PA .40 Ultra Light

[Larry Fernandez]

What is the ideal starting point to set the pipe length (plug to first baffle) for the PA .40 Ultra Light?

Larry, Buttafucco Stunt Team

[Steve Helmick]

See Randy's pipe length chart pinned at the top of the engine setup forum. All Randy's engines use 135 deg. exhaust timing. Then you need to decide what your rpm will be. Typically around 10k +/- 500. 

By the way, Randy Powell advertised his (used) on facebook CL Classifieds, just in case anybody wants one already broken-in. I often noticed Randy using a Thunder Tiger Cyclone 11 x 4.5 on that engine, along with his custom muffler.  Steve

[Larry Fernandez]

See Randy's pipe length chart pinned at the top of the engine setup forum. All Randy's engines use 135 deg. exhaust timing. Then you need to decide what your rpm will be. Typically around 10k +/- 500. 

By the way, Randy Powell advertised his (used) on facebook CL Classifieds, just in case anybody wants one already broken-in. I often noticed Randy using a Thunder Tiger Cyclone 11 x 4.5 on that engine, along with his custom muffler.  Steve

Thanks Steve!
Looks like 17.75 inches is the magic number.

Larry, Buttafucco Stunt Team

[RandySmith]

Thanks Steve!
Looks like 17.75 inches is the magic number.

Larry, Buttafucco Stunt Team

Larry
Typical  is  16.8  to  17.8  depend on the prop  used ,  the  RPMs  being slowed or increased  will determine the length , Shoot me  a  email  if you have problems, and  tell  me  what  prop you will use and what you think the RPMs  will be

Randy

[Brett Buck]

What is the ideal starting point to set the pipe length (plug to first baffle) for the PA .40 Ultra Light?

   Good advice so far, but in addition, I would suggest getting in touch with Michael Sholtes. His is far and away the best-running PA40/PA40UL I have seen locally, really exceptional.

    Brett

[Larry Fernandez]

Larry
Typical  is  16.8  to  17.8  depend on the prop  used ,  the  RPMs  being slowed or increased  will determine the length , Shoot me  a  email  if you have problems, and  tell  me  what  prop you will use and what you think the RPMs  will be

Randy

I plan to start with a Bolly 11.25 x 4.25
I have many props I can cut down and repitch.
As always, I am open to suggestions from the “Big Shots”

Larry Buttafucco Stunt Team

[Mike Scholtes]

Hi Larry - That's the prop I have on my PA40UL, though it is packaged as an 11-4. There may be a newer version that is 11.25-4. The pipe is a "skinny" pipe, I think from Randy Smith, run at 17.5 from plug to first baffle inside pipe. Does not seem to be super critical on length. Plug is TB 4-stroke/big bore. Fuel is Powermaster GMA blend 10-11-11, but I have some custom Gordon's Brew that is mostly synthetic oil I have not yet tried. Launch rpm is about 10K  but hard to tell with Fromeco tach. This is in a 605 inch Oriental Plus (Dee Rice design). According to Brett I have by some stroke of luck got the best-running PA40UL in captivity. After much scolding from Brett I have (mostly) mastered the spinner-back-snap starting procedure. First-snap starts normally, IF primed and prepared right.

[Brett Buck]

Launch rpm is about 10K  but hard to tell with Fromeco tach.

   I am sorry, but I forgot  - is this the one with the black plastic window all the way across the front?. If so, cut about a 3/4" hole in the window, right in the middle, taking care not to damage the sensor. Then cut a bit of brass or plastic tubing about 1/2-3/4 inch in diameter, 3/4" long, paint it flat black, and then glue it around the sensor. This should *tremendously* improve the performance. The material doesn't really matter, as long as you can paint and glue it, even a rocket body tube will be fine.

    If it is the version with the sensor at the bottom of a 3/16 silver tube, I will have to think about it to figure out how to fix it.

    Brett

p.s. here is what I suggested David do with his, this fixed it and is what he uses all the time:

[RandySmith]

Hi larry  that's  a great choice to start with , and should work really well for you, follow the chart  use a  20% total oil fuel with  3/4 of it synthetic oil , if the plane is small  you may even wanna  trim to 11 inches
There are a  huge number of extremely  great running  40 Merlins out there, and  I am sure you will get you just like you want
The motor has a very wide envelope it runs in ,and is  very tailorable  up  or  down,  It is  not finicky  so  you should  get quick results, That engine has  done  fantastic in planes  from 490  to 725 sq in.  Little  Ares  to  Super  Ares  to  USA-1   and  many Modern ships  like  the  Satona  Staris   Shrike   Standard  VECTOR  and  many other
Send me a photo  of your setup  and  a  email  telling  me  how  its  going

Randy

[Larry Fernandez]

Hi larry  that's  a great choice to start with , and should work really well for you, follow the chart  use a  20% total oil fuel with  3/4 of it synthetic oil , if the plane is small  you may even wanna  trim to 11 inches

Randy

It will be used in a Vector 40 based plane.
Would you consider this to be small enough to try an 11 inch Bolly three blade?

Larry, Buttafucco Stunt Team

[RandySmith]

It will be used in a Vector 40 based plane.
Would you consider this to be small enough to try an 11 inch Bolly three blade?

Larry, Buttafucco Stunt Team

Hi Larry

if it is a  11 x 4 N  narrow small hub 3 blade  then  yes  that  works very well on the  40 UL

Randy

[Larry Fernandez]

Thanks for the advice guys, much appreciated.
And yes I fly my planes😎

Larry, Buttafucco Stunt Team

[Gerald Arana]

Thanks for the advice guys, much appreciated.
And yes I fly my planes😎

Larry, Buttafucco Stunt Team

Yes! And I can vouch for you to Larry. They are some of the most beautiful ships I've ever seen up close! And they fly great!

Jerry

[Richard Walbridge]

Yes! And I can vouch for you to Larry. They are some of the most beautiful ships I've ever seen up close! And they fly great!

Jerry

Larry does awesome Monokote work...

[Mike Scholtes]

(Apologies to Larry for semi-hijacking thread) My Fromeco tach has a red plastic window across front, but otherwise sounds the same as the modified one in the picture - sensor bulb at inside end of alloy tube maybe 1/4 inch in diameter. I will modify it as suggested and give it a whirl this weekend. Or maybe I should wait to hear if Brett has a better suggestion. The problem is it won't settle down, rpm jumps around by hundreds of rpm.

Larry, have you been to our newly paved Alameda circle? You can safely fly your best stuff here (and that's saying a lot). A far cry from the gear-ripper we had until last November. Deep grass infield and apron areas.

[Larry Fernandez]

Larry does awesome Monokote work...

Thanks Rich, check out the Monokote job on this bad boy

Larry, Buttafucco Stunt Team