Propellers

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smartkid222
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Re: Propellers

Postby smartkid222 » February 17th, 2010, 2:20 pm

on the PP Harlan bearing there is a hole there is an .018" hole in the front. Thats it in the front. In the back however the setup is more complicated to describe, but it's not just a hole in one piece of metal. It's really two pieces of metal that the shaft goes through. You can can pop the shaft out of the back and then take it out of the front hole.
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Re: Propellers

Postby blue cobra » February 17th, 2010, 3:34 pm

But wouldn't the hook in the shaft block it's way out the hole? Maybe I just have to see it.
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Re: Propellers

Postby smartkid222 » February 18th, 2010, 11:39 am

no the shaft is able to go through the hole.
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Re: Propellers

Postby jander14indoor » February 18th, 2010, 2:37 pm

Careful here. If I read this string correctly, bluecobra is talking about a Ikara prop hanger, not a pigtail hanger. You can't remove the prop from the Ikara bearing. The bearing and prop slip out of the hanger, and you have to have extra bearings to allow easy prop changes.

On a pigtail hanger there are two rear ends, the fronts are the same.
- one rear the rear is a twist like a wire cork screw, the rear hook literally screws out of this style hanger. Then you wiggle the wire out of the front hole. It doesn't come out straight, you have to turn to follow the wire hook.
- The other rear is a flat piece with a split down its length through the shaft hole. The two legs are split, one forward, one aft. To remove, you pull the shaft forward till the beginning of the hook hits the split. Now, look down on that split, turn the shaft till that bend suddenly lies in that split, it just slides up and out now. You then proceed like the other, wiggling the shaft out the front, turning to follow the bends.

Hope that helps a little.

If not, I'll try to take some pictures if I can find a suitable camera, unless one of you bright young ones beats me to it.

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Re: Propellers

Postby DallasM » February 20th, 2010, 5:48 pm

Can anyone help with pitch? I don't know how what to change it to in relation to the number of turns and the rubber band size. Is it a big factor on how the plane flies?

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Re: Propellers

Postby jander14indoor » February 20th, 2010, 7:54 pm

The most competitive flyers seem to like a higher pitch, but it is tricky to get work right. I use lower pitch props and get times in the same range as the best SO flyers. As an adult I don't actually compete with them so don't ultimately know if its as good.

MORE important in my mind is getting the proper MATCH between prop and rubber. Thats how I get my lower pitch prop to at least compare in performance with the guys using high pitch.

As to how to change pitch, you propably need to understand helical pitch first (see http://www.allstar.fiu.edu/aero/flight63.htm or http://www.propellersexplained.com/. Then you need a pitch gauge, couldn't find one, but there are some designs out there somewhere. Finally, you have to twist the prop spar to the new pitch. Three ways I've heard of. Twist by hand till youv'e bent it permanently, takes more talent than I have. Cut and reglue, some do this successfully, I find it tricky. Apply heat to soften the shaft, twist to new position, let cool and be done. I've had most success with this.

Oh, and you can select different pitches. The different size and type of Ikara props have different pitches. I use the narrow blade prop that has a lower pitch and cut to diameter, as opposed to the wide blade prop which has a higher pitch.

You can also trim the leading or trailing edge to change pitch.

Hope that's clear

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Re: Propellers

Postby duckiegirl2 » February 21st, 2010, 1:55 pm

Is there a certain material that is lighter to use for the propellers? Is it important to get that wait down so it doesn't nose dive? Our plane has been very inconsistent, it has nose dived then the next flight got stuck it the rafters. The only thing different was the number of turns on the rubber band.
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Re: Propellers

Postby blue cobra » February 21st, 2010, 2:21 pm

Ikara props are pretty light and probably the best for Wright Stuff.

A nose dive is probably caused by the CG being too far in front of your wing, but could be something else.

Something must have changed to get dramatically different flights. Something might have been bumped during the nose dive. Once you get it trimmed mark every position to use as a baseline.
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Re: Propellers

Postby jander14indoor » February 21st, 2010, 3:33 pm

Can't really select the material for the props. Rules require a commercially available plastic prop. Only thing you can do is modify it.

What kind of prop are you using? The Ikara ones probably need the least modification to be good, already pretty light weight. Other props may need signficant modification to loose weight before being suitable for WS.

As to the variation in performance, difference enough will cause very large difference in results. But if not very different, I have to second blue cobra, something changed. Look for it.

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Re: Propellers

Postby blue cobra » February 21st, 2010, 4:08 pm

DallasM wrote:Can anyone help with pitch? I don't know how what to change it to in relation to the number of turns and the rubber band size. Is it a big factor on how the plane flies?


jander14indoor wrote:<SNIP>Then you need a pitch gauge, couldn't find one, but there are some designs out there somewhere.<SNIP>


Such as this one.
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Re: Propellers

Postby jcollier » February 25th, 2010, 5:27 am

DallasM wrote:Can anyone help with pitch? I don't know how what to change it to in relation to the number of turns and the rubber band size. Is it a big factor on how the plane flies?

My first ? for you is "How many props do you have to play with?" I have a half dozen props that our High School coach gave us that HS students attempted to repitch. They are all out of balance and basically worthless. You CAN repitch props if you make a gauge and are very, very careful. You have to be sure you are only twisting the base of the prop and not pulling it forward or backward, then get both sides EXACTLY the same pitch. IMHO, it is much, much easier to match the rubber size to a prop that has not been modified, especially for a 12-15yr. old builder/flyer. I don't doubt that repitching a prop can be a small advantage at times, but I'd be very surprised if it was significant, or could not be almost duplicated by doing something else.

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Re: Propellers

Postby eta150 » March 4th, 2010, 1:01 pm

Is it possible to change the camber of ikara prop plastic
(Note, this is for the Phys. science lab event, and we are using the sheets with toothpicks that you buy off of the freedom flight website.)
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Re: Propellers

Postby StampingKid » March 4th, 2010, 1:25 pm

Thought about that for PSL but did not know whether it would "fly" . Found in sanding Ikaras that to much pressure deformed the plastic. Don't know about camber. But let us know how it goes. What type of #'s are you getting. I had a blade that I got 1800 Fast and 1200 Slow on a Walmart box paying attention to the earlier caveats on that thread but it broke and I could not get it to repeat .
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Re: Propellers

Postby eta150 » March 4th, 2010, 1:44 pm

The blades are doing pretty well (not quite sure of the efficiency, I'm doing this for a teammate), but we figured we should try Ikara plastic. We bought it, and there was WAY to much camber, even for experimenting with free flight blades (which is what they're for). I still see more merit in a balsa design, but I think this could be worth a shot if we can get it right.
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Re: Propellers

Postby StampingKid » March 18th, 2010, 7:01 pm

What is a good angle to depitch the ikara broad blade to? I need to take care not to break the spar.
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