Richard_Strahl

Hey guys, been flying for a while but I've never really journeyed into modding or scratch building for myself yet. I'm really wanting to do a long range FPV pusher jet, but not really liking anything on the market. I've been playing around with the idea of taking a LX F-35 and doing a pusher conversion, but I'm not sure if I can fit a prop between the elevators. By going off of measurements just taken from pics, I'm estimating I'll have about 5.5" to work with if I disable the vector thrust. Would a 5" prop be large enough for such a large scale plane? Also, if anyone happens to have this model, could you tell me if I'm close of my measurement guess?
I'm also open to other suggestions if anyone knows a better route to go. I really want some sort of fighter and retracts are a must. I figured it'd be less of a pain to get a plane already set up with retracts than to install them from nothing [HobbyKing's SU-35, for example].
Thanks in advance!

Richard_Strahl

Would making it a slot prop be a better solution in order to use a bigger prop, or is that a whole other can of worms to deal with?

BMatthews

Off hand I would say that a 5 inch prop would not do the job. There's a bunch of reasons. In no particular order are;

• The exit duct is very close to 5" in diameter so that is going to blanket much of the prop. You could arrange for air to flow through the model but it would still not run at anything like full efficiency.
• The motor that turns the 70mm EDF unit will not be properly loaded down with just a 5 inch prop. So it will not generate the same amount of power. You'd need a larger prop at least. Some homework on the motor power and suitable replacements and props would be in order. At the very least it would require slotting the stabilators for a larger prop to be fitted. And that's still no guarantee of good performance. Pushers are well known for being less efficient for a given motor power output.
• To fly at the speeds it does, and assuming that is what you want, it won't save any appreciable power by using a small pusher prop compared to the EDF.

You also asked about doing a prop in slot conversion. Again the large size of the fuselage means that a good portion of a prop in slot will be blanketed by the fuselage cross section. So power transfer to the air will be low and you would need to go to some greater lengths to use a larger motor to get the same or less performance. On top of this you'd be trying to cut a really big slot into a key structural portion of the model. Prop in slot designs are designed with the slot in mind. They don't just cut a slot into existing model designs and call it a day.

If the EDF isn't what you want then I'd move on to some other design. The modifications you're considering are just not really a good idea.