Benson blades on a gyrobee

[mike271]

Hi guys I am new here and was wondering if any body could give me some info on G-4 Benson blades? I have heard bensons are good rotor blades and I have found a used 22ft set for sale. I am build a gyrobee and would like to install these onto it to use as beginner blades.
1. has anyone put these on a gyrobee before and how did they perform?
2. what would be a fair price for these without a hub
3. what would I be looking for when I inspected these other than guages,dents,tip damage,failed fastners?( person selling does not know anything about these rotors, friends uncle had them in garage and he died.)

[choppergabor]

Hi Mike. Welcome to the forum The very first thing you need to know is that the name is Bensen not Benson. Igor Bensen. As soon as someone sells or talks about Benson everyone knows they don't have a clue and normally want nothing to do with them. Sad but it is true. So I am just saving you right now LOL. Anyways. There is a lot that goes into picking blades. Your total weight your altitude and the style of flying you want to do. Sooooo a little more info needed to make a semi intelligent suggestion for you.Oh one more thing. These guys are picture junkies. Supply them with pics so they can analyze them and pick things apart. Welcome aboard. Cheers

[scandtours]

Scrolling once Ralph's construction plans, he recommended the Bensen and/or Ken Brock rotor blades because they are draggy. He did not advice low drag blades for reasons that are obvious.

[mike271]

choppergaber unfortionaly no pictures available only info off from data plate,the blades are 3 hours away and i was hoping to get some info to help decide if it was worth making the the trip look at them. I had planned on picking the rotors to be my final build step after weighing the swhip but these came up for sale and if I could get them for a good price I would look into them.I had planned on using dw but am a little worried about blade flapping and thought these might be less prone to this until I have logged some flight hours and then could upgrade.

[choppergabor]

Well Mike I am not sure about the statement just how prone DWs are to blade flapping opposed to Bensen blades..... What I know is they are very popular high lift well respected blades being produced by and supported by Ernie who is always a phone call away and you can be sure of the 0 hour time on your blades. While I can buy a bottle of purple polish and make some blades look brand new and sell them as one! The blades are the hearth of your machine. 22 footers sound good if you have a TRUE ultralight and if you are not planning to fly at say....8000 feet MSL. Almost no one has those! (notice I said almost.....thanks to adjustable scales a lot are claimed to be though) Just be careful and sometimes a 3 hour drive is not too bad to pick up some really good stuff. If you are not an expert I'd think it would be advisable to take someone with you who knows his stuff though.Just to be on the safe side. Good luck with it Mike
Cheers

[NoWingsAttached]

Originally Posted by choppergabor

Well Mike I am not sure about the statement just how prone DWs are to blade flapping opposed to Bensen blades..... What I know is they are very popular high lift well respected blades being produced by and supported by Ernie who is always a phone call away and you can be sure of the 0 hour time on your blades. While I can buy a bottle of purple polish and make some blades look brand new and sell them as one! The blades are the hearth of your machine. 22 footers sound good if you have a TRUE ultralight and if you are not planning to fly at say....8000 feet MSL. Almost no one has those! (notice I said almost.....thanks to adjustable scales a lot are claimed to be though) Just be careful and sometimes a 3 hour drive is not too bad to pick up some really good stuff. If you are not an expert I'd think it would be advisable to take someone with you who knows his stuff though.Just to be on the safe side. Good luck with it Mike
Cheers

Not sure about 22 ft Bensens from personal experience, but have heard some good things about this combo on a Bee from other guys. Should be a good setup. They'll spin up quickly!

I know one guy flying 22 ft Dragon Wings on a single place Dom. This is unusually heavy loading, and higher AS is required to maintain flight. This can also lead to scary, if not disastrous consequences when landing, and RFD will not recommend this. But we just turned our question away from Bensen 22's to DW 22's. Apples and oranges.

As to Gabor's message, these are my thoughts.

Ralph Taggart and I discussed the issues affecting pilot control and rotor selection for the Bee he designed at some length, and I listened as he and Ernie had a pretty good discussion at Mentone covering this subject. Other high-time, well-respected pilots who have flown the Bee have weighed in on the DW discussion regarding rotor disk diameter and loading, and flight characteristics in changeable, moderate-to-heavy winds when landing,

According to Ralph, the Taggart Bee was designed around, and intended to be flown with, 24-foot straight blades, with a near 8-in cord. This typically includes the likes of Sky Wheels, Sport Copter and Rotordynes.

Turning to the use of RFD Dragon Wings, let's look at the pros and cons.

Pros of using Dragon Wings

1. At any given cruise throttle setting, DW’s may fly a gyro up to 10% faster through the air. This is a direct result of the narrower cord and the lower drag profile of the airfoil shape, lending to the overall reduced drag of the rotor disk. They are the most efficient design we have today, at speed.
2. DW’s are one of the most affordable rotor sets to purchase.
3. DW’s have a high reliability factor and service life.
4. Easy to obtain, both used and new. RFD is able to supply DW rotors very quickly.

Cons of using Dragon Wings
1. The low-drag profile, coupled with the increased angle of attack at the outer 1/3 of the blade (6 degrees vs 3 degrees of any other blade) produces less forward component of lift, the vector of force that makes the autogiro rotors spin and confounds the understanding of so many people who try to grasp how gyroplanes can get us off the ground. This results in several disadvantages:
a. Starting DWs is more difficult, ergo
i. a mechanical prerotator is required
ii. longer take-off distances are required
iii. blade-flap at take-off is more common
iv. blade-flap on rough terrain at take off is more problematic
v. aborted take-offs are more common
b. Rotor speed decays more rapidly, therefore
i. Blade flap during certain routine, low-G maneuvers is of greater risk, such as leveling off after a steep climb.
ii. Routine landings in shifting cross winds are a far greater risk due to unpredictable and sudden loss of sufficient lift to maintain being airborn.
2. DW’s reportedly feel more prone to “ballooning” in winds.
3. Dragon Wings are much more flexible than any other rotor I am familiar with. This also makes them more much more prone to flapping both on the ground and in the air.


High-time pilots flying DWs in a heavily loaded configuration, say 22 ft dia on a machine weighing well over 300 lbs empty, have reported a scary loss of lift when landing in shifting, moderate cross winds. Other, less-experienced pilots, myself included, have destroyed their gyros while landing in these conditions, with properly loaded disks of 23 ft over 300lb gyros, due to this unpredictable, sharp loss of lift at low AS and RRPM.

For 23 ft DW's on a Bee, DO NOT ATTEMPT TO FLY THIS SETUP IN CROSS WINDS EXCEEDING 8 MPH UNLESS YOU ARE AN ACCOMPLISHED GYRO PILOT.

I now have 24 ft DW's on a Bee and this combination lands MUCH better. The loss of lift due to rapid rotor decay is not nearly so sharp, and it is much easier to manage safe landings in heavier winds. This is better for a new pilot like me, but this configuration IS DANGEROUS IN LIGHT LOADING CONDITIONS and EXTENDED TAKE-OFF DISTANCES ARE A MUST. Blade flap WILL occur during most every take-off with this larger 24' DW disk, NO MATTER WHAT YOU DO, so rotor management is tricky at best when getting off the ground. RFD may not even sell you a set of 24 ft blades if they know ahead what you are planning to do with them. They do not recommend this larger, lighter-loading.

I recommend you pre-rotate any DW setup to 130-150 rotor rpm MINIMUM before rolling to take-off, so be sure you have a great prerotator and engaging system.

Or you can just use 23' or 24' straight blades, like the designer suggests, and have a normal, predicatable, stable, simple, easy-to-handle gyro in all stages of flight and all wind conditions. And you can always hand-start them.

If you are new pilot, I recommend you avoid DWs. It really is easier to manage your rotor and gyro in many conditions of flight and ground operation with the stiffer, straight blades. Later on, when you want to race the other guys to breakfast at one of the fly-ins, I recommend getting a set of DW’s – and be ready to throttle up to get out of a bad landing. Of course, this works on any rotor system.

I don't know much of anything about 22 ft Bensen blades that is of any help here, except that there are a fair number of gyros in the same weight class as the Bee that have successfully employed them with little adverse effect reported.

[gyromike]

Skywheels are much more limber than Dragon Wings. So are Bensens. All you have to do is look at the amount of droop in the Skywheels and Bensens when the machine is parked. I have attached a photo of my Bensen with 23 foot Dragon Wings next to an Air Command with 23 foot Skywheels. Compare the angles of the hub bars to the droop in the blades.

Except for the need for a prerotator* I haven't experienced any of the things Gerg wrote about.


* And I have been able to hand start Dragon Wings on my Bensen, but it wasn't easy. An electric prerotator will work with Dragon Wings even though it doesn't spin the blades up as fast as other systems.

[NoWingsAttached]

Interesting. I guess that the increased coning of the DW and hence the need for higher towers and teeter bolt placement is a result of it being a stiffer blade? Doesn't add up. I think the photo reference is fun, but useless here, no telling how much stress is on the tie down straps of the two machines, two totally different gyros, completely different heads, completely different stops, the front wheels and keel angles are different and the angle of the hub bars are not the same...side-by-side.

Perhaps if we hang them side-by-side from the teeter bolt that would be a good comparison.

I was going to strip my post out nearly completely, as I didn't want to stir up the pot and realized this is not a good thing to do. But yes, I have had one of the most respected gyro pilots we know come up and tell me that, after hundreds upon hundreds of hours flying DW and never experiencing what I describe as loss of lift in shifting winds while landing, it did indeed happen to him at Mentone 2011, and scared the crap outta him. Anyone watching from the ground would not have known it, but he confided to me afterwards that he is now a believer in my whacky train of thought.

You are welcome to fly my Bee with the DWs on it and experience first-hand the issues of blade flap that occur nearly EVERY time you take off. And you are also welcome to ATTEMPT a grass field take-off after spinning these things up to just 100 RPM in calm winds. You'll only need about 1200 ft of runway, if you can do it at all.

[gyro]

Originally Posted by gyromike

Skywheels are much more limber than Dragon Wings. So are Bensens. All you have to do is look at the amount of droop in the Skywheels and Bensens when the machine is parked. I have attached a photo of my Bensen with 23 foot Dragon Wings next to an Air Command with 23 foot Skywheels. Compare the angles of the hub bars to the droop in the blades.

Except for the need for a prerotator* I haven't experienced any of the things Gerg wrote about.


* And I have been able to hand start Dragon Wings on my Bensen, but it wasn't easy. An electric prerotator will work with Dragon Wings even though it doesn't spin the blades up as fast as other systems.

Mike there is no way of knowing how much pressure is on the tie downs and they look about the same on the rear. I have flown DW...they are ok but there are some other really nice ones out there. DW are a limber blade and when static they droop so much that there are wrinkles on the underside. I dont see this as being unsafe but I would definatly support them if not being flown on a regular basis.

I have flown nearly everyblade out there at some time or another and while one blade...let say bensen may fly great on a bumble bee my not fly that great on a AC. but one can narrow blades down that fly very good on just about anything. which IN MY OPINION skywheels, sport rotors, rotordynes.

[Redbaron]

the stick shake in my bee has disappeared, even with the stick floatin.

trade secret!

[gyromike]

The reason Dragon Wings use a teeter bolt hole 1.5" higher than other blades is because the blades are lighter than most, yet turn approx. the same RPM.

Heavier blades will fly at a flatter coning angle because centrifugal force is trying to sling the blades flat, with the load is trying to bend them up. Lighter blades at similar RRPM's and load will have a greater coning angle.

As far as stress on the blades in the picture above, we don't pull the blades down as hard as we can. When I slip my tie down on, the rotor head is not against the forward pitch stop. Neither is Mikes A.C. above. The only stress is to overcome the trim spring.

But take a look at the rear blades in the picture. There is nothing pulling them down but gravity. The skywheels hub is tilted more nose down yet the rear blade tip is no higher than on mine.

Ther reason the DW's have a crinkle in the bottoms is because they aren't flat-bottomed blades. The "oil-canning" comes from the static droop trying to bend the bottom skin into a compound curve. Flat-botomed blades like Rotordynes won't show any oil-canning.

[BUD ONEAL]

I have flown just about every blade out there and I can tell you that the bensen blades give up way before the dragon wings do. I ,as several more old folks out there learned on bensens blades and all will tell you that bensens will make a good pilot of you because you had better have it all together at the flare. If you flare at 1" or 10 ' you will be in contact with the ground at flare because the bensens will quit flying at flare! The dragon wings will float a bit and coushion the landing and make it look as if you know what you are doing.

[Timchick]

Originally Posted by NoWingsAttached

..............You are welcome to fly my Bee with the DWs on it and experience first-hand the issues of blade flap that occur nearly EVERY time you take off. And you are also welcome to ATTEMPT a grass field take-off after spinning these things up to just 100 RPM in calm winds. You'll only need about 1200 ft of runway, if you can do it at all.

Greg,
If you almost flap your blades on every take off you need to get with an instructor and change your technique. I flew exclusively off grass strips with my KB-2 with Dragon wings. During all that time there was only one time I had to abort my takeoff and it was due to a prerotator problem and me not being experienced enough to get the blades up to speed during my takeoff roll without it. Also, why would you only prerotate to 100 rpm on a grass runway? I easily got 200+ rpm with my Wunderlich prerotator and was off the ground in a very short distance.

[Mike484]

If you buy a set of blades without the hub bar how difficult will it be to get a hub bar matched up to and balanced with the blades?

[gyro]

Originally Posted by Mike484

If you buy a set of blades without the hub bar how difficult will it be to get a hub bar matched up to and balanced with the blades?

If it is a hub bar made for the same brand blades then it should be normal tweeking.

However skywheel hubs being matched with different blades can be a problem as the holes will not line up.

bensen, brock,rotodynes...etc. If you have any experience with setting them up such as stringing, slinging, balancing, pitch setting, rotorhead centering all these things can be done to get them spinning fairly nice. I've even experience rotating the head 180* which changes how the rotor disk balances out between the towers and in turn makes for a smooth flying blade.