i know this is probaly something that wouldn't work but the thought just pondered my mind

for the dual rotor type autogyros, would it not be posible to use correx for the rotors? Providing that you rounded of the LE and TE with some tape and also put some weight within the flutes to give it a bit of force for going round with.

thanks for any input, i know its fantasy but i'd love to have agyro that you didnt always have to be repairing those damn balsa rotors :stupid:

as i said its only a thought that pondered my head so please dont send any vicous replies saying "how could you be so stupid" ect

thanks,

Hi,

Just wondering what is"correx"? Is that the same as coroplast, the material used for making signs.

I started molding blades about a year ago for the same reason that you mentioned. It's a bit of a process getting setup but once you have a good mold it's easy to make the blades. If there is enough interest I can write up a document on the process.

Phil

yeh, corex is the the same as coroplast, what makes those damn ugly spad planes , but also very crash resistant planes, hehe

Hello Again, VTOL....

Interesting idea! Worth a try. It might help if the blade could be strapped over an airfoil-curved surface and heated in an oven, then cooled to give the material an airfoil shape???

Bill

Hi Phil

I would be glad to hear how you make your rotor blade mold ,and then mold the blades. i have been thinking of ways to do it for the last year or so, i wanted to make the mold out of two maple boards about 30 inches or so long and and have them hinged at the leading edge, the only problem is to route the female airfoil shape out of the two hardwood boards, i had planed on doing it on my router table, but have since given up and i am now looking for someone that has a CNC router, but so far have had no luck. I had planed to wet the material out on wax paper, insert it in the mold and then fill it with spray insulation foam before the resin hardens up . I dont know if it will work, but i plan on giving it a try -- someday. thanks

Earl.

Hi Earl,

I also talked with a machinist and showed him one of my blades and he said that it would be difficult to create a female mold with that exact shape. It would take many hours with a CNC and it would still have little steps or ridges that would have to be polished out. Just a quick overview on how I made my mold.

You start with a plug, a blade made from popular or any stable wood, and sand very smooth. Double stick it to a piece of window glass and fill the gaps on the edges of the blade between the glass and plug with modeling clay. Wax everything and spray with PVA, a release agent. Brush on a layer of polyester or epoxy resin. After that starts to setup start laying several layers of fiberglass cloth and soak with your resin. Make a wood frame about 1/2" larger all around than your plug and press down on your fiberglass and resin. Add more resin inside the frame to insure good contact. After it cures lift off the glass. Now you have the first half of your mold. Now setting on the frame with the plug facing up, wax and spray with PVA then paint a layer of resin. After it starts to cure start putting your layers of fiberglass cloth and resin and again press another wood frame, the same size as the first, into the cloth and resin. After it cures, drill a hole at each end through both frames. You will put pins or dowels in these holes for alignment later. Separate the two halves and remove the plug. You now have a mold.

Phil

Just wanted to mention that Bill Friedlander is also working on a similar method of molding the blades. Maybe he is ready to share his experience.

Phil

Good Morning from Wisconsin!!...

To keep this thread going a bit longer here are a couple of thoughts:

Some time ago I explored the possibility of having blades made by the process of "pultrusion". In this process a die, somewhat like an extrusion die is formed to the outer profile of the shape desired...in this case an airfoil.

Then strands of fiberglass, or carbon soaked in an epoxy resin are fed into the die and pulled through into a curing chamber. The shape that is formed can be as long as the strands of fibers.

For rotor blades, the parts could be cut to length.

I found a company in Pennsylvania (I think) that does this process, but the cost of making the die and the amount of material that the whole autogyro world would use, is simply not economically practical.

As far as a CNC die is concerned, there is a fellow near Chicago who has made molds for Michael Selig at the U. of Illinois for his airfoil studies. The name is Yvan Tinel, 1904 Techny Court, Northbrook, IL 60062. He reckons that a mold (top and bottom) would cost about $1500-2000. In order to avoid ridges he takes several days of constant milling to make the cavities. Usually runs automatically over a weekend. Phone is 847 509 1805.

Maybe we could get several of us to share in the cost to get a mold, then pass it around?????

Bill

Those "Ugly" SPAD Correx planes can be made in an evening. Some I've seen look better than many balsa things I've seen covered in film.

You can make an aerofoil blade (wing) in tens of minutes. The correx is folded in half over a wooden yard stick ~ SPAR. I don't think they would require any addtional weight as the material is heavier than Balsa. Normally the Planes end up lighter as they don't require any framework (ribs, logerons etc).

There is frequently a lot going on on the SPAD Forum:
http://www.rcuniverse.com/forumdispl...s=&forumid=235

i may think there ugly but it doesn't mean i dont like them

heck, i'm trying my own first spad out soon!

I've also been thinking of making Blades from Correx. I have a GIANT Huff & Puff with a 21cc McCulloch Petrol Engine still in need of it's blades. The project keeps getting put back further down the list.

I hope you try some Correx blades, be interested in how they work!

i've decided to replace my broken rotors with new balsa ones but as sson as they break then i'll try some correx ones, which probaly wont be long!!

Hi ya'll
I hear all of you, bottom line seems to be time and labor required
to produce blades, correct?
If you could have a fine precise blade in one hour would that be
to your liking? and no labor envolved.
If interested the method and details are on the Model Airplane
News web site. Address> modelairplanenews.com
Once there click on "Quick and Dirty blades"
You won't be sorry for the look see!
Have fun!

Hal deBolt [email protected]

Isn't there a router bit that comes close to the shape we want? If you glue a hardwood leading edge to a strip of balsa and then feed the whole thing through a router with this bit, it would come out the other end with a consistent shape. Once it is set up, you could make a new set of blade blanks in 30 seconds.

I have no idea what it costs to make a router bit to suit, if there isn't one already on the market.

It would be possible to use a surface planner. Take a typical 12" planner and grind the shape for the top of the blade in one area and grind the shape for the bottom in another area. I think some of these new surface planners use only two blades and sell for under $400. Probably would work. Maybe we could get Bill Friedlander to try it in his spare time.

Phil

Hi ya'll again?
Two things come to mind concerning your thoughts>
Correx> don;t know a darn thing about it. However it appears
to be flexible?
Know this> rotor blades must be STIFF, both span and chord wise. If not there would be trouble with a capital T.
Apparently the material is used for wings by bending the top piece over a spar which must create stiffness?
However blades are quite thin, a good airfoil is 10% of the chord
thick. So, a 3" chord is .3" thick.
Can that be created as a wing is with correx?
Machine shaping wood blades>
My factory had the ability to shape balsa wood, we did leading
and trailing edges, ailerons any lengthly piece in an airplane that
required a contour.
How was it accomplished?
First you must have a precision router machine. Not just one
of the portable type. Proper machine has a table and a fence.
Another machine is a planer which is a different breed.
The secret to shaping balsa is the cutter's rpm. It takes a high
rpm to cut smoothly. The router rpm is at least 10 tmes that of
a planer.
Needed cutter tool> we made our own, not difficult but is precise
work with tempered steel.
We did it "farmer style", the hard way but also within the ability
of most any craftsman.
Bottom line is if you have the machine and cutter you could
produce about 800 blades an hour.
Anyone need more info just E-Mail me, OK?
Sig Mfg. offers shaped stock but the airfoil is lousy and the
machining leaves something to be desired.
Again I say, forget this method. Go to the Model Airplane News
web site and click on "Quick and Dirty" blades.
You won't find more precise blades which are a perfect match
for each other and the method is simple modeliing plus very llittle
effort and time required and they work just fine!
OK? Have fun!

Hal deBolt [email protected]