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  #1  
Old 10-22-2004, 06:45 PM
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g-man g-man is offline
Frank Geter
 
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Default Two blade vs. Three blade composite prop

I have been reading up on building a wood/composite prop. Looks like I could do this but a two blade prop looks a lot simpler than a three blade prob. Anyone have an idea on what are the trade offs in terms of performance on a Cozy between a two and three blade prop? I am mainly interested in cruise performance.

Thanks
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  #2  
Old 10-22-2004, 08:42 PM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by g-man
....Anyone have an idea on what are the trade offs in terms of performance on a Cozy between a two and three blade prop?
If you're a member of the canard-aviators mailing list, you can read the archives (maybe you can read them if you're not a member - I don't know) starting at this message #:

http://groups.yahoo.com/group/canard...messages/19348

We just concluded a long discussion about this very topic. There are a number of folks that haven't a clue, but you can just read the postings from those that do :-). The long and the short of it is, assuming you purchase/build a well designed propeller, unless you're racing, you won't know the difference (speed wise). Noise and vibration are generally lower with a 3, but not always.
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  #3  
Old 10-22-2004, 10:55 PM
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Quote:
Originally Posted by g-man
I have been reading up on building a wood/composite prop. ... I am mainly interested in cruise performance.
Thanks
Have never heard that some times a two blader has less felt fibration than a 2 blader..... in general the FEWER the blades, the better the performance.

Actually read of a guy that made a 1 blader, had a ball with it as it looked really.....cool!

also for some more thoughts see

http://canardaviationforum.dmt.net/s...ght=blade+prop

And of course, for max performance, a constant speed prop gives you the best of both worlds, except the banking one!
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Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
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maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
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  #4  
Old 10-22-2004, 11:13 PM
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google al wick. built his own prop for $100. Is there anything more purfect for a Rutan aircraft?

In the entire discussion Al's comment was the most incitefull. If you choose a two blade you can build your own.

Another point is one can carry a two blade in the plane. Cant (or perhaps very hard) with a 3.

Marc's list is a very cool place, sometimes. But we are better looking and nicer.
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  #5  
Old 10-23-2004, 10:40 AM
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Frank Geter
 
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Default Thanks for the input, but no yahoo

Largeprime Dust, and Marc

Thanks for the summary. I do appreciate the feedback and help.

Marc

My personal preference is not to join yahoo groups and would have to in order to read the thread you linked to. Nothing against you or the members of that group. You took the time to provided me some feedback and I appreciate that and I am sure the group you refered me to a good forum; however, I wish it were not on yahoo. Yahoo has one of the worst privacy policies because it is full of exceptions and loopholes. They can share a users personal information with any of their "trusted partners" who then can use it help yahoo or one of their "marketing partners". Of course the user has no control or say over who their "trusted partners" or "marketing partners" are. The following is from their privacy statements.

[quote]
from yahoo privacy statement:

Yahoo! collects information about your transactions with us and with some of our business partners, including information about your use of financial products and services that we offer.
Yahoo! automatically receives and records information on our server logs from your browser, including your IP address, Yahoo! cookie information, and the page you request.
Yahoo! uses information for the following general purposes: to customize the advertising and content you see, fulfill your requests for products and services, improve our services, contact you, conduct research, and provide anonymous reporting for internal and external clients.

...

We provide the information to trusted partners who work on behalf of or with Yahoo! under confidentiality agreements. These companies may use your personal information to help Yahoo! communicate with you about offers from Yahoo! and our marketing partners. However, these companies do not have any independent right to share this information.

...

We transfer information about you if Yahoo! is acquired by or merged with another company. In this event, Yahoo! will notify you before information about you is transferred and becomes subject to a different privacy policy. [quote]
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  #6  
Old 10-23-2004, 11:23 AM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by g-man
My personal preference is not to join yahoo groups
Your choice, of course. We could get into a whole discussion about the issues of perceived vs. real privacy, and what happens when you hand a credit card to a 17 year old busboy in a restaurant that you've never been in before, or when you surf a web page with email information in your configuration, but that's not for this forum :-).

With respect to fabricating props yourself, LP implies that you can only build 2 blade props - this is not correct, if that's what he's implying. Nick Ugolini has fabricated (and described on his web site) a 3-blade prop. He says it's somewhat more complex than a 2-blade, but not substantially so.
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  #7  
Old 10-23-2004, 12:59 PM
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I did imply that. It was not my intent. Al suggested the 2 blade was much easier to build and to balance.

Thank you Marc.

What a 17 year old will do, and CAN do with my private information, and what Yahoo Inc, Or GOOGLE Inc will do and CAN do with it are worlds apart.
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  #8  
Old 10-23-2004, 08:16 PM
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Frank Geter
 
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Default I could do either.

I know I could fabricate either a 3 blade or a 2 blade. As Marc stated:

Quote:
He (Nick) says it's somewhat more complex than a 2-blade, but not substantially so.
I guess I was hoping that there was compelling, documented reason for the added complexity of 3 blade prop. Here is what I see others are saying about a 3 blade compared to a 2 blade.

Three Blade Pros:
1. Smaller diameter and thus slower tip speed so maybe less noise.
2. Less noticeable vibration in the turbulent airflow behind cozy.

Three Blade Cons:
1. Will weigh more
2. More complex to build
3. You can't carry an extra one with you.

Has anyone constructed both using the same design criteria, software and construction procedures and tested them on the back of a cozy?
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  #9  
Old 10-23-2004, 08:28 PM
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I no experience with either, but some people run a 3 blade and have a 2 blade in a FedEx box ready for shipping at their home base. No need to carry around an extra prop.
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  #10  
Old 10-24-2004, 05:09 PM
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John Slade John Slade is offline
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Quote:
have a 2 blade in a FedEx box ready for shipping at their home base
That's what I was planning to do, until I spoke to Clark Lydick of Performance Props about it. Clark said he doesnt think he could build a 2 blade prop for my power range (approx 280HP) of a small enough diameter for a Cozy. I'll be asking around at other prop manufacturers, but it seems that a 2 blade may not be an option for me.

By the way, I'm not sure if it's been mentioned, but the 3 blade is supposed to cut down on the noise and vibration from airflow off the strake hitting both blades of a 2 blade prop at the same time.

Bulent Alieve recently completed a home built 3 blade prop for his turbo rotary Cozy IV. He said he'd never do it again. It was way too much hard work for the cost savings.
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  #11  
Old 10-24-2004, 07:19 PM
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Quote:
Bulent Alieve recently completed a home built 3 blade prop for his turbo rotary Cozy IV. He said he'd never do it again. It was way too much hard work for the cost savings.
I guess it depends on how much money one has verses how much time and work someone is willing to do. If have little time but I have even less money so saving $1000 to $1500 is pretty attractive. I have looked at several web pages on building a prop (mostly based on Nigel's work). Is there a definitive step by step instructions somewhere on a web page?

[quote]Clark said he doesnt think he could build a 2 blade prop for my power range (approx 280HP) of a small enough diameter for a Cozy. I'll be asking around at other prop manufacturers, but it seems that a 2 blade may not be an option for me.[quote]

Makes sense because the cozy can only take a prop that is so big and you have a lot HP with that turbo rotary.
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  #12  
Old 10-24-2004, 11:17 PM
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John Slade John Slade is offline
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Quote:
Is there a definitive step by step instructions somewhere on a web page?
Nigel's is the only one I've seen. Do you have a link to it so others can take a look?
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  #13  
Old 10-25-2004, 05:28 PM
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Default Everything but

I seen plenty of other web pages that talk about the Nigel's work but nothing directly that is Nigel's. It kinda like scholars who say they can reconstruct the New Testament from comments and quotes made by the early church fathers if they lost all copies of the New Testament. Well I think I reconstruct Nigel's work by quotes from others but sure would like the have the original inspired manuscript!
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  #14  
Old 10-26-2004, 02:33 AM
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taking my own advice a googled al wick. Dont tell him...

http://www.maddyhome.com/canardpages...wick/prop.html
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  #15  
Old 10-26-2004, 06:49 PM
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Steve parkins Steve parkins is offline
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Default prop link

http://mywebpages.comcast.net/unick3/Downloads/4OUT.TXT
i tryed the link but not good , mabe this one will go to the spot
happy proping
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