Out of curiosity, what are the biggest engines that you have run on a 40 size Big Stik (or similar)?

I have two Stiks, one with a Rossi 45 that absolutely screams, and one with a rather puny OS .40LA (not knocking the engine) that I want to replace. In the future I want to build a .60 size plane possibly powered by a 4 stroke. Is there an engine out there that would fit in that category but also power the .40 size Stik and handle well in the meantime? Has anyone gone through this same process? What modifications are needed???

By the way, both Stiks are tail-draggers, so big props aren't a problem. Also, the one that I want to switch the engine on is an older Stik that is tail heavy as-is so I think balencing will be a small issue only. I will be recovering this plane also so it is a good opportunity to make modifications if necessary (beefing up the firewall, bigger tank, other strengthening issues etc).

I have had a .60 sized engine on a .40 big stick. An old Fox Eagle I which weighs just a bit more than the K&B .60, needed just one ounce of tail weight. Actually the .40 sized Big Stick is almost as large as the old .60 Ugly Stick. About 2 or 3" less span. The K&B .60 weigh's just a little more than a .50 engine so I would chose that engine.

I am thinking about a Rossi or MVVS 61 size. I am really impressed with the power of the 45 Rossi I have.

Does the 40 size Stik (this is an old one) need any beefing up assides the firewall to cope with the more powerful engine?

I had an OS 70II 4-stroke on mine swinging a 13 x 8 APC prop and it was a blast. Sounded and looked good doing slow passes just over the runway. That big prop let me do outside loops at 1/3 throttle. Not blindingly fast but it would accelerate straight up and then keep going as far as I dared to take it. Moved quickly but not what I would consider fast. Maybe 80mph? Mine was a tail-dragger also. I had to add an ounce of lead in the tail. Lost *sob* to a mid-air. Fuselage hit a rock after a 400 ft drop with the remains of the wing (less the panel the other plane sawed through, snapping my wingbolts) fluttering cross country. Smashed the OS 70II and that ounce weight was IN the fuel tank after shredding it's way through the servo tray.

It was a darned fun plane.

When changing to a larger engine, you need to consider more than just engine weight. A Saito .91 weighs only 20.5 ounces with muffler on my digital scales compared to 16.5-17.5 ounces for most .46 engines (not the Rossi, which is heavier). But, you need to factor in a heavier motor mount and a heavier prop. All that being said, I have a Goldberg Extreme 330 that was going to be tail heavy by a few ounces and the big Saito balances it perfectly.

Most modern .61s and the bored out .75s and .91s in the same case weigh in at 25 plus ounces so a Saito .91 or even a Magnum, 22.5 ounces for mine with muffler, are a better choice. You will need a longer gear. You might need to mont both the elevator and rudder servos in the tail. I am using my Big Stick 40 for an engine break-in plane for .46 size engines or I would have done this mod myself. Mine has had an OS AX, a GMS and a couple of Mag .52s on it already.

I would fiberglass the firewall. The 4-stroke should use less fuel than a 2-stroke so you might want to use the same tank. I also would add 2-56 bracing wires on the tail. These will strengthen the tail and add a little weight in the rear.

Why go to a 60-size engine when a 75-size engine weights the same, may be even some 90's. Look into it.
My friend put a tower hobby 75 on his 40-size Duraplane. It started to scream, unbelievable verticals.

Do you want to end up with only a 60 later on a 60 plane?

I think the tower's 75 will be cheap and give you 2.2 hp, that would be better for a 60 plane later.
For now the balance issue of that and the 60 will be the same.

Have fun, and remember, when in doubt: just go a little bigger.

I think I might have a few people screaming at me on this soon.

Later

Flew the snot out of a GP Big Stik 40 wuth an OS 91 Surpass 4-stroke. It's demise was due to a dumb-thumb, not a failure of the aircraft.

Well, I just got restarted recovering and repairing the Stik, still a fair bit to do. In the process I am converting it to dual aileron servos and putting larger ailerons on it. Also chucking out the plastic wing tips and tail tips, I will probably also enlarge the elevator slightly if I can't re-use the same piece of balsa.

I have opted for the Magnum .52 (2 stroke) for this one. I flew my other Stik on Friday with a Rossi R45 and it scared the crap out of me, boy it screams!

Hopefully I'll have this one up in the sky by mid next week....

I'll leave the MVVS .61 craving for next year and for a bigger plane, and actually maybe get the MVVS .77.....

BOSS 351 I have a Magnum .52 in my Global Lucky stik and it goes straight up after a 5 foot take off roll. The climb out is as fast if not faster then a home sick angle. My (un) lucky Stik weighs in at a tad over 6 pounds. The .52 will hang on the pipe for a little while after running at WOT but it idles and transitions great.

Dru.