Variable Pitch goes BIG!!

[MalaysianFlyer]

oops, double post, sorry guys

[ouch!]

Can you give us a rough estimate on prop rpm/ tip speed, I'd assume that this setup would swing more rpms than your standard DA but no prop can actually hit supersonic speeds. They fall short of it.

[EddieWeeks]

I have run the prop flat at full power and it starts making that high pitch, ear pearsing crack... >7500 rpms (680 mph).. Once I apply the pitch I can cut the RPMs in half..

Most likely I will need a DA150 to do the job of a 100 with these props....
How much more power will I get with tuned pipes.. ? I need about 5 lbs more thrust..

[EddieWeeks]

Major problem today... I put a 50lb digital scale behind the plane to
see how much static thrust I was getting...

15 lbs.. that's all... My grandfather Fox 15 has more thrust than this POS...

I ran the pitch higher and higher and got 12.. 14... 15... 14.. 13... damm
thats it.. ?

Now wonder it did not go vertical... I spent all day making some new props..
maybe they will do better..... I wonder.. Made a video of how its built...

www.corpcomp.com/weeks1/movies/V_Pitch.wmv

anyone want to trade a D150 for one of VPP.. ? hahah

Eddie Weeks

[AirMcNair]

SWEET!! Very nice craftsmanship! If your not trying to get it to nose down hover, then why don't you put a slight amount of pitch on the props in the milling process. maybe make it so that when you fly you have 70% efficiency forward and 30% back wards??
Does that make any sense????? it does in my head

[EddieWeeks]

	Quote: Originally Posted by airmcn_3
	SWEET!! Very nice craftsmanship! If your not trying to get it to nose down hover, then why don't you put a slight amount of pitch on the props in the milling process. maybe make it so that when you fly you have 70% efficiency forward and 30% back wards?? Does that make any sense????? it does in my head

Good idea... Will someone still buy it, if it can only back up on the ground,
and make a landing 10 foot long.. ?

[RappyMan]

Here's some ideas... or guesses. A friend and I built a reverse pitch for my E-flight Ultimate foamy before the VPP had hit the magazines. I'm guessing we weren't the first, but one of the first.

Go bigger diameter - more disk area will give more thrust & you can dial in the pitch you need. I tired helicopter tail blades first, but couldn't get enough thrust. Then we went to a 400 sized main blades that were trimmed down just enough to not hit the ground. This made it happen. You might try a wider chord blade too. They seem to help.

You might try some curvature - this would still give you forwards vertical, but not as much thrust for reverse pitch.

This really looks cool! It's kind of beefty looking - but there's a lot of force there trying to take it apart. Good luck & hope the magic prop shape comes along soon for ya!

Thanks
Terry

[AirMcNair]

	Quote: Originally Posted by EddieWeeks
	Good idea... Will someone still buy it, if it can only back up on the ground, and make a landing 10 foot long.. ?

I guess my thought was using it more for slow down lines and some interesting new maneuvers, along with backing up and very short landings. As for the answer to your question. I'm sure it will totally depend on the cost
Your doing great work!

[MalaysianFlyer]

Eddie, 15lbs is very low for a DA100. Most 100cc class engines should give at least 40lbs of thrust. You said your cutting the rpm by half from 7500 when you pitch the prop, maybe you have too much pitch? Most gasser engines seem happiest at around 5-6000 rpm, and develop their full power there.

Is there any way for you to measure your pitch when you apply just enough to get the RPM to roughly 5000? Then convert the degrees to actual pitch in inches? if you have 10" of pitch then it should be flyable, since thats the recommended pitch on DA's site. I plugged in the numbers on the prop calculator, a 28x10, Mejzlik prop, gives the following readings.

2000rpm-5.65lbs
2500rpm-8.82lbs
3000rpm-12.71lbs
3500rpm-17.29lbs
4000rpm-22.59lbs
4500rpm-28.59lbs
5000rpm-35.3lbs
5500rpm-42.71lbs
6000rpm-50.83lbs

It looks to me like you have too much pitch, and are bogging the engine down to 3k+rpms only [assuming this from your statement about half the rpm from 7500] which is limiting your thrust potential. Is it possible for you to set a lower pitch amount or set the pitch control on a knob or slider so you can apply it gradually? Then you can see where the optimal pitch setting is, hopefully.

Guys please chip in and correct me if I have said anything wrong in this post as I don't want to be responsible for an exploding motor at Eddie's!!!!!

Looking forward to hear more on your progress

[EddieWeeks]

Thanks for the positive comments...

During the thrust test.. I varied the pitch and found the Max thrust to be 15 lbs...
I did not measure the RPMs... but it sounded right..at 15 lbs...

I have a new theory... at 15 lbs the angle at the tips is around 30 deg same as hub.....
I know from airfoil design, that no wing / prop can product much lift at 30 AOA...
but since the prop is moving the air the AOA goes way down....

There is a good chance, my props are not moving enough air to lower the angle
so the tips are not stalled.. and when I do lower the pitch so they are not stalled
the pitch is very low and does not accelerate the air.....ie.. really bad design..

I think the next step is far wider props... New props take a while to make
so I think I will gear up to do two at a time... and mount the tach to the front of the plane...

btw.. during all high power test, I will not get near that thing...
I just sit in the truck..LOL

This may be a case where smaller dia, may give more thrust.. that would
be wierd..

[JeeUm]

	Quote: Originally Posted by EddieWeeks
	Thanks for the positive comments... I think the next step is far wider props... New props take a while to make so I think I will gear up to do two at a time... and mount the tach to the front of the plane... .

Eddie, I was just going to mention that. I think your blades are too narrow out towards the tips. I remember the Menz ultra series props were pretty much worthless also, and they had a very narrow cord.

[EddieWeeks]

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