Author Topic: Efficiency of propeller blades.  (Read 4394 times)

Offline MattB

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Efficiency of propeller blades.
« on: September 03, 2016, 11:01:17 PM »
Hello Forum,

I saw these prop blades on board a cruise ship. They are secured to the deck with the help of eyelets.

My question is:- Does having the eyelet fastened to the prop make the propeller as a whole, inefficient? Do they remain on the blade or are they removed and the remaining hole 'filled in'? See attached cropped photo.

Regards,

Offline lappino

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Re: Efficiency of propeller blades.
« Reply #1 on: September 04, 2016, 01:04:53 AM »
They are screw-on eye bolts, easily removed.

Cheers

Vlad

Offline Frank Buckley

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Re: Efficiency of propeller blades.
« Reply #2 on: September 04, 2016, 04:44:31 PM »
Hi Matt Boy,
The reason for the eyebolts or lifting eyes is foremost for ease and safety while handeling the blades as they are some times because of their shape and form and weight quite difficult to lift and move. In 2001 I was in Rolls Royce in Ulsteinvik Norway when the Fore-man in the blade  grinding Department almost severed his leg off below the knee because it slipped out the crane while he was moving it about in the work place. Normally there is a hole bored through the blade. This hole is also chamfered (or slightly tapered at both sides).Then a special split plug is made which is fitted from both sides and retained by a bolt. The plug is fitted to the Blade and the blade is machined in two set ups on a 6 axis CNC Machning Center. First the face of the blade where it is bolted to the blade carrier on the propellor hub (and the hole patteren drilled). Then it is stood up vertically and the form or profile of the blade is machined with the plug in place. Then the finished machined profile is rough ground (by hand) and finished ground  still with the plug in place. Later for ease and safety reasons  while assembling the complete propellor the plug is removed.It refitted to the blade when finished for hydronamic reasons. The counter bore for the bolt head is sometimes filled with plastic resin and carefully smoothed off to give the apperance of that there is no hole in the blade. I hope that you can understand this. I have a lot of photos but first I must find then and upload the them but time is my problem (I have very little of it) Matt. I am not like Lappino I have to work for a living.  Sorry Vlad my apologies  its only a joke!!!
Best regards,
Frank

Offline Frank Buckley

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Re: Efficiency of propeller blades.
« Reply #3 on: September 07, 2016, 09:40:42 PM »
My pleasure MattyBoy. I am happy that you understand what I was trying to say.

Best regards

Frank

 

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