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- Newsgroups: rec.models.rc
- Path: sparky!uunet!iphase!iex!usenet
- From: djones@iex.iex.com
- Subject: Re: Props
- Message-ID: <1992Jul27.225145.1783@iex.uucp>
- Sender: usenet@iex.uucp (USENET news)
- Organization: IEX Corporation Inc.
- References: <1992Jul22.222910.27329@iex.uucp> <1992Jul23.153612.20836@rtsg.mot.com>
- Date: Mon, 27 Jul 1992 22:51:45 GMT
- Lines: 56
-
- In article <1992Jul23.153612.20836@rtsg.mot.com> svoboda@rtsg.mot.com (David
- Svoboda) writes:
- >
- >"Double the diameter and add the pitch" is an old rule of thumb that I use to
- >determine engine loading. So an 11x6 prop produces a "load index" of 28, as
- >does a 10x8, so those props will give approximately the same engine load.
- Note
- >that a lower pitch prop will unload in the air more than a higher pitch
- >prop (with the same load index), and will make the airplane fly more slowly,
- >and climb more positively.
- >
- Thanks! Does this hold for both 2c and 4c engines? And would it be safe to say
- that if a plane is a little underpowered, that a higher pitch for a given load
- index would be preferable? For example if the manufacturer suggests a 11x6 as
- the optimum
- prop, and the plane is a little heavy, then a 10x8 would be better. Or are
- really loading then engine down MORE and thus making the plane even more
- difficult
- to fly?
-
- Do you set a lower pitch prop a little richer on the ground or does it really
- matter. I was taught to fill the tank 1/2 way, warm the engine, peek the
- RPM on a tach and then back off about 500 RPM. Fill the tank and go fly. This
- technique was taught to me more for 4c than 2c but I expect it would work
- in both cases.
-
- >Changing prop brands will skew this rule a bit, because different airfoils,
- >blade widths and planforms will produce different drag.
- >
- There appears to be no easy answer!
-
- >|Can't wait to build my SE5a!!
- >
- >Cool! Tell us about it.
- >
-
- It is a Flair Sport Scale SE5a. It is about 1/6th scale. I have seen a
- completed
- plane and it looks great!! The kit is quite complete and includes all
- hardware. The cabane struts are aluminum for easy of assembly and disassembly
- and really don't look bad. I recently completed a Magnatillia from Flair
- and LOVE flying it!! It looks great, flys great, and I get lotsa comments
- about her. There is nothing like it at our field! The SE5a looks to be
- just as easy to assemble as the Mag was. I am really excited. I hope to
- get my work bench cleared off soon and get started! I will post more as I go
- if there is interest.
-
- Doug
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- both Time and Space' | IEX Corporation
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