gchdavid

Hello guys,

First off, I know about the known issues/complaints about the FL-70. So far, mine hasn't given me any issues so as long as it keeps running, I will keep using it so lets keep the bashing of the particular engine out of this thread

I just finished a GP Escapade and I swapped my FL-70 into it from a H9 Cherokee that gave its last breath last week. The engine is broken in, idles acceptably and is pretty reliable. In the Cherokee, I had started out with a MA K-series 12X8" originally but with that prop it would sometimes backfire, to my knowledge that is common of overloaded 4 strokes, probably more noticeable here because its a non-ringed engine and the compression hits hard (I will attest that this was when first starting to tune this engine right after break-in and that is was my first 4 stroke). I then went to a Zinger 12X7 and it was great but it seemed slow for my taste so I changed it to an APC 11X8" and that is what I was running until now. The Cherokee was a heavy model so I didn't expect or want much vertical and the 11x8 gave it good speed. Now with the Escapade, I would still like speed but also vertical and the 11X8 is just falling short.

Should I try a 12X7 again but APC this time?

Go back a 12X8? Different brand?

What have you guys used?

I'm afraid if I go too big like a 13x6 it will have all the vertical in the world but fall on its face speed wise.

Thanks in advance.

Chris

w8ye

My Feedback: (16)

I've never seen a FL70 but the APC props turn the most rpm

gchdavid

^ Thanks for the reply. I do like APC props, I just need input on size...

I just read another thread, does anyone think I am "under-propping" this engine?

Chris

w8ye

My Feedback: (16)

I run a APC 13 X 6 on a Saito 62 and it seems to do OK

gchdavid

^ What airplane? How is it compared to a .46 with a 10X6 or 10X7?

Thanks for the input.

Chris

jimmyjames213

My Feedback: (2)

try a apc 12x8 and 13x6 see which one u like more

gchdavid

^ Is an APC 13x6 similarly loaded to a 12x8 or is closer to a 12X7??

Chris

w8ye

My Feedback: (16)

I consider some APC props to be made better than others.

Also props are a personal preference thing

You are going to need to try a few and find one you like.

gchdavid

^ I completely agree. My question is because tomorrow I will go to the hobby shop to buy props. I already have a 11X8 APC which I didn't like, I will for sure buy a 13X6 tomorrow. I want to buy another one to test, should I test the 12X7 or 12X8?

I know they are only 4-5bucks a piece but it still adds up, specially if I will end up not using them again ever but I wouldn't mind trying a few. I will definitely stick with APC though.

Thanks.

Chris

Harry Lagman

^^ Good advice

They are the two I'd try. Estimated rpm for these is a little over 9K for the APC 12x8 and somewhere in the mid to high nines for the 13 x 6. An APC 12x8 imposes quite a bit more static load than an MA 12 x 8 but in my experience performs materially better on any given model.

I'd also include an APC 12 x 7 in the set to try (for mid to high nines rpm).

ajcoholic

My Feedback: (10)

For wehat its worth, here are some numbers I took while testing this engine years ago when it came out. Props were Zingers, fuel was Wildcat 10 and 15%.

A fellow club member & friend of mine is still flying the test engine still on a scratch built pattern style plane, its running well.

AJC

Run #1 - Wildcat 10% Premium Xtra fuel

Prop Max RPM
12x8 9,150
12x10 8,320
13x6 9,120
13x7 8,160
13x8 8,130
13x10 7,050
14x6 7,800


Run #2 - Wildcat 15% Premium Xtra fuel

Prop Max RPM
12x8 9,330
12x10 8,430
13x6 9,150
13x7 8,160
13x8 8,190
13x10 7,140
14x6 7,890

w8ye

My Feedback: (16)

Looks like 13 X 6 & 12 X 8 are where it's at?

gchdavid

I am heading to the LHS to buy a 13X6 as well as a 12X8 so I can test them out this weekend. I will also test a Zinger 12X7 that I have.

We'll see where it goes from here. I will not have any RPM figures, just perceived flight performance to go off of. Regardless, I will post my findings.

Thanks!

Chris

gchdavid

Today I tried both 12X8 and 13X6 props. I have to say the 13x6 flew the plane with much more authority and that although I am pretty sure it hurts top speed, it makes up for it with vertical.

Today was really windy so its hard to determine what the top speed with each one was. As of now, 13X6 wins for me.

Chris

w8ye

My Feedback: (16)

We are glad you are getting somewhere with props for your FL-70

NM2K

My Feedback: (14)

I was going to say that my ancient Enya 60 & 80-4C engines (the .80 is really a .74 CID engine) love a MAS 13x6. Don't believe it? How about climbing knife-edge flight when powering a 7 plus pound CGM Anniversary Cub? I feel almost certain that your FL-70 will produce as much power as either of my old Enya four-strokes.


Ed Cregger