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Author Topic: 4-stroker SV11  (Read 2864 times)

Offline Sean McEntee

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4-stroker SV11
« on: October 03, 2011, 05:17:42 PM »
       This is mostly targeted for Randy Smith, but anyone with data is welcome.

       How well would a Saito .56 or larger slide in? 


Thanks,
Sean McEntee
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Offline wwwarbird

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Re: 4-stroker SV11
« Reply #1 on: October 03, 2011, 10:42:21 PM »
 I don't know the fitment specs on this, but I bet it would be one heckuva combo. y1

 If you are buying an engine for this project you might as well go with the .62, same physical size and noticably more power than the .56. For info sake, when Keith put the .56 in his Legacy he just moved the engine mount location rearward one hole from what the plans showed and shortened the models nose accordingly. This was a simple "guesstimate" to aid balance with the heavier 4-stroke engine. Turned out to be spot on, it was an excellent flying model and dead stable everywhere.
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Offline wwwarbird

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Re: 4-stroker SV11
« Reply #2 on: October 07, 2011, 10:44:34 PM »
 No other opinions on this? Weird. D>K
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Offline bob branch

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Re: 4-stroker SV11
« Reply #3 on: October 08, 2011, 05:30:59 PM »
I'd be a little concerned regarding the cg with the four stroke. I ran into this with the strega with a saito .72 big time. Regarding the SV-11 I fly an arf sv-11 (so not as light materials as Randy's kit or a scratch build) that is electric powered. The electric power system is lighter than a corresponding piped glow motor system and its cg is further aft. I originally flew it with a brodak aluminum spinner (build thread on the electric forum) and found the plane was a bit on the nose heavy side. I did not get the balance that this version performed best with until I replaced the heavier aluminum spinner with a very light weight transparent plastic spinner. Net weight drop was 1.25 oz.  Don't know what version of the plane you are working with but just offering this up for a heads up to check it out early on.

bob branch
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Offline Bob Reeves

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Re: 4-stroker SV11
« Reply #4 on: October 11, 2011, 02:46:09 PM »
Quote from: wwwarbird on October 07, 2011, 10:44:34 PM
No other opinions on this? Weird. D>K

If it was in the 4 stroke section I would have seen it earlier, seldom check to see whats going on here. Your first post has pretty well said what needed to be said, good post.

All I would add is don't get too worried about the CG being a little further forward, with a four stroke the airplane won't know it. I have an airplane with a Saito 62 I shortened the nose on and ended up having to add two ounces of lead to the nose. This is a Monokote finish so it wasn't because I put too much paint on the tail.
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Offline Douglas Ames

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Re: 4-stroker SV11
« Reply #5 on: October 11, 2011, 03:52:08 PM »
Quote from: wwwarbird on October 03, 2011, 10:42:21 PM
<snip>
 If you are buying an engine for this project you might as well go with the .62, same physical size and noticably more power than the .56.

 For info sake, when Keith put the .56 in his Legacy he just moved the engine mount location rearward one hole from what the plans showed and shortened the models nose accordingly. This was a simple "guesstimate" to aid balance with the heavier 4-stroke engine.   Turned out to be spot on, it was an excellent flying model and dead stable everywhere.

*Sounds like you have no faith in a 1/1 cu. in. comparsion of 2S vs. 4S. No reason to go bigger if propped right, with the right fuel and rpm. Bob R. and others at Tulsa Glue Dobbers aren't lacking in power. Heck, I think he spends more time trying to de-tune the things. They don't run away in a dive or bog in a climb, You'd swear they had a governor on `em. I'm sold!

*Weight and balance is easy - Weight x Arm = Moment

ex. Say you had a model designed for a Fox .35 with a nose arm of 8" (measured from CG to center of mass of engine). 7.5 oz. x 8 = 60, so you want to put in a modern schnerle of 9.5 oz.. 60 divided by 9.5 = 6.32" or...move the new engine back 1.68".
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Offline peabody

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Re: 4-stroker SV11
« Reply #6 on: October 12, 2011, 05:22:42 AM »
I believe that Mike Ostella had a 4-stroke in his prototype Legacy....it flew well...
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Offline wwwarbird

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Re: 4-stroker SV11
« Reply #7 on: October 13, 2011, 11:34:47 PM »
Quote from: Douglas Ames on October 11, 2011, 03:52:08 PM
*Weight and balance is easy - Weight x Arm = Moment

ex. Say you had a model designed for a Fox .35 with a nose arm of 8" (measured from CG to center of mass of engine). 7.5 oz. x 8 = 60, so you want to put in a modern schnerle of 9.5 oz.. 60 divided by 9.5 = 6.32" or...move the new engine back 1.68".

 Doug,

 I'm going to admit that these formulas are all above my head. Back in the day, I spent all my time in math class doodling airplanes. ;D

 Question though, in the above I see how you get to the 6.32" figure, but how do you arrive at the 1.68" dimension?
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Offline Bob Reeves

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Re: 4-stroker SV11
« Reply #8 on: October 14, 2011, 06:54:41 AM »
Quote from: wwwarbird on October 13, 2011, 11:34:47 PM
Doug,

 I'm going to admit that these formulas are all above my head. Back in the day, I spent all my time in math class doodling airplanes. ;D

 Question though, in the above I see how you get to the 6.32" figure, but how do you arrive at the 1.68" dimension?

8 - 6.32 = 1.68

As I eluded to above, for some reason (no one has ever really been able to explain) an airplane with a four stroke can have the CG quite a bit forward of the two stroke CG and not lose the turn. I flew a Twister with the CG almost on the leading edge with a Saito 40 for several years all the way through Intermediate to the middle of Advanced and it would turn with the best. My Latency has the same nose moment as a Legacy and it has a Saito 62 with no additional tail weight. It's weird but it works...
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Offline Mike Callas

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Re: 4-stroker SV11
« Reply #9 on: October 14, 2011, 06:38:20 PM »
Bob,
Do you think a Saito 56 is enough for an SV11?
I just picked up the ARF and am debating getting a 62 or just using my BR Saito 56 (Otais).
Mike
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Offline wwwarbird

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Re: 4-stroker SV11
« Reply #10 on: October 14, 2011, 07:41:21 PM »
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Offline Bob Reeves

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Re: 4-stroker SV11
« Reply #11 on: October 15, 2011, 03:11:28 AM »
Quote from: Mike Callas on October 14, 2011, 06:38:20 PM
Bob,
Do you think a Saito 56 is enough for an SV11?
I just picked up the ARF and am debating getting a 62 or just using my BR Saito 56 (Otais).
Mike

If I already had the 56 I wouldn't hesitate to use it, my first big 4 stroke was a Score that weighed 68 ounces and a 56 flew it just fine. I run the same props on both the 62 and 56 so to me the two engines are pretty much interchangeable.
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Offline RandySmith

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Re: 4-stroker SV11
« Reply #12 on: November 16, 2011, 04:10:44 PM »
Quote from: Sean McEntee on October 03, 2011, 05:17:42 PM
       This is mostly targeted for Randy Smith, but anyone with data is welcome.

       How well would a Saito .56 or larger slide in? 


Thanks,
Sean McEntee

Hi Sean

It has been done before so I would not have a problem with the 4 stroke in an SV-11  it will fly very well.  also are you thinking KIT or  ARC?

Randy
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Offline Mike Callas

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Re: 4-stroker SV11
« Reply #13 on: January 18, 2012, 08:44:17 PM »
Quote from: Bob Reeves on October 15, 2011, 03:11:28 AM
If I already had the 56 I wouldn't hesitate to use it, my first big 4 stroke was a Score that weighed 68 ounces and a 56 flew it just fine. I run the same props on both the 62 and 56 so to me the two engines are pretty much interchangeable.

Bob,
Is it OK to mount the 56 on the current rails (inverted), or should I cut them off and install a new firewall to accept a sideways RC mount?

Thanks

Mike
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Offline Bob Reeves

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Re: 4-stroker SV11
« Reply #14 on: January 19, 2012, 03:06:14 AM »
It will work inverted but in my opinion side mounting is worth the trouble. This does a couple things that I believe really helps, not only am I convinced they oil better but it gives you a leg up on speed regulation. Side mounting a 4 stroke puts the intake outside the fuel head. Think about that for a minute.. Airplane slows down, centrifugal force on the fuel head decreases and fuel head pressure decreases, engine leans out a bit and speeds back up. Airplane speeds up, fuel head pressure increases, engine richens up a bit and slows back down. It's subtle because muffler pressure is minimizing the effect and also acting as a damper on what is basically a closed loop regulator. Another item that hopfully won't happen, is should something go slightly wrong and the ground/pavement end up 2 foot higher than it should have been. Guess what is going to be the first thing to hit with an inverted engine.

I haven't seen the SV-11 and not sure how the front end is built. If you can cut off the maple mounts and epoxy a 1/8 plywood doubler to the firewall you are almost home free. Try to keep the thrust line in the same location but don't be too worried if you end up needing to lower it a bit. I personally like the two piece SIG mounts (SIGEM001) because they allow the intake to be positioned back against the firewall.

Installation isn't real difficult, first drill one of the mounts for the engine positioned as far back on the mount as you can with the intake just ahead of the rear of the mount so it will clear the firewall. With the engine bolted to the mount, position it in the airplane and mark the firewall for that mount. Install the blind nuts and bolt the mount with engine in the airplane. Now all you need to do is position the 2nd mount and mark the holes. I have had good luck taping the mounts for 4-40 and using cap screws with a star washers over a flat washer to mount the engine. Long drill bits come in handy and you might need to remove part of the maple mount or ?? in the tank compartment to clear the blind nuts. I would probable go in with a Dremel and grind off a large portion of the maple mounts in the tank compartment anyway.

Good luck and good flying.

4 strokes are what electrics are trying to emulate  ;D
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Offline john e. holliday

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Re: 4-stroker SV11
« Reply #15 on: January 19, 2012, 09:36:58 AM »
I like that last line. #^ #^ #^
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John E. "DOC" Holliday
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