Propellers 2011: MT vs. Whirlwind

[Darin Bishop]

Kevin & Kendal,

 

I know that after Sun-n-fun this year you guys were headed over to Zellwood to do some testing of the Whirlwind propeller Kendal is flying and compare it to the MT.

 

Can you share with us what you learned? I know many of us are probably curious if the WW is a viable alternative to the MT.

 

Thanks!

 

Darin

[Kendal Simpson]

Hey guys the short story is that yes the Whirlwind is definitely a viable alternative to the MT!  The un-opinionated facts are this.  They pull the same on the scale, the MT is 4lbs lighter, and the Whirlwind is $3400 cheaper.  

Now here's the long story...  

  I was hoping to have pictures of the pull test but the way it works I guess it's not possible.  As I was running the airplane at full power, Kevin would go behind it and look at the dial gauge on the giant "fish scale". He told me that the needle vibrates about 100lbs so he just tries to average the middle of the needle blur. We pulled my Whirlwind first and got 1650 lbs.  When I got done pulling the MT he said it was the same 1650 average as the Whirlwind had pulled a few minutes earlier.  Then he said it possibly was a bit more, but too hard to say, it was a wash and they were the same.  Hind sight we Should of video taped it so interested parties could see the blur and make their own interpretations. 

After the pull test i made a short test flight with the MT on my airplane  This was my first time flying a zero time MT. It was much smoother than any other MT I've flown. There was still  wire buzz at most RPMs but not nearly as bad as the other ones I've flown. Still not quite as smooth as the Whirlwind but nothing to complain about. I could still find the smoothest sweet spots at full power, around 2600, and around 1950 RPM just like the other MTs I've flown.  This works out good for most situations. There are only a few RPM ranges where I get slight wire buzz with the Whirlwind. I have 90 hours on the Whirlwind now and no hint of vibration or balance issues I've felt with all 5 of the other MTs I've flown on M14s. 
 Vertical penetration, top speed and cruise speeds seemed exactly the same to what I'm used to seeing with the Whirlwind.  Basically getting 2300' of vertical and 192 MPH indicated flat out.  The only performance difference I could see or feel from my test flight was braking action. When I pulled the power off on the MT it didn't slow quite as much as the Whirlwind does. This became very obvious on landing. Don't get me wrong there is a lot of brake effect, just not quite as much as the Whirlwind. I wish I would of had time to do more elaborate test flights with recorded data but my schedule wouldn't allow it. I can guarantee there would be very little difference in performance numbers from what I did experience. 

 This particular MT didn't surge on me at all.  I've never had any surging with the Whirlwind and I've flown it with two different stock governors.  I know it's pretty rare not to have surging at some point with the MTs with the stock governor but I didn't experience it with this particular prop.  From what I understand MT has modified some stock governors and then developed a new governor altogether to help with the surging issues.   
 
 All up the MT is definitely lighter. We weighed the entire assemblies. Hardware, prop, spinner, backplates etc. as a whole unit. The MT weighed 88 lbs while the Whirlwind was 92 lbs. We weighed just the spinner domes and found a 2 lb difference there between the flexible Kevlar MT and the rigid Carbon Whirlwind spinner.  I'm sure the steel flange adapter required on the Whirlwind like on the other MTs adds up for the other difference.  I'm trying to get the weight of a single blade from Whirlwind.  It would be great to compare single blade weight if we could get the MT blade weight as well. I'm guessing the hollow carbon Whirlwind blades would be lighter than the wood filled MT but I can't confirm that yet. Lighter blades would mean less stress on the crank and less gyroscopic effect.

I guess the only other thing I can think of is Whirlwind lists for $14500 including spinner and all hardware.  I recently saw a quote of $17880 for an MT prop and spinner. I don't know what their new governor sells for. 
 Those are the facts as I know them. Let me know if you have any questions. 
Kendal

www.acronut.com

[David Weber]

We have virtually eliminated the surging by doing at least 6 warm weather and 8 cold weather (and having preheated)

full strokes of the prop control  with a pause of maybe 5 seconds at the low rpm position

 

these engines need more clearing of the air in the system then what our flat engines typically do.

 

this Hint came  from  of a "round motor " motor crop duster

 

 

Thanks

Dave

David Weber

dwe...@mwishop.com

979 775-5841w

979 204-9473c

 

 

---

From: pit...@googlegroups.com [mailto:pit...@googlegroups.com] On Behalf Of Kendal Simpson
Sent: Monday, April 18, 2011 9:45 AM
To: pit...@googlegroups.com
Subject: Re: [Pitts12Google] Propellers 2011: MT vs. Whirlwind

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[Kendal Simpson]

Wow that's interesting Dave!  I actually did a lot of deep prop cycles on the ground before I flew it since we had just installed it and I wanted to make sure everything was ok. Kevin was surprised when I told him it didn't surge at all when I flew. You said "virtually eliminated" I'm guessing you still experience it sometimes?  Does it just happen on final when you push the prop full forward or do you get it on vertical uplines and other phases of flight too?

Kendal

www.acronut.com

[David Weber]

We were seein the surging on takeoff,  really gets your heart pumping.

I don't move the prop control much during flight,  (more of a gentleman's type of acro)

 

"Pretty gentle" on the prop forward during landing, seems to give it time to work.

 

I'll have to think about when surges occur in the air, but they are the exception not regular, 

I'll need to schedule some research to make sure I know the details,  but memory seems to be in a rolling type of turn is when it happens

 

 

 

Thanks

Dave

David Weber

dwe...@mwishop.com

979 775-5841w

979 204-9473c

 

 

From: pit...@googlegroups.com [mailto:pit...@googlegroups.com] On Behalf Of Kendal Simpson

Sent: Monday, April 18, 2011 10:36 AM
To: pit...@googlegroups.com
Cc: <pit...@googlegroups.com>

[Marc Jones]

Kendal

How much ground clearance do you have with the Whirlwind prop?  Wondering if the Whirlwind will work with standard height gear.

Marc

[Kendal Simpson]

I'll measure it tomorrow Marc but I think it would be real close with the standard gear.  Kevin do you or anyone else know how much clearance there would be with the long blade MT on standard gear?  I'm pretty sure the Whirlwind is even a bit longer...

Kendal

www.acronut.com

--

[kevin kimball]

Marc,

The standard gear is not long enough for the 102" MT or WW.  The 98" Mt will absorb the power of your BPE engine and will have a slightly higher top speed compared to 102" props.  The difference will be on the hover end of the spectrum.  The 102" has an advantage there.  102" prop of any brand requires the longer landing gear.

Sincerely,

Kevin Kimball, Vice President

Jim Kimball Enterprises, Inc.

PO Box 849

5354 Cemetery Road

Zellwood, FL 32798-0849

407.889.3451 phone

407.889.7168 fax

www.saettaboats.com

www.pittsmodel12.com

www.jimkimballenterprises.com

Email:  Ke...@jimkimballenterprises.com

[Kendal Simpson]

Hey Marc I just measured and the Whirlwind is 104" and I've got 14" of ground clearance in the 3pt. attitude with the tall gear. 

Kendal

www.acronut.com

[Kendal Simpson]

For curiosity could someone tell me the ground clearance with the standard gear and the 98" prop?

Kendal

www.acronut.com

[Kevin]

Level flight attitude on the ground is the concern. Some fly the airplane this way on take off and the long prop on short gear would have 2" clearance with zero squat of the gear. 

Short gear and 98" prop is just under 13" at 3'point  if I recall correctly. A Long prop would be 2" less. 

Sent from my iPhone

Kevin

On Apr 21, 2011, at 1:22 PM, Kendal Simpson <ken...@acronut.com> wrote:

[Marc Jones]

Great info...thanks Kendal and Kevin for the insight.