Re: LPP/PP length measurement at USIC 2013

From: Don Slusarczyk <don_at_slusarczyk.com>
Date: Fri, 25 Jan 2013 12:55:07 -0500

As a bit of history on this 20" OAL rule, the reason as I recall it
being added was due to Jim Clem using very long "teflon washers" (like
1.5" long) so the prop was in front of the nose bearing about 1.5". The
old rule was 18" OAL from front of the nose bearing to the back of the
model. I believe he was trying to get the wing as far forward as
possible then using the long "washer" to get the correct CG. So the 20"
OAL became the new rule to prevent that. With this new rule excess side
thrust and boom offset could make a model illegal. In a discussion with
Doig at the time of the change the though was most people would still be
building models at the old 18" rule length so that was not an issue even
with big flaring props, only those who wanted to make longer models
under the 20" OAL rule would then have to be careful not to exceed the
20" when side thrust and boom offset were taken into consideration, that
is the choice they make so have to deal with the extra effort. So I
would say the prop should be horizontal in that 20" OAL measurement.

Don S
>
> Here is the proposal for checking the 20" maximum overall length for
> LPP and PP:
>
> Two parallel vertical surfaces will be furnished spaced at 20" apart.
> The assembled model will be placed between the surfaces with the
> leading edge of all prop blades touching one of the surfaces. All
> parts of the tail of the model must clear the other vertical surface.
> Pushing the model against either surface while making the measurement
> will not be permitted. The prop may be placed in any position the
> competitor desires to make the measurement.
>
> Please reply with any concerns about this procedure.
>
>
Received on Fri Jan 25 2013 - 09:55:16 CET