4-stroke vs 2-stroke

4-stroke vs 2-stroke

Post by Don Eving » Wed, 01 Jan 1997 04:00:00



I have a question concerning 4-stroke engines.

I have a new, in the box, OS FS-90 engine, that I bought several years
ago from someone for a bargain price. Soon after I dropped out of the
hobby. I'm back now, and would like to build a larger plane, one
appropriate for this engine.

But the more I think about it, I wonder if that's such a great idea.
I've never had any experience with a 4-stroke, and I wonder if having
*one* of these and several 2-strokes would be a hassle. I know you
need different fuel, is there anything else you have to do different
for these 4-strokers? My thought was maybe I ought to trade it off
for a .60 class 2-stroker.

I was at a hobby shop today, and mentioned to the guy behind the
counter that I had this engine, and that I didn't know if I should get
involved with 4-strokes. His eyes sort-of lit up and he asked me how
much I wanted for it? Is this a particularly good engine? Note that
it's not one of the current models, it is not a Surpass, it has the
push rods behind the cylinder.

Your comments would be appreciated.

Oh, also, I consider myself to be an intermediate level pilot.
Flipping through the latest Tower catalog on page 42 I saw the
Goldberg Super Chipmunk. I've always liked the looks of this plane, I
had a control line version many years ago. It has a 64" span, for
45-.61 2s or .60-.90 4s engines. I've never flown a tail dragger. Any
comments about this plane and possibly the above engine coupled with
my skill level?

-Don

 
 
 

4-stroke vs 2-stroke

Post by Sigurd Stenerse » Thu, 02 Jan 1997 04:00:00


Keep (and use) the engine.  If it doesn't bother you to have two kinds of
fuel and two kinds of glow plugs, there wont be any problems.  I used the
same engine you have in a ModelTech Cap 21, and it was excellent.  It may
not be as powerful as an FS91S, but the difference is marginal and you
certainly don't want to pay for a new FS91S when you have a FS91.  Also,
the linkage is located behind the cylinder on the FS91S as well.  That's
where the carburator (how to spell ?) is located.

I also think that the FS91 will be an excellent engine for the CG Chipmunk,
although I haven't tried this plane myself.

Sigurd


Quote:
> I have a question concerning 4-stroke engines.

> I have a new, in the box, OS FS-90 engine, that I bought several years
> ago from someone for a bargain price. Soon after I dropped out of the
> hobby. I'm back now, and would like to build a larger plane, one
> appropriate for this engine.

> But the more I think about it, I wonder if that's such a great idea.
> I've never had any experience with a 4-stroke, and I wonder if having
> *one* of these and several 2-strokes would be a hassle. I know you
> need different fuel, is there anything else you have to do different
> for these 4-strokers? My thought was maybe I ought to trade it off
> for a .60 class 2-stroker.

> I was at a hobby shop today, and mentioned to the guy behind the
> counter that I had this engine, and that I didn't know if I should get
> involved with 4-strokes. His eyes sort-of lit up and he asked me how
> much I wanted for it? Is this a particularly good engine? Note that
> it's not one of the current models, it is not a Surpass, it has the
> push rods behind the cylinder.

> Your comments would be appreciated.

> Oh, also, I consider myself to be an intermediate level pilot.
> Flipping through the latest Tower catalog on page 42 I saw the
> Goldberg Super Chipmunk. I've always liked the looks of this plane, I
> had a control line version many years ago. It has a 64" span, for
> 45-.61 2s or .60-.90 4s engines. I've never flown a tail dragger. Any
> comments about this plane and possibly the above engine coupled with
> my skill level?

> -Don


 
 
 

4-stroke vs 2-stroke

Post by DMich270 » Thu, 02 Jan 1997 04:00:00


I'd say keep the engine as well.  Regarding different fuels, the only
difference between 2 stroke and 4 stroke fuels is that 4 stroke has less
oil than 2 stroke.  Many flyers who have both typesof engines run 2 stroke
fuel in both types of engines.  It would not hurt your engine to have a
little extra oil.  By running only 2 stroke fuel, you don't have to worry
about putting  4 stroke fuel in a 2 stroke engine (not enough oil).

As long as you're sure you're ready to fly it, the Goldberg Chipmunk would
be a very nice combination with your engine.

 
 
 

4-stroke vs 2-stroke

Post by Rob Rede » Thu, 02 Jan 1997 04:00:00


I would keep the 4 stroke, I have four Surpass engines a 120, 91, and two
70's. I also have several Webra 2 stroke's, I run them all on 10% 2 stroke
fuel and it works fine for me.

Rob


Quote:
> I have a question concerning 4-stroke engines.

> I have a new, in the box, OS FS-90 engine, that I bought several years
> ago from someone for a bargain price. Soon after I dropped out of the
> hobby. I'm back now, and would like to build a larger plane, one
> appropriate for this engine.

> But the more I think about it, I wonder if that's such a great idea.
> I've never had any experience with a 4-stroke, and I wonder if having
> *one* of these and several 2-strokes would be a hassle. I know you
> need different fuel, is there anything else you have to do different
> for these 4-strokers? My thought was maybe I ought to trade it off
> for a .60 class 2-stroker.

> I was at a hobby shop today, and mentioned to the guy behind the
> counter that I had this engine, and that I didn't know if I should get
> involved with 4-strokes. His eyes sort-of lit up and he asked me how
> much I wanted for it? Is this a particularly good engine? Note that
> it's not one of the current models, it is not a Surpass, it has the
> push rods behind the cylinder.

> Your comments would be appreciated.

> Oh, also, I consider myself to be an intermediate level pilot.
> Flipping through the latest Tower catalog on page 42 I saw the
> Goldberg Super Chipmunk. I've always liked the looks of this plane, I
> had a control line version many years ago. It has a 64" span, for
> 45-.61 2s or .60-.90 4s engines. I've never flown a tail dragger. Any
> comments about this plane and possibly the above engine coupled with
> my skill level?

> -Don

 
 
 

4-stroke vs 2-stroke

Post by alaska2.. » Thu, 02 Jan 1997 04:00:00


Quote:

>Oh, also, I consider myself to be an intermediate level pilot.
>Flipping through the latest Tower catalog on page 42 I saw the
>Goldberg Super Chipmunk. I've always liked the looks of this plane, I
>had a control line version many years ago. It has a 64" span, for
>45-.61 2s or .60-.90 4s engines. I've never flown a tail dragger. Any
>comments about this plane and possibly the above engine coupled with
>my skill level?

>-Don

 Keep the 4 cycle and run regular 2 cycle fuel through it. If your worried
about being able to fly the Chipmunk, put the .90 on a .60 sized big stik
get your thumbs loosened up then go for the chip.

Andy.

\/\/\/\//\/\/\/\/\/\/\/\/\/\/\//\/\/\/\/\/\/\//\/\/\/\/\/\/\/\/\/\/\/\//\/

 Andrew Laska                           KA1SLG
New Canaan R/C Society
AMA 132883

  Ho ho ho yourself. Get that sleigh and them funny lookin' goats off my
roof tubby!

 
 
 

4-stroke vs 2-stroke

Post by Don Eving » Thu, 02 Jan 1997 04:00:00


Quote:
>> I have a question concerning 4-stroke engines.

Thanks to everyone for their comments so far.

Well it seems everyones opinion is that I should either keep and use
the FS-90, or sell it to them! I was unaware that you could use
2-stroke fuel in a 4-stroke engine. I've been using Cool Power fuel
with 10% nitro for my 2s engines. I can't find anything on the label
that would indicate what percentage oil it has, has anyone got any
experience with this fuel in a 4-stroker? Can I use it?

Also, regarding the Goldberg Super Chipmunk, I went back and actually
read the whole desciption (grin). Seems it's aimed at the intermediate
flyer, and has a 64" SEMI-symmetrical wing so it ought to have
reasonable low speed handling. I'd be very interested in hearing
comments from anyone who has any first hand knowledge about this
particular kit. Will I need any special servos? I've never built a
plane this large.

 -Don

 
 
 

4-stroke vs 2-stroke

Post by Kelly Steel » Thu, 02 Jan 1997 04:00:00


Quote:

> I was unaware that you could use
> 2-stroke fuel in a 4-stroke engine. I've been using Cool Power fuel
> with 10% nitro for my 2s engines. I can't find anything on the label
> that would indicate what percentage oil it has, has anyone got any
> experience with this fuel in a 4-stroker? Can I use it?

Don,

I use Cool Power 15% In all my 4-stroke engines, from Saito .50's to YS
1.20. No problem at all. The 10% should work just fine. Also, try an OS
"F" plug. It's a little more money but works great and lasts a long
time. I have one in a YS 1.20 That's going on 2 yrs. old. Hope this
helps!

Kelly Steele

 
 
 

4-stroke vs 2-stroke

Post by Rob Rede » Fri, 03 Jan 1997 04:00:00


I use 10% cool power 2 stroke fuel in all my 4 strokes with no problems. As
to the chipmunk its a great plane I got a buddy that had one it WAS a good
flyer. Watch out for steep slow speed turns with full flap the last step is
a killer.

Rob


Quote:

> >> I have a question concerning 4-stroke engines.

> Thanks to everyone for their comments so far.

> Well it seems everyones opinion is that I should either keep and use
> the FS-90, or sell it to them! I was unaware that you could use
> 2-stroke fuel in a 4-stroke engine. I've been using Cool Power fuel
> with 10% nitro for my 2s engines. I can't find anything on the label
> that would indicate what percentage oil it has, has anyone got any
> experience with this fuel in a 4-stroker? Can I use it?

> Also, regarding the Goldberg Super Chipmunk, I went back and actually
> read the whole desciption (grin). Seems it's aimed at the intermediate
> flyer, and has a 64" SEMI-symmetrical wing so it ought to have
> reasonable low speed handling. I'd be very interested in hearing
> comments from anyone who has any first hand knowledge about this
> particular kit. Will I need any special servos? I've never built a
> plane this large.

>  -Don

 
 
 

4-stroke vs 2-stroke

Post by wb4.. » Fri, 03 Jan 1997 04:00:00


Quote:

>2-stroke fuel in a 4-stroke engine. I've been using Cool Power fuel
>with 10% nitro for my 2s engines. I can't find anything on the label
>that would indicate what percentage oil it has, has anyone got any
>experience with this fuel in a 4-stroker? Can I use it?

I have been using 10% Cool Power (green stuff) in my Saito 150 for two
years.
This year I tried Wildcat 15% nitro, 18% oil for the Saito. If I remember
Saitos instructions, they said to use 2 stroke fuel and NO castor oil,
only synthetic oil.

Dan
Ham radio WB4GUK
AMA 32873  EAA 60974                     T                    
J3-2026m   PA20-2217a      ---------o-O-o--------

Treat others today like you would like to be treated, for tomorrow you may
work for them!

 
 
 

4-stroke vs 2-stroke

Post by Dave Tatosi » Fri, 03 Jan 1997 04:00:00


[snip]

Quote:
>Also, regarding the Goldberg Super Chipmunk, I went back and actually
>read the whole desciption (grin). Seems it's aimed at the intermediate
>flyer, and has a 64" SEMI-symmetrical wing so it ought to have
>reasonable low speed handling. I'd be very interested in hearing
>comments from anyone who has any first hand knowledge about this
>particular kit. Will I need any special servos? I've never built a
>plane this large.

Don: I'm about two-thirds done building that same CGM Super Chipmunk, and
you'll be happy (I suspect) to know that the wing is actually fully symmetric
(you can flip any pair of ribs and they'll match perfectly). The description
in Tower's catalog is definitely in error (wouldn't be the first time!)
I'd been thinking about building one of these for a while but was put off by
the ad. Fortunately a kit showed up in my local so I had a chance to check it
out quite closely and confirmed that the wing is symmetric...

The low-speed handling (assuming this is correct) is likely due to
(a) moderate wing loading (range should be somewhere between 20 and 26 oz/sq
ft - 23oz/sq ft if you hit the 7lb middle of the expected weight range),
(b) the verging-on-high-aspect ratio wing - not as extreme as the Kaos wing,
but getting there, and (c) a rather inordinate amount of dihedral.
I'm not looking for the utmost in low-speed stability, so I've taken half that
dihedral out so it closely matches the dihedral used on the wing of my
UltraSport-60 (which is fairly stable as it is).

Also, the plane is designed to use standard-size servos, so no problems there.

I'm also using an OS 4-stroke - a .91FS - so I'm facing some of the issues
you'll need to work out if you go ahead with this. Basically, I compared the
length (and weight) of this engine with the (antique) K&B .61 2-cycle that the
plans are built around, and found that I'd need to move the firewall back at
least 1/2" to get the cowl nose ring to end up in the right place. This ought
to help with balancing the plane as well, and the back of the TruTurn spinner
will be 1/8" in front of the cowl when it's all done.

Other changes I'm making:
- the kit comes with a lot of ABS (cringe). Between the cowl, wheel pants,
wing tips, belly fairing, and***pit details (!) there's almost as much
plastic as a Lanier Stinger (yucko!) Sooo...I've replaced the cowl and pants
with R/C City glass, and I carved my own balsa wingtips and belly fairings
(I'll probably keep the plastic***pit interior ;^) The result looks sharp
and I won't have to deal with painting all those plastic bits (and that would
melt if I tried to put film over them).

- I've installed flaps roughly following the plans using a central servo in
the wing, but I've installed dual aileron servos in the wing (you can *just*
squeeze standard size servos between ribs 8 & 9 if you lay them on their sides
and work out the mounting). If you follow the CGM aileron design (central
servo, LONG pushrods and bellcranks) I think you'd end up with significant
linkage slop leading to deadly flutter, not to mention sluggish response.

- I completely sheeted the top-side of the wing - as I want to follow the Art
Scholl trim scheme but don't like painting over film, and would rather not use
fabric (or glass) and paint either - too much weight involved. The trim scheme
used on the top-side of the wing is "busy" with stripes, too busy to reliably
piece the film together on my glass benchtop and then pull it over the wing,
as I usually do, but with the full sheeting under the base white film layer I
can apply the red striping with an iron and have something to press against
(not possible with open bays).

- Instead of laminating together the lite ply firewall per the plans (almost
impossible to come out truly flat, plus the quality of the ply in my kit
really sucked), I used 1/4 AC grade ply, and beefed up the reinforcement to
survive the engine that'll be dragging this 'Munk around. Might not be
necessary but it makes me feel more comfortable.

- generally made sure that any critical high-stress areas are "ruggedized", in
particular the gear mounts, wing bolt blocks, firewall, and the fuse area
immediately behind the wing bolt block (which looked frail to me). I glassed
6" of the wing center as well. I don't mind adding a bit of weight when it
comes to preservation of the aircraft on our less-than-manicured
runways, and I don't want to worry about parts flying off the first time I
throw my 'Munk into a *** snap ;^)

The instructions are pretty good - easy enough to follow and well
illustrated. Read them a few times over before diving in. Full size
plans - hand-drawn, unfortunately, folded (BOO!) and with some detail
obscured, and some technical data not provided - like incidences and thrust
angles. Material quality varied: excellent balsa, decent hardware, but the
worst lite ply I've ever seen (really *** stuff). Take plenty of time
dry-fitted the fuse together and you'll end up with it nice and straight.

Whoops! Just noticed how long this has gotten (I'll put a warning in the
title!) but I hope you (and others) find it helpful. Taking a glance at the
finished wing and half-built fuse, I figure another couple of weeks before
it'll be ready to cover. If anything turns up along the way I'll let you know.

Cheers!

/dave

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4-stroke vs 2-stroke

Post by Sam and Sonja Sor » Fri, 03 Jan 1997 04:00:00


I have built two Chipmunks and flown one of them extensively for
several seasons.  Beef up the landing gear mounts.  I did and they
still split out on me.  I put some "Klett" gear up front of the wing
saddle and it's been great ever since.  It does fly and land somewhat
faster than my Astro Hog but I've never had it snap.  With the flaps
partially deployed it will crawl along with no problem.  One of my
favorite planes.
Sam

Quote:

>>> I have a question concerning 4-stroke engines.
>Thanks to everyone for their comments so far.
>Well it seems everyones opinion is that I should either keep and use
>the FS-90, or sell it to them! I was unaware that you could use
>2-stroke fuel in a 4-stroke engine. I've been using Cool Power fuel
>with 10% nitro for my 2s engines. I can't find anything on the label
>that would indicate what percentage oil it has, has anyone got any
>experience with this fuel in a 4-stroker? Can I use it?
>Also, regarding the Goldberg Super Chipmunk, I went back and actually
>read the whole desciption (grin). Seems it's aimed at the intermediate
>flyer, and has a 64" SEMI-symmetrical wing so it ought to have
>reasonable low speed handling. I'd be very interested in hearing
>comments from anyone who has any first hand knowledge about this
>particular kit. Will I need any special servos? I've never built a
>plane this large.
> -Don

 
 
 

4-stroke vs 2-stroke

Post by Mark O » Fri, 03 Jan 1997 04:00:00


You can use 2 stroke fuel in a four stroke....should not be a problem...just
use a brand new type F plug.....most of the guys at my club now use 2 s fuel
in their 4 strokes...I have used 2 s in my .70 surpass with no probs. The
extra oil actually will prolong life...just make sure that the nitro is at
least 10%....to keep the plug hot. I would keep the 4 s. they are MUCH
cheaper on gas. My  OS .61 pump uses more gas then a 1.20 4 stroke...almost
and ounce a minute!!!. Keep the 4 s....you'll like it.

Mark

Mark