Author Topic: Engine choice? (Read 4233 times)

Bill Little · « **on:** July 08, 2011, 12:19:25 PM »

HI All,

I have a Pat Johnston P-47 (the big one!) that is going together thanks to a board member. Wing is foam and the rest is to the plans. Basic fuselage shell is made, engine bearers installed. A great looking design and BIG! LOL!! The original design was done for a Saito .72, but I don't have any such animal. Can't go the "electron" route right now on this one, either........ I can make the engine mounts fit whatever the popular choice is, I do believe. I am expecting the finished model to be in the mid 60 oz. range, somewhere around 65 oz, but not over 70 oz. (this is a BIG stunt model! LOL!!)

What engine do you think would be best? I have a couple great PA .61REs (and will use one of Randy's "can" mufflers off the header) that I can pick from, but I don't have anything "bigger". I am open to suggestions. And the possibility of obtaining a good, used, example of whatever the "popular" consensus ends up being.

So, come on guys, your choice and reasons for it!

Thanks
Big Bear

Dick Pacini · « **Reply #1 on:** July 08, 2011, 12:29:00 PM »

How about the new EVO 60 CL?

Mike Palko · « **Reply #2 on:** July 08, 2011, 12:52:28 PM »

Hi Bill,

Maybe Bill Richards will chime in with some info. He has a P-47 with a PA .75 RE in it. The airplane has been difficult to trim, but some of it might be weight problems. Another contributing factor is the dihedral (our home field is turbulent). A target weight of 65oz seems low for how big the airplane is, but I guess anything is possible. One thing to keep in mind regardless of the finished weight is the drag compared to other more conventional designs. I don't recall ever hearing what Bene's weighed or anyones for that matter.

I believe at least one other has flown with a OS LA .65

Mike

James Mills · « **Reply #3 on:** July 08, 2011, 07:25:10 PM »

Quote from: Dick Pacini on July 08, 2011, 12:29:00 PM

How about the new EVO 60 CL?

I haven't ran the EVO, but I have a couple of PA 61's and doubt the EVO would be better power. I like my PA's, wish they were still available.

James

Martin Quartim · « **Reply #4 on:** July 08, 2011, 10:06:08 PM »

Bene can build very light, I am not sure how heavy his P-47 but I do know that he used a OS 70 Ultimate (17oz with muffler) and end up putting about 4.0 Oz in the nose. Windy flew his P-47 and found the OS 70 4 stroke to be weak for the plane. I have been flying with the OS 70 Ultimate and it feels a bit weaker then my Saito 72. So I suggest you get the biggest engine you can.

The Saito 72CL still available for $209. It needs a few modifications which it won't cost to much if anything, see Bob Reeves articles.

The OS 65LA is another option, but if you figure out the cost of converting to C/L plus a new muffler, the Saito 72 will end up a much better deal. The Saito is lighter, burn a lot less fuel and it will not leave your plane with a ton of oil to clean. In my opinion the Saito works as good as any top notch power train. No wonder that we always see more then one Saito been used by top 10 at the W.C.

Martin

Bill Little · « **Reply #5 on:** July 12, 2011, 12:37:19 PM »

Thanks, guys.

Dick, I would go with the PA instead of trying a new to me engine. Still haven't seen any of the Evo's being run.

Martin, Those are great ideas, but I am not interested in going to a 4 stroke at this point. next step away from the PAs, etc., will probably be electric (oh, no! LOL!!).

Mike, I wish I had been able to get a PA .75 when I could have, but the cost "new" was out of my range at the time (family finances and a wife I have had now for 40 years prevented that... !!). I am pretty positive I can get this one in under 70 oz. The 65 oz. figure is my goal, who knows? (It will take all the lessons learned from Billy Werwage and Bobby Hunt to do so. LOL!!) Probably the differences will turn up in the finish applied.

Sounds like the PA .61 so far with a can muffler hanging off the header...........

Big Bear

Dwayne · « **Reply #6 on:** July 12, 2011, 01:24:50 PM »

How about a K&B 61 abc $110.00 + shipping 104 for the ringed.
https://shop.mecoa.com/shopdisplayproducts.asp?id=29

Randy Powell · « **Reply #7 on:** July 12, 2011, 02:41:16 PM »

Pat flew his big Bearcat with several engines. I think the last one had an ST51, so I would imagine the PA 61 would be killer in it.

Gordan Delaney · « **Reply #8 on:** July 12, 2011, 06:50:08 PM »

Bill,

I`m using a stalker .81 in my tony. It was a good choice after I took out the Saito 72. Good power and lighter than the 4 strokes..
I put in a larger venturi and run 10% nitro. Ran a 13.25X6 three blade.

Gordy

Ed Keller · « **Reply #9 on:** July 13, 2011, 08:48:45 AM »

Are the Stalkers still available? Ed

John Leidle · « **Reply #10 on:** July 13, 2011, 09:49:01 AM »

Alan Resingner sells Stalkers ..he sold me a .51 & .81

FLOYD CARTER · « **Reply #11 on:** July 13, 2011, 10:40:27 AM »

For really big and heavy, the RO-JETT 76 is a good choice. My Spitfire is a whopping 75 oz.! (retract gear accounts for about 6 oz.). The RO is available without much waiting.

Floyd

Bill Richards · « **Reply #12 on:** July 13, 2011, 09:54:12 PM »

Hi Bill, keep in mind that this P47 was designed for the saito 72- 4 stroke,a heavy engine. With my PA75 in the nose I needed around 6oz. of nose weight, and I am having power issues, I believe, due to the enormous amount of drag. I will be experimenting, hopefully before the end of summer, swapping out the PA75 and trying a saito 72 to see if loosing some nose weight might help, and a bit more power. If you can keep it light, I tend to build heavy, and can lengthen the nose to accommodate the lighter engine that would help.

Bill Little · « **Reply #13 on:** July 13, 2011, 11:04:11 PM »

Quote from: Bill Richards on July 13, 2011, 09:54:12 PM

Hi Bill, keep in mind that this P47 was designed for the saito 72- 4 stroke,a heavy engine. With my PA75 in the nose I needed around 6oz. of nose weight, and I am having power issues, I believe, due to the enormous amount of drag. I will be experimenting, hopefully before the end of summer, swapping out the PA75 and trying a saito 72 to see if loosing some nose weight might help, and a bit more power. If you can keep it light, I tend to build heavy, and can lengthen the nose to accommodate the lighter engine that would help.

Hi Bill,

Thanks for the comments on yours.I am thinking the major problem will be, as has been mentioned, drag and weight. I am going to do everything I reasonably can to keep this one down on the weight side of things. It is the biggest Model I have ever built as far as "bulk". Pat seems to think the PA .61 will do the job if I can keep it where I want it on the scales.

A "new" engine purchase is out of the question right now for something that I would consider using other than the PA of the ones listed so far. And excellent previously owned examples seem to be rare!

Bill

Pat Johnston · « **Reply #14 on:** July 14, 2011, 06:29:52 AM »

Might as well weigh in on this one. The Brazilian design P-47 was patterned after my big Bearcat which weighed in at 65 ounces with the Saito 56. I kept the tail components light so no lead in the nose was needed. The 56 was swinging an APC 13-4W which produced buckets of torque for a very comfortable power loading. With that, I would say that a mid 60 ounce P-47 with the PA61 should be very good. I am assuming that the PA61 has at least the power of an ST60. As far as the "drag" from the nose is concerned, I think that is a lot of fear based in ignorance. How's that for blunt? I noticed no functional problem with the drag of the radial engine setup at all. Of course, I do use props which overcome drag with gusto.
BTW, for bragging rights, my first big Bearcat weighed 58 ounces.
Pat Johnston
Prop and Design Studio
Skunk Works

RandySmith · « **Reply #15 on:** July 14, 2011, 02:22:08 PM »

""I am assuming that the PA61 has at least the power of an ST60.

'

The PA 40 will Power a ST 60 plane with ease, Just look at Paul Walker's 64 ounce 700 Sq IN IMPACT with a PA 40 in Lubbock.
the 51 and 61 have way more power than the ST 60

Randy

Pat Johnston · « **Reply #16 on:** July 15, 2011, 12:34:25 PM »

Sorry if I ruffled a feather, there, Randy. I have no direct experience flying a PA61, but have flown the ST60 a lot and know it to be a good stump puller. Since the PA61 outproduces the ST60, then it would be a spectacular pick for the P-47, without a doubt. BTW, this P-47 is around 685 squares.
Pat Johnston
Skunk Works

RandySmith · « **Reply #17 on:** July 15, 2011, 09:01:23 PM »

Quote from: Pat Johnston on July 15, 2011, 12:34:25 PM

Sorry if I ruffled a feather, there, Randy. I have no direct experience flying a PA61, but have flown the ST60 a lot and know it to be a good stump puller. Since the PA61 outproduces the ST60, then it would be a spectacular pick for the P-47, without a doubt. BTW, this P-47 is around 685 squares.
Pat Johnston
Skunk Works

Hi Pat

No problem, no ruffles :-) I am just giving Info, I think it would make a great combo also

Randy

Randy Cuberly · « **Reply #18 on:** July 15, 2011, 09:38:16 PM »

Quote from: Pat Johnston on July 15, 2011, 12:34:25 PM

Sorry if I ruffled a feather, there, Randy. I have no direct experience flying a PA61, but have flown the ST60 a lot and know it to be a good stump puller. Since the PA61 outproduces the ST60, then it would be a spectacular pick for the P-47, without a doubt. BTW, this P-47 is around 685 squares.
Pat Johnston
Skunk Works

I have a fair amount of experience with both ST60's and PA61's (I have two one side exhaust and one rear exhaust) and can tell you without reservation that the PA's have more power and also are easier to deal with and are much more consistent in runs.
My side exhaust 61 is a real Sweetheart...it runs like a swiss sewing machine and flys the pattern on less than 6 oz of fuel with great authority. A real flip and fly machine.
I know you certainly trust what Randy S. says but just thought I'd add my confirmation to his!

Randy Cuberly

Bill Little · « **Reply #19 on:** July 19, 2011, 06:41:31 AM »

Looks like the PA .61 will be in the nose of the P-47 unless someone donates a PA .65 or PA .75 to the cause! LOL!! I do have a couple ST .60s, but the PA works better to my liking. Large can muffler attached to header.

Big Bear

Pat Johnston · « **Reply #20 on:** July 20, 2011, 07:18:30 AM »

Good Lawrd, Bill! I'm going into DT's waiting to see some photos from you or Gerald on P-47's. Doc, you too! If you can keep that beastie under 70 ounces, then you will have a great plane. I flew Thomas Case's P-47 and it was very close to 70 ounces and flew well. It did need a little more elevator movement to flap movement to reduce the wrist muscle demand. Be advised that an adjustable throw elevator is always a good item. My big Bearcat just took about 1/8" slide up on the elevator horn to add what felt like power steering. Amazing what a little change can make.
Pat Johnston
Skunk Works

Bill Little · « **Reply #21 on:** July 21, 2011, 02:59:08 PM »

Quote from: Pat Johnston on July 20, 2011, 07:18:30 AM

Good Lawrd, Bill! I'm going into DT's waiting to see some photos from you or Gerald on P-47's. Doc, you too! If you can keep that beastie under 70 ounces, then you will have a great plane. I flew Thomas Case's P-47 and it was very close to 70 ounces and flew well. It did need a little more elevator movement to flap movement to reduce the wrist muscle demand. Be advised that an adjustable throw elevator is always a good item. My big Bearcat just took about 1/8" slide up on the elevator horn to add what felt like power steering. Amazing what a little change can make.
Pat Johnston
Skunk Works

HI Pat,

Among other things, my new camera won't turn on! New batteries, etc., etc., and nothing. Well it is actually two years old.......

I am using Morris controls with a slider elevator horn and a left hand threaded insert on the elevator end of the pushrod so that the length can be changed also.

Right now, sub 70 oz. is the goal! More than that and I will be greatly disappointed. So far, I have never had a model close to 70 oz. (64 oz. SV 11 was heaviest) so I wouldn't know what to do with one! LOL!!

I could go with a Big Jim Hemi ST .60 that is in excellent shape, but I think I have finalized my decision on the PA .61...........

The Timewave and P-51C (redrawn Bob hunt Mustang) are nearing the painting stages (should paint them both at about the same time) and work on the P-47 is increasing. With the new acquisition of the vacuforming machine, I am going to carve a plug for the P-47 Canopy soon! (still have to work out temps etc., of the machine to pull canopies but I have gotten the machine down stairs to the work shop! LOL!!)

Big Bear

john e. holliday · « **Reply #22 on:** July 22, 2011, 07:10:56 AM »

Well the bottom of the P-47 is planked and I am starting on the top side.

Author Topic: Engine choice? (Read 4233 times)

Dwayne

John Leidle