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Author Topic: Folding Propeller Designs  (Read 1009 times)
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Laminar001
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« on: April 04, 2017, 05:45:10 AM »

Hello

I don't know too much about folding propellers so thought I would ask the following:

I am looking for a good folding propeller design, if anyone might know of one? By good design I mean particularly the folding arrangement, ie the hinge points, hinge type, alignment and yes blade shape and type. 

Are the blades better laminated balsa or solid, should I cover with light glass fibre? What thickness should the blades be sanded to?

Where does one buy those tiny hinges required such as the old Jasco brand/type that used to be used? I.e Beautiful Bess BP: 

http://outerzone.co.uk/plan_details.asp?ID=2127

Is it better to buy a proprietary ready made item or make my own?

I would appreciate your feedback.

Kind Regards

Marc.
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hastf1b
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« Reply #1 on: April 04, 2017, 06:01:30 AM »

Have a look at here: http://volareproducts.com/BUY/index.php?main_page=index&cPath=70_74

Heinz
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Bredehoft
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« Reply #2 on: April 04, 2017, 08:05:04 AM »

There are also hinges on this page:

http://volareproducts.com/BUY/index.php?main_page=index&cPath=70_79

--george
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Laminar001
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« Reply #3 on: April 04, 2017, 07:15:02 PM »

Thankyou.
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faif2d
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« Reply #4 on: April 04, 2017, 07:44:01 PM »

Look for the Dwarf Dip III coupe plans.  They are on this site I think, if not they are on outerzone.  The designer Charlie Sotich gave very good instructions for a good folding setup including a jig to get the double compound angle for the tubing that acts as the hinge so the blade folds flat against the fuselage.
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Warhawk
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« Reply #5 on: April 05, 2017, 12:43:41 AM »

I've used the R/N type of folders, and I've even built some from 1/32" ply that had a twist that provided the angle that laid the blades pretty flat against the sides.  Now, for smaller models, I use a square aluminum tube, drilled with the prop shaft and two holes on the sides for the blade pivots.  I grind out the top and bottom to accommodate the aluminum tubing I use to hold the prop blades.  Then I use 1/16" aluminum tubing for the pivots and simply squeeze the ends with pliers to keep them in place.  Relatively simple, and they work reliably once everything works smoothly.  I put one on my Comet Cloud Buster (not flown yet), which should allow it to break my current record of 1:25 for that design.

Justin
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Laminar001
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« Reply #6 on: April 05, 2017, 05:19:01 AM »

Hello Justin

Thankyou for the information.

You could start a new thread on your Cloud Buster, people would like to see it.

Regards

Marc.
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Warhawk
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« Reply #7 on: April 09, 2017, 11:50:45 PM »

I'll try to post a few things on the Cloud Buster - we're prepping to move, so it's going to be crazy around here for a while.

Justin
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Hepcat
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« Reply #8 on: April 10, 2017, 07:11:39 PM »

Marc,
You have not had much response except the advice to buy what you need from ‘Volare’ Products.  I believe their service is excellent but as I make all the parts on my aeroplanes I have no first-hand knowledge so I will just say what I do myself. To clear up one point first; in the early days of folding propellers they were usually made from a balsa block, like a freewheeler with the hub and blades in one piece. The blades were cut away from the hub and then rejoined with hinges.  Round about 1950-60 things changed and since then the normal has been to make the blades separately, either carved from balsa sheet or laminated or moulded from wood or other materials. The hub is something completely different. When I first adopted the idea of separate blades I assumed the best way would be several layers of thin balsa glued together, twisted to a helix and left to dry.  For me they did not retain their helical shape so I changed to  carving from balsa sheet ½” thick and that is what I shew in the photographs.  I think that moulded blades with carbon included are better than mine but I have not had the materials (or the energy) to make any as yet.
First picture. I cut a rectangular blank for each blade, support it tilted at 45 degrees, and twiddle a piece of sharpened 1/16” wire through to pierce a pilot hole where the hinge will be.  Doing this at this stage when the rectangular blank can easily be held accurately easily trumps trying to jig a thin helical prop blade for drilling.  Also in this picture is the template for cutting the blade shape.
Picture two shews the side template in place which marks the cutting lines to give the blade its helical shape.  When marking these lines one blank is put on the top of the other.  There is nothing technical about this, it just means that the template has a plain part ½” wide at the bottom which makes it stronger and lets it sit flat on the bench. When one blank has been marked they change places so that the other on is on top and can be marked. 
Picture 3 shews the blanks with the side template removed. Note the liberal marking of the blanks with ‘LE’, ‘TE’, ‘TOP’, ‘BOTTOM’ and the scribbles on waste wood.  You omit these at your peril. Now carve the blades. Take it easy. There are no big pieces to chop off. I use calipers or a mike all the time to ensure parity of the blades.  Take care around the pilot hole. From there to the root needs to be about 3/16th (4-5mm). This can be seen in the foreground of the next photo. 
Picture 4 is cluttered because the base has been used for several things. All that matters at the moment is the piece of 1/16th wire glued horizontal to a vertical piece of balsa and is holding a piece of brass tubing in the pilot hole and the triangle for holding the blade at the correct angle at the three quarter radius point.  My triangle happens to be adjustable but a fixed triangle cut to the correct angle would be as good or better.  When the blade is accurately set up a drop of cyano is put in the pilot hole.  Picture 5 All that remains is to add a 1/32nd ply disk at each end of the brass tube, neaten the blade end and I cover with glass fibre and add blade stops of carbon fibre.  Picture 6 shews that the hub of these propellers is nothing more than a piece of 1/16th wire, attached to the spinner back plate and with a right angle bend at each end.
I am running out of time but I do have some other information on nose assemblies if there are any questions.
John
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denis
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« Reply #9 on: January 21, 2018, 02:36:58 PM »

Merci pour cette explication aussi simple qu'élégante.
Bonne soirée
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