OK, after having a Brodak "Tigercat" kit sitting in my office for over 2 years, I have decided to take the plunge and build the darn thing.  I have had some experience in the past few years with twin engine planes, but never with a Carrier twin.  I recently bought 2 NIB Thunder Tiger 18's for use in this plane.  What I need are some ideas, problems, suggestions etc on building and flying this plane.  I am open to any suggestion except '" Forget it!" HELP!!!
Joe

Joe,
never built the kit, but the ones I have seen come out heavy ( typical Twin problem anyway). I'd look for ways to lighten it, also I've heard the cowls are too thick. OK for scale but violates the carrier fuse thickness spec. It probably would be a better plane with electrics for carrier, but I don't think you will go that way.
John

I'm dabbling in twins, too.

I finally built a 1/2 A twin and got it to fly OK on the first attempt.

The secret of my success is building a 2-engine mockup of the plane and confirming that I can get the two engines to perform properly before going any deeper.

There might be a twin carrier job in my future, but only after I assure that I can get the two engines throttling right on a stand.

That is one of the reasons that I plan on the next Tigercat of doing external controls.  There is not enough room for a decent fuel tank.  The props on mine are just ahead of the cockpit/pilot area.  Also starting and adjusting both engines is no problem if you take time to run each engine first and adjust it.   May have to make minor adjustment after a flight.   But, don't we do that with single engine planes already.

I don't see any point in entering Class I or II without the 100-point scale "bonus" (actually more like a non-scale penalty).

As far as a Tigercat entered in Profile, I would view the fuselage as the the fuselage and consider the engine pods as "reinforcement needed for safety".  Good luck.

In my opinion, the Achilles heel of all twins is the need the beef up the structure between the two engines to avoid vibration and stress issues.  Any point bonus given to twins is well-earned.
 

 Although probably not the wisest choice for serious competition, twins are nothing to be afraid of. It's just another thing that too many people overthink in my opinion. Well designed and built and with dependable, user friendly engines, they are not a problem. Weight can be an issue, but it's managable. As far as wing vibration/strength or whatever like mentioned above, I don't consider that a true problem either. My 64" span PBY stunter uses standard a "D-tube" construction wing with 1/4" square spruce spars and constant 1/16" center sheeting between the engine nacelles. It runs and flies smooth as silk with two Saito .40's. The only additional structure I added into the wing was an extra 1/4" square top and bottom spar running between the engine nacelles, about halfway between the main spar and wing T/E. Some designs use this extra "mid spar" anyway, so in a sense it's not even "extra".  

 I've got a Brodak Tigercat and two NIB LA.15's on the shelf as well that I would really like to get going on. Might even be the next project. It will be built just for fun sport/stunt flying without throttles. On it, one thing I plan to consider is spacing out the wing ribs just a bit to gain a little wing area. Maybe like 1/4" to 1/2" each, sure won't hurt. That would help wing loading a little without deteriorating the semi-scale appearance.

Hey Doc, how about some photos of your Tigercat?

I scratch built this 41" span Tigercat (F7F-3N) version for CL scale and it has two OS-15FP's for power and would not get off the deck with that for power. The model was built before John Brodak released his kit so this model is now quite old. The external controls that I have works great and it has electronic controls built into the fuselage, wing and naccelles which meet the 3/4" rule.  The wing is also scale 18% thick at the root and 12% thick at the wing tips. The model flies great and has hundreds of flights on it now.

The Naccelles and fuselage are 1/16" balsa sides with 1/2" balsa sticks on the inside making the thickness just under the 3/4" rules. Note that the Naccelles and the fuselage do no have any plywood doublers and they are doing just fine....the doublers are not needed. I covered the model with Sig Koverall and then Sig Dope finish, so the structure is not even have fiberglass which could strenghten the structure even more.

Hopefully the .18's would be enough power to get something off the deck, the 15's I have on my model would not be up to the job.

Good luck,
Fred Cronenwett

All this Tigercat talk has reminded me of another one. Published in FM 1968 by Bob Adair, a bit larger than Brodak's  but builds light. FM still sells the plans. It would be nostalgia legal also.

Some more pics

Well, first of all thanks for all the advice.  I without a computer for 10 working days and it has taken me some time to catch up with over 200 emails to answer.  During all that "down time" I have been pulling out my hair trying to get a standard 3-line bell crank setup to work on a test board.  The first thing I did was to make a copy of the Brodak plans and mounted it flat on my testing board. I drew lines reflecting the position of the engine etc and proceded to get the system to work.  Boy am I glad I didn't build the wing an d attempt allthe "teaking" needed to get the system working at what I call 80% efficient.  Not good enough, even for this ham handed builder.  Then it dawned on me....."Joe you dunce, why not use a 2.4 system?"  Even with my limited manual skill I found the 2.4 easy to use in two other ; but yet unflown Profile ships.  So, my next trip to Radio Shack will bring home a new battery pack with on-off switch included.  Then a quick trip to Tower Hobby for a Splitter wire and I should be on my way!  Other personal and hobby projects are still in the way, so I wont be starting the Tigercat just yet.
Again, Thanks to all for the advise etc.  Your all just great! (well most of you anyway)
Joe Just

later today a picture or two of my latest .15  Carrier plane.  Time for the release will of course depend on getting the local TV station and newspaper people here to view it.

Joe,
Good luck on your project. You have encouraged me to finish my Bob Adair Tigercat, but alas as an electric. If not this year, then in a year far away.
john

One of the tricks I use to sync the engines on my twins is this procedure

1) start left engine, adjust needle valve for full power and verify idle, shut down engine

2) start right engine, adjust needle valve for full power and veriy idle, shut down engine

3) start both engines and run to full power and slowly pull back throttle stick until both engines shut down, but take notes on which one quits first

4) Take the engine that shut down first and lengthen the pushrod between the servo and engine by turning the clevis maybe two turns.  You will have to disconnect the pushrod from the engine to do this. Making the pushrod longer makes the engine run faster.

5) Repeat step #3 and #4 until both engines quit at the same time, very minor adjustments in the clevis position from the servo will sync up the throttles. Trying to Sync up the engines with the high speed need valve never worked.

Twins are a blast.....Ever since I have used this trick all of my twins Idle at the same setting. Unless you fool with the pushrods or engines you don't have to do this every flying session, although I do run both engines in the pits before putting up a flight just to make sure.

Fred C.