.15 modern stunters

Stuka Stunt Main Forum · 20 of 20 known posts recovered

Chris Brainard · Nov 02, 2001 11:33 PM

I'm what some refer to as a lurker, reading posts, absorbing the input and then moving on. One recurring subject in several forums, concerns appropriate engines for the SIG Akromaster. Often, the .15 size is suggested. Having built one dead stock (somewhat heavy wood) and powering it with a TeeDee .09 (very good performance) I'm surprised at how often a large (.15 - .19) engine is used. If built using contest grade wood and careful construction, this would fall more readily into the 1/2A category.
In my opinion, this airplane is a scaled down Twister. I've wondered, if this airplane was scaled up to an appropriate size to accomodate a modern .15 (schnuerle) engine with the "Fancher" modifications, would it prove to be a good airplane to practice on using some of the smaller fields which are often open when other (larger) fields are "tied up" because of football, soccer, baseball, etc. practice.
Initial thoughts are; 320-350 sq. in. Flying weight of 15 - 18 oz. Engine in stock condition running high rpm/low pitch prop setup.
I'm very interested in hearing input/suggestions to build a .15 powered stunter using modern engines and "numbers". Also, I own several very nice running MVVS .15 diesels. The same questions apply concerning a design for this engine. I'm thinking of a 400 - 430 sq. in. wing area. Any thoughts/comments regarding this idea.
I'm not aware of any modern kits or plans for the schnuerle .15's. Do any of you think it worth the effort to attempt to develop a stunter in this size range, and if so, what suggestions do you have?

Chris Brainard

jacobite · Nov 03, 2001 03:50 AM

#1 source

In My opinion ( NOT an expert....) a good plane for a 15 deezul is an oldy, a Keilkraft Sceptre, I had one with a PAW 15, which I liked a lot.
I have ( tatty ) plans if you want a copy.

Dave Moffitt

grzly23 · Nov 03, 2001 06:41 AM

#2 source

Lt Col Tom McClain

I recently was going through some magazine articles on 15 size stunt ships to find one that I could use as a trainer and a stunt ship combined. I found several. Here they are:

Joe Demarco's Fox 15 powered Bearcat and Zero from FM 1976
Dale Kirn's Zeroette American Modeler
Frank Ehling's Econostunt American Modeler.

Let me know if you want copies.

Tom McClain

gcb · Nov 03, 2001 08:40 AM

#4 source

LAST EDITED ON Nov-03-01 AT 08:45 AM (CDT)

Chris,
If you check your plans of the SIG Akromaster, you will find that the Fox .15 baffle (with no muffler) was used on the original. I think the kit was designed to have a relatively new modeler successfully complete a plane. It flies well (for sport) even when it's a little heavy.
Almost any plane can fly with a smaller engine, especially an engine that puts out nearly the power of the larger one, if you hand select wood and keep it light. As you know, the TD .09 is a very powerful engine for the size.
An all-time great for a modern (?) .15 like the MVVS diesel would be a full fuselage Peacemaker. George's original was powered by an Oliver Tiger .15. I would suggest building it from plans rather than locating a Top Flite kit. Beautiful ship, and it uses a constant chord wing.
And for goodness sake, don't lurk, jump in. We all taste our feet occasionally. That's what opinions are for
George

Tony G · Nov 03, 2001 08:31 AM

#3 source

Chris, your reasoning is sound to me..I think that if you can
build light enough(7-9oz/sq')you can go as large as 430sq" for
your MVVS.15D . Bare was using one in a 400sq" slow combat type
80mph model that flew very well..much tighter turning than the
typical stunt model..this plane actually flew around 83mph...
on 60'x.015" lines ..it had to be slowed down to be legal!...Also
I dont believe any modifications are necessary to a scaled up
Akromaster...My extremely porky Akromaster (17 oz..silver swallow
.15d) will fly the entire modern pattern..your scaled up Akro..
would fly significantly better..This is all relevant only if you
wish to continue with the Akromaster design..You asked if other
designs/kits are available...Yes..build a Flite Streak from
Brodak..this is an awesome stunt design..if your wing loading is
light enough,this design will outfly any stunt design that I know
of...don't worry about power loading limitations..I recall that
Dennis L..flew his Flite Streak with an MVVS Junior(2.0cc-.12cu")
and also using 60" lines...it's an excellent flyer.....
Good luck Chris...Tony
Oops..post script: I also have a scratch built Akromaster that
weighs 10.5 oz's..powered by an MP-JET 1.0cc diesel...this is
to validate your conclusion that the Akro. is almost a 1/2A size
model...

Chris Brainard · Nov 03, 2001 11:12 AM

#5 source

Tony,
I do have a full size (Topflite kit) Flite Streak and have powered it with my MVVS .15 diesel (as well as a .19 PAW diesel and .25 O.S. FP glow) All perform well, although I favor the MVVS diesel because it runs so silky smooth and no butchering of the leading edge to fit a large enough tank is necessary. In fact, I just bought plans from Bare for the Flite Streak (very nicely done!) and anticipate building from them (someday). The biggest disadvantage I've found is a serious degradation in performance when a landing gear (to take off from grass)is fitted. Since I most often fly by myself, a landing gear is required to launch from a stooge.
The Peacemaker is a beautiful ship and on my "must build" list for the future. As I recall, the original .15 Oliver Tigre is quite a bit lighter than most other diesel .15 s and probably more powerful than the .15 Schnuerles. I have a vintage Fox .29 stashed for that project.
The thought process concerning a modern .15 size stunter would include a longer tail moment, both for a smoother flying model as well as to balance out a somewhat larger landing gear. An example of a model which might scale well is the Pathfinder. Presently, both the 1/2A and full size from Brodak's is available. Something somewhere in between might make a good platform for a modern .15 which weighs more and has significantly more power than the older baffle versions. However, since I already have both a Twister (with full size plans) and a disassembled Akromaster, it will be easiest to "Fancherize" the Twister and scale it down.
I believe a good flying .15 size stunter with modern "numbers" scaled to accomodate the power and weight of the modern schnuerle engines would be a lot of fun and perhaps a good transition for the beginner ready to move up to higher performance without as much investment in time and money as a traditional full size ship.
Other thoughts, comments?
Chris Brainard

Chris Brainard

Chris Brainard · Nov 03, 2001 12:16 PM

#6 source

Oops!

I forgot to include another important piece of information. Mufflers! I fly on a football field at a local Jr. High School. If I had not been using a muffler all these years I'm sure a complaint to the local police would have eliminated this very close and conveniant field. A modern .15 size would have to be designed to accomodate one.
Chris

Chris Brainard

Tony G · Nov 04, 2001 04:30 AM

RE: .15 modern stunters..more thoughts#8 source

Sure Chris,and GCB..the Peacemaker is a great choice, and so is
your enlarged and modified Akro. concept...I just thought going
with the Flite Streak would be a simpler path...I thought you
wanted a "practice" model..I hope you can find someone to fly
with..that way you can omit the l.g..and thus improve the model's performance...I don't have to use a muffler where I fly
so I can't address that issue..diesel .15's don't seem to make as
much noise when using 9" props as glow .15's.. I'm not sure about
the Oliver mkIII being more powerful than modern schnurle .15s..
..did you mean glow 15's. The Oliver is definitley(sp?)lighter
at 5oz's..your MVVS has quite a bit more frijoles than the Ollie.
and as an interesting side note: the CS repro Ollie is also more
powerful than the original..1K more turning an 8x4".. even with
the usual suspect quality....I've tested both..same fuel,day prop....I just had another thought....return to the subject...
build the Flite Streak for the goal of practice flying and also
go ahead and develop a .15 stunter for the wealth of the experience attained...both different concepts.. I sincerely
believe that a well trimmed Flt.Strk. can take you all the way
to expert status...

Larry F · Nov 03, 2001 01:25 PM

#7 source

Chris --

You are no longer a lurker, but a contributer. Keep on keepin' on.

Larry F

mkedave · Nov 04, 2001 04:49 PM

#9 source

how about a light (all balsa) skyray?

or this
http://www.netax.sk/hexoft/stunt/thetiny.htm

Just found it surfing... interesting ideas.

Dave

Tony Elmore · Nov 05, 2001 07:21 AM

#10 source

In last but one PAMPA mag Iain Neillands' article was about this very subject - the AVIA design looked particularly good....

The Kiwi · Nov 05, 2001 09:45 AM

RE: .15-sized modern stunters#11 source

>In last but one PAMPA mag Iain Neillands' article was about
>this very subject - the AVIA design looked particularly
>good....
>
Zawada had some excellent articles in MA, and accomplished some good work on the veritable shoestring, from the sound of it. The Avia article is worth reading, whether or not the reader has any interest in that size model (for the non-initiate, it's a quite attractive profile design, with coupled flaps).

DaveGardner · Nov 06, 2001 04:39 PM

#12 source

I've been flying an El Diablo, (built light, by others!) with an OS FP-15 with the stock muffler....the WHOLE stock muffler, not the shortened one. Using a 9-4 APC, it turns about 11K on the ground on 10% fuel, and runs at a steady slightly rich 2 cycle.

Flies about 5 sec laps on 60' .012 lines (legal for 15's!)

This airplane is about 430 sq.in. (that trailing edge / tips are hard to measure!) and weighs about 20 oz dry.

I haven't seriously checked the fuel consumption, but it would seem that 2 oz would work for the pattern. Paul Walker's B-17 uses 4 of these and uses 8 ounces so it seems about right.

As far as noise is concerned, the stock muffler is amazing! Folks on the other side of the circle did not know the engine was running when I started for the handle! From the center, it almost sounds like an electric, with the prop noise being most prevalent.

Igor Burger (Slovakia) has developed a small plane he calls "The Tiny" with about 350 sq.in., for use with .15 size Max III, FP and LA engines. He has developed a very neat foam wing, with an epoxy coated paper covering....the wing prices are reasonable (about $40), but shipping from Bratislava is a bit pricey!

I'm working on a "mini-Impact", based on scaled Impact numbers to fit the 350 wing and the 15FP....no, it won't used a pipe!

Note that Tower has a 'universal muffler' for the 15FP which consists of an exhaust manifold, facing rear, with a snug fit to the engine, for remote muffler mounting (muffler included). This could be tucked back under the fuselage, much as a pipe, for balancing purposes.

Also note that I'm a diesel nut, as well, and, in 2.5cc, have an original Oliver Tiger, the CS replica, the MVVS, an older Webra, as well as a PAW 15. These are all BB engines except the PAW, which, IMHO (and some test running), is not as strong as the FP.

I think that the 15FP is as strong as them all, except maybe for the MVVS DSFR. The diesels are significantly heavier than the FP, by about 2 oz, but do use less fuel, so the tank size is a tradeoff. From a sound standpoint, the FP is the quietest, but the diesels (with a stack of some sort) are not bad.

Just a nickel's worth (it ran longer than two cents), but I really like the 15 size concept for smaller fields, lighter lines and smaller airplanes (the pattern seems more 'roomy' with smaller airplanes!).

Go for it!

Dave Gardner

Jim T. · Nov 06, 2001 11:35 PM

#13 source

The numbers being discussed sound reasonable. I hadn't chimed in because I don't own any modern 15's. One thing to think about, modern 15's, from reviews I read, put out as much or more HP than a Fox stunt 35 (.45 HP at @ 11,500). The catch is that they do so at fairly high RPM's, so one has to deal with that. Many modern 15's, I suppose, are close to the Fox in weight as well.

The idea here, for sport and less than world-class competition, is that 50's and 60's magazines have a plethora of smaller stunt/sport airplanes designed for the Fox 35 which would do fine with a modern 15. The El Diablo mentioned above is one of these.

My G20-15 diesel Tigres turn a Tornado white 9 x 4 at 11,800 -12,000. This does fine, but they are happier with an 8 x 4 APC taking off at 14,000. Not bad for a 1960 engine. I think I quoted test figures on the MVVS 2.5 cc diesel in another thread sometime back. I would expect around 10,500 on a 9 x 4 from an original or CS Oliver, either one.

Jim Thomerson

Currell · Nov 07, 2001 07:06 AM

#16 source

>The numbers being discussed sound reasonable.
> I hadn't chimed in
>because I don't own any
>modern 15's. One thing to
>think about, modern 15's, from
>reviews I read, put out
>as much or more HP
>than a Fox stunt 35
>(.45 HP at @ 11,500).
>The catch is that they
>do so at fairly high
>RPM's, so one has to
>deal with that. Many modern
>15's, I suppose, are close
>to the Fox in weight
>as well.
>
>The idea here, for sport and
>less than world-class competition, is
>that 50's and 60's magazines
>have a plethora of smaller
>stunt/sport airplanes designed for the
>Fox 35 which would do
>fine with a modern 15.
> The El Diablo mentioned
>above is one of these.
>
>
Jim: For what it is worth: The Foxes actually are closer to .5 HP than .45. I'd say a "bad" one is closer to this lower number. As an example of tough luck in sampling, Peter Chinn's Engine Reviews in MAN in the 60s did a string of McCoy .35 Redheads, as they were updated. One of the latter ones (can't remember if it was the Lightning Bolt or not) were barely able to hit .4 HP at peak. An earlier, similar .35 (might have been the one with the center plug) had outperformed it.

you're right about the weight. FPs are pretty heavy when compared to baffle designs. Of course, there is no free lunch for ABC or ABN technology. Enyas, even baffled ones, tend to be heavy, too.

And I am always amazed that a humble McCoy .19 Redhead weighs in at a hefty 6 ounces.

It is a shame that there aren't more .15 models kitted today. Kimura, the Japanese company, had a line of .15 models in the 70s that, design wise, were outstanding. Typical Japanese kits; you got everything, including a tank and bellcrank, and all of the parts are already nicely cut out and even sorted for you. The one big problem is the mystery wood that many of the parts come in. Heavy.

The Veco/Dumas and "now" Aero Engineering kit line has a number that can be used for .15s.

Currell

Currell · Nov 07, 2001 07:06 AM

#17 source

you're right about the weight. FPs are pretty heavy when compared to baffle designs. Of course, there is no free lunch for ABC or ABN technology. Enyas, even baffled ones, tend to be heavy, too.

And I am always amazed that a humble McCoy .19 Redhead weighs in at a hefty 6 ounces.

The Veco/Dumas and "now" Aero Engineering kit line has a number that can be used for .15s.

Currell

xain · Nov 07, 2001 04:12 AM

#14 source

Hi Chris,

I'm in a similar position as I only have access to modern engines. I've recently been flying a 340 square inch 38" span home-design plane, which weighs in at 18oz. I was flying it with a PAW 09 contest and it wasn't too hot.

However, I switched to my OS10FP without the muffler and it went like a rocket. I could throw it around the sky like no tomorrow. When I added the various stages of the muffler it went back towards the PAW levels of performance (but it was very quiet!)

So I think that your idea sounds about right. It sounds similar to my plane in size/weight, and mine needs the full power of the schneurle 10. It seems that I'm right on the edge of underpowering it. So if you need the muffler, a modern 15 could be a fine choice.

Of course there are other reasons that my plane isn't tip-top
So I'm going to try the Akromaster (for a solid known design) with the 10FP, no muffler. Then I'll see if I can get away with the muffler too. If not I may try a PAW15 or an ASP glow 15.

We should compare notes!
Jon

gcb · Nov 07, 2001 06:52 AM

#15 source

LAST EDITED ON Nov-07-01 AT 06:56 AM (CST)

There are lots of good .15's to choose from. Of course you can't please everyone so you may read testimonials about how bad a particular engine is. Some of the .15's I've tried and like that come in a CL version and are readily available: Fox, OS(I have FP's, have not tried the LA), NORVEL (AME and BigMig), MVVS (glow and diesel), Thunder Tiger, PAW, CS Oliver.
There are also engines that have RC carbs that can be converted or used as-is, such as MECOA (may be available in CL), AP-Yellow Jaket, Magnum. Conversion venturis are available from various sources, including our board provider, Leonard Neumann (Stuka Stunt Works).
There are probably other engines, but these came to mind.
Something to consider, if you REALLY mean modern stunter, a high revving .15 with a low pitch prop is probably preferable. If you are doing a sorta-scale stunter of an old plane, such as a WW1 bipe, you might want a .15 that will swing a larger prop slower (like a diesel) because of the drag.
Good luck
George

Chris Brainard · Nov 07, 2001 05:39 PM

#18 source

I've really enjoyed and appreciated reading all this input. Since first starting this thread, I have begun building a Twister (from a kit) and am making a series of modifications. The thought process is to draw the modifications over the original plan and if they result in a good flying model, to photocopy the modified drawing to a reduced size appropriate for a modern .15 engine. These are the modifications I plan to make:
1. stretch fuselage 3 1/4 in.
2. add doubler and tripler to inboard side of fuse with recess for tank.
3. change shape of tail - add more area like "Fancherized" Twister
4. add extra ribs to increase wingspan to 56"
5. power with a modern schnuerle .40 w/tongue muffler
6. adjustable leadouts, weight tip box
7. aluminum l.g.
8. increase span of stab (maybe also thicker)
9. use one of the Tom Morris flap horns w/"corrected" geometry
10. 4" bellcrank

Any opinions or input to the logic of this approach?

By the way, two different sizes may result, one to accomodate the modern .15 schnuerles and another for the MVVS .15 diesel (a real sweetheart and favorite of mine)

Chris

Chris Brainard

grzly23 · Nov 08, 2001 05:29 AM

#19 source

LAST EDITED ON Nov-08-01 AT 07:05 AM (CST)

LAST EDITED ON Nov-08-01 AT 07:01 AM (CST)

Lt Col Tom McClain

Have fun with your "Fancherized" Twister. Here is a picture of mine and I enjoy it immensely. It has a Big Art Tower 40 FP on the front and it swings a 10x6 3 blade propeller.

[photo not recovered: 3bea81e94aec0a6e.jpg]

Tom McClain