Re: Re: Motor weight, size density? from Bill Gowen on 2010-06-02 ([Indoor

From: Bill Gowen <wdgowen_at_gmail.com>
Date: Wed, 2 Jun 2010 16:41:14 -0400

Ben
Do you use the grams per inch for the strand or for the motor?

  ----- Original Message -----
  From: Benjamin Saks
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Wednesday, June 02, 2010 4:10 PM
  Subject: Re: [Indoor_Construction] Re: Motor weight, size density?


  I use grams/inch for my F1D motors. I find it much easier to hit the target of .6 grams for a motor when I know the weight per unit length. That allows me to do simple math to predict the length for a full motor. I agree with Kang about the variable thickness in the TanII and Supersport batches. I have seen this range in .010 plus minus, so measuring only the width is not accurate enough.

  On Wed, Jun 2, 2010 at 4:01 PM, Yuan Kang Lee <ykleetx_at_gmail.com> wrote:



    I would prefer to use what most people use, which seems to me to be just the width of the motor in thousands of an inch. E.g., .025" for a light EZB, .080" for LPP, etc. I talked with other experienced flyers at USIC, including my Pro partner, Tom Sova, and all refer to rubber sizes this way. In all the plans I've come across from the U.S. and U.K., rubber motors are indicated this way. E.g., ".025 x 12", ".050 1.25g", or ".042 x .055 x 15.5 1.075g" -- that is, all describe the width of the rubber in .001 inches.

    I only recently, about 2 weeks ago, started stripping my own rubber. There are two main reasons I am currently using g/in to measure rubber instead of using the width of rubber in .001 inches:

    1. the Harlan rubber stripper does not output a rectangular cross section -- it is trapezoidal. It's difficult enough for me to measure rubber's width when the cross section is rectangular. With a trapezoidal shape, I would have to measure the long and short bases of the trapezoid and take the average. Yuck. This is the first reason I went to g/in.

    2. I've found that the "thickness" of Tan Super Sport to be different than that of Tan II. For reference, I was using 04/10 TSS and 03/02 Tan II. Tan II's thickness is about 0.042", while that of TSS is about 0.046. If I strip the two rubber with the same setting, the stripped rubber has different g/in and don't perform the same. Perhaps this is a non-problem, but because I primarily use TSS, I wanted to be able to compare TSS and Tan II. This is another reason I went to g/in.

    But I prefer to use what everyone in the U.S. and U.K. use, if I could overcome these two obstacles.

    --- In Indoor_Construction_at_yahoogroups.com, Nick Ray <lasray_at_...> wrote:
>
> I have been using inches per milligram of untied loop. I think because knots
> are not consistent, and increase in relative mass as the rubber size
> increases the untied loop is the way to go. The reason I started using
> inches is because I didn't have meter stick handy. I would say meters are
> probably better if we wanted to create universal system. I don't think using
> grams or milligrams matters much as its just move thing decimal places
> around. It would be ideal to use as many significant digits as possible in
> order to get a more precise result.
> NIck
>

> On Wed, Jun 2, 2010 at 1:07 PM, Fred or Judy Rash <frash_at_...>wrote:

>
> >
> >
> > Bill,
> >
> > Thanks for all your help on many items.
> >
> > I think that everyone will work in grams. Probably we should eliminate
> > ounces from AMA, NFFS, etc Indoor (and maybe Outdoor) rules whenever
> > possible.
> >
> > The unit for length is harder. Most of Europe and the rest of the world
> > would argue for meters and probably we should also. I believe that most use
> > g/m of the untied strip. I think in grams naturally from a lot of chemistry
> > lab time as well as model building time, but do not automatically think in
> > meters. I can live with either inches or meters. If I use inches, I always
> > use decimal inches. I never write down a mixed fraction. If I try CAD which
> > I do occasionally, I never use mixed fractions there either.
> >
> > I would even be so extreme as to argue that our schools should teach
> > decimal fractions before mixed fractions. This should start a strong
> > off-topic thread. <GRIN>
> >
> > Fred Rash
> >
> > On 6/2/2010 12:41 PM, olbill61 wrote:
> >
> >
> >
> > I'm wondering if there is any way of describing motor weight per unit
> > length that is more prevalent than others. The way I started out is by
> > dividing total weight of a finished motor in grams by the motor length in
> > inches. I think Kang has started using grams per inch for untied strip. I
> > think Leo is using grams per meter.
> >
> > Can any others who have switched to weight per unit length describe how
> > they do it? I'm early in the process of doing it this way and could switch
> > to a different system without much trouble. I'd like to hear from English
> > and European fliers also.
> >
> >
> >
> > No virus found in this incoming message.
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> >
> >
> >
> >
> >
>

  --
  BEN SAKS
  www.bensaks.carbonmade.com


Received on Wed Jun 02 2010 - 13:47:12 CEST