a Couple Questions on Bolly 3 blades

OK..am trying to get a couple of PA 65s and Bolly three Blades 13x4.5 setup correctly and have a couple of questions.

1. Is it normal to have to remove .010" in thickness over 2/3 of two blades to get one of these into balance? It appears that the original hole is molded in so the hole being off isnt very likely?

2. Is it possible to stall one of these narrow blade props? ie. we keep adding pitch and running higher RPMs to get lap speed up to 5.2. But it isnt improving. It occured to me that we might just go back to 4.0 and 10100 or 10200 and see what happens.

THanks

Curt,
I am certainly not an expert, but if you are adding pitch AND increasing RPM's, with no change in airplane speed (or very little), it sounds like you have a pretty draggy setup. As I recall the drag is going something like the third power of the airspeed, so it takes a lot of extra thrust to significantly increase the airspeed. A three blade prop is also suppose to be less efficient than a 2 blader, since any blade sees a bigger effect of wash of the preceding blade (why the speed guys like 1 blade props).

I suppose the blade could be stalling, but that would give zero thrust (something I am sure you would notice in a hurry!). Also it would be stalling at takeoff (where the angle of attack is the greatest), not at max airspeed (where the aoa is lower).

My 2 cents.

>OK..am trying to get a couple of PA 65s and Bolly three
>Blades 13x4.5 setup correctly and have a couple of
>questions.
>
>1. Is it normal to have to remove .010" in thickness over
>2/3 of two blades to get one of these into balance?

That's not unheard of.

>
>2. Is it possible to stall one of these narrow blade props?
> ie. we keep adding pitch and running higher RPMs to get
>lap speed up to 5.2. But it isnt improving. It occured to
>me that we might just go back to 4.0 and 10100 or 10200 and
>see what happens.

It's very unlikely that the prop is stalling, and it would be far less likely to stall in the air, than on the ground. In fact, I would say it's essentially impossible for it to be stalled in the air in level flight.

I really don't know what is going on, but I would guess based on previous experience 4" of measured pitch on a Bolly, and 10100 RPM, is way too slow. Of course it depends very strongly on the pipe setting as to how much it unloads.

I would suggest just going back to the setup described in the instructions in every detail, and then if it's too slow, add pitch. This is not exactly treading new ground.

I don't have a .65, but I seem to recall for the other engines that it says something like 16 3/4" and about 10800, which has proven to be pretty acceptable for a 4" pitch Bolly. But if it says something different in the instructions, then do that instead.

Thanks Alan and Brett:

Sounds like we just need more. The balance problem is mine. The speed/pitch problem is someone elses I fly with.

We think we want to launch at 10100-10200 and run kinda soft 2 cy.
at 5.2 laps. We're going to get better measured data on the prop this week. I suspect that it is 4.0 or so. If it is, then it sounds like we just need to take it up some to maybe 4.5.

I took great note of the responses to Peabody's earlier post on re-pitching--never did find out what pipe length he was using but otherwise sounds like the setup is same.

We're trying to go right down the line with Randy's suggestion on Pipe vs. RPM and do not want to run in the high tens range.

As delivered, both of the Bolly's we have had SEVERE washout. One of my blades was at 2.5 tip. (4.4 center.)

WE'll have a go testing it with a little more pitch.

Thanks again

Curt,

I have used 3 blade Bolly's on a PA .51 and have run a 4.2 helical(sp?) and then put 4.3 at the last station on a pitch guage. That helped in maintaining a little better overhead tension. A .65 should have no problems of that type though! I'm running an RO Jett .61 now and using a 12.5" 3.75 helical Eather cut down from 13" prop and the plane is doing well in the overhead tension department set up that way. We'll see how well I can fly after having two flights since November next weekend at Huntersville, NC.......
can you spell L-A-S-T!!

Regards,

Gentlemen:

I guess I have shown my ignorance here in refering to the Bolly tip washout. Randy took the time to let me know that the Bolly three blades are DESIGNED to have progressive pitch toward the tip since the tip is more efficient than the root. So the blades that are at 4.7 root going to 3.5-4 at the tip are done that way intentionally.

I would like to say that it was not my intention to indicate that I was displeased in any way with this prop--or Randy's advice. I am in a steep learning curve at the present time, being new to the piped /three blade set-up, so was trying to find out if what I was seeing was common or just me.

I thank Randy Smith for his support.

>Gentlemen:
>
>I guess I have shown my ignorance here in refering to the
>Bolly tip washout. Randy took the time to let me know that
>the Bolly three blades are DESIGNED to have progressive
>pitch toward the tip since the tip is more efficient than
>the root. So the blades that are at 4.7 root going to 3.5-4
>at the tip are done that way intentionally.

That's *regressive*, not *progressive*. Progressive means the pitch increases towards the tip. You can try it as is, but I bet it works better with straight helical pitch.

Brett

p.s. I realized there may be some confusion in terminology. Progressive pitch "distribution" is not the same thing as progressive pitch, at least in the boat propeller definition of the term. Progressive pitch in the boat propellor world means varying the pitch over the *chord* of the prop. In effect, it's the same as camber (although they are actually measuring the *undercamber*). This makes a certain amount of sense in a boat propellor where the blade aspect ratio is so low, and does take into account an important element to performance.

Pitch *distribution* is varying the pitch along the *span* of the blade. This corresponds to washin (progressive, more pitch at tips) and washout (regressive, less pitch at tips, like most stock props *measure* (althouth not really perform like). I refer back to several previous threads on the topic of prop airfoil camber for more explanation. BB

Curt and fellow board members,
Related question on balance: Falcon Hobbies who carry Bolly up here in Canada (importers for North America) now list the carbon props as factory balanced based on their size/use guide listings. This is a change from what they use to show on their site. You could purchase a prop in a "un-balanced" state at a savings. Are Bolly in fact finishing the props to a higher "near ready to use" degree then in the past? Or is this a service that Falcon are performing as a middle man vendor for Bolly? Brian Eather props are sold as RTF units straight out of the box. (custom re-pitching is of course left to the end user for both brands) I've heard that the un-finshed Bollys do take some time to bring into fully trimmed, pitched, ready to go mode. Thanks.

I cant really answer your question Tony. For as long as I can remember, they have been listed both balanced or unbalanced available from AeroProducts.

I can say that I have previously flown several Bolly 2 blades and have gotten them balanced easily and flown well right out of the package. They are very nicely made and the finish is smooth and splinter-free.