Author Topic: Saito .72 for a PAt Johnston "Brazilian P-47" (Read 9558 times)

Bill Little · « **on:** December 06, 2011, 10:05:02 AM »

Ok, Guys and Gals, I searched here and need some help. I have a Saito .72 coming to use in a HUGE P-47 designed by Pat Johnston. The one designed for the Brazilians who mostly used the .72.

I have no experience with a 4S....... I will need to break it in, and need suggestions for a break in prop, fuel, and suggestions for flying props. How about the UHP C/L intake manifold? Fuel tank size? (thinking a 6 oz. plastic clunk set up for uniflow) I just want a good set that will haul this monster all over the sky with authority.

Thanks!
Bill

John Christensen · « **Reply #1 on:** December 06, 2011, 12:35:08 PM »

I had a Saito .72 in a Strega (kit) that weigh 74 oz. I could not get consistent runs runs from this combination. I had used the .72 on a profile and had great runs. In both cases I was using the RC carb. I replaced the .72 with the .56 and the UHP venturi kit and get great runs all the time now. The .56 has more than enough power for the Strega. I also have a .56 in a SIG Magnum at 68 oz that uses the RC carb and it also is rock steady in running. Use the RC carb to break in the engine. I use a APC 12-6 to break in the .56, as I figure that the weight of the prop helps to keep the engine turning at low RPMs. Good luck.

Bill Little · « **Reply #2 on:** December 06, 2011, 12:47:20 PM »

Thanks for the info, John. For now I have to go with the .72 since that is what I will have and another 4S is out of the budget right now. Pat designed the Jug for the .72 per request of the Brazilian fliers and a friend here made me a very good deal on a .72. Soooo.................

I remember watching the Chinese team using the .56 during the World's in '04. Their top flier had a Golden Knight .56 which I thought was cool.

Big Bear

Bob Reeves · « **Reply #3 on:** December 06, 2011, 05:54:01 PM »

Might want to check out the piece I did on modifying the RC carb, the 72 shouldn't be much different.

http://www.tulsacl.com/SaitoCarb.html

Martin Quartim · « **Reply #4 on:** December 06, 2011, 06:58:24 PM »

Hi Bill,

I broken in my Saito 72 with a 13x6 prop, Byron 20/20, and used the R/C carb to control rpm. I ran the engine for short times in the beginning, 1 then 2 minutes, and then I ran several full tanks and increase the rpm as I went. I used 1 gallon on the bench. My Saito only became reliable after the 2nd or 3rd gallon.

I made a special venturi which works amazingly well. I will send you a drawing if you want to have it made.

Once you get used to a 72 it is not a big deal. The 72 is just enough for the P-47 in my opinion. I have always been using a 70 4S so for me this engine size is pretty normal like a walk in the park, nothing extraordinary.

For flying I like the JXF 14x6 and 14x7 Electric props, never tried some of the 3 blade Carbon Fiber but I friend loves'em.

I use a Sullivan 6 Oz RST plumbed as Bradley Walker recommends, perhaps you have seen some of his plans for Saito engines which ilustrate how he does the tank. Very important to sit the tank with 1/4" offset on the rear so the engine will quite at once at the end.

It will depend on how you will setup your venturi to control the power, but expect to use from 3.7 oz to 5.5 oz. of fuel. Never use anything but 4s 20% Nitro 20% straight synthetic fuel.

4S does not like to run rich, the prop and the venturi has to match each other so you run slightly rich.

I also recomend you make the tail as light as you can, the guys that built the P-7 end up having to put quite a bit of lead in the nose using the 70s 4S. Or make the nose abit longer.

You will be so impressed with the sound of the engine in this P-47 in particular. The wide body reverbarates and enhance the sound of the 4S engine, you will love it.

Martin

Edit to fix a stupid mistake

Bill Little · « **Reply #5 on:** December 07, 2011, 11:52:25 AM »

Thanks, Martin.

I will start breaking it in and getting use to it before too long. Hopefully it is just the ticket for the Jug. Originally the motor mounts were drilled for a Merlin .75, but the engine never materialized in my shop.

Bill

proparc · « **Reply #6 on:** December 07, 2011, 02:08:30 PM »

Quote from: Bill Little on December 07, 2011, 11:52:25 AM

Thanks, Martin.

I will start breaking it in and getting use to it before too long. Hopefully it is just the ticket for the Jug. Originally the motor mounts were drilled for a Merlin .75, but the engine never materialized in my shop.

Bill

Welcome to the "Big Block" club.

proparc · « **Reply #7 on:** December 07, 2011, 06:33:08 PM »

For Bill Little,

This should get you in the 4 stroke mood.

!

Martin Quartim · « **Reply #8 on:** December 07, 2011, 08:19:56 PM »

I should note that Brazil was the only S. American country who fought with the Allies in WWII. The Brazilian flew P-47s in Italy attached to one of the USAF squadron.

In 2007 Thomas Case sponsor a group of 20 Brazilians to come to the US NATS to clebrate that.

Martin

proparc · « **Reply #9 on:** December 07, 2011, 08:39:43 PM »

Martin was your Supermarine Spitfire 4 stroke powered?

Martin Quartim · « **Reply #10 on:** December 08, 2011, 04:06:53 PM »

Hi Milton,

I wish I had a Super Marine Spitfire, it is on my wish list. I will soon order one from Pat.

I had P-51 with the Saito 72, but I sold it.

Martin

SteveMoon · « **Reply #11 on:** December 21, 2011, 03:04:19 PM »

Bill: Of course, I would highly recommend the UHP manifold/venturi set.
But, not just because it's my company. I have run 4S motors for 10 years
now and have always found our setup to be the smoothest running. Even
better than Saito's dedicated line of CL 4S motors. My brother Doug has
a Saito 62 CL motor he was using in his last Furias and we just couldn't
seem to find that solid, smooth run. We finally took the stock venturi
off and added the UHP system and the motor instantly ran better; much
smoother. Even on the CL setup the barrel insert tends to vibrate. This is
what happens when you wire open an RC carb also. THe barrel in the
carb will still vibrate just a little and cause a slightly inconsistent motor
run.

Doug and I use Sullivan tanks in all of our planes. For the Saito 72 I would
use the 6 oz. tank. Make sure it is the hard side tank and not the flex tank.
Plumb it with the pressure line making a u-turn and coming back to the
front of the tank and facing to the inboard side of the plane. I would think
a 13 x 5 or 13 x 6 prop should work.

Later, Steve

Mike Callas · « **Reply #12 on:** December 22, 2011, 10:58:54 AM »

Doug and I use Sullivan tanks in all of our planes. For the Saito 72 I would
use the 6 oz. tank. Make sure it is the hard side tank and not the flex tank.
Plumb it with the pressure line making a u-turn and coming back to the
front of the tank and facing to the inboard side of the plane. I would think
a 13 x 5 or 13 x 6 prop should work.

Later, Steve
[/quote]

Steve,
I'm afraid my build a boat-in-a-bottle technique is a little weak. How do you install a u turn pressure tube into the fuel tank? Getting it into the stopper then into the tank seems impossible to me.

Thank you and Merry Christmas
Mike

SteveMoon · « **Reply #13 on:** December 22, 2011, 12:19:42 PM »

Mike: It takes a lot of patience and a lot of fiddling, but it
can be done. I've done it at least 25 times; probably more.

Steve

Martin Quartim · « **Reply #14 on:** December 22, 2011, 02:46:43 PM »

Steve,

I am sorry about my unfair report about the UHP Venturi, shame on me. After reading again what I wrote I felt pretty stupid. I was a novice at the time I use it and probably did not know exactly what I was doing. Unfortunately my memory kept the wrong impression about it and I want to take back what I wrote about it.

Your product is very well made and I am sure many are using them with success. Probably the most used venturi around. I remember we bought all your stock at NATS 2006.

I am sure I would not have any problems with it today.

My sincere apologies

Martin

Bill Little · « **Reply #15 on:** December 22, 2011, 03:01:21 PM »

Quote from: SteveMoon on December 21, 2011, 03:04:19 PM

Bill: Of course, I would highly recommend the UHP manifold/venturi set.
But, not just because it's my company. I have run 4S motors for 10 years
now and have always found our setup to be the smoothest running. Even
better than Saito's dedicated line of CL 4S motors. My brother Doug has
a Saito 62 CL motor he was using in his last Furias and we just couldn't
seem to find that solid, smooth run. We finally took the stock venturi
off and added the UHP system and the motor instantly ran better; much
smoother. Even on the CL setup the barrel insert tends to vibrate. This is
what happens when you wire open an RC carb also. THe barrel in the
carb will still vibrate just a little and cause a slightly inconsistent motor
run.

Doug and I use Sullivan tanks in all of our planes. For the Saito 72 I would
use the 6 oz. tank. Make sure it is the hard side tank and not the flex tank.
Plumb it with the pressure line making a u-turn and coming back to the
front of the tank and facing to the inboard side of the plane. I would think
a 13 x 5 or 13 x 6 prop should work.

Later, Steve

Hi Steve (and all who have replied!),

I appreciate all the help and information. This one is a C/L engine so I can break it in, etc., before I can consider (and save up the money! LOL!!) the UHP intake, but it is on my list.

The engine is absolutely brand new with all the tools, etc., and I guess I will follow the instructions about break in. WOW! setting valves that tiny will take some getting use to. Have done it a thousand times in full size automotive racing engines, etc., it will just take some getting used to. Hope I don't have to wear an optivisor! LOL!!

I have heard things about the mufflers, anything to consider there? Anything about them coming loose and messing up the threads?

This has me a wee bit excited. All these years and now a .72 4 cycle plus an electric set up. It will all be nice to learn about.

Thanks, guys!
Bill

Martin Quartim · « **Reply #16 on:** December 22, 2011, 05:44:07 PM »

Hi Bill,

I check the valves before running in and then after, making adjustments if necessary. After that I never had to bother with it again.

Martin

Bill Little · « **Reply #17 on:** December 22, 2011, 05:47:20 PM »

Quote from: Martin Quartim on December 22, 2011, 05:44:07 PM

Hi Bill,

I check the valves before running in and then after, making adjustments if necessary. After that I never had to bother with it again.

Martin

Thanks, Martin! I will do that. I do need to get some fuel for this one, I think.

BIG Bear
AMM

Leester · « **Reply #18 on:** December 22, 2011, 10:08:31 PM »

Gee Bill If I had a way to get it to you I have an unopened Gallon Of Powermaster YS/Saito 20% syn oil fuel I'd give ya. Anybody going from Illinois to N. Carolina

proparc · « **Reply #19 on:** December 22, 2011, 10:29:28 PM »

Once Bill gets a taste of that big block power, he'll be so preoccupied at the flying field, pumping out patterns back to back, that he won't have time to delete all our illegal posts of everything from hot RC ships, to links to the Playboy channel.

Hmmm, what other hot tips can we give him about the 72.

By the way, once I got my rig going, I once pumped out 24 flights in one day. That 72 was talking my talk!!

This should get him pumped up.

Douglas Ames · « **Reply #20 on:** December 24, 2011, 06:23:11 AM »

Quote from: Bill Little on December 06, 2011, 10:05:02 AM

Ok, Guys and Gals, I searched here and need some help. I have a Saito .72 coming to use in a HUGE P-47 designed by Pat Johnston. The one designed for the Brazilians who mostly used the .72.

I have no experience with a 4S....... I will need to break it in, and need suggestions for a break in prop, fuel, and suggestions for flying props. How about the UHP C/L intake manifold? Fuel tank size? (thinking a 6 oz. plastic clunk set up for uniflow) I just want a good set that will haul this monster all over the sky with authority.

Thanks!
Bill

I highly suggest you read several articles (threads) from Bob Reeves. His approach to 4S is a sound and proven combination of eliminating air leaks from the R/C Carb., loading the engine with higher pitch prop at moderate RPM's and managing the manifold pressure (throttle) with an adjustable screw. This puts the engine in it's torque band for maximum use of power (torque).
You don't drive your car down the highway in third gear?...

Bill Little · « **Reply #21 on:** March 15, 2012, 01:20:22 PM »

Hi Douglas,

This is a factory C/L version so I am not sure how to add Bob's tips.

Thanks!
Bill

Bob Reeves · « **Reply #22 on:** March 15, 2012, 02:18:38 PM »

Hi Bill,

I've kinda stayed out of the 72 threads because other than modifying a few intakes for others I have no direct experience with the 72. Not likely to get any as I simply wouldn't want to be on the handle end of an airplane that needs anything bigger than the 56/62.

The CL intake for the 72 is built just like the 62 and can be modified just like I do the RC carb, see link I posted above. The only difference is you won't need to make a replacement barrel, the aluminum one from the CL intake can be drilled and taped for a 1/4 nylon screw. The fuel feed spigot-spraybar still needs to be removed and cut off but that isn't real difficult.

proparc · « **Reply #23 on:** March 16, 2012, 10:31:17 AM »

Quote from: Bob Reeves on March 15, 2012, 02:18:38 PM

Hi Bill,

Not likely to get any as I simply wouldn't want to be on the handle end of an airplane that needs anything bigger than the 56/62.

If I come up to Kansas, I'm going to force you into "big block" territory against your will.

When I finish with you, you will be completely corrupted.

The last reports we will hear from you is that "he is in the shop, hopping up .82s".

Bob Reeves · « **Reply #24 on:** March 16, 2012, 02:07:56 PM »

Would love to have you drop by, but doubt you could influence me a whole lot on trying a 72.. Although I'm 6 foot tall I only weigh 145 pounds. A Genisis 46 size stunt ship is plenty big enough to take me as high up the ladder as I care to go in this hobby.

proparc · « **Reply #25 on:** March 16, 2012, 05:11:11 PM »

Quote from: Bob Reeves on March 16, 2012, 02:07:56 PM

72.. Although I'm 6 foot tall I only weigh 145 pounds.

I think we better skip the 72. LOL