gkamysz

My Feedback: (19)

So I have this prop., Well half a prop. Actually, it wasn't even mine. Andy W sent it to me after I asked him if he had any. I told him half of a prop would do for this project. And that's how I ended up with it. The rest of the story remains to be told.

[link=http://www.edfinfo.com/x/temp/propslice.jpg][/link]

OK, pic all fixed now.

ChicaWolverina

Ok... lemmey guess... It's a prop-re-propagating-mold system and birdhouse?

[&o]

RocketRob

My Feedback: (1)

Greg,
Starting to worry about you?

gkamysz

My Feedback: (19)

Just wait until next weekend. All is well.

Sandmann_AU

Half a prop is great for stirring paint...

skaliwag

My Feedback: (1)

Mr. Sandmann.... Now we all have Witchetty Grubs in our monitors.

Greg... If you need more broken props, I have plenty.. and there is sure to be more around here.

gkamysz

My Feedback: (19)

This one in particular was a Cox 7x3.5. I could find one when I was looking. Add some CAD, cnc milling, and we just might have something.

Tee Bee

I have found the Cox 7x3.5s very hard to find in the last couple of years. I've only got a few of them left and it seems that the Cox .09s I've run only seemed to perform their best with those props. I've got several .09s lying around unused and would consider building some more of those size planes if the props were easier to come by. I'll be watching to see what you come up with on this thread.

SGC

I bought 4 - 7x3.5" cox grey props from Bernie a few weeks ago, maybe try asking if hes got anymore stashed away.
Stewart

DeviousDave

I have always heard of other pilots "Planting Props". Maybe Greg has figured out a way to get more than one to grow?

Bipe Flyer

Nice, clear cross sections there. I guess once you have it in CAD you can CNC a prop just about any size you want. Will you be able to tweak the pitch?

gkamysz

My Feedback: (19)

So this is the stage it's at right now. I was sick and things are just going slow in general. I could make pitch whatever I want, but duplicating the prop is the current intention. I did manage to buy a whole 7x3.5 this weekend. I'll be able to compare when I'm done.

[link=http://www.edfinfo.com/x/temp/cox735.jpg][/link]

Japanman

Greg,
Hats off to you. I have been liking the Idea of machining a prop out too. i look forward to your progress!
Are you planning to make a mold, or machine the props from something like wood?

S

gkamysz

My Feedback: (19)

I'm going to machine an aluminum mold if everything goes well. I've not done mold design in Solidworks before. It gets tricky once you start thinking about the limitations of your tooling, inside & outside radii, and parting lines. Chances are very good I'll scrap the first attempt at machining this.

Japanman

you might want to check out this site:
http://www.supercoolprops.com/

When i have a bit of time to kill I like to read through his articles. He is a smart guy, and funny too.

you might be particularly interested in these:

http://www.supercoolprops.com/articl...llmoulding.php

and

http://www.supercoolprops.com/articl...pdrairfoil.php

Stefan

gkamysz

My Feedback: (19)

Yes, been following his site for at least 10 years now. There are some bits of treasure on those pages.

gkamysz

My Feedback: (19)

I've done a bit of CAD work and the details are becoming tricky. I don't know what airfoil was used in the original design. Any airfoil shape I choose will need to be modified for an acceptable trailing edge thickness. Multiple airfoils will need to be created as the thickness increases substantially toward the root beginning at about 40% radius. The very root of the blade will need to be fudged as there are no stations there. The blade curvature is hard to see in the screen shot, but it looks good. This will take longer than expected, as usual.

[link=http://www.edfinfo.com/x/temp/cox7351.jpg][/link]

Japanman

That looks cool!

J.M

Tee Bee

Keep up the good fight. This is neat stuff.

KidEpoxy

Cant we just bury any hub fudging inside a Spinner?

gkamysz

My Feedback: (19)

I meant fudging from the duplication standpoint. That part of the prop doesn't do anything other than hold the rest of the blade.

I downloaded XFLR5 to mess around with airfoils, it can handle the thickening and trailing edge thickness issues, and output the coordinate file for the CAD software. Basically I'll increase the thickness of the trailing edge enough to make it strong, but maybe thinner than the original. Now I can pick virtually any airfoil I want so I'll have to think about this a bit. The UIUC website lists only 1550 airfoils http://www.ae.uiuc.edu/m-selig/ads/coord_database.html

The more I work on it the more it looks like I'll end up with my own design. The Cox prop is said to be very good. I don't know if I can make anything better.