Forerunner advice

[Duke.Johnson]

Went to the Skyraider swap meet today with my boys and came home with a slightly used Forerunner.  Thanks Steve!

Just wanted to get a couple opinions, even though Steve is most likely right on the money.  I should have asked Steve more questions. 

I already have a couple OS 40FP's and a Tower Hobbies 40, I could put one of them in it.  They both have carbs though.  What ventri and NVA should I go with?

Should I use a different engine? But, I did spend all my plane money today.

If I go with one of the above engines, what size and length lines?  I'll be using the new Ted Francher hard point handle kit I picked up today.  And what prop at what RPM's?

Thanks

[Randy Cuberly]

Either of those two engines will work OK.  My personal preference would lean to the Tower 40 since it's a real ABC engine.
The standard FP or LA 40-46 venturi will fit and work fine.  I prefer the one that is .284 ID with a ST Needle Valve Assembly, but the Stock OS FP needle assembly will work fine also.
The ST Needle valve assy will require drilling out the cross hole in the crankcase and venturi to .156 diameter...the OS will fit in the .140 dia hole already in the parts.  I do think the ST Needle assy works a little better...I don't like the spring resonances that often occur with the OS Needles.  It can cause inconsistencies in needle settings.  However a lot of people use them.
My real personal preference would be to get an LA46 and use that.  A little more power and easier to use...more consistent runs.  However either of the 40's will work fine on that airplane.  Out of curiosity...If the airplane is built is the engine mounted inboard on the Fuselage, a lot of those were setup that way and it seems to work OK.  I don't think it's any better however.  I think most of the guys that did that just weren't using hot plugs and it probably did work a little better with colder plugs.  Theoretically it kept the plug better scavenged...personally I tend to doubt that.  Given the pressures inside the cylinder during the run cycle I seriously doubt that the centrifugal force makes much difference.
I had two of these things a long time ago and they are good fliers, but need to be kept reasonably light.

Randy Cuberly

[55chevr]

My Forerunner flies fantastic with a Scorpion 3020-10.  Equivalent to a 40 FP power.  This is the best flying profile I ever flew. 
Joe

[Randy Cuberly]

My Forerunner flies fantastic with a Scorpion 3020-10.  Equivalent to a 40 FP power.  This is the best flying profile I ever flew.  
Joe

Fly an Imitation some time!  

[SteveMoon]

Randy is right on the money on the engine advice. As far as line length goes,
I would recommend somewhere in the range of 60' on .015. Having built and flown
several Forerunners over the years this is usually a good starting point. If you
end up with a slightly more powerful motor such as the OS LA 46 then you can
probably add about a foot to the line length.

The Forerunner is a great flying profile, probably my all time favorite. You should
enjoy it! Also, the Forerunner was originally designed with the motor mounted on
the inboard side. This is how Tom Farmer designed it. Tom is a local flyer here in
Dallas and I have seen him flying various Forerunners for over 20 years now. Tom
was quite a competitor in his day, having won National Championships in free flight
and Top Alcohol drag racing. Tom has always believed that having the motor
inboard yields more consistent runs on a profile ship.

Later, Steve

[Jerry Eichten]

Duke - Is your Forerunner maroon with yellow and silver accents?  If so, I had an FP 40 on it originally and it flew great.   

[Duke.Johnson]

Thanks all.
Randy- The engine mounts on the outboard side.  And I'll dig around to see if I have a LA 46.
Jerry- This is the same plane.  Steve told me it was yours.  It still has your numbers on it.

[Steve Helmick]

Duke...When I flew that 4Runner, the setup I used was the OS .46LA with the MACS #6650 (see link below). Makes a very nice setup with the wing mounted LG, but often interferes with a fuselage gear. I know the 11.5 x 4 APC works very well on that setup. With either the T.40 or .40FP, the same setup would work very nicely...except the prop will have to be smaller. It needs to be right around 4" pitch, and it needs to peak (leaned out) at 11k or a bit more, because you need to launch it at right around 10.2k, and it needs to be a bit rich there, or it will sag in the overheads.

Scott Riese used to like the Tornado 3 blade 10-4, but both Mike Haverly and I tried that prop and we didn't like them at all. And, of course, they're no longer made. I see that MACS Products has a "Scotsman" line of mufflers that are similar (and cheaper), but they are somewhat different, so I'm not sure that one would work the same. I do not suggest any of the stock mufflers for either T.40 or FP, because it will need even more tailweight than it already has! And I'm not really a fan of tongue mufflers (most especially the ones that are shaped like a tongue and soldered together!).  I would try the 10.5 x 4.5 APC, 11-4 APC, and TT 11-4.5, for sure. I almost hate to suggest a Zinger, but the 11-4 Zinger Pro series might be ok with some rework. The TF Power Point 11-4 might work better, or the MA S2 Scimitar. I have those, having tried them on the KISS! with the Magnum XLS .36.
     
The plane is an "OPP" (Other People's Plane), with the engine on the outboard side as Jerry E. built it, though it wouldn't be that hard to change it over to inboard side mounting, except having to add a bunch of tipweight. Having flown it a few times, I think it will work well with .015 x 62' cables to start with...adjust from there!  Steve
  http://www.macspro.com/onepiece.asp 

[Duke.Johnson]

Well I think I'll start with the T.40  with a 11x4 APC prop, I have that already. 

Steve- On the lines, are they 62' eye to eye? Or center of plane to center of handle.  I have some lines made that would it at about 62' center to center.  And can make a good set after figuring what works best.

On the ventri. Randy mentioned a .284" I.D. ventri, is this the same as the 25LA ventri Peter mentioned?  If not, were do I find the .284" ventri? 

After looking at the muffler prices, is this really needed for a beginner?  I didn't pay the engines NIB.  I know in the hands of Steve or any other "Expert" it does, but me?

[Steve Helmick]

The stock .40/.46 LA venturi should be right around .285", but like all machined parts, they have tolerances, and we don't know what tolerence OS put on them. That's what you want with the MACS Muffler, anyway. The stock .25 LA venturi is about .265" as I recall. Pat and Mark like that setup with other mufflers. 

Remember that you can always put a few layers of pantyhose fabric over the venturi with an O-ring to effectively make the venturi smaller. Or start with the .25 FP/LA venturi and drill it bigger until it suits you...then add pantyhose fabric to make it seem smaller again. I think Brett said that one layer is roughly .010" reduction, but if you stretch it tighter than Brett does, it would be less effective. One layer stretched pretty tight is never a bad thing, if it keeps some stuff out of your engine.    Steve

 

[Brett Buck]

I think Brett said that one layer is roughly .010" reduction, but if you stretch it tighter than Brett does, it would be less effective.

   I don't think it's nearly as much as .010 per layer no matter how tight or loose it is stretched. The old Bru-Line "fine" filter element may have been that much. One layer makes hardly any difference in the overall power or flow capability. What it does do, pretty effectively, is keep the air turbulent, and makes it run more evenly through the pattern.

    Brett

[Randy Cuberly]

Well I think I'll start with the T.40  with a 11x4 APC prop, I have that already.  

Steve- On the lines, are they 62' eye to eye? Or center of plane to center of handle.  I have some lines made that would it at about 62' center to center.  And can make a good set after figuring what works best.

On the ventri. Randy mentioned a .284" I.D. ventri, is this the same as the 25LA ventri Peter mentioned?  If not, were do I find the .284" ventri?  

After looking at the muffler prices, is this really needed for a beginner?  I didn't pay the engines NIB.  I know in the hands of Steve or any other "Expert" it does, but me?

The .284 venturi was the original size for the FP/LA40/46 and is a little on the large side for the stock OS needle assembly with the .140 diameter spraybar.  It works very well with the ST Needle Assembly which is larger in diameter at .156.
The RSM tongue muffler with everyother hole drilled out to .125 diameter works very well on these engines.  Stock it is a little too restrictive especially for the LA46 but also for the T40.
 It's light and inexpensive!   The OS25 venturi (.265) is OK for the FP/T40 with the stock OS needle assembly but is too small in my opinion, for any of these engines with the ST Needle Assembly.
The .284 diameter is the best bet because it's easy to restrict it (as mentioned earlier) with a couple of layers of panty hose held on by an O-ring if necessary...which frankly it usually isn't.  Especially when feeding the slightly higher port timing of the two 40's mentioned.  
A little more nitro can do wonders if the break is a little too hard also.

Randy Cuberly

[55chevr]

My son Joe has an FP40 on a Top Flite Tutor.  A friend who is a machinist made 5 venture-s for me. Sized from .265 to .290. So far the .275 is the one that makes the engine "Stunt Happy". Big improvement over the stock one.  Yesterday he did have one runaway but I think that is related to tank foaming. 

Joe

[Jerry Eichten]

The Custom Models Forerunner Duke now owns was the second CL model I built after quitting RC in 1996.

This is my first try posting pictures so I hope you see something that looks like the plane at Delta Park before the first flights.

-Jerry

[Steve Helmick]

Great job posting the pictures, Jerry...it looks much the same, except for the holes punched in the rear of the fuselage (I didn't do it!).

And Duke, yes, I meant 62' eye to eye on the line length. I don't much care how many kilometers that is.  Steve

[Duke.Johnson]

Jerry- I didn't put the holes in the plane either.   And it still looks pretty good.  I hope to practice a little more on my Holeshot before switching to the Forerunner.  Hope I can bring it to the Spring Tune Up and do it justice.  I need to show up my boys.  

Steve- I'll hook up a set of line to messure the length.  I'm need to order the ventri and NVA, the local hobby shop didn't have them and Tower Hobbies have them back ordered.  Tried the LHS first, I like to go through him id I can.  We'll need to set up a time to fly and you can tell me what I'm doing wrong. Or maybe you should start with what I'm doing right, shorter list.

Thanks for all you're help guys.

[Steve Helmick]

I'd suggest ordering the venturi and NV Assy from Randy Smith. His NV Assy. is THE BEST.  Steve