Why park a timber prop horizontal?

[Guest ozzie]

with all the rain over christmas, this thread reminds me i have to take the bathroom door off and seal the bottom as it has swelled up and won't shut. It does not get wet, just sucks up the humidity. not hard to realise what happens to an unprotected wood blades in the open.

 

 

[turboplanner]

Congratulations Destiny on a very methodical approach, results certainly surprised me.

 

 

[Guest Qwerty]

Thanks Destiny, Interesting result, I'm looking forward to further results.

 

Just to tighten up on our proceedure and to silence any potential critics of the results we need to have a controll for the scales. Mat I suggest a couple of sealed glass jars with dry gravel/rocks in them, as a check/control on the consistancy of the scales. One jar at about 2300 g and one jar at about 1200 g. Simply test the scales with these prior to and after each prop weighing to ensure accuracy.

 

How are you weighing each end. I guess that you are aware that it must be done precisely the same way each time.

 

I wish I had a spare prop and a set of scales, I'd do it too.

 

Cheers.

 

 

[Guest Qwerty]

.........Flaws - I guess someone could come up with some.

No worries Destiny, if your experiment tests your hypothesis and your method is consistant and you calabrate your your gear, then we have a robust experiment. Steel capped work boots can be legitimate laboratory equipment. Your method seems sound to me mate.:thumb_up:

 

 

[Tomo]

]Flaws - I guess someone could come up with some.

Only the one underneath all this... ;) :big_grin:

 

I'm surprised at the skepticism about storing the wooden prop horizontal, even if I new nothing about the old ways, or techniques, or wasn't a pilot for that matter, I'd store the prop horizontal...

 

Why? If anyone has worked with timber before you would know that.

 

First, you don't walk into the hardware store and see all the timber standing up on end, they don't just do that for storage ease! When a tree has moisture in it, it flexes back and forth, a bit like mild steel. When it dry's out, it becomes hardened steel, or brittle. So any little bit of moisture that it happens to get in or out (atmospheric changes is enough), it is going to turn into mild steel again, and bend or warp if it has to hold weight.

 

Second, what happens if you get a paddle pop stick (for example) and dip it in a cup of water, pull it out and don't shake or jiggle it? Water droplets cling to the bottom... what is at the ends of a piece of timber? How do trees get water to their leaves...? You guessed it... Get a bit of food colouring in say about 10mm depth of water and put the PP stick in it standing vertical... what happens? (say over night)

 

Thirdly, If water can come UP a stick... it certainly can go down it too!

 

Forth, Get a piece of steel, say 50x3 flat, and stand it up on end, it's very hard to keep straight, Lay it down, narrow side down, easy, wobbles back and forth but is solid as a rock the other way... Grab a prop and it wobbles back and forth as well, try and get movement out of it the other way!

 

Sealant, is great when it is there... but what is a propeller doing most of the time? spinning around at a million miles an hour, it WILL get moisture in there, I'd almost guarantee it, you can never seal something porous fully, especially when it is getting moisture driven into it.

 

I could go on for ages, but I think you'll get my point... I've been playing around with timber for possibly near on 12yrs now, and moisture is something you have to work with and around.

 

 

[Guest sirius]

We all know from basic principles of flight theory that the air in which we fly is a fluid in a gaseous state. Therefore any expansion or contraction, - humidity increase or decrease, will involve a fluid. A timber propeller expands and contracts due climatic changes and needs regular torque adjustment.

 

This is a fact. I have irrefutable proof in the form of recovered parts of air separation of a timber propeller which could easily have cost me my life.

 

A more practical reason if you are still not convinced is to consider the prospect of an insurance claim if it is proved the operator did not comply with the manufacturers recommendations.

 

I have a Sensenich propeller and I comply with their recommendations.

 

But then again, what would they know?

 

 

[Guest sirius]

results of my experiment 1

 

 

 

[Guest sirius]

results of my experiment 2

 

 

 

[Captain]

Well another fortnight has passed on my experiment and I find that the prop has put on a bit of weight overall, 44g. However it has been put on uniformally. It is still 1g heavier on the original light end. Which confirms to me that it was not subject to air circulation when it was lying on the hard floor for months and has now dried to a natural state & is just subject to slight absorption & drying conditions even though it is vertical but completely "aired".My conclusion is that it probably doesn't make a lot of difference how you leave it providing you have your aircraft in a hangar & don't get caught out in showers/rain. Perhaps if the aircraft was left in the open subject to dew, rain, sunshine etc uncovered or even covered there could be a significant impact on balance if not dressed horizonatally (not to mention life expectancy).

 

End of the day, I would always leave a timber prop horizontal as the argument sounds plausible. For short periods I doubt it would matter.

 

I have no little letters after my name so this experiment may mean exactly zilch, but was interesting.

 

Cheers

 

Dexter

Thanks DF ..... a lot ..... for your effort and time in doing these tests.

 

Very interesting outcome.

 

Regards Geoff

 

 

[skydog]

Fabulous work DF.

 

I am sure a lot of people have learnt a lot about these 'old wives tales' in aviation.