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Old May 28, 2012, 06:59 AM
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How to build your own folders or.....

..stop wining and get your a$$es at the workbench!!

As it is difficult to get oversquare folders and some of you(me either) are sick of this broken nitro-props i want to show a simple way to get into that prop laminating stuff.
Even though most of the commerial prop manufacturers treat designing and building props as a secret voodoo magic i have to say that at least the building is pretty simple.
Designing is different,there is prop designing software available but if you (like me) are not in close touch with all the computer stuff and have no milling options its easier to modify your favorite fixed prop to a folder and take a mould of it.

The shown example is a 7" nitro-prop which have a massive inner blade-base.
In difference to the smaller 5" cam props the airfoil starts to get effective about 35mm from the center so i am confident that the efficency drop is much less than the 5"folders compared to the 5" cams.

Next post with pictures in about 1 hour,resin starts to get sticky

Yello
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Old May 28, 2012, 07:11 AM
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may be its the "re-invetion" of the wheel.

the oldest "making of" I found into the "MTB" number 9 from 1984.

the complete process was also decribed just years ago (2008-2009) in german rc-network about making a folder from the 8 "x 12,5" eagle prop - the fastest at this time.
no milling, no computer.....


there are 2 sources:

-using a gas prop and making a new middle part
-using a big hotliner folder with the wanted pitch and shorten and reprofile(!) it.

then making gfk- molds from these props or using a pair of identically rebuilt blades.
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Old May 28, 2012, 07:50 AM
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Quote:
Originally Posted by scorpion-fan View Post
may be its the "re-invetion" of the wheel.

the oldest "making of" I found into the "MTB" number 9 from 1984.

the complete process was also decribed just years ago (2008-2009) in german rc-network about making a folder from the 8 "x 12,5" eagle prop - the fastest at this time.
no milling, no computer.....


there are 2 sources:

-using a gas prop and making a new middle part

-using a big hotliner folder with the wanted pitch and shorten and reprofile(!) it.
then making gfk- molds from these props or using a pair of identically rebuilt blades.

its a more or lass cheap way. as far is true.
but compared with our actual calculated and milled forms we found, that these "old way" made props definately don't perform as good as what we use now.
using "java-prop" programm (made by dr. martin hepperle) calculating is not really difficult.
and to mill only one small mold for the blade is about 200 euro including the material - p.e. by stefan heuel in germany.
so with 5-7 pairs you will reach the break even campared to buying ready made props - imo a good rate.
Hallo Ralf,
So you think this would be a more or less useless thread?
Well i was asked to show my version of converting nitroprops to folders and as many of the guys here are not able to read german building instructions or have the option to design and machine props and moulds for me it seems not useless.

I agree,special desinged props for a specific application are better in performance than the modified ones.
I did not want to give the impression that modified props are on the same level but they have one advantage,you do not have to beg for it and they are actually available!
The new F5d folders are able to perform well in a small window,if you are out of this window efficiency drops and the advantage i gone.
Do you really think the massive 8x23 designed for somewhere arround 8kW is able to compete with a special f5d folder in the 2 Kw region?

Or do you think its better to stick with the available nitroprops and continue waiting and waiting until maybe you or marcus start to sell the good stuff?


But let the community decide, should i continue or stop??

Yello
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Old May 28, 2012, 08:51 AM
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not useless!
I think of course continue!
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Old May 28, 2012, 08:57 AM
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Originally Posted by Mreyello View Post
Hallo Ralf,
should i continue or stop??
Continue please. Even it's a boring topic for someone with 5+ years experience in folder building under his belt, this doesn't mean it's a waste of bandwith when someone who has the experience to build folders will share his knowledge with ignorants like me.
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Old May 28, 2012, 09:34 AM
What is Highspeed ?
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lass dich nit bekloppt machen yello

I say THANKS A LOT Yello for the experience you wont to give to everyone here, if someone not interested its like by watching television, you can sap to the next chanel.....

- AND I think my words speak for a huge lot of guys here in this forum, AGAIN thx. Yello.
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Old May 28, 2012, 11:03 AM
Carbon fiber is our friend
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APC is ok, but in many cases you can do better. For example, the CAM 5x5 is much better than the APC 5x5.

You only need one blade mold, so you can cut your plug from it's hub and alter it however you like. You can add pitch or make it fold better (not that important for speed planes). I usually start with something that is way too big and I cut, twist and sand them in to a new shape. I'm just using it for material really.

For the mold surface, I use JB industrial weld that I find at the local auto parts stores. It's tough to mix well, but a tip from Troy really helped there. Once you think it's mixed up, pour it from your mixing cup in to a second cup. Often the material in the bottom corner of the cup doesn't get mixed well, so this fixes that. It helps also if it's warmed up a bit.

Put a pivot pin in the plug before you make the mold. This will then fit in the mold then and give you something to wrap tow around. When the prop is cured, just grab the pin and give it a twist and it will come right out. If you don't do this, you'll have to drill every prop and hope the hole is the same on each one.
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Old May 28, 2012, 11:53 AM
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Mould-surface resin needs some time to get sticky so i have time to continue.


The prop i build should have the same size and pitch as the fixed one .
If you want to modify pich or diameter its now time to decide this.
Be aware that every prop (should) have its specific pitch progress that means that you have different,lower angels of the airfoil the more you get from inside to outside.
If you want to increase or decrease diameter at the inside you will change this and efficiency drops.
I perfere to cut proptips for reducing diameter to keep pitch progress, i never tried to extend diameter.

Same with pitch.
An example
If you have 50° at the inside and let me say10° at the tip and add 5° pitch ,you will have 55°( +10%)at the inside and 15°(+50%) at the tip so you will have the expected advantage only somewhere in the middle of the blade at the inside pitch is too low ,at the tip pitch is too high!

Thatswhy i recommend only small changes in pitch or diameter(at the inside)to keep efficiency!!
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Old May 28, 2012, 12:05 PM
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Thank you Steve for your input.
Sorry,cause i am building the mould right at the moment while i am trying to get these posts done i am not able to read and answer your comments emmidiately.

But i agree,there is lot of improvement potential, just want to set the basics now!

Quote:
, pour it from your mixing cup in to a second cup.
Did that a couple of minutes ago!
Yello
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Old May 28, 2012, 12:09 PM
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What a great thread ,, continue please...
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Old May 28, 2012, 01:07 PM
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ok, next step:

To get the prop -root done you need to add material.
As the prop-nylon material doesnt bind well with polyester or epoxy you have to sand the glued surface well.
I use a mix of short cutted caronfiber with resin, you can also use a poyester glasfasermix from your auto parts store
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Old May 28, 2012, 01:56 PM
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After resin got hard( i use L285 with fast hardener and add heat so it was hard after 1 hour) you can take out the shaft by turning and pulling as steve mentioned!
Remove prop from board
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Old May 28, 2012, 01:59 PM
FlipF5D
Joined Nov 2007
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Quote:
Originally Posted by scorpion-fan View Post
"good stuff":


for f5d a 10" x 20" prop can be with less than 2 gramm/blade! much thinner and also smaller in blade depth.
btw. jan used this weekend a f5d model with the 8,5x23 and other massiv folders succesful for speed. (347km/h)

so your thread will be interesting for all modelers, who didn't have our possibilities by their hands!
Ralf,

I saw it on saturday, do you really think that these set up was effizient ?

Br
Jens
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Old May 28, 2012, 02:16 PM
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you never will find the "all in one prop" for all kind of flying and every model.
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