DarZeelon

As I repeatedly wrote in this forum, I always start all my engines by back-flipping the prop - bump-starting against compression...
I tell others to prefer this method because it is safer than forward-flipping

Today, my Saito .72 repeatedly started backward, perhaps it was over-primed, or the fuel tank overfilled to a point the muffler could 'draw' fuel through the breather...

It did it three times.


So, without thinking too much, I proceeded to try flipping it forward over compression...

Yup! It was with the 'meat cutter' APC 11x6 four-blade prop.


The results appear in the photo.

rcdude7

My Feedback: (264)

Ouch, I would'nt wish that on anyone. Get a little glow fuel in there and it really smarts.......[:@]

djlyon

Don't you folks have chicken sticks over there. When I look at how cut up my chicken stick is I know I don't want to use finger not even for back flipping. In the old days when my hands were young and fast and the props I used were wood only, I used my bare finger and still suffered a lot.

Denis

nothinbetr2do

looks like you have gotten your middle finger before. you should buy a chicken stick

djlyon

A little CA will fix that right up.

Denis

Motorboy

You must be glad you do not lost your finger. The APC are too sharp as razor blade.. buy or make own chiken stick of hard wood with rubber hose around.

Cyclic Hardover

My Feedback: (3)

Looks like a "R/C Revver Brothers" gang sign. Yo!

AMB

Dar they also make a black rubber guard that goes over the flip finger ( I use one) if you do not use a chicken stick looks like we are are members of the S.U.F.S ( sliced up finger society) I really do not like the initiation requirments however all kidding aside it could have been a lot worse happy healing martin

Jim Thomerson

At least get a heavy leather glove.

Flyboy Dave

My Feedback: (21)

Yo, Cyclic....here's the correct "hand sign"....left handed....[sm=red_smile.gif]

FBD.

blw

My Feedback: (3)

Ouch. Glad it wasn't worse.

BTW, what kind of RPMs are you getting with the 11x6?

RaceCity

DAR!!!! Gee whiz man....what did you do with those starter parts I sent you anyway??

FWIW....this is the best starter on earth. 3/8" oil cooler hose slid over a piece of wooden dowel. Cost about $1.00 to make, and lasts for years before the rubber hose needs to be replaced.

If it won't start with this, you can use it to beat the engine to death.

nothinbetr2do

that's a good idear, next time i need a chicken stick thats the way i'll go. but i preferr the stomp method

DarZeelon

They are installed and the starter is set up and later I used it...

(I still made two flights after this injury)



I am so used to the back-flip that I don't bother to take the starter out of the flight-box...

This was my first blood-draw in over five years... (I actually don't remember when the last time was)

I never hurt any finger that badly, anyway.


Thanks to all the well wishers - I appreciate that.

krayzc-RCU

My Feedback: (31)

http://www2.towerhobbies.com/cgi-bin...?&I=LXL405&P=7

http://www2.towerhobbies.com/cgi-bin...&I=LXC019&P=ML

Hey tower doesn't call this Chichen stiicks

DarZeelon

It is a fact that with the four-blade prop, the next blade arrives where the flipping hand is, earlier than would the next blade of a two-blade prop...

After all, there is just 1/4 of a turn between blades... not one half of a turn.


What hit my fingers was the advancing 'next' blade... It was not even the flipping index finger that was hit.
I just could not move my hand out of the way fast enough...

This may have not happened had it been a two-blade prop.
And with a 'curved-back' tip, rounded leading-edge of a Bolly Clubman, it would not have resulted in such a nasty gash (even if it would have hit).

It nearly 'scalped' that finger...

DarZeelon

Barry,


It is in the RPM forum.

10,850 RPM is the number.


Had it been higher, I would have needed another prop... the recommended red-line for this Saito is 12K...

Hobbsy

My Feedback: (102)

Take care Dar, I did similar a while back when I carelessly flipped a Diesel engine. The engine had run out of fuel on my test stand, I carried it back into my shop and placed it on the workbench to remove it from the PSP. I gave it a flip and whack. I knew better, just didn't think.

blw

My Feedback: (3)

Thanks. Good figures for the prop. I agree that 10,800 is about enough on the ground.

pe reivers

I hate chicken sticks and always use backflip OR an e-starter OR an archer's glove for the small diesels (leather fingers only, strapped to wrist)
On a 4-stroke, a spinner is handy to backflip. These guys are heavy on anything that touches the prop whilst starting.
Good healing DAR!

AMB

Hmm bad week for cuts and gashs was rough housing with my wolves and got nailed by a dew claw (Dar saw the wolves when he has over here )about a 2 inch gash on my forarm . they were just playing but wolf skin and hair a little tougher than human skin martin

DarZeelon

Thank you, Dave and PĂ©.


As I wrote, it comes from a total disregard of my own advice, together with my not taking into account the light prop (despite its four blades), the higher cylinder pressures of the Saito four-stroke, as well as (maybe) my flip having become slower.... all which culminated to bring the prop's next blade and my fingers, to occupy the same space at the same time...

After having bandaged this injury, I did make a couple of flights and even managed to break two of these props... despite the increased ground clearance... expensive!

Maybe this was revenge...

I have been flying with this prop for the last four months, without such a mishap.

blw

My Feedback: (3)

Other than the propensity of the prop to slice your finger, how do you like the performance of it on the .72?

DarZeelon

Barry,


The static and the low-speed thrust of this prop is unbelievable!

It 'prop-hangs' this plane and one of the easiest things to do is to abort a landing, even right out of the flare, inches off the runway!

In flight is seems to lack some speed, however.


It behaves like it has a lower pitch than what is stated and is is a bit lighter than ideal for this engine (I would prefer to prop it to about 9.9-10K RPM).


The blade roots seem less robust than those of other props, since they are narrower - what leads to complete blade breakage if the ground is contacted, or even if going into thorny grass, or shrubs, that other props simply ignore...
After this happened on the first flight Saturday, I was intending to restart and fly again, before I noticed the prop only has three of its blades...

The fact that this frail, ankle high bush caused a blade to break-off, surprised me...

Motorboy

With your old age fingers [sm=49_49.gif], it is time to buy electric starter to save [sm=drowning.gif] your fingers from sharp propellers [sm=lol.gif]