Twin engines

[Philip THOMAS]

Greetings wise ones. I am about to start a  Brodak Tigercat ( build something different says my son!) said to be built for two 15’s but I plan to use for sport stunt. Question is, is two (probably) Enya 15s enough for this application? Are two 15s equivalent to one 30? I’m not sure why but my instincts tell me that they might produce more thrust than a 30!
Thoughts?
Best regards, PT

[GERALD WIMMER]

Hello
The Tiger Cat specifies and shows two Fox 15BBRC schnuerle ported engines which may be a lot more powerful then the Enya 15's depending on the model. I currently have two Enya 15 MkIV's on a Twin Mustang profile and they run well but are not late model powerhouses like the Enya 15CX. The wing on the Brodak Tiger Cat is not that well suited to stunt flying with only 354 square inch area and a thin section with lots of sheeting but the model does say for sports stunt flying or semi scale and suits trainer style carrier use.

Regards Gerald

[Ken Culbertson]

The answer to the "why 2x15 <> 30 lies in the surface area of the two prop circles.  Assuming a 10" prop on the 30 and 8" on the 2 15's you have about 35% more area on the 2 15's.  Size, RPM and pitch naturally alter that, but it is still the technical reason.  The real reason is it sounds so cool!

Ken

[Jim Hoffman]

I built a similar F7F Tigercat profile stunter in 1998 (approximately).  I powered it w/ OS 15 FP motors swinging 8-4 APC props which provided more than enough power for my model.  I ran the motors in a rich 2 cycle.

My model was from the Flying Models (FM) plans from the Bob Adair article in the March 1968 edition of FM.  My model has 405 sq. inch of wing area, profile fuse and nacelles and finished weight of 36 oz.  It can fly a reasonable AMA stunt pattern considering what it is.

Paul Walker used the same power train (X2) in his B-17 weighing 100+ oz.

[Philip THOMAS]

Nice work!  Thanks!  I happen to know that the Fox 15 Sch. and the Enya 15 have the same mounting holes so will build for the slightly bulkier Fox and can retrofit the Enya's if I get bored.
Tight lines and fair winds!  PT.

[Motorman]

Two Fox 15 Sch engines will grossly over power a 354 sq in wing plane for sport stunt use. I believe the Enyas will be lighter and much higher quality. YMMV

MM

[Scientifiction .]

The Answer of course , is NITRO . 

If you wanted a ' REAL ' F2B capeable TIGER CAT , youd get the ORIENTAL PLAN , and Tigercat it .

Two .15s would fly it fine on 60's . Blah Blah . the nitro & the tourque go hand in hand . As does easy starting & broad needle tolerance . But RICH is Tourque .
Enyas had a reputation as a Nitro Motor . Where the OS ( 20s ) would run on none, and fly a 43 ounce muffled Ori / 262 on the outer thru wingovers & rounds.
On 70 foot of .012. ( in the calm. ) FIRST settings tested on the 015 x 60 , as a fast run could snap the .012's . Theres a thing. Now you know ! .



As youcan see , if all the bits are the same ( size ) and the injuns areat 7 inch out . ( both ) the nacelle sits onna rib . Theyre differant spaced . The Crank / prop isat the SEVEN INCH .
and does real good P.A. pattern , sharp , smooth , and clean . Easy to fly . Except if your stuck inverted on the outer in a gale . Inwhichcase Allways go DOWN on recovery . Not Up .

Naaa Na Na Na Naarrr ,


Moments and areas Oriental , asis WING . Tho is pulled in to 7 inch chord , Aft of spar , on the Woilwind .

Put the Mosq. in SPEED . 90 on 60s & 15 % nitro on 8 x 6's ifIremember Right . These ALL fly a Real Clean Pattern .

You can see a TIGERCAT'd be pretty much like the 262 . Just scribble over the O plan . The 262 is steadyist , mosq. jumpiest. Better for Combat . 

The W Wind was bouncey / porpoiseing , un poised! ( not much ) on 60 foot .016 solids on first flights in a good rural breeze . INCREASING the Handle Spaceing reduced the stretch / moment ration
and goot it  S M O O T H . Two Fox .19 plain Bearing nitro motors . Rocket Ship . 8x6's or 9 x 4s for aerobatics. Two Vecos in De H . ; G-15s , MVVS , FSR & FP 25s E.T.C. inny Da Messyschmidt .
OS 20 in rignil in 75 as was the W Wind . Were 40 ounce odd . But PICTURED are all 60 or better . Like 70 + . And'd match anyfing for P.A. on 70 ft .018 with 25s . If the Pilot got out of the right side of bed .

Have a fink .

[Scientifiction .]

Hell yeah.
I’ll take two sets for the Enya 35; one I’ll wear around my neck as jewellery and the other I’ll fly.

This leads to a funny story : Put Two OS .35 in the Mosquito , with big heavy props . The inner wouldnt needle , kept richening it . ON LAUNCH the
inner cleared , Full rich . Stafgger Stagger . And The Outer went to full tit . At the Pilot. Its done this before , Least Four Major out of control ( LOW SIDE AREA ! )


SO , if the NEEDLES dont MATCH , and Dont Set Right. HOLD IT . And SORT IT OUT . Or It'll Get Ya .

Collekt proceedure = IS . Start of week , Clear Needle , Flush Motor . Fuel one , start , Hold Vertical , needle in , then out two ( or Three ) Clicks . Shake the snot outof it ( Held Nose Up )
The doit on the uther . THEN they should BOTH be same r.p.m. and suchlike . And be set about right . ( Id use 8x6's or 8 x 4 onyer enyas ) .

IF you dont , youll waste fuel / flights , getting em runningwright . So PROCCEEEEDUREEE is everefing . MATE . Usuall damp , check fuels up , ' Bump ' Each & your set for one flick ( Backplip ) on each .
Evenon G 15 FI's .

good Plugs . 10 % or better Nitro . GOOD LINES . Check & PULL TEST . Nail the Control System in well . so if it cuts across the circle , it doesnt keep going , when it gets to the other side . BRACE the bell cranlk mount !.

[Steve Dwyer]

I recently built my Pathfinder Twin around two OS LA 15s and found it to be a bit anemic so I went to FP 25's and discovered the plane came alive and performed much better in the pattern. I'd be a little mindful of loading up a 350 in model with two 15 engines, it comes down to wing loading along with power. The 15s were snappy even with 20% nitro but with a 600 in thick wing and at 60 ounces they didn't have it. The TC will probably fly but the airfoil leaves me wondering what more you'll get out of it. Whatever you do keep it light!!
Steve

[Scientifiction .]

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[Scientifiction .]

B great big one . profiles allthats neccessary , though .

[Ken Culbertson]

Thank you for posting that video.  I am building a large twin right now and that was an inspiration.  I am going to make an observation that perhaps should have it's own thread.  Look at the overhang on Wendy's handle and the rather long flats in his round eight intersections, especially the vertical.  Is there a relationship?  Don't misunderstand, I can't come close to that pattern, I am only looking for cause and effect.

Ken