jjoos99

My Feedback: (12)

I am looking at getting an engine for a 59in katana that would be in the 7.5lb range. My question is can you overpower and have too much engine weight for a plane? I am looking at a evolution 10gx at 22 oz. I have been told it will fly the katana well as a sport plane but was recommended the 15gx which is 31oz for 3d. Looking at weights and the vvrc 20cc engine is the same weight as the evolution 20cc. How can you ever tell if your are overpowering or putting too much weight on a plane? concerned it might be too much weight or the airframe wont take the power of the large 20cc. I had this same model several years ago with a .70 surpass and needed to put the battery on the engine box and weight on the engine beam. so It wont be terribly nose heavy. Any opinions?
thanks
jeff

Steve Percifield

My Feedback: (14)

My opinion only. A 59" airplane is in the .60 glow size range. Which you said you proved using a .70 4 stroke. The 10 cc gas is a .61 ci, the 15cc is .90, and the 20cc is a 1.20 ci. engine. So you see the 20cc is doubling the engine size and in my opinion too much . If you had a .70 stroker and had to add weight, then the 15cc (.90) might be the right choice, just replacing dead weight with the engine. Believe it or not the left stick moves, so if it is too much power, throttle it back to a comfortable range. Engine selections, these days, are all over powered, because everyone has to hover , etc. People have forgotten that planes actually "fly". Now, just use common sense about reinforcing the engine box and front end. You said you fly, so you should have experience in this area. If in doubt, seek out a club member who can look at the plane and make recommendations.

Gray Beard

My Feedback: (-1)

You can over stress an air frame with too much power but like Steve said, the left stick moves. You can also get a plane too heavy and it will still fly but it can also have some strange stall problems. I have done both. I try to use engine weight to attain the CG though on planes I know will be tail heavy. I used a YS 1.10 on a small plane designed for a .50 two stroke but when Ziroli designed the Swoose he also needed about a pound of lead in the nose so I used the big engine and the heaviest spinner I could find to add the nose weight. I still needed lead up front. As heavy as the plane is it flies very well? The Katana is a very nice plane and can take the power so engine choice can be made by weight. Power is better then lead.Been a long time but I don't recall the Katana being that tail heavy tough?

jjoos99

My Feedback: (12)

The kantana I had previously did have the .70 and I needed more weight up front. It was also underpowered. It would fly it but the take off and departure was questionable untill I gained some speed. Horse power wise the 10cc is 1/2 horse power more and 3 oz heaver in weight. I am being wishy washy but dont want to spend $200 on an engine that might not be enough power.
thanks for the opinions
Jeff

Gray Beard

My Feedback: (-1)

I have zero experience with the new small gas engines but have been told they put out about the same torque/power as a four stroke glow engine. I never go by rated HP or RPM other then the RPM limits or working RPM range. The manufacture can adjust that just by using different sizes of props and props we would never use in real life.
If you go into the gas engine forum you can talk with people that are really using these engines and get more facts from a lot of users.

dandeeman

Jeff, it is a trade off, even though more power with a heavier engine, the extra weight may mean adding some more weight tailwise, all this "weight" now means the plane is heavier and now must fly faster to maintain flight. I too like to take the power / weight ration 1 step higher, just don't go 2 or more steps. Funny but I actually just completed a strange experimental project from a .75 size glo extra 300 I crashed this summer, the tail end from behind canopy back was unharmed, so I took it to club meeting & told them I was going to make it fly by adding a 36" wing and a nice brushless motor etc... the cg is the biggest concern. It is radical looking hope to fly it next Sunday They laughed so I am hoping to make them cry when it flys!
Dan

jjoos99

My Feedback: (12)

Thanks everyone for the advise. I just ordered a new 10gx. I think it will be a good choice for the type of flying that I do.
Jeff