wood props

[W.D. Roland]

never seen this posted so i will post it
make sure wood props are stored horzontaly.
if not the moisture in wood will settle to the low end and make props out of balance--sometimes bad enough to imediatly shake airplane and prop apart!
on full size aircraft i have seen the aftermath--prop exploded and engine pulled off fire wall
saw it happen on airboat--also broke back of boat off and broke crankshaft--scary as hell!
he was warned ahead of time--hard headed he was!(doctors know to much)
he did want me to build him a new engine one day--well did that and a new boat sooner than he wanted

my dad tought me this when i was young--never happend to me -yet

David

[Bob Reeves]

I have heard this but don't believe it, at least on the size props we use, no experience on larger props.. I have several boxes of props all stored on end, couple months ago after hearing this I pulled a bunch at random noting which end was down and stuck them on my GP prop balancer. Couldn't see any marked trend one way or the other, some had the heavy blade up, some had the heavy blade down and some were right on.

[W.D. Roland]

Hi Bob
do kinda agree with you and i think storage time/moisture of wood when sealed/finished has something to dowith it and size.
when i flew in competion back in 60s/70s props didnt need much balancing these same props stored for all these years
--some used-lots new-are wwwwaaayyyy off(vibrate the plane out of my hand off almost)

shocked me how far off every prop i have checked is.

maby im pickyer than i was at the age of 17/18--would this make up for cant see anymore?

[Richard Oliver]

David and Bob are booth right. Depending on where you are and where your props have been they can get out of balance with moisture. Direction of how they lay plays a small part as even a horizontal laying prop will get out of balance although somewhat less than one standing up. As Bob said is was not something he picked up on but under the right circumstances it will happen to him. He just hasn't had them yet. The wood makes a difference in how it may get out of balance. If one side is more dense than the other it will stay dryer as it has less pores to suck in water. We used to store our racing props in plastic bags with silica packs to keep them from changing. You can also expect your carbon props to do the same as they are also porous and will take on water. This can also be more or less on one side or the other. The RPM you spool up your props comes into play as to wheather they will show any noticeable vibration. You can also use the old trick of rotating the prop 180° to try and get it on the correct side of the stroke and use it to help counterbalance the piston weight. Just like the counterbalance on the crank does. This is not a good idea to always do as it also will speed up wearing out the bearing with a unbalanced radial thrust load. Mostly the front bearing. Just more dribble to worry and obsess about!
RO

[W.D. Roland]

Thanks Richard!
i had forgotten the rotate 180 thing!
we quit c/l competion in mid 70s and the sport and scale ive flown since didnt require the atention to detail as rat and combat--got lazy and never even checked props unless airplane vibrated.
no older and picky and been running self crazy balancing to the extreem--will get em close and rotate for balance!

thanks agin!
  David