Author Topic: a set of 9" blades  (Read 4987 times)

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willib

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a set of 9" blades
« on: February 13, 2006, 01:27:55 AM »
They are nine inches long because i wanted to test the process out before i attempted a larger set.

I cut them out of insulation and fiberglassed the outside , well most of it .

The glass made them very rigid..


below is the leading edge

 http://www.otherpower.com/images/scimages/2965/IM001429.JPG 87KB


the inside

http://www.otherpower.com/images/scimages/2965/IM001430.JPG 91KB


the trailing edge

http://www.otherpower.com/images/scimages/2965/IM001427.JPG 76KB


the twist

http://www.otherpower.com/images/scimages/2965/IM001438.JPG 59KB


two more on the way!

http://www.otherpower.com/images/scimages/2965/IM001432.JPG 84KB


They will be 12.5" radius or 25" in dia. when mounted on a hub.

it really spins nicely , i put it on a small hub , and used a fan on it.

each time the blade passed the air flow it sped up.

i cant wait till i get all three done !

« Last Edit: February 13, 2006, 01:27:55 AM by (unknown) »
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ghurd

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Re: a set of 9" blades
« Reply #1 on: February 12, 2006, 11:21:33 PM »
Never saw any taken to that extreme at the root!


Fans suck as a substitute for clean, real, outside wind.  Meaning if it works much at all in front of a fan, it'll scream outside!

G-

« Last Edit: February 12, 2006, 11:21:33 PM by ghurd »
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willib

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Re: a set of 9" blades
« Reply #2 on: February 13, 2006, 09:10:16 AM »
I used this info in the warlock blade program..

num blades = 3

tsr = 6

efficiency  .4

blade radius = 1 foot


and below got this info out..


http://www.otherpower.com/images/scimages/2965/blade_info.GIF 28KB

« Last Edit: February 13, 2006, 09:10:16 AM by willib »
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kitno455

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Re: a set of 9" blades
« Reply #3 on: February 13, 2006, 09:15:40 AM »
ghurd what not suggesting that your profile was wrong, but rather that most folks are too lazy to build that big part at the root. there is so little power there anyway. but it should help low-speed start up nicely.


they look good. you gonna fill the grooves with some bondo or something?


allan

« Last Edit: February 13, 2006, 09:15:40 AM by kitno455 »

Dan M

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Re: a set of 9" blades
« Reply #4 on: February 13, 2006, 10:13:23 AM »
I think it's wonderful to see someone actually pay attention to the inner 1/3 of the blade design.  So many blade designs we see essentially "throw away" the inner 1/3 of the blade by having such a huge angle of attack that it's almost always stalled.


I haven't actually calculated it, but I think the power available in that inner 30% of the blade is far from negligible.  The velocity is low compared to the tips but the lift vector is pointed in a much more useful direction than at the tips.


Have Fun,


-Dan M

« Last Edit: February 13, 2006, 10:13:23 AM by Dan M »

willib

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Re: a set of 9" blades
« Reply #5 on: February 13, 2006, 10:15:05 AM »
Here i'm glassing the blade to the cedar root segment

i covered the resin & glass with 'Glad cling wrap' to feather the edges.

i'm not sure if you can see or not but in previous pics i didnt use the cling wrap,

but last night i tried it and it really works well.

i also used scotch tape to hold the ends of the glass down against the blade.then the cling wrap over that..

http://www.otherpower.com/images/scimages/2965/IM001439.JPG 88KB
« Last Edit: February 13, 2006, 10:15:05 AM by willib »
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willib

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Re: a set of 9" blades
« Reply #6 on: February 13, 2006, 05:14:24 PM »
Thanks :)

the grooves will be covered with fiberglass .
« Last Edit: February 13, 2006, 05:14:24 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #7 on: February 13, 2006, 05:17:07 PM »
since i make them from the root out to the tip , i could maybe check their performance as i go..


.

« Last Edit: February 13, 2006, 05:17:07 PM by willib »
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RP

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Re: a set of 9" blades
« Reply #8 on: February 13, 2006, 09:23:36 PM »
Okay, I'll bite.  What's the deal with Mr Lawson?
« Last Edit: February 13, 2006, 09:23:36 PM by RP »

willib

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Re: a set of 9" blades
« Reply #9 on: February 13, 2006, 10:21:12 PM »
it is just as it reads , i got this email , i replied , but it got sent back ..as undeliverable ..

No  reply yet, i'm gonna wait till tomorrow AM.

.
« Last Edit: February 13, 2006, 10:21:12 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #10 on: February 14, 2006, 09:58:38 AM »
I was able to get the other two started last night.

Those pegs are screwed down from the other side, and i used resin on them  just in case


http://www.otherpower.com/images/scimages/2965/two_new_blabes.GIF 78KB

« Last Edit: February 14, 2006, 09:58:38 AM by willib »
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Experimental

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Re: a set of 9" blades
« Reply #11 on: February 14, 2006, 10:18:05 AM »
    Hi Will,

   Looks great, and you can use foam for the hub as well -- just drill oversize holes at the bolt locations -- glue a wooden dowel in and drill your mount holes into the dowel -- this gives you a "hard point" to bolt to, and won,t crush the foam after glassing in !!

   Very nice, Bill H.......
« Last Edit: February 14, 2006, 10:18:05 AM by Experimental »

willib

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Re: a set of 9" blades
« Reply #12 on: February 14, 2006, 03:04:20 PM »
thanks :)

i'm having  a hard time picturing what you described?
« Last Edit: February 14, 2006, 03:04:20 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #13 on: February 14, 2006, 10:05:24 PM »
Thanks , i'd have to agree about the inner 30 percent of the blade .

How would one go about calculating that?
« Last Edit: February 14, 2006, 10:05:24 PM by willib »
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paradigmdesign

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Re: a set of 9" blades
« Reply #14 on: February 15, 2006, 02:33:19 PM »
What is the length of the final blade you are building?  The airfoils that I gave you were for a 6 foot blade, I belive they were 8 inch sections between the airfoils.  If you go off too far from that length, you will start to get aerodynamic losses.  Looking  better with the glass on it thouhgh.  You may also want to look into a jig to keep your airfoils in the correct place.
« Last Edit: February 15, 2006, 02:33:19 PM by paradigmdesign »

Experimental

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Re: a set of 9" blades
« Reply #15 on: February 15, 2006, 03:42:24 PM »
   Hi Will,

   The center hub is what I was speaking of -- if you make the hub, that you will be mounting your blades to -- where you intend to bolt it to a shaft or hub, if made of foam, with fibreglass cover -- you need a "hard point" to bolt to -- so you don,t crush the foam..

   The ones I made, I drilled a hole in the foam, about 3/4" in diameter -- coated a wood dowel with epoxy, push it into that hole in the foam -- then glassed over it and after all was cured -- the shaft, or hub mount holes, are drilled thru the glass, and aprox center of the wood dowel -- say a 1/4" hole in the center of a 3/4" dowell-- when the bolt is tightened down with a large flat washer -- it gives you a "hard point" to bolt to, without crushing the foam hub !!

   Hope that is understandable -- but if your center hub is wood, you won,t have to worry about it, just a lot heavier !!

   I had built several prop sets, with, the foam and glass cover, and used a carbon fibre Arrow shaft, on several -- to act as a stiffening spar -- they worked good, but I finally went back to wood, seems like less work !!!

   Looking foreward to seeing your finished product, Bill H.......
« Last Edit: February 15, 2006, 03:42:24 PM by Experimental »

willib

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Re: a set of 9" blades
« Reply #16 on: February 15, 2006, 09:57:51 PM »
The large  set that i'm working on  are going to be 50 inches , 10 sections , 5 inches between airfoils  .about 4.2 feet

with the airfoils you gave me i was able expand and contract them as needed to get the chord length right for each section.

as for the small set i've found that if i square up the blocks before carving i should be able to keep the leading edge much straighter than the first one.

more pics to come

« Last Edit: February 15, 2006, 09:57:51 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #17 on: February 15, 2006, 10:09:32 PM »
I get ya now , thanks :)

the hub is foam, at the moment .

the dust gets all over , i do wear a mask when carving and sanding,

Carving isnt that bad but sanding would be a lot  more fun if it was warm and i could do it outside.
« Last Edit: February 15, 2006, 10:09:32 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #18 on: February 18, 2006, 08:27:35 PM »
A few people here have used the blue foam insulation for making blades , i think.

one problem is , it is extruded styrofoam which does not like being in contact with fiberglass resin (polyester resin) .

Somone recomended somewhere that i should paint the styrofoam with latex paint before i use the fiberglass and resin on it? has anyone tried this?
« Last Edit: February 18, 2006, 08:27:35 PM by willib »
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rotornuts

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Re: a set of 9" blades
« Reply #19 on: February 19, 2006, 08:49:33 AM »
I have and I'll say it's a no go. I have tried using a waterborne clearcoat varnish though and on a small scall it performed well. I've read that Minwax Polycrylic may work as well.


the project below was done with a double coat of latex primer and it worked but not without an unacceptable amount of distortion. The shear size of it allowed me to smooth it out but with a small blade it would be ruined.


Mike

« Last Edit: February 19, 2006, 08:49:33 AM by rotornuts »

rotornuts

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Re: a set of 9" blades
« Reply #20 on: February 19, 2006, 08:51:15 AM »
The image intended for above...




« Last Edit: February 19, 2006, 08:51:15 AM by rotornuts »

willib

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Re: a set of 9" blades
« Reply #21 on: February 19, 2006, 06:35:58 PM »
that is a really cool design , have you hooked it to a generator yet?
« Last Edit: February 19, 2006, 06:35:58 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #22 on: February 19, 2006, 06:57:51 PM »
here is a guy who uses the minwax Polycrylic with out resin !!

it sounds promissing..

http://www.rcgroups.com/links/index.php?id=4018
« Last Edit: February 19, 2006, 06:57:51 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #23 on: February 20, 2006, 12:55:51 PM »
i bought some Minwax Polycrylic ,its curing , will post pics of the results.

it looks promising

i coated some blue foam with it , and applied some glass fibers to another piece

at the very least it will allow fiberglass resin to be applied on blue foam , hopefully

In the best scenerio it could be used as is , with glass fibers.
« Last Edit: February 20, 2006, 12:55:51 PM by willib »
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rotornuts

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Re: a set of 9" blades
« Reply #24 on: February 20, 2006, 06:01:10 PM »
willib, I never hooked the above to an alt because I didn't like the way it turned out. As it happens I origionally had made it to be a straight blade unit based on a bunch of small model experiments I did. I at the last moment decided to give it the helical design and it didn't turn out quite right. Someday I'll make another but leave it straight.


I'm interested to hear how the polycrylic works out and BTW that's exactly the site I learned about the polycrylic on. RC modelers are a wealth of good info.


Mike

« Last Edit: February 20, 2006, 06:01:10 PM by rotornuts »

willib

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Re: a set of 9" blades
« Reply #25 on: February 20, 2006, 08:45:26 PM »
This is just the polycrylic and glass fibers in the top two pics..

and one coat of polycrylic on the glass

those two parallels on the top weigh 1.12lbs total









the two pics below is three coats of fully dried polycryllic with glass fibers and polyester resin.

This was after an hour with the resin applied ,i'm not sure about how well it worked , since these pics were taken the resin has sunk in just about flush with the top of the foam.its been about two hours since i started the test .






Conclusion :

I'm not positive , but i think the build up of heat has more to do with the melting of the foam, than the dissolving of the foam by the resin, i'm gonna try curing it in the fridge.the polycryllic seemed to slow down the dissolving , but did not stop it .

i'm also gonna try just a thin layer of resin on the polycrylic coated foam and see what happens..

the first test with just the polycrylic , the polycrylic did not eat the foam in any way , and hardened nicely, but even though it is stiff enough to hold the two parallels , it is not as stiff as  resin coated glass .

the reason i did all this testing was to try and get away from the dust from the polyisocyanurate insulation, but the resin did not touch that at all , so i guess its back to the cyanurate..

i do really like the way the blue foam sands though , i just wish there was something to coat it with so the resin did not eat it at all, Mike have you tried polyurethane? i wonder how that would work?



« Last Edit: February 20, 2006, 08:45:26 PM by willib »
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willib

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Re: a set of 9" blades
« Reply #26 on: February 21, 2006, 10:12:45 AM »
Great news , i hope ,

i tried an el cheapo enamel paint, that looks very promising !

it is a 'true value' brand 'tru-test' alkyd base paint..

i used it on the bare styrofoam and the coated foam ( with polycrylic), and both look very good so far..
« Last Edit: February 21, 2006, 10:12:45 AM by willib »
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