Need help selecting the proper size engine
 

I am doing a scratch buildup of a Boeing B-29, i baught the plans online, they look to be a copy of an old controle line model. This plane has an 84 inch wing span, and is 58 inches long. The person i got the plans from claims this plane is designed for 4 .15 to .25 size glow engines. I feel that smaller engines would work, i was considdering 4 of the Norvel .74 engines. If anyone has any sugestions at all PLEASE e-mail me at [email protected]

Thank you
Adam

RE: Need help selecting the proper size engine
 

Hello!
I would use 4 OS .15LA engines swinging 8x5 APC props( I use these in my Kyosho PBY Catalina that weight 2,6kg). .74 engines might be to small...but all depends on the weight.
Regards!
Jan K
Sweden

RE: Need help selecting the proper size engine
 

What is the expected flying weight? I know the B17 flown at Bomber Field use 4 91 fourstokes. I would probably use 4 Saito 30 or 40 fourstrokes if it is under 10 lbs. I would up it to 4 Saito 72 or 91 fourstrokes up to 15 lbs. Hope this helps!!!!

RE: Need help selecting the proper size engine
 

the other issue to consider is the smaller a engine is the harded it will be to find 2 never mind 4 to run the same, all of them have a varience in them but I would not go with a .074 I think either the .15LA or .25LA would be a good choice, The LA engines are reliable and run well for a lower price and in a bomber you won't need a higher reving BB engine.

Hope this helped some
Dauntae

RE: Need help selecting the proper size engine
 

Adam,
.074's would do nothing for this size plane. 15's would be the absolute minimum if you built light enough. I flew a Royal b-17 with OS .25 BB engines and it was a great combination and the 17 is a 78" span.
Remember if you are underpowered there is nothing you can do but get bigger engines but, if you are overpowered you have a throttle to slow her down.

Todd

RE: Need help selecting the proper size engine
 

THank you for the info, it was very informative... BTW what is the weight of your b17? this model looks to be designed very light, but im going to have to change a lot of major design elements and im sure it will up the weight. I was also wondering, how the wings seperate from the fuse on your b17, this design is made for the main wing section to be fully attatched to the fuse with removable wingtips, and this is not acceptible to me, so im going to have to redesign it to have a fully detatchable wing. Any information would be great.

Adam

RE: Need help selecting the proper size engine
 

One tip that came to mind from a friend that has a twin is that he went with a servo for each throttle and they don't react even and one engine spins up a little faster and he said the plans he built from sugested to use flex cable with one center mounted servo and this was the reason, With 4 engines it might be harder to connect the linkage to one servo but you could use 2 servos and have one for the 2 outside engines and one for the 2 inside so if one spins up the engines faster than the other it won't make the plane yaw.

Just my $0.02

Dauntae

RE: Need help selecting the proper size engine
 

Thats what match boxes are for!!! Very low weight and and I would junction the two engine on side to each other, otherwise i would use 4 micro servos, like the HS-81 on each engine ganged and syncronized thru a match box. I have been looking at tubed wing designs they are much easier to transport and hold down the amount hangar rash to my wings and planes.

Have fun
Will

RE: Need help selecting the proper size engine
 

To be honest I knew about those but it slipped my mind, Good piont as I go sit in the corner with my dunce cap on[&o] LOL Keep us posted on this one, Seeing that twin fly was real cool BUT seeing a B-29 flying by would put me in in the back of me seat it should be a awsome sight to see with 4 engines roaring by.

Dauntae

RE: Need help selecting the proper size engine
 

Thank you for all of your help. Its going to be a long process... i have to compleetly redesign the plans to convert to a removable wing, add retracts, and a bomb bay. Keeping weight in mind i have decided to use the .25 la engine. Can never have to much power. I hope to re-direct the exhaust pipes with mid pipes and hide them as much as possible, i may up size the engine pods to do this, but i am trying to keep this thing as realistic as possible. If anyone has any advice on these kinds of modifications please let me know.

Adam