PDA

View Full Version : Prop choice



WWhunter
11-29-2014, 08:51 AM
Ok, all you KF guru's, I have the $64 question. I have three props in my posession that I can put on the uncompleted IV I just purchased. The GSC 3 blade, a 2-blade Warp Drive Taper tip (70"?), and a 3-blade Whirlwind of 70".
While the Whirlwind is currently on another plane I am thinking of ordering one of the new Whirlwind 75" STOL props for that plane and if I do the 70" will be available for use.
I think the Whirlwind is the best prop but since it may be a while before I can afford the 75" I will use either the Warp or the GSC.
Is the Warp Drive a better performing prop than the GSC? My personal experience with this 2-blade Warp was that it had excellent climb and very good cruise numbers but it seemed to be 'harder' on the 912. It also was not nearly as smooth as the 3-blade Whirlwind that replaced it.
I have read on here both pros and cons to the GSC but I seem to still see alot of them being used so they can't be all that bad.
I may send the Warp back to the factory and see if it needs balancing. Or just sell it.

jiott
11-29-2014, 10:22 AM
The factory is currently installing the 3-blade Whirlwind on the SLSAs. Its a beautiful prop using the latest scimitar shape technology.

jrevens
11-29-2014, 10:52 AM
Do you know if it is the 75" one, Jim?

jiott
11-29-2014, 12:01 PM
I'm pretty sure its the 70".

WWhunter
11-29-2014, 07:57 PM
Jim, I totally agree that the Whirlwind is a nice looking prop. As I stated in my original post, I already have one in 70" and it is on my RANS S7. This plane originally had the Warp 2-blade I mentioned, but at higher RPM, there was a buzz/vibration throughout the plane that I was not comfortable with. I researched props and bought the WhirlWind. I looked at the Kiev prop which looks very similar to the Whirlwind. I had read very good reports on the Kiev and was close to buying one but then I read that, occassionally, getting replacement blades could take several weeks. That is something I was not comfortable with.

I think I will try the GSC prop before giving up on it. I do like the look of the wood prop on the Kitfox. Plane itself has a 'vintage' look and the wood prop just seems to fit.

I don't have the money at the moment to order the 75" STOL prop but I am hoping to sell the Warp for enough to offset the cost a bit. I really liked the performance I got from it but I want to go on floats and the blades either need to have the nickle edge installed or new blades purchased.

Flybyjim
11-29-2014, 08:25 PM
I bought the Keiv 3 blade from Ted at B&B in Md. and have it on my Rans S7. I like the prop a lot, smooth no vibrations like I had on the 2 blade Sensenich ground adjustable composite prop. I had a drumming effect on the wind screen at 5200 on my rotax 100hp. I think I will try the Whirlwind on my Kitfox SS7 also due to the situation with the blade replacement.

john2
12-04-2014, 05:41 PM
HI Folks,
I'm not endorsing any prop at this point, still building a Just Aircraft Superstol and have already purchased a Catto, but you may want to check out some of the threads on the Wings Forum Just Aircraft sight on prop choice. THere has been quite a bit of discussion lately. Most of you have probably heard of Steve Henry, the dead stick take-off guy, and he has tried just about all the propular props including the Whirlwind. His favorite at this time for all around performance is a Prince prop. There are a couple of other guys giving very good reports on the Prince also. Again I don't know anything about them other than reports from several people at the other site on how well they perform in takeoff and cruise. Also there is some discussion on prop choice on the "Backcountry Pilot" site in the "912 Big Bore" thread. I don't have a dog in the hunt, only submitting this as food for thought.

Take Care,
John

Av8r3400
12-04-2014, 07:18 PM
Thanks for dropping by with some "out of the box" thinking.

I, too, have been following discussions on "Wings" and "Back Country Pilots" on the topic of the newly emerging fixed pitch, high tech, props being offered by Prince and Catto.

WWhunter
12-08-2014, 12:02 PM
Never argue with a wife....especially when she tells you to order the new prop while it is on sale!!!! Whirlwind had a discount valid through the 2nd of Dec. and since the spousal unit was here visiting me for Thanksgiving, she TOLD me to go ahead and order it. :) Called WW and they had one is stock and shipped it out that day. It arrived a few days later. WOW!!! I thought my 70" WW was a nice looking prop, this new 75" is even nicer. Carbon fiber material itself can be seen through the clear coat that is on the prop. Nice white tips, and the prop looks almost like it belongs on some kind of high speed Lancair/Glasair with an IO-550!!! Couldn't believe how much bigger just 5" of blade can appear. :eek:
I have been told size matters! I am talking props here! :D

I couldn't wait for more reports on the Prince or Catto, just too impatient I guess.

I will use the GSC (maybe) on the Kitfox for a while and then take the 70" WW off my RANS S7 and put it onto the KF. Put the 75" on the RANS since it has the Zipper motor and 29" AkBushwheels. I think the KF with the smaller tires (currently has the 21" Nancos) might be too close to the ground for the 75" prop. First thing is to get the plane flying I guess and go decide what I want to do.

kitfoxnick
12-08-2014, 01:19 PM
You are probably aware of some of the GSC problems. I think many people have had good success with them. There have been some instances of them shedding blades. That's why GSC put a 5 year 500 hour TBO. I think most of the problems were from over torquing or corrosion.

Here is a link to the Service Bulletin http://www.ultralightprops.com/bulletins/051799_sb.pdf


May 17, 1999
GSC SYSTEMS SERVICE BULLETIN

AFFECTED MODELS All GSC Systems 2 and 3 blade ground adjustable
GSC Systems has been in the business of producing quality props for over 15 years for many types of aircraft.
Over the course of these 15 years, it is possible that the original aircraft and/or the GSC propeller may have
changed ownership several times. During the transfer of ownership often the instructions and maintenance
procedures of our propellers have been lost. To that end, many propellers receive incorrect maintenance.
The most critical assembly procedures of our propellers are that the hub and root ends not be tighten past the
recommended 100 in/lb torque specification. It is also possible that due to the over tightening of the attach
bolts, that the space between the aluminum hub halves is no longer visible. The result of this improper assembly
or maintenance could result in premature blade failure resulting in either injury or death.
If you do not presently have a set of GSC assembly instructions please contact GSC Systems and one will be
forwarded to you.
REQUIRED SERVICE Immediate inspection
1. Inspect to insure that a visible gap between the Aluminum hub halves is detected. If no gap is visible contact
GSC Systems.
2. If you are the initial and original owner of a GSC Propeller, are you certain that the hub has never been
torqued past the 100 in/lb MAX torque specification, if not contact GSC Systems.
3. If you are not the original owner of a GSC propeller can you be assured that the GSC propeller hub has
never been torqued past the 100in/lb Max torque specification, if not contact GSC Systems.
GSC SYTEMS TBO
GSC systems have documented user times of over 1000 hours but due to the nature of the exchange and selling
of our product we are implementing a 500 or 5 year TBO for all GSC propellers.
If you require further information please feel free to contact GSC Systems. Our goal is to continue the supply
of a quality and safe product.



If it were me and I was going to use this prop I think I would put some sort of cable around the motor mount and around the firewall. If a blade departs there would be a good chance that the unbalanced prop would rip the engine off. With the cable you could keep your CG and make an emergency landing.

tommg13780
12-09-2014, 08:49 AM
We just had an incident (Friend) that involved a GSC 2 blade with some VW derived engine in a direct drive situation. The blades were trimmed short to stay within 80% mach 1 tip speed at around 3600, full throttle RPM. Unfortunately the blades separated form the hub after about 4 hours flying.
Fortunately both blades left the engine simultaneously. The motor mount fractured at one point but three points did not fail. The engine stayed with the airplane revving way high with no load until ignition was killed.
The pilot (300+hour student) was able to return to the field and dead stick land without damage to the Kitfox 1. As I understand it when the engine separates from the airplane the resulting imbalance will make the airplane hopelessly uncontrollable. This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experimenters that this was going to be risky business. Perhaps the inertia value was exceeded?
Nick's comments caught my attention because "shedding blades" is such a harmless sounding expression.

WWhunter
12-09-2014, 09:36 AM
Okay, you guys have just convinced me that to remount the GSC prop to this plane could be hazardous to my health. The prop looks like new and was only test run for a couple of hours so I doubt it would have any issues but my life and the well being of the plane are more important than keeping the prop on the plane.
Since I have two other props I can use I will 'flip a coin' and see which one I will use. Most likely the 70" Whirlwind will win. ;)

Av8r_Sed
12-09-2014, 05:10 PM
This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experim

Tommy,
I understand your personal choice to avoid a risk. On the other hand, It wouldn't be appropriate to reject all VW direct drive derivatives and all GSC props due to one incident with a combination of the two on a Kitfox. There have been many postings here indicating direct drive VW derivatives might not be a good match for a Kitfox, while there are others like Sonex drivers who wouldn't have anything else. Many Kitfox pilots have flown behind GSC props for many hours. With good maintenance and storage they can be very reliable and smooth.

The upshot is, it would be best to work with the prop manufacturer and heed their advice on good and not so good engine/prop combinations.

tommg13780
12-10-2014, 06:59 AM
Paul, I can appreciate your point of view. I've had many (200-300) trouble free hours flying with GSC on a rotax 2 stroke/gearbox application.
For some reason, possibly a naturally occurring fracture of 1 blade, I made an inquiry for replacing that one blade and the GSC representative advised me to order 3 new matching blades as the only feasible option. Of course that would cost equal or greater than a new Warp, or IVO.

I believe this "shedding of blades" incident was somewhat disturbing to me because it could be something I probably would have tried myself. Those blades were both retrieved and they both looked like they were in a vise and someone carefully ran a chainsaw vertically from the inboard end down to the thru bolt slot. I found that mental image to be rather emotional. It was kind of a "foxhole" moment when the guy next to you takes a head shot.

I'm sorry if my preference here seems irrational but to some extent perhaps it is. I really get a lot of pleasure from the Kitfox buying, selling, building and flying activities and would hate to see the whole thing spoiled by a senseless incident.

jamesmil
12-19-2014, 04:34 PM
want to weigh in on this topic and give my 2ct worth. have 250+ hrs on the keiv prop with no problems and very happy with the performance on our ss7 with 912 uls and 850 tires. routinely see 1200 to 1300 ft per minute climb and 113 mph ias, at 5300 rpm and very smooth. Ted Bryant at b&b and i have become good friends and I am going to be doing some testing on the new keiv electric veritable pitch hopefully soon and will post the results here when done. that said the w/w wins the sex appeal contest hands down, best looking prop out there.