changing propeller rake?

[Powerabout]

Props are art
can you write a book on how to piant a masterpiece?
First theres a good prop, then there's science to try and work out why

[Fastjeff57]

..."as soon as you apply heat to any metal you will change its molecular structure,and hardness.
not always a dramatic amount,but it will change for sure."

Like when it's cast, for example!

Unless heat treated, as cast stainless object is annealed, meaning it's as soft as it will get. Reheating it--for bending--will not make soft any softer! Nor will it wreck the grain structure UNLESS the metal is destructively overheated, as I explained.

Jeff (graduate mechanical engineer)

[phillnjack]

Ok lets just go back a bit here

ron hill made this statement
1. Pictures 1,2 and 3...An old ZERO RAKE BRASS prop...As stated above somewhere, cup increases the rake...
Flat part of the blade...zero degrees RAKE. Cupped are 10degree RAKE.....................

now the part where it says cup increases rake is 100%wrong.
the rake of the propeller is the trailing edge angle compared to root hub.
its fixed unless you start gringing all the way along the trailing edge.
when you cup a prop if anything you would be decreasing the rake not extending it.

cup make smore pitch not more rake..........
ive got 2 props for a little suzuki,both same pitch but one has a lot more rake, the one with more
rake has so much that ive had to cut the trim tab for it to fit the engine.
.
It seems that over on scream and fkly there has also been debates on the subject of rake who says what it is.
pics to



Here is what it realy is in very simple terms and even a picture of 3 props eplaining it..e
even bill might understand this.
.
http://boatpropellers.iboats.com/pro...utorials/rake/



i think too many people have got their wording mixed up with the actual meaning of rake.
Rake is not blade angle all across the blade area, its only the trailing edge that is truely called rake.

but like ive said before maybe in the usa you have totally different meaning of rake than the rest of the world.


phill

[rumleyfips]

Good one Bill. I can't understand what is motivating the hostility either.

Ron: The heat treating and blacksmithing info was great.

John

[phillnjack]

yes very informative, just such a shame nobody here is understanding what effects welding has to metal structure.
we all know if anything gets too hot it melts and we all know (i would imagine ) that heat softens metal, or there would be no point at all in using the heat.

[Fast Fred]

heat tempered, the art of makin metal stronger uesin heat.

[Ron Hill]

yes very informative, just such a shame nobody here is understanding what effects welding has to metal structure.
we all know if anything gets too hot it melts and we all know (i would imagine ) that heat softens metal, or there would be no point at all in using the heat.

Who said anything about welding?

Trhere is a MAJOR difference between "HEATING METAL" and "Melting Metal". Look at it like this, you take butter out of the frig, it warms some, and you can put butter on your toast. If you melt butter to put on popcorn, when it cools in the bottom of the popcorn bowl, it isn't butter anymore. You heat stainless to a zillion degrees to melt it.....If I get to the shop today, I'll take a picture of our melt prob..a digital temperature gauge. I'll show you me ovens, the melter and the press needed.

Do a Google search and read about heat treating stainless. (17-4 and 15-5).

[rumleyfips]

35 years ago, Tommy Marcel showed up at Chrstal Lake NY with a Czaplewski ASH wheel coloured blue and purple. Tommy said the prop was streched ( hammered blacksmith style) annealed in a heat treating oven. It cost more, but at the time, running 18+" hights a lot of props broke. Tommy liked having a wheel with the stresses removed and that was a bit less brittle.

Using heat and hammers as prop working tools doesn't seem to be anything new.

John McManus

[Ron Hill]

35 years ago, Tommy Marcel showed up at Chrstal Lake NY with a Czaplewski ASH wheel coloured blue and purple. Tommy said the prop was streched ( hammered blacksmith style) annealed in a heat treating oven. It cost more, but at the time, running 18+" hights a lot of props broke. Tommy liked having a wheel with the stresses removed and that was a bit less brittle.

Using heat and hammers as prop working tools doesn't seem to be anything new.

John McManus

Julie Seaman was quite a driver. She was a second generation driver. She won the A Hydro Nationals is Wakefield when there was probably 60 entries in her class. Julie retire from racing and was an attorney in California. She never married, but adopted several children. The last time I saw her she came to Bakersfield to sell her old propellers. Chad was racing the NEW 15A in J Runabout and KG-4 props were working well. I bought two of Julie's 15 props. One was her Czaplewski two blade Record I saw her win the Nationals with.

The never ran good on our J Runabout, but that prop on a J Hydro, and you could not lose. I loaned it to kids that had never trophied, and they won.....Then, I ruined it, trying to get it to run on the runabout. John Czaplewski was a master of masters. I'd bet he had a hundred hours in every prop he ever made!

[Ron Hill]

All these pictures are from Hill Marine's Propeller factory: We make Signature Propellers Anyway, Chad tells me stainless is heated to 2950 degrees before we pour it.

1. Digital temperature probe
2. $75,000 thing melts stainless in a very short time
3. New melt bars are melted
4. This is what props look like after being cast and the shell removed
5. Re-Melt stainless, used for hunting props as remelts are harder than new metal. Hunting props need to be hard as hell to cut through mud, rocks and logs...
6. Sanded props ready for the "Drag Finish" machines. (Hill Marine casts about 100 Signature propellers a week).
7. Heat treat oven....You can't melt stainless here but you can get it hot enough to bent it..

8. Serious press, with the right blocks you can repitch just about anything....I think we could crush Goldfinger's Lincoln Continental.

A prop dosn't have to be melted to be bent...