3dinsane

I have a os max 61 fx and was wanting to put a prop on it 13/ 4 wide prop from apc was wondering if it would work on this engine I want this sort of prop to be able to give best pulling power thanks for help if anyone can I also have 13/6 apc and some 12

the Wasp

My Feedback: (1)

the 13x8 is 100% out.
what muffler what fuel??
I had an OS 61fx for years, made well, not overly powerful, and heavy. it will handle an APC 12x6 ok with the stock muffler.. with an old restricting pitts muffler I only got 10,400 RPM burning 15% Niro. I feel the 13x4 will be too much for it.
never the less if you have a Tach I would like to see the RPM number it would push with the APC 13x4.
the 61 is an ABC engine, no ring. and I have heard better pilots say you do not want to run an ABC engine too rich to keep it cool, because you will hurt the liner, so if you run a larg 13x4 you will have to run it richer to cool it. it makes since. the liner has to be hot to exspand.if you had an older OS ringed 61 runing it rich would be no problem. in that case you could probibly ok.

you should find a Saito 65 or 72, they will handle the APC 13x4 much much better than the 61fx will.
the Saito 72, 80, 82, & 91 are lighter engines, the 65 & 100 weigh the same as the 61fx, 550g.

Jim

3dinsane

I should of looked this up before getting this engine did not know it has same power as the ones you mentioned well all for learning. Anyway I will be using a tech with it and I’ll let you know what I get out of it

jaka54

Hi!
a 13X4 is just fine for any 10cc (.60) two stroke engine.
A little too little pitch but it will work.

the Wasp

My Feedback: (1)

the Saitos are 4st engines, they naturally turn lower RPM and turn larger props than the same size 2st will. your question for using the 13x4 on the 61fx is highly opinionated gestion because a lot of people fly engines at lower RPM with big props. you just don't see that up here. as I said, the 61fx is well made, so the engine will turn the 13x7, you will have to richen the engine considerably, and throttle response will be low.
glow engines run very well and very smooth with longer props because the longer prop has more momentum and that produces more of a flywheel effect. you can also set a lower idle with a longer prop. a heaver prop will produce more momentum too but not as much as a longer prop, adding more pitch without adding length or weight will only load an engine more.

Jim

3dinsane

Wel I tested it with a 13/4 wide apc got around 11000 to 12000 rpm seems to be fine I say around that figure because it’s not 100% tuned but that’s on 20 percent fuel from Weston models needs fine tuning now but seems to have the pulling power I want should get it hovering hopefully that’s on the os max 61 fx by the way

the Wasp

My Feedback: (1)

my 61fx must have been a very sick puppy!

Jim