LA .40 rpm

Hi could someone please tell me what the take off rpm for a LA .40 is?
Thank you
Dwayne

I been told 10500 and let it go.

Paul Taylor

~I wish I knew everything you have forgotten about C/L.

Check out my Blog@
http://rootbeard.rcuniverse.com
A link to a slide show of a fun day: http://www.youtube.com/watch?v=V-_sR0ZydSQ

That is not a simple question to answer. The take off rpm will vary with prop size, motor setup, model size and tank installation. The 10.5k rpm quoted in the last answer is pretty close to what a stock motor with an 11x4 apc prop would be. If that is your case I would start at about 10.5k rpm and then go up or down from there.

Thanks guys
Yup it's an 11/4 on my EZ-tunt .40 about 580 squares and will start with 64 foot lines.
Thanks
Dwayne

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Attachment #1, (jpg file)

This is for an OS Max 40fp.

Anything you do different will change the launch set up.

Attempting to replicate my TEOSAWKI set up on my new Rayette.

I have measured some items and so far I have:

.302" venturi.

> Venturi diameter= .302 inches
> Venturi radius = .151 inches
> OS diameter = .1365 inches
> ST diameter = .1565 inches
>
> A=3.14 X r squared
> A= 3.14 X (.151" X .151")
> A= 3.14 X .01661"
> A= .071595"
> Effective choke area with no restrictions
>
> OS needle area
> A= lw
> A= .302" X .1365"
> A= .041223"
>
> ST needle area
> A= lw
> A= .302" X .1565"
> A= .047263"
>
> Effective choke area of venturi minus OS needle area
> .071595" minus .041223" = .030372"
>
> Effective choke area of venturi minus ST needle area
> .071595" minus .047263" = .0243"

I am running the OS needle valve in mine

#44 or .086" holes in tongue muffler with twelve holes.

APC 12 X 4 Sport prop cut to 11 inches.

4 3/4 ounce 10% nitro with 25% castor and 3% synthetic oil in 70 degree weather, go up in nitro when the temps go up.

58' lines measured eyelet to eyelet.

9,800/9,900 release rpm.

Gives about a 5.2 second lap.

Will run about 7 minutes.

Any adjustment different will change run factors.

Allen

>This is for an OS Max 40fp.
>
>Anything you do different will change the launch set up.
>
>Attempting to replicate my TEOSAWKI set up on my new Rayette.
>
>I have measured some items and so far I have:
>
>.302" venturi.
>
>> Venturi diameter= .302 inches
>> Venturi radius = .151 inches
>> OS diameter = .1365 inches
>> ST diameter = .1565 inches
>>
>> A=3.14 X r squared
>> A= 3.14 X (.151" X .151")
>> A= 3.14 X .01661"
>> A= .071595"
>> Effective choke area with no restrictions
>>
>> OS needle area
>> A= lw
>> A= .302" X .1365"
>> A= .041223"
>>
>> ST needle area
>> A= lw
>> A= .302" X .1565"
>> A= .047263"
>>
>> Effective choke area of venturi minus OS needle area
>> .071595" minus .041223" = .030372"
>>
>> Effective choke area of venturi minus ST needle area
>> .071595" minus .047263" = .0243"
>
>I am running the OS needle valve in mine
>
>#44 or .086" holes in tongue muffler with twelve holes.
>
>APC 12 X 4 Sport prop cut to 11 inches.
>
>4 3/4 ounce 10% nitro with 25% castor and 3% synthetic oil in
>70 degree weather, go up in nitro when the temps go up.
>
>58' lines measured eyelet to eyelet.
>
>9,800/9,900 release rpm.
>
>Gives about a 5.2 second lap.
>
>Will run about 7 minutes.
>
>Any adjustment different will change run factors.
>
>Allen
>

A response with numbers is great! A response with every number I could think of to ask is a miracle!

Any office you care to run for, you got my vote!

Larry Fulwider

Larry,

I told my wife when I retired from teaching, that if I evennnnnn thought about running for any political office, she should find the largest boots with the roughests treads and apply them as vigorously as possible to my south end heading north.

I help when I can.

For those of you who like to piddle around with these sorts of numbers, here is the reverse calc. That is, given a net cross-section area (venturi area minus spraybar area) and a spraybar diameter, what is the “calculated” venturi diameter?

Where,
D_v = Venturi diameter as Measured
d_s = Spraybar diameter
A_e = Effective (net) Venturi Area

D_v = -2*(-d_s-(d_s²-Pi*-A_e)^.5)/Pi

which is a tad messier than it intuitively seems it should be. That is because the venturi insert diameter has both a linear effect on net area (spraybar clipping) and an exponential effect (area of circle).

A major caveat is that the actual effective cross sectional area of a tube transporting an inherently turbulent airflow that is also pulsating at 10,000 or so times a minute is not predicted by simply calculating the cross sectional area. That is, a sprinkler, ST nva and OS nva all with same net effective areas would likely not flow the same, and finding equivalency is more complex than the over-simplified high school algebra above (as the hands-on crowd is quick to point out).

Larry Fulwider

OUCH !!
That made my head hurt. I think I pulled something.


Paul Taylor

~I wish I knew everything you have forgotten about C/L.

Check out my Blog@
http://rootbeard.rcuniverse.com
A link to a slide show of a fun day: http://www.youtube.com/watch?v=V-_sR0ZydSQ

Wow! Thanks Allen!
Dwayne

I know, I know, you asked me what time it is and I told you how to build a watch. Ding, dong the witch is dead. Go see "Wicked", great show.