|Feb 16, 2003, 12:51 AM|
Grand Prairie, Texas
Joined Feb 2002
Establish a (reference) line from the top to the bottom of the container, now create a second line (off set) at 30% from the first. Draw your prop using the second line as the leading edge or center.
This procedure will be explained in detail where ever you find peanut scale FF modeling.
|Feb 16, 2003, 06:52 AM|
Here is a picture of a styrofoam coffee cup showing the same technique. When you have your blades glue a spar(toothpick or other hardwood stick) down the middle. Then make a hub from a peice of tubing. Drill a hole in the hub for your prop shaft. Stick the spars into the hub. Now you have a yogurt pot prop.
If you need more info let me know there are numerous websites
describing this technique using balsa sheet formed on a cylinder instead of plastic. The plastic is more durable but heavier than balsa. You can increase the strength of a balsa blade by adding material to the front like tissue(i have used leftover christmas ribbon).
A good alternative to plastic and balsa is styrofoam. Fits in between them weightwise and strengthwise methinks.
|Feb 18, 2003, 12:57 AM|
There are "bottle props" and "bucket props"...
The difference is that one comes from a cylinder and the
other comes from a cone. Generally, a prop that
comes from a conical piece of material stands a better
chance of having a good pitch distribution than something
made out of a cylinder.
Years ago a friend of mine, Fred Rash, worked out the math
for making a helical pitch prop on a conic form. Ya might
try a web search for "Bucket Prop"... I seem to remember an
article in an old issue of the NFFS Symposium.
Making props ain't easy, but it is...
If you have a prop of the same pitch you're trying to make lighter,
put it in the yogert can and do a "best fit". That'll be
the angle that ya need to make yer cuts along.
For a helicical pitch, the blade angle is:
a = arctan ( pitch / 2 * pi * r)
where a is the angle from the prop shaft and r is the radius from the hub.
If you need to know more, let me know,
I don't know everything. Who does?.
All I can say is, the more props I make, the better they work.
|Feb 18, 2003, 02:16 AM|
I was trying to look on your webpage for information a while back. I cant remember what info or where I found out about it.
Anyways the link I followed didnt go anywhere.
It was probably an old link that referenced something you put on there temporarily.
|Feb 18, 2003, 10:21 PM|
There is a good description in Wayne's World.
You can make quite a variety depending on the shape and material of the "bottle".
|Feb 19, 2003, 01:01 AM|
I tried that 2 liter bottle prop thing and the prop ended up ridiculously heavy for small models. The plastic on those bottles is a bit flimsy also. A better plastic is the plastic on plastic cups if you can find smooth ones. I guess if you can find the right yougurt container this would work as well.
@Del I think I was looking for something about A-6 plans or props.
|Feb 19, 2003, 03:55 AM|
Prop-calc araises from its ashes
risen from its ashes. With some new info.
Y'all can find it at:
If ya wanna have some fun, try to get an article about making
props published in R/C Microflight. I got told that no matter
how slow the prop turned, or how little it weighed, no prop construction
article would be published by Air Age! It might put somebody's eye out!
Yet, they have no problem advertising the crap out of speed 300 ARF's...
Is anyone out there old enough to remember when Model Airplane News
had articles about _building_ model airplanes?
p.s. wish me luck. got a new indoor model on the bench. trying to get
a 120 sq in rffs-100 model to come in at a gross weight of around 10 grams...
|Feb 19, 2003, 12:37 PM|
I think that is what I was looking for.
|Feb 19, 2003, 04:12 PM|
Re: Prop-calc araises from its ashes
You really can't blame Air Age. A single lawsuit could end publication of all their magazines forever.
I've also seen carbon fibre prop blades molded on and cut from a bottle, if you think the blades from PETE are too heavy. Might have even been described on this board.
|Feb 20, 2003, 01:19 AM|
Glad the prop-calc page comes close to what you were lookng for.
but why? When I'm carving prop forms, I know what pitch I'm going
for and what diameter. All I need to know is what angle to mark
on the end of the block. I'll leave it alone for now..
Input radius and angle, and out comes pitch.
What _is_ the pitch of a U-80, or whatever, prop?
Most folks talk about the maker's model number, but that doesn't tell
me what I wanna know...
Have a big time.
|Feb 20, 2003, 02:04 AM|
Re: Re: Prop-calc araises from its ashes
subscriber. And I thank John and Tom for the good work they've done.
But Air Age Publications in general seems to me to have contributed
to a dumbing-down, of model mags. In essense, Model Airplane News, and
Backyard Flyer have become little more than illustrated catalogs for
Even the AMA rag, Model Aviation, seems to have gone over to the
dark side of the force.. Fewer construction articles, fewer column
inches for sub-groups like indoor and outdoor Free Flight.
OK, ok, maybe I'm just an old fool who wants to make consumers
suffer through learning to cover with tissue paper.. But I also think it's
way-cool to watch something that ya hatched from between yer ears
fly. I learned to make models by reading design and constuction articles.
And I see them less frequently...
Enough! I'm off the soap box...
Anyhoo, back on props..
On the kitchen counter sits a Kentucky Fried Chicken foam cole slaw container.
My wife asked, "Why are you keeping this?" I responded, "Wouldn't a
propeller with Col, Sanders' picture on it look cool?" She just shook
her head and walked away with a look that said, 'I should have known better
than to ask...'...
|Feb 20, 2003, 02:22 AM|
That's a bunch of work for a prop that _might_ work.
I'd rather belive that I think I know what I'm dealing with in terms of pitch distibution, and strive toward an optimum prop/gear/motor combo.
Assuming that's possible...
|Feb 20, 2003, 08:34 AM|
Best I can tell, using your pitch program, the U80 is 3.125"D x 1.5"P. First time I ever tried to "read" a prop, so if someone else would double check me that would be great.
To clarify this, I measured a 25 degree angle, 1/2" out from the prop center.
Del, PS per your email, ..Herr walnut (17" s&t) Cessna 180, very slowly.
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