28-10 shootout. PT models vs. Mejzlik

[KrisW]

Hi guys. .I just got through reading all the information on the site concerning the PT Models line of CF props. . so I am pretty sure I am not creating a redundant thread here.

I've seen some RPM figures for the 3W 106 with the PT Models 27-10 . .about 6200 rpm for that combination according to Vic Aponte, so that makes the PT props seem draggier than their Mejzlik counterparts, since most Mejzlik 28-10's are in the 6400-6600 rpm with the 106 and standard diverter exhausts (or so it seems), and the 27-10 Mej is about 100 rpm stronger usually.

What I am looking for with the PT is for it to be quieter, but have similar performance to my Mejzlik 28-10 on my BME115/KS1060 powered MX-2. So, I'll be doing a side by side comparison of the two propellers when the weather gives me a clear sky to play with. I'll be looking at static rpm in the pits, perceived noise level in the pits and while flying, and overall flight performance from a purely subjective point of view when considering vertical performance, acceleration, pulling out of a hover, downline braking, and P factor/spiraling slipstream affect during pulls and pushes, as well as KE flight.

Granted this will be mostly a purely subjective testing procedure. . but we all KNOW how our planes fly, and can tell a difference when something changes. I'll be able to tell very quickly if the PT is an improvement, about the same, or a disapointment. The big test will be . .does the PT stay on the plane, or join my pile of discarded props in the corner (about 10 props laying there at the moment), or get put in the back of my hauler as a special application prop because it is better than the Mejzlik for certain things.

My biggest consideration is NOISE, since even with a draggy 27b Vess prop on the front the MX-2 had more than enough conjones to do triple vertical snaps if flown properly. The second consideration will be overall flight performance, especially ease of throttle transition and vertical penetration. The third consideration will be how much I have to correct the planes flight path due to differences in slipstream and P factor. Anyone can make corrections in flying technique, trim, and mixing to counter changes in the last consideration, but sound footprint and overall thrust and transition are a function of the props shape itself, and will quickly tell the tale of whether the PT is up to the task at hand. . .in this case being IMAC type flying with a little 3D thrown in on the side.

I expect to be flying the props on Monday, my next day off.

[Flyinrazrback]

I think you will like the PT 28x10, one thing is its about 3oz lighter than the mejzlik, spools up instant.

[paffy]

That's very cool. When you are at it, could you also measure the static thrust using a scale, so we can have something other than subjective results ?

[KrisW]

	Quote: Originally Posted by Flyinrazrback
	I think you will like the PT 28x10, one thing is its about 3oz lighter than the mejzlik, spools up instant.

Do you have a LIFE????

Two whole minutes on the site and you are already replying ! ! !

Geesh!!!!!! You must camp out here, waiting to ambush unsuspecting people. .

[KrisW]

	Quote: Originally Posted by paffy
	That's very cool. When you are at it, could you also measure the static thrust using a scale, so we can have something other than subjective results ?

paffy, you are almost as bad as FlyinRazrback. . . . .

I don't really have anything set up to make that comparison. . but I've also foiund in the past that props that make really good static thrust on the ground, with an unmoving plane, usually have poorer flying thrust in the air.

[Flyinrazrback]

I am sitting at work not doing Jack!

[KrisW]

	Quote: Originally Posted by Flyinrazrback
	I am sitting at work not doing Jack!

I'm sitting at home not doing jack either .. boring day with terrible weather here in the SE. Guess I'll drill this prop and check the balance on it.

[Ch!eF]

I wants some answers NOW!!!!!!

also on thew new Mejzlik 27x12th versions where is the info dooohh i cant see anything....... are they more quiet than the normal mejzliks. come onnn telll me..

[Marmaduke]

Hey Kris

Are you going to compare their performance in a "downwind turn?"

[Fixed Wing]

Kris,

I am interested in your subjective results and opinion. Also, if you can get your hands on a Radio Shack sound meter it would be nice to have some db measurements of the PT props. Not sure if the following is useful but here are some readings for a Mejzlik 28x10 for you to compare against:

Motor - DA100 with stock mufflers (no cans)
Full Throttle RPM - 6,360
Reading @ 9' - 101
Reading @ 25' - 91 (IMAC distance)

These readings were taken in the Houston area with high humidity and a temperature of about 85 degrees. Following are other parameters of how the sound measurements were taken:

* Sound meter was set to weighting "A"
* Sound meter was set to slow response
* Sound meter was positioned down wind of model
* Sound meter was positioned 24" above hard ground
* Sound meter was positioned perpendicular to the fuselage
* Sound meter was positioned in line with the prop arc

I have found that airframe structures can make quite a difference in noise. Fully sheeted structures such as a Carden or Aerotech have measured quieter with similar engine, muffler, prop combinations. Also, prop tips speed approaching greater than 70% mach measure exponentially greater.

I agree with you that you have to get a prop on a plane in the air to "feel" its performance and how you like it. I too have several props that have only been flown a few times either due to noise or performance issues. Just thought I'd throw this piece of data out there FYI. I know sound/noise can be a very subjective issue and I hope this doesn't start a prop debate that strays from your topic.

[AHP]

I hope your report is as unbiased as possible being that I've never heard you say a positive about the PT props in the past. With that being said, I've used a few and have been very happy with all of them. Any chance can take a few pics comparing them to each other? I'm running a PT 27x10 on a BME 110 and would like to go to a 28x10. I haven't decided on the PT or Mejzlik (would prefer PT as they're easier for me to obtain) but will ultimately go with the better performer. Does the PT 28x10 have a narrower blade than the 27x10? I know the Mejzlik 28 is narrower than it's 27 counterpart. Looking forward to the results!

[KrisW]

Okay. . .a few non-subjective comparison facts.

Length of blade:

Mejzlik: 27.875"
PT Models: 27.5"

Weight:

Mejzlik: 9.5 ounces
PT Models: 7 ounces

Balance: both props were dialed in for tip-tip balance from the factory, the Mejzlik required adding about 1/4 ounce of weight to the side of the hub to get it balanced in that direction. The Mejzlik had several "pin holes" in the back of the blade where balancing epoxy had been injected to get it to balance from the factory, the PT Models had one place for this purpose.

Overall fit, finish, and appearance: Both are quite good .. Excellent!!

Overall impressions. The Mejzlik has a slightly wider hub, the thickness of the hub is within 1/16" of eachother. The PT models uses a less wide tip 1" from the end than does the Mejzlik (see picture), and the tip overall angles sweeps slightly more to the rear than the Mejzlik. LE of the PT models is slightly straighter for the first 2/3 of the blade compared to the Mejzlik which first curves forward then aft toward the same point on the blade. Grabbing each blade in two hands, at the tips, and trying to flex the blades end-end with my thumbs, the PT actually appears to be slightly stiffer than the Mejzlik. Trying to twist the blades is a no go for both props. I can't get enough leverage with my hands.

One thing I do NOT like. . the lettering on the PT prop looks like something that came out of the Cartoon Channel. A different font would be preferable .. something understated and straightforward would be more appealing. You look at it and expect the guy who is doing the layups to be listening to an Ipod with his hat on backwards over his long dirty hair, need some Oxy10 for his pimples and be popping bubble gum as he is rolling on the resin. . . .whereas the lettering on the Mejzlik tells me that some thin, short haired German guy with wire rimmed glasses and a pocket protector was meticulously measuring out each gram of resin and carefully smoothing the CF with a foam brush. .. just my impression.

[KrisW]

	Quote: Originally Posted by AHP
	I hope your report is as unbiased as possible being that I've never heard you say a positive about the PT props in the past. With that being said, I've used a few and have been very happy with all of them. Any chance can take a few pics comparing them to each other? I'm running a PT 27x10 on a BME 110 and would like to go to a 28x10. I haven't decided on the PT or Mejzlik (would prefer PT as they're easier for me to obtain) but will ultimately go with the better performer. Does the PT 28x10 have a narrower blade than the 27x10? I know the Mejzlik 28 is narrower than it's 27 counterpart. Looking forward to the results!

Actually, I've never said very much at ALL about the PT props, simply because I have never had an opinion on them. I really don't go around saying BAD things about anyones products, so the lack of a positive word is no reason to presume bias into something I have not said. Even 3W's. . . get a fair handed shake from me.

[paffy]

	Quote: Originally Posted by KrisW
	paffy, you are almost as bad as FlyinRazrback. . . . . I don't really have anything set up to make that comparison. . but I've also foiund in the past that props that make really good static thrust on the ground, with an unmoving plane, usually have poorer flying thrust in the air.

You could take a rope with a spring weighing scale. It's not going to be precise, but for comparative purposes it should do.

You're absolutely right that static thrust has very little to do with flying, but it sure comes handy in a pullout from hover !

P.

[AHP]

Kris, we had a brief discussion about them in the chatroom many months ago. I don't recall the specifics, but your opinion of them at that time wasn't positive. Like I said, I'm looking forward to the results either way.