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Author Topic: Paper Prop blades  (Read 2311 times)
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outofbalance
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« on: February 06, 2008, 01:30:12 AM »

These blades are made from index cards; I use 4 x 6 inch but most stiff papers will probably work. This is not my idea, but I can't recall how I started doing it, maybe something from Flying Models or the Don Ross book on rubber models.

I face two cards, putting the lines to the inside and I cut a piece of Tyvek fiber material to go in between the cards, with the Tyvek a bit larger. To begin, I size the Tyvek and then with tweezers, separate the two parts starting at a corner. The fibers are evident, whispy and narley as you do this. I put wax paper down and take yellow carpenter's glue and put a lot on one card (photo); I smear it around with my finger until the complete card is covered on one side. I let it set for a moment, them put the Tyvek on it so the Tyvek sticks over the edges. I glue up the other card and put it against the Tyvek so I have a nice sandwich with all the glue inside the sandwich, not oozing out- tricky to do. You can get Tyvek in postal mailers or from a building site (house wrap).

I let this sit for a few minutes until the pieces do not swim against one another- it's starting to dry. NO glue is oozing out! I place the sandwich on a big , smooth surface glass jar and wrap it with an Ace bandage- nice and tight and secure it with those little medal things (photo). I take it to the oven and put it inside at 200F for an hour. I leave it there over night. If glue oozes to the glass jar, you're going to curse the next day!!!

The next day, I take it out of the oven, remove the bandage, and draw the prop blade shapes on the dry sandwich (photo). I do this while the sandwich is on the jar; sometimes I have to put a bit of tape to keep it in place. I use templates as in the soda bottle props. Remember the angles to use? Next, I remove the sandwich; it wants to curl a bit. Okay. Then I take scissors and carefully cut out the blades. Notice that the blades have a line on them where I will align the prop blade shafts. The rest is like the soda bottle props so I won't go into it.

These props are tough. Tyvek is a poorman's Kevlar. With the paper sandwiching the Tyvek, you have a blade that can withstand a lot of abuse. Because paper and wood glue so well to one another, I don't bother to use a broom straw to help hold the blade to the shaft BUT I put enough glue (I use Sigment airplane glue) to make sure I have a solid joint.

These paper bladed props are a bit heavier than soda bottle ones, but not as heavy as the plastic Peck six incher even though the ones I make are a half to three-quarters of an inch longer. The Peck six weighs about 2.0g. These are less.

The paper sandwich edges can be sanded with fine sandpaper, BUT, Tyvek does not like to be sanded; sometimes it get owlly and just wants to show a fluffy edge. Sometimes I just add a bit of glue around the edges if I've made a mess of the sanding. It holds the fiber ends fast.

I use bamboo shafts but I have used toothpicks, balsa square shafts, and basswood square shafts without using the aluminum hub. Sometimes the wooden shafts break on impact, but I can't recall I've ever had a shaft break with the aluminum hub approach with the bamboo skewers. The photos are below.

 
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Paper Prop blades
Paper Prop blades
Paper Prop blades
Paper Prop blades
Paper Prop blades
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julio
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« Reply #1 on: February 06, 2008, 08:26:49 AM »

outofbalance

Thanks for this cristal clear tutorial and the soda botlle props too. They are of great help for building light custom props.
Thanks again.

Julio
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outofbalance
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« Reply #2 on: February 06, 2008, 10:11:26 AM »

Hi Julio,

Thanks for your kind words.

I have made these props after finding out my landing gear legs were too short in the case of ROG; instead of cutting off the prop tips (or putting on bigger wheels), I made a prop that was scaled down to fit the situation.

Being able to change from one prop to another, or being able to increase or reduce the prop pitch is an advantage too.

Mostly it's about being able to have the prop you think will do the best job. I call that model engineering. After a while, I got the idea of taking the finished prop and dividing the length by the weight. This gave me a ball park number so I could estimate the prop weight in advance. For instance, the top paper prop in the picture weighs 0.28g per inch, the Peck 0.337g per inch and the soda bottle 0.242g per inch.

Below are some props and their weights for indoor.
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hermit
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« Reply #3 on: February 06, 2008, 10:45:51 AM »

Interesting, another unlikely type of material I'll have to start looking for. Could be handy in a number of situations to strengthen a part.

Doug
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outofbalance
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« Reply #4 on: February 06, 2008, 10:50:45 AM »

Hi Hermit,

I also use it when laminating flat wingtips, and at some dihedral joints.

oob
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« Reply #5 on: June 24, 2008, 03:35:32 AM »

what a novel idea, I have used Foam coffee cups from GLoria jeans for a long time now and they work well. They can break, but they do not break as easily as balsa does. What is Tyvek? I live in australia and was wondering if it was the same material over here as where you are?

Secondly, I saw that you have an alluminum hub to join the prop blade shafts together. Don't you find that the alluminium wears away at the bamboo, thus making it a slopy fit after a while? I have used lolipop sticks to avoid this problem. Have you tried this?

regards
Matthew
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Ployd
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« Reply #6 on: June 24, 2008, 08:38:22 AM »

Matt

Tyvec is quite common in OZ; used for those white disposable overalls (coveralls?) worn by painters and as insulation covering on new houses. Try Bunnings.

Ployd in OZ
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« Reply #7 on: June 26, 2008, 07:27:38 PM »

You know I use a plastic bottle as a form when I make thin balsa wood props but I never thought of using the bottle lol  Thanks for the ideas.

jeff
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crashcaley
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« Reply #8 on: July 16, 2008, 10:05:42 PM »

OutofBalance, That is quite a novel way of making props. I must search a few building sites for scrap Tyvek. Sure they will let me have a piece or two. What sized models can you use these on? I'm currently building a SortaSenator Bostonian. Is this model a good candidate for such a prop?

Caley
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outofbalance
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« Reply #9 on: July 17, 2008, 08:33:35 AM »

Hi Crash,

I have only used these paper props on small models like Embryo and Bostonian, mostly though, I have not designed the props for a particular model. I have tried the six and seven inchers on no-cal, stick body (Skinnycat by Ramon Katigbak) and a few others. I use 3 x 5 inch note cards but I think if longer props were needed, one could use heavier paper.

I have found that Tyvek® is a strong, resilient fiber coating. I cut the pieces to enlarged size, separate the layers, and glue one side and apply the Tyvek® to the paper prop blade, then coat the other paper shape and create the sandwich. I trim the Tyvek® flush along the edges of the paper prop, then wrap the prop around a round cylinder, the size of which will give me the curl at an angle of 15 degrees. I wrap the can or bottle with wax paper and then an athletic stretch bandage trapping the prop between. Sometimes I put the whole thing in the oven at 200 degrees F for 15 minutes and then after the oven shuts, leave it until the next morning

I usually make the hub from balsa but I have made some from basswood. I have a box full of props from experiments. Some were ineffective because I used only partial Tyvek® covering- these props broke near the hub. I have used a spar connecting the two blades of 1/8 inch basswood and offset angularly carved flat spots for the blade base.

I have also tried using a thin plywood spade that strengthens the prop at the hub attachment point, a kind of doubler. The hub was slitted and the blade base inserted.

Both balsa and paper are lighter than plastic. And, if I have done my measurements and sanding just right, I can balance these props much better than plastic. Sometimes I coat the props with 50/50 clear dope and thinner. If the prop is heavy to one end, I can add a bit of extra dope to the light end.

Currently I'm working on a paper prop with Tyvek® to use on my folding mechanism.

I use thinned carpenter's glue for the mastic but I have used Duco Cement, and Sigment. The Tyvek® is absorbent so plenty of mastic needs to be applied.

Outofbalance


Tyvek® does not like to be sanded!
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crashcaley
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« Reply #10 on: July 17, 2008, 08:46:48 AM »

OOB, Thanks. I may try one on my SortaSenator. If I can't get Tyvek, I will just stay with plastic coke bottle blades.

Caley
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outofbalance
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« Reply #11 on: July 17, 2008, 09:50:46 AM »

Crash,

I think that postal envelopes are also made of Tyvek®. Hit the PO!!!!!

Outofbalance
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crashcaley
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« Reply #12 on: July 17, 2008, 11:15:49 AM »

OOB, Roger, Wilco.  Smiley

Caley
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albackstrom
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« Reply #13 on: July 17, 2008, 11:28:13 AM »

Caley; Outofbalance is correct, go to the PO, Tyvex is very hard to tear, a large envelope goes a long way.
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« Reply #14 on: July 20, 2008, 03:45:07 PM »

Just for the "H" of it: here is an idea for an adjustable paper or balsa sheet prop form. Go to Lowes, and in the roofing dept they sell rolls of aluminum flashing material. Just loosen or tighten the roll till you have the desired
diameter. You can make different size props from now till the roof leaks.
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« Reply #15 on: July 20, 2008, 04:39:32 PM »

I realise that I'm straying from the prop subject, but I can recommend laminating Tyvek with balsa for a tubular fuselage (with the tyvek on the inside). It makes a bomb proof fuselage, and I've had motor breaks in coupe & P30 fuselages made that way, with no damage.

Not my idea I might add, I got it from the Don Ross book. Also I note that the decorating overalls suggested by Ployd are now available in dollar or pound shops - mighty cheap!

Peter
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« Reply #16 on: July 20, 2008, 05:09:46 PM »

I got curious about if anyone on EBay might be selling this stuff. And there are several. One is selling 9x1 ft pieces at $1.55 which I guess is probably fair if you don't need a whole roll. I would imagine that this size piece would make a lot of prop blades or rolled fuselage tubes. http://cgi.ebay.com/TYVEK-groundcloth-sheet-9-WIDE-Backpacking-Hiking_W0QQitemZ200240493695QQihZ010QQcategoryZ36120QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Caley
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tbolt
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« Reply #17 on: August 11, 2008, 01:01:57 AM »

Fed EX envelopes are the easiest place to get tyvek.
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