally if you don’t drive a Porsche and fly a Cavalon your just a dick !
For the record the cavalon is just not my thing ( yes I’m instructor rated on it so I can have an opinion 🤪) personally I like all the hardcore adjustments and easy to fabricate goodies on the RAF 👍
 

GyroRon

Former Gyro know it all
Joined
Oct 29, 2003
Messages
16,665
Location
Fort Mill South Carolina
Aircraft
Vans RV4 / Dominator 582 Ultrawhite
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ALOT
Do the drop keel mod!!!

The horizontal Stab does little to stop a power pushover ( bunt )

The H stab's main purpose is to make the gyro less sensitive in pitch, to help you to avoid PIO which can lead to unloading of the rotor, and the resulting PPO. Think of the H stab as the shock absorber on your car, or a damper on a screen door... It is just to Dampen the action of whatever it's used on

The drop keel mod will lower the engine ( which is not ideal ) which in turn lowers the prop ( which IS ideal ).

The BEST thing you could do would be to raise the cabin higher, and find a different reduction drive that places the center of the prop BELOW the engine rather than above it. These mods would give you centerline thrust and would make PPO nearly impossible. Obviously, a new Redrive, and moving the cabin higher are both expensive and major modifications... Doing the drop keel mod is actually a very easy and inexpensive mod that although won't be a complete cure for the imbalance in the gyro, it will be a step in the right direction.

I have seen where some builders mount the radiator above the engine, even the battery as well.... Anything you can place higher than the prop helps with the thrust offset.
 

grevis

Member
Joined
Oct 14, 2019
Messages
37
Location
Hamilton, New Zealand
Aircraft
Mosquito XE285, RAF2000(Building)
I wondered if the D-Motor would be a good solution on RAF's. No redrive necessary so the motor could stay put but the prop ends up a lot lower.

Also, has there been any discussion (or calculations by those more knowledgeable) on angling the existing motor so its slightly down at the front. A very small angle change would represent quite a change in thrust line, but then could the mast still be positioned correctly, cg attained etc etc
 

Martin W.

Active Member
Joined
May 10, 2020
Messages
326
Location
Winnipeg
I wondered if the D-Motor would be a good solution on RAF's. No redrive necessary so the motor could stay put but the prop ends up a lot lower.

Also, has there been any discussion (or calculations by those more knowledgeable) on angling the existing motor so its slightly down at the front. A very small angle change would represent quite a change in thrust line, but then could the mast still be positioned correctly, cg attained etc etc
.

I agree on the angle .... Cierva tilted his engine to position thrust line where he wanted ... in his case it was a tractor but same idea you mentioned

.
cierva thrust line.JPG
 

C. Beaty

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Apr 16, 2004
Messages
10,099
Location
Florida
For an engineer, it is important for the propeller thrust line to pass through the CG.
Since most modern gyroplane designers are stylists and not engineers, it is no longer important.
 
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Doug Riley

Platinum Member
Joined
Jan 11, 2004
Messages
6,586
Bensen angled the McCulloch down at the front end by, IIR, 3 degrees. No telling if this was to improve prop clearance or more nearly to to line up the thrustline with the CG.

Vancraft went its own way, angling the engine the other way (aft end down) to "direct propwash onto the H-stab". Hmm.

FW planes sometimes have high thrustlines, IF dictated by the mission. For example, amphibs like the Lake have mile-high thrustlines, to allow the tail boom to clear the prop. But they have big, immersed H-stabs with substantial negative incidence to help with the pushover tendency. This, of course, adds drag, but the drag is the price we pay for the Lake's (very cool) mission. I wouldn't pay that price for the sake ONLY of styling or a seat that's supposedly easier to get into.

On the latter point, sign up for some tai chi and limber up.
 

Rene Genest

Member
Joined
Apr 24, 2006
Messages
52
Location
Quebec
Aircraft
Bensen and RAF 2000
Vance,

The drop keel allowed the ability to lower the engine and reduce some of the high thrust line by 6 inches.

Wayne
Very interesting. Is there any pdf file to get plans to do this keel drop? Your HS seems great, have made it yourself? If not, where did you got it?

Thank you

Rene
 

Rene Genest

Member
Joined
Apr 24, 2006
Messages
52
Location
Quebec
Aircraft
Bensen and RAF 2000
Hi Vance, as Wayne mentioned above and as I understand its lowering the line of thrust (with respect to the machines vertical centre of gravity). When researching the RAF mods I found there were actually quite a number of these machines over here in NZ, and a number of them have had the keel drop done with pilots having before and after experience. I have not been able to find or talk to all of the owners yet, but of the ones I have the general consensus seemed that the RAF in its original setup was overly sensitive to wanting to nose over with any light g's and power, and it became a more predictable machine to fly with the mod done.

I of course wont have before and after experience to comment on as I am doing the mod at the start, but you try and make the best informed decision you can when building experimental aircraft like this. That blue machine in those photos above will be one of the RAF's over here in NZ, and the red one in the attached photo is local to me. I am only dropping the keel by 4", it appears most do a 6" drop, and I have seen mention of machines overseas doing an 8" drop.

GaryView attachment 1152097
Beautyful machine. The HS looks great. Have you made the HS yourself?
 
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