IC Engine uggestions for a 600 sq. in. twin engine stunter

[Gerald Schamp]

Looking for suggestions for a IC powered 600 sq. in twin engine stunter. I have two of the old OS .30s engines. FP and LA .20 & 25's are hard to come by. Are the Brodak .25 engines capable? Thanks ahead of time.

[RandySmith]

Looking for suggestions for a IC powered 600 sq. in twin engine stunter. I have two of the old OS .30s engines. FP and LA .20 & 25's are hard to come by. Are the Brodak .25 engines capable? Thanks ahead of time.

the  old  OS 30s  will fly it easily , I have lots of them, and they are  great motors

randy

[Randy Cuberly]

Gordon Delaney's Pathfinder Twin flew very well with OS FP15s.  I think it's slightly more than 600 squares.   If you look around you can find some!  LA25s would also work but might be a little overkill depending on how much the airplane weighs!  It's also possible to find LA25's.

The OS30s mentioned by Randy S. would definitely work but unless he has some I'm not sure how available they are.

Randy Cuberly

PS:  There is a lot of two OS FP15s on E-Bay right now for sale for $59.  Here!  http://www.ebay.com/itm/Lot-of-2-OS-MAX-15-FP-Airplane-Engines-W-Mufflers-/292096185617?hash=item44024a1511:g:pQkAAOSwE0JY~rD2

[Dave_Trible]

Veco.19s would be a good choice.  They can be had new from Mecca or you can find them often and reasonable on the bay.  I've bought 4 new ones there in the last year or so.  If RC, they convert easily.  Even Fox .25s would be good. 

Dave

[Tim Wescott]

Enya 19?  There's tons of them on eBay, but they last so long there's also lots of different versions.

I think your OS30's will be a good choice, given my experience with the OS25S.  Dual 20FP or 25LA would be more than enough, but yes, you have to find them first.

[wwwarbird]

 If I'm reading this correctly Gerald you're actually asking for airplane suggestions? Two great candidates for your .30's would be either the P-38 Lightning or the B-25 Mitchell from Don Hutchinson.

[Brett Buck]

Looking for suggestions for a IC powered 600 sq. in twin engine stunter. I have two of the old OS .30s engines. FP and LA .20 & 25's are hard to come by. Are the Brodak .25 engines capable? Thanks ahead of time.

   2 25FPs is WAY too much. I would suggest 15FPs.

    Brett

[wwwarbird]

   2 25FPs is WAY too much. I would suggest 15FPs.

    Brett

 Here we go... 

[pat king]

A pair of .15 engines should be plenty. What size engine would you put on a 300 square inch airplane? Unless the .25 engines will not pull a fat girl off of a toilet they are too much for a 600 square inch airplane. The easiest way to size engines for twins is to divide the wing area by 2 and apply the engine size you would for the airplane with half the wing area of the twin. Stunters for .061 engines are in the 230 to 240 square inch range.

Pat

[Randy Cuberly]

Well if the question was actually for recommendations for an airplane, why did you limit it to 600 sq inches.

The "Pathfinder Twin" of Gordon Delaney, now kitted by Eric at RSM, is 610 sq inches and the OS30's would certainly fly it but they would probably be very heavy for that size twin.

You might contact Gordon and ask him...He most definitely is the real authority on CL Twin's.

Bob Whitely's LA Heat is 825 Sq inches and he used 2 OS35S (10 in diameter props turning around 9000 RPM) engines to make the Top 10 at the Nats... missed top 5 by 1 point!

Remember the Propellor area and thrust on a twin with 10" diameter props is about the equivalent of a 13 to 14" prop on a 60 size engine.

Gordon's Too Much twin was over 1100 sq inches and flew very authoritatively with two puny Fox 35's. (10 inch diameter props at about 9,000 RPM)

Randy Cuberly

[Trostle]

We need to go back and read what Randy Cuberly just said about Gordan Delaney's Twin Pathfinder.  It is a profile, has a 54 in. span, 640 sq. in., has two OS .15 FP's.  Several top fliers, including National Champions, have flown this and all have expressed how well it flies.  It flies a very competitive pattern.  It is probably one of the most capable profiles I have seen and flown.

Keith

[Avaiojet]

I've been reading more about the ASP .21 in the R/C Forums. There's always downsides but most of what is said is favorable.

48.95 and there's plenty of them.

https://hobbyking.com/en_us/gas-glow-engines/glow-engines/asp.html?___store=en_us

CB

[Howard Rush]

The "Pathfinder Twin" of Gordon Delaney,...

Sitting ignominiously in an unused horse stall at JCT Manor as we speak. It should be flying in Profile in Portland today, boo hoo.  It is a great stunt plane well matched to its engines.

Those .15 FPs add up.  I have seen stunters with four of them, and they had no trouble getting through the tricks at  100+ oz.

[Bill Little]

OK, I can definitely not argue with most that have posted, Nats Champ, so eminent engineers (sad with all due respect)  and many others who are more proficient in this hobby/sport!

I have all intentions of building the F5F Short kit I got from Walter.  Jack Sheeks powered the original with two slobbering Fox.35s.  I mentioned MY intention of using the same or even a pair of DS. Classic .40s which are not really much more!  I got blasted out of the air worse than a lone Bf 109E with a gaggle of Hurricanes and Spitfires on his tail!!!!!!!!!!!

I am AM ALL TO AWARE of how much power an OS .15FP, OS .20FP, or even an LA.25LA  will produce running in a fast 2 cycle will produce!  I have used that knowledge to my advantage myself!  But I DO like to remain faithful to the Classic Original model.  If Jack did it then why not use it on mine?  His was NOT a guided missle on the end of the cables!

So to me the use of one or the other is simply how much I want to cater to the original and just flail around the circle with a huge smile on my face 

BIG Bear <><

[Al Ferraro]

 The La.15 is a great engine and you can still buy it new. The guys in our club use the La.15 in sportsman Clown racing and it's a top performer that holds up to the abuse of racing. After running a dozen different LA.15 engines, I found out that they are easy to break in and maintain a nice piston and liner fit.
Al

[Air Ministry .]

Veco.19s would be a good choice.  They can be had new from Mecca or you can find them often and reasonable on the bay.  I've bought 4 new ones there in the last year or so.  If RC, they convert easily.  Even Fox .25s would be good. 

Dave

And the Veco's sound really mean with Rossi R5 plugs ! ( just got a few more , so acousticaly sound again .  )

The FOX 25s on 9 x 5 Zingers arnt bad . A 19 & a 25 , with say 1/4 of the 19s prop , and the Ear knows which isnt on line .

BUt LAs and FPs sound like less bother , if you can find some light mufflers that work .
My Magnum GP 25s ( FP clones ) have 150 ex timing , so 9 x 4s might be betterer .

Late Foxes have black steel prop driver , and gruntier timing .

[wwwarbird]

We need to go back and read what Randy Cuberly just said about Gordan Delaney's Twin Pathfinder.  It is a profile, has a 54 in. span, 640 sq. in., has two OS .15 FP's.  Several top fliers, including National Champions, have flown this and all have expressed how well it flies.  It flies a very competitive pattern.  It is probably one of the most capable profiles I have seen and flown.

Keith

 What does it weigh and what lines is it flying on?

[Trostle]

 What does it weigh and what lines is it flying on?

In the magazine article on the Twin Pathfinder, Flying Models, August 2010, there is a table giving the specs on the design.  Engines: .15 -- .25 two -strokes: weight: 41 -- 55 ounces; Lines:  .015" x 66'.  John Miller wrote the article and mentions some 4-engine bomber that had 4 OS .15FP's and that he had experience with an "overpowered" twin 78" twin Flight Streak with a pair of .20's led to the decision to use the two OS .15FP's.  Also in the article, John does mention that other engines and sizes up to .25's an be used for this twin.

I am not sure what the weight of Gordan's Twin was when I flew it, but it was probably in that lower 40 ounce range.  But again, it is probably one of the finest profile stunt ships I have ever flown.

Keith

[john e. holliday]

Well I am flying a Ringmaster Twin with LA 25's.  Just need to go to lower pitch props.  Even with the 9-6's it seems fine to me and I was told it was way too much power. I flying on 65 foot .018 lines.

[Ted Fancher]

In Class A Stunt (WAM years) we flew airplanes as big as Gieseke Noblers, Banshees, Twisters, Dolphins etc. on just one Veco .19BB.  First ever ships we flew with low pitch/high revs on 4 pitch props and they all flew better way better than the same airplanes with then common Fox and OS etc. .35s with the ubiquitous 10 X 6 props.  Should'a taught us something about our "Pro" stunters but, no, we had to follow the crowds. 

Two of those .19BBs on 600 square inches would be a real hand full.  I guarantee line tension would not be an issue.

Ted

[Gerald Schamp]

Okay,  now that I've got a bunch of good input, that I totally appreciate, thank you, and I  really mean that. I know there are already some good twin engine designs out there, I've seen the Twin Pathfinder fly and like everyone says its a super flying plane. Now, I want one that is kind of my own aesthetic design, even though I will probably borrow, steel, copy and whatever else I can come up with, from other peoples designs and have what I am working toward. I have the plans drawn, it will use one of Randy Smith's Vector wings in the 610 to 630 sq. in. range. The weight I'm shooting for is in the mid 40 range and this will be a profile fuse with the twin nacelles. The reason for the OS .30s's engines is the weight at 7 ounces, so that is 14 ounces of engine weight, plus they only use about 3.5 ounces of fuel, and a 9x6 prop of some brand, probably wood. That is 18 inches of prop zipping around. Hopefully I can get the remainder of the 26 to 30 ounces of weight together in an achievable fashion.

The other reason for the OS .30s engines is I have a couple and Randy says he has some, so they are not unobtainable (yet). At best this is an experiment to see if it will work. Hopefully by use of other peoples ideas and designs it has a somewhat probable chance of working.

[Brent Williams]

I will defer to any revision that Gordan may wish to add.  In my conversations with Gordan on the topic of his Pathfinder twin, he mentioned that OS FP20's might have possibly been a more desirable choice at our high elevation.  We live in Northern Utah with a static elevation around 4400ft and summertime D.A. levels cresting over 7500ft.

With the elevation to contend with, the OS FP15's were run at a higher nitro level to compensate for the power loss.  Fuel was 20% nitro. ( confirmed by The G.S.O.)

At the lower elevation contests where so many top level fliers were able to experience this ship, ie Golden State, NW regionals and Tucson, ect, I am sure the 2x15FP setup was awesome.  I have never heard one negative comment from Gordan nor anyone else who flew it.

[Randy Cuberly]

I will defer to any revision that Gordan may wish to add.  In my conversations with Gordan on the topic of his Pathfinder twin, he mentioned that OS FP20's might have possibly been a more desirable choice at our high elevation.  We live in Northern Utah with a static elevation around 4400ft and summertime D.A. levels cresting over 7500ft.

With the elevation to contend with, the OS FP15's were run at a higher nitro level to compensate for the power loss.  Fuel was somewhere around 15-25+% nitro. ( if I remember the conversations correctly.)

At the lower elevation contests where so many top level fliers were able to experience this ship, ie Golden State, NW regionals and Tucson, ect, I am sure the 2x15FP setup was awesome.  I have never heard one negative comment from Gordan nor anyone else who flew it.

OK.
But I would mention that Tucson is at 2300 ft altitude... with Density Altitudes of over 5000 ft...  not exactly Sea Level and the 15's worked really well.

I'm actually building one now and it will have FP15's..I also have 2 FP20's but seriously doubt that they will be needed at anything other than Extreme altitude such as Denver or maybe Utah.

Randy Cuberly

[Trostle]

(Clip)

The reason for the OS .30s's engines is the weight at 7 ounces, so that is 14 ounces of engine weight, ...

(Clip)
 

One interesting thing to note about the OS .30S.  According to the OS spec sheet, the OS .30S weighs in at 200 g.  The OS .35S weighs 188S, or 7.05 oz  and 6.63 oz respectively.  So, the combined weight of your two OS .30's is about almost 1 oz heavier than would be two OS .35S engines.  (The difference is because of the heavier cylinder liner in the .30 than the .35.)  This is not to cast a despairing remark against the OS .30S.  It is a great engine for CL stunt, as is the OS .35S.

Keith

[Gordan Delaney]

Just thought I`d help out on some facts that are wrong on my Pathfinder Twin> Hope this helps. Gordy

Wing span  56 inches

Wing area  640 sq. inches

Weight   47 oz.

FP  .15`s

APC props 9-4 cut to 8-3/4
 
Airfoil   2.125 at the high point

Don`t remember the %

Power Master fuel  YS-20-20







































5

[Avaiojet]

Just thought I`d help out on some facts that are wrong on my Pathfinder Twin> Hope this helps. Gordy

Wing span  56 inches

Wing area  640 sq. inches

Weight   47 oz.

FP  .15`s

APC props 9-4 cut to 8-3/4

Airfoil   2.125 at the high point

Don`t remember the %5

Gordan,

Are you using the original airfoil?

CB

[Mark Scarborough]

Gordan,

Are you using the original airfoil?

CB

CHarles, what on earth are you talking about, he designed it, of course its the original airfoil, come on man, stay with us

[Randy Cuberly]

Just thought I`d help out on some facts that are wrong on my Pathfinder Twin> Hope this helps. Gordy

Wing span  56 inches

Wing area  640 sq. inches

Weight   47 oz.

FP  .15`s

APC props 9-4 cut to 8-3/4

Airfoil   2.125 at the high point

Don`t remember the %

Hi Gordy,
How are you doing?  Hope you're well!

Area is close enough not to argue about and I'm sure your's is what you say, however the plans I have from the kit cut by RSM with plans by John, calculate to 628 sq inches.  Like I said 12 sq in is not enough to squabble about but there is usually some difference between the original and kit plans as I'm sure you probably are aware of!   

Randy Cuberly

[RandySmith]

The  2  OS 30S  engines  will easily  fly a 700 sq in  twin

Randy

[Gerald Schamp]

Thanks Randy, I'll give you a call tomorrow about the OS .30 engines.

[Randy Cuberly]

Hi Gordy,
How are you doing?  Hope you're well!

Area is close enough not to argue about and I'm sure your's is what you say, however the plans I have from the kit cut by RSM with plans by John, calculate to 628 sq inches.  Like I said 12 sq in is not enough to squabble about but there is usually some difference between the original and kit plans as I'm sure you probably are aware of!  

Randy Cuberly

Well it seems I made an error in measurement the first time around.  More careful scrutiny and calculation of the area on my plans yields 647.25 sq inches.

Sorry!  I do have a question about asymmetry there is no asymmetry from the center of the fuselage to each wingtip, but the outboard nacelle is .5 inches closer to the fuselage than the inboard.  I assume this is intended to create a increase in inboard wing area from some imaginary balance point between the two engines.

Randy Cuberly