H5487

Hey Guys,

I'm contemplating building a Carl Goldberg Sr Falcon with a pair of Saito 40s and was wondering if any of you had any thoughts on this. (Who am I kidding? Guys on RCU without an opinion??? )

I'm not rebuilding an ARF; the plane will be built from a kit and the building hasn't started yet. Besides building two motor mounts in the wings and beefing up the wing between the two motors, I'll also modify the fuselage with a rounded nose where the original engine would've been installed. I haven't decided between a nosegear or taildragger yet but I suspect that the gear will probably be retractable. (I'm an experienced builder and am capable of tackling such mods.)

Anyway, I'm open to comments and suggestions. (I'm probably gonna regret saying that! )

Harvey

Prop_Washer2

My Feedback: (26)

Do it, what you waitingm on mouth...???

WMB

My Feedback: (1)

Post a build of this one. I will be doing 2 Saito 45's on a 4*60 wing fit to an LT-40 fuse. I could use ideas for the engine pod's.
Thanks

jrf

My Feedback: (551)

The Sport Utility Twin plan from Model Aviation (AMA) would be perfect for you. It shows the necelles and rudder mods needed to convert a 60 size high winger to a twin using two 40s.

Jim

R8893

My Feedback: (20)

I have done three such conversions although on other kits. It ought to work. I have had 2 Falcon 56's. Only issue I can see is ground handling. Tricycle gear would probably be better especially considering the Falcon has such a small rudder. You might want to consider twin tails if you decide on a taildragger. My models (all current ones are tail draggers) that have rudders in the prop wash are better behaved on the ground. One other thing I learned the hard way: don't compromise the wing spar. Turning the wing structure into a "D" tube to maybe a couple rib bays outboard of the nacelles might be a good idea.

Chuck

H5487

Jim,

I read the Sport Utility Twin article when it came out in the magazine sometime back. I had already obtained a copy of Goldberg's Skylark 56 plans that showed how to build it into a twin and I have purchased the AMA's Twin Trainer plans in order to learn how to set up the nacelles, fuel system, throttle servos, etc. but your mention of the SUT article reminded me that much of it would also apply to my Falcon project. Thanks!



Chuck,

I, too, have had a long (and happy) association with Falcon 56s; hence, my selection of the Sr Falcon for my twin project. (There's some degree of securiy in staying close to our roots!) The Twin Trainer plans almost inspired me to go the twin tail route but I prefer that my project retain as many of its original distinguishing Falcon features as possible. In order to increase the single rudder's effectiveness (especially during an engine-out situation) I will likely enlarge the Falcon's fin and rudder.

The Falcon 56's wing has always been considered a weak point in its design and I already plan to beef up the center section in order to handle two motors. However, I had not considered continuing this strengthing outboard of the engines much. Maybe I'll also replace the kit's entire balsa spar with basswood.



WMB,

I'm considering using prefab (plastic) cowls for the fronts of my nacelles. If you'll go to the Tower website and enter "cowl" in the search box, it'll bring up all of the replacement cowls that they stock for the Great Planes kits as well as a few others. Then it's just a matter of selecting the style you like, in a size that will work, and building a nacelle with matching lines behind it. That's my plan, anyway. (While companies like Fiberglass Specialties undoubtedly offer more robust cowls than the thin plastic kit cowls that Tower sells, the Tower website conveniently gives dimensions whereas Fiber Spec does not.)



Gentlemen,

Your suggestions are appreciated. Keep 'em coming!

Harvey

PT21Flyer

My Feedback: (1)

Go for it!! I scratch built my Sr. Falcon Twin from original plans. I added 12" to the wingspan and built the wing in three sections with the nacelles on the center section. It flies great with two O.S. 40FP's. I also built floats for it. There is a picture in my gallery.

Jerry

H5487

Jerry,

I checked out the picture of your Sr Falcon Twin. What a neat plane! Got any additional pictures?

Thanks for the encouragement. Do you have any pointers, tips, or suggestions? (Engine thrust angles, wing incidence, balance point, etc?)

Harvey

jbarnes

Go here to see my Senior Telemaster Twin, probably similar to what you are looking for. Flys great, put about 40 flights on it this year.
http://www.rcuniverse.com/forum/m_70...tm.htm#7008113

PT21Flyer

My Feedback: (1)

Harvey,

The only other picture in my computer is this one landing with floats. I used the same amount of down thrust in the engines that is shown on the plans. I placed the firewalls at half the distance between the single engine firewall and the CG figuring two weigh twice as much as one so half the distance. I have my CG at about 35% of the chord to make it more manueverable. It flies great. I have flown it on a single engine with the wheels on several times including single engine take-offs.

Jerry

ps2727

Go for it! It will make a good flying twin. This is my brother's twin made with a Great Planes PT-60 and using two old OS .25 engines. He's got lots of single engine practice on this old bird.

Paul

WEDJ

Do it!

I would take almost all of the dihedral out. Maybe leave an inch or so. Yes, beef up the wing as others have mentioned.

Blue Note

Any progress yet? I have been contemplating this exact project using a couple 2-stroke 45s. I learned to fly when I was a kid on a Sr. Falcon and thought this might be the perfect twin modification. I hope to also us it a a glider tug, when the need presents itself. Although, I will probably go to a symmetrical airfoil, remove the dihedral, and go tail dragger - so I guess it's not really a Falcon after all, is it???