Hi Guys,

Will someone please explain how the rear exhaust PA 40 and the rear exhaust PA 40 Ultra Light engines are different?  Weight, configuration, exhaust requirements, etc.

Thanks,
Jim

Thanks Marshall--asked you the same questions in a PM before I saw this post.

Jim

Hi Guys,

Will someone please explain how the rear exhaust PA 40 and the rear exhaust PA 40 Ultra Light engines are different?  Weight, configuration, exhaust requirements, etc.

Thanks,
Jim

Hello Jim

The New Merlin series Ultralite 40, is more the case width of a FOX 35 or  Magnum 36, however it has 4 exact mount holes that are the same as a Super Tiger 35,40,46.
It is longer however than the ST so No prop shaft extensions would be necessary, and the twin ball bearing can do a better job of support.

The Larger case PA 40 is  10.5 ounces, the Merlin PA 40 UL  is  just about 8 ounces. It can and will produce more power than an OS 40 VF, and can easily fly a plane as  large as an IMPACT, or  as  small as an ARES. You MUST however use the correct size venturie and head shims in order to do this. The motor is very tailorable up or down to what the needs  are. The motor has flown a very large range of planes all over the world. Example It flew A SKY WRITER, ( normally a 60 size ship) at the 2004 WCs, and  you will see  many of them in Noblers, Chipmonks, and  ARES,....not to mention a few  COBRAs  :-)


Regards
Randy

Jim,

Here is a copy of the review I posted over on SS just after the 2004 WC's. You will not be dissapointed in either engine.




"PA 40 Ultra Light / Ultra Great!"
 
   I had a problem. I had fitted my PA 51 to my SkyWriter to replace the smooth running but not so powerful Double Star .60. The difference in performance was significant. Overhead eights were now under my control instead of some mysterious being from above. There was just one little problem. Weight! It was now harder to get the crisp corners and rock steady bottoms that this plane normally delivers. The plane was originally laid out to accomodate a much lighter engine. I now had two ounces of lead in the tail plus three more in the engine and muffler not to mention the extra ounce of fuel.
Then an email from Randy said PA 40 at 8 ounces. My plane without engine only weighs 42.5 ounces. Within nanoseconds, I was the owner of two of he first PA 40 Ultra Lights on the market. I also ordered the carbon muffler some extra venturis (#16,15,14,12) and a few of the new 12x4 thin narrow blade props. After some substantial chages to the nose of the plane, it was installed. New all up weight 52.1 ounces.

The following observations are based on some 250+ flights made in the weeks leading up to and including the 2004 WC.

Modifications to the engine from stock: added one 5 thou head shim.

Venturies tested (#16,15,14)

Prop Used Bolly 12x4 narrow two blade.

Prop Pitches used: 12X4, 4.2, 4.5

Plug used: Thunderbolt Four Stroke Product # 115490

Muffler: Carbon Fibre three chamber (not a mini pipe) modified with muffler pressure tap

Muffler Mount: 5/8" aluminum header, silicone tubing, Wire ties.

Tank: double angled wedge on outboard side. Uniflow venting with uniflow 3/32 from fuel pickup.

Fuel: 20% oil - (75% Klotz, 25% Bakers Castor) Nitro: 5,10 15%


We started with the 12x4 and 5% fuel with the stock # 16 venturi. Break in consisted of running 1 gallon of fuel through the engine with run times limited to four minutes and RPM's ramped up and down from a very fast four stroke to 11,000 RPM.


The engine started on one flip most times by sucking eight times with the venturi sealed, then flipping briskly eight times without the plug attached. This became a two flip process as we went to the #14 venturi. We also reduced the number of pull throughs to 6.

I tried all venturis and all fuel mixtures with the 12x4 prop. At my altitude 590'ASL and at an average temperature of 72 degress, the engine was completely predictable putting out more or less power in a very controlled fashion as I diesired.

At the WC, due to to the lack of air density, I went up twice in pitch to 4.2 then 4.5. Nitro was increased to 10 then 15%. I all cases the engine performed flawlessly. Power was abundant and controlled. I could easily have increased the pitch more if I needed.

The final configuration was 12X4.5 with 15% nitro and approximately 10100 RPM ground speed. This yielded a 4.9 - 5 second lap time on 64 foot lines (eylet to eyelet).


It must be noted that the plane suffered a fatal encounter with strong wind. This was not the fault of the engine. Just minutes earlier Igor Burger's plane also got caught in the wind and crashed and during the lunch break (fifteen minutes before I flew, Han Xing Ping almost lost his plane doing the same manoeuvre I lost mine on.


Summary:

The Aero Products PA40 Ultra Light is an exceptional engine. Flexible in configuration and not tempremental at all. The power available is enormous! This engine would have no trouble powering a plane in the 55 ounce range. I highly reccommend this engine.


Disclosure: I paid full retail price for my engines and was given lots of help in a fast friendly manner by Randy Smith.


Kim Doherty
2004 WC Competitor

 

Robert,

I truly do not remember if I did or did not met you. Did we talk?(maybe over near the diorama that they were taking the model pictures at?) I would definetly like to meet you sometime. You build some very nice models!

Unfortunately, my most vivid memory kind of wiped most of the other ones away. (see below)

Thanks for the kind words.

Kim.