The Black Art
03-17-2005, 02:22 PM
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The Black Art
Call me nuts, call me crazy, but I'm thinking about carving q40 props. I got my handy pitch gauge, a template from Darrol, and 5 blanks to get started. For some reason, I remember a "how to" or something like that on a someones site a while back.
Anyone want to share some tips on sanding/carving tools? Anything to help get me started without re-inventing the wheel?
Anyone want to share some tips on sanding/carving tools? Anything to help get me started without re-inventing the wheel?
03-17-2005, 03:05 PM
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RE: The Black Art
Darrol's site has a pretty good "how to", for prop carving.
smoke
BTW - told Rocket Ray to sign us up on 46 for Ft.Lauderdale. You just need to send you check.
smoke
BTW - told Rocket Ray to sign us up on 46 for Ft.Lauderdale. You just need to send you check.
03-17-2005, 05:35 PM
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RE: The Black Art
I thought there was something on Darrols site, but I couldn't find it this morning and sent Darrol and email. I looked again this afternoon and found it:
http://www.darrolcady.com/Propellers...eller_faq.html
Randy, I haven't seen a sign up sheet for the Ft Lauderdale race yet, but I'm all set to go. Still trying to find a hotel that they recommend.
http://www.darrolcady.com/Propellers...eller_faq.html
Randy, I haven't seen a sign up sheet for the Ft Lauderdale race yet, but I'm all set to go. Still trying to find a hotel that they recommend.
03-17-2005, 05:58 PM
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RE: The Black Art
There is a great way to make a good wood prop... I was told this by many of the top racers...
Make 10 of them... Out of the 10 you may get one that goes as good as the black prop...
Then break it on landing and start all over.......
Mr. Pessimistic
Make 10 of them... Out of the 10 you may get one that goes as good as the black prop...
Then break it on landing and start all over.......
Mr. Pessimistic
03-19-2005, 09:24 AM
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RE: The Black Art
Ok, I got a start here. Any ideas of the best tools to carve/sand these things. Should I start with a 60 grit sanding block?, Carving knife of some sort? Razor Blade?
Any other recommendations?
Any other recommendations?
03-19-2005, 10:47 AM
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RE: The Black Art
Dave,
Go to the AMA website and search through the Model Aviation digital archives to find the May 1999 edition. In it, Duane Gall's pylon column is dedicated to the "black art".
I would post the link but I doubt that it would work because a password is required.
Go to the AMA website and search through the Model Aviation digital archives to find the May 1999 edition. In it, Duane Gall's pylon column is dedicated to the "black art".
I would post the link but I doubt that it would work because a password is required.
03-19-2005, 11:23 AM
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RE: The Black Art
Dave,
talk to Jacob Raquet or Bruce Coffey...they carve alot of props and i herd that most of the Jett guys were usin them and goin really well...Lee Ulinger is another person who has this art masterd...prolly one of the best ones i have seen has came from Lee...maybe they can help u out
Cole
talk to Jacob Raquet or Bruce Coffey...they carve alot of props and i herd that most of the Jett guys were usin them and goin really well...Lee Ulinger is another person who has this art masterd...prolly one of the best ones i have seen has came from Lee...maybe they can help u out
Cole
03-19-2005, 05:00 PM
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RE: The Black Art
Jakob and Bruce definately know what there doing when it comes to the Jett motor, Lee seems to have his Nelson props down too, he's been smoking the last couple q40 races I've seen him fly.
Thanks,
Thanks,
03-21-2005, 11:41 AM
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RE: The Black Art
Bruce gave us the numbers for the props... Some are a little longer at say 7.5" diameter
station 3 thickness at .120-.125 thousands on the micrometer...
staion 5 thickness at .95 to .110 thousands
station 7 thickness at .60 to .65 thousands
station 8 thickness at .30 to .35 thousands
Lee's prop I measured it and it was identical to Bruce's numbers, except it was shorter diameter 7.3"
station 5 at 7.1 to 7.3 pitch and station 7 at 7.5 to 7.8 or as many do check the black prop and try to copy it and you can make the thickness numbers smaller if the wood is good...
A practical way to avoid shock-waves and keep the C/D acceptable is to have a thin tip or camber... The numbers I gave you will accomplish this goal and reduce the amount of shock-wave drag...
A nice pocket nife will do the job, most people keep the high point around 25% or so from the leading edge, take you're knife and clear out all that wood that is behind the high point and then shape you're leading edge and then form or sand the airfoil you want...
then mark you're stations and mike them all the way out until the numbers match especially from station 5 to 7 and 8..
The thinner the better until you get some prop flutter, the stronger the wood the thinner you can go, I was happy to get them to the numbers I gave you, that is very thin and the prop tapers to nothing when looking down the blade from the tip... No sharp tapers or angles, smooth is important... The tip is almost flat, no airfoil at all almost... ITs so thin, its hard to see if there is a high point, but most say have the high point at 40-50% at the tip...
I make mine from Rev-up blanks and then make the entire prop... When I am done I heat with a heat gun and twist up to the pitch I want... A lot of guys run the 7.4 or 7.5 by 8.0 to 8.5 and some up to 9.0 or even more... Check the black prop and decide what you want to try... Instead of cutting my tips down, I just de-pitch if I want more rpm or pitch up if I want less... 23,200 to 24k is in the range, I have found the majic 23,500 number to be right on....
I have one of the old permigrit pieces to shape my tips, I then carve most with good pocket knife with good sharp edges, get a sharpening block... After its shaped, I then sand it with 220, then 600 then 1200 then poish with 1500...
ONce its ready to run, I put a few coats of ca to seal it, polish it with steel wool and 1500 and get that smooth finish....
I am not the best prop maker, do not have the paitence, but I have been told these methods by some of the guys that do know how to make them go... The one I did get to go as good as the black prop I spent about 3 hours on... Constantly miking and checking and making it as perfect as I could... If I could get one to go as good or better than the black one, it would all be worth it I guess...
I will keep trying......
Hope this helps JZW
station 3 thickness at .120-.125 thousands on the micrometer...
staion 5 thickness at .95 to .110 thousands
station 7 thickness at .60 to .65 thousands
station 8 thickness at .30 to .35 thousands
Lee's prop I measured it and it was identical to Bruce's numbers, except it was shorter diameter 7.3"
station 5 at 7.1 to 7.3 pitch and station 7 at 7.5 to 7.8 or as many do check the black prop and try to copy it and you can make the thickness numbers smaller if the wood is good...
A practical way to avoid shock-waves and keep the C/D acceptable is to have a thin tip or camber... The numbers I gave you will accomplish this goal and reduce the amount of shock-wave drag...
A nice pocket nife will do the job, most people keep the high point around 25% or so from the leading edge, take you're knife and clear out all that wood that is behind the high point and then shape you're leading edge and then form or sand the airfoil you want...
then mark you're stations and mike them all the way out until the numbers match especially from station 5 to 7 and 8..
The thinner the better until you get some prop flutter, the stronger the wood the thinner you can go, I was happy to get them to the numbers I gave you, that is very thin and the prop tapers to nothing when looking down the blade from the tip... No sharp tapers or angles, smooth is important... The tip is almost flat, no airfoil at all almost... ITs so thin, its hard to see if there is a high point, but most say have the high point at 40-50% at the tip...
I make mine from Rev-up blanks and then make the entire prop... When I am done I heat with a heat gun and twist up to the pitch I want... A lot of guys run the 7.4 or 7.5 by 8.0 to 8.5 and some up to 9.0 or even more... Check the black prop and decide what you want to try... Instead of cutting my tips down, I just de-pitch if I want more rpm or pitch up if I want less... 23,200 to 24k is in the range, I have found the majic 23,500 number to be right on....
I have one of the old permigrit pieces to shape my tips, I then carve most with good pocket knife with good sharp edges, get a sharpening block... After its shaped, I then sand it with 220, then 600 then 1200 then poish with 1500...
ONce its ready to run, I put a few coats of ca to seal it, polish it with steel wool and 1500 and get that smooth finish....
I am not the best prop maker, do not have the paitence, but I have been told these methods by some of the guys that do know how to make them go... The one I did get to go as good as the black prop I spent about 3 hours on... Constantly miking and checking and making it as perfect as I could... If I could get one to go as good or better than the black one, it would all be worth it I guess...
I will keep trying......
Hope this helps JZW
03-22-2005, 10:39 AM
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RE: The Black Art
Sure no problem.... The problem with making a good wood prop is that knowing what to do, having the formula, and actually doing it are two different things... Just like knowing how to fly the course and actually flying the course are two different things...
JZW
JZW
03-23-2005, 01:24 AM
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RE: The Black Art
Dave, I tried the heat method once,,, ended up burning my finger tips and turning the prop into a lump of charcoal. 
Anyways I've found the best way for me to "pitch a prop" is by using a utility razor blade and scraping the backside of the blade. Removing material at the LE of the blade will increase pitch and to decrease the pitch you'll need to scrape off the wood at TE.
As for the top and the high point,,, I guess its all about preferance but it never hurts to try different high points and different tips. For me 25% from the LE was a good starting point and it did ok for me while in Phx at the last Race. Also you may want to use the same cord measurements from the black prop 3, 5 and 7 stations for starters.
JZW has the thickness numbers there that I've used(great post John) and they'll work just fine but again its a never ending search for the right combo so get that big bag of wood props out.
BV
Anyways I've found the best way for me to "pitch a prop" is by using a utility razor blade and scraping the backside of the blade. Removing material at the LE of the blade will increase pitch and to decrease the pitch you'll need to scrape off the wood at TE.
As for the top and the high point,,, I guess its all about preferance but it never hurts to try different high points and different tips. For me 25% from the LE was a good starting point and it did ok for me while in Phx at the last Race. Also you may want to use the same cord measurements from the black prop 3, 5 and 7 stations for starters.
JZW has the thickness numbers there that I've used(great post John) and they'll work just fine but again its a never ending search for the right combo so get that big bag of wood props out.
BV
03-23-2005, 11:05 AM
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RE: The Black Art
Good points Bill, nothing is set in stone, you want to experiement with new ideas from time to time... If you find something that works, keep it secret, except for me of course, email me right away and tell me what has worked for you...he he he
I have been trying some new things, high point forward, less of a sharp leading edge, different tip shapes and so on...
There are so many variables going on at the same time, its hard to know how it all works together, but of the research I have done, one of the most important things is having consistant airfoil sections where you want them... That means you must be pretty good at making straight edges, angles and all the things that come into play when shaping wood... I have never been real good at those things and I am sure this is why most of my props are down from blackie... Someone that is good at this, say a craftsman, should be able to make the airfoil exact and consistant...
PS... the blade has to be hot, but charcoal.... That is too hot, try again, it does not take that much heat to twist them up, I can still hold the tips after I have heated them, you want it hot enough to twist, but not so hot you cannot hold it... Shoot you can twist up some props with no heat and they will hold for about a minute... Do it with heat and it will relax a little, then stop and stay...
MDP uses a relax heat step that heats the fibres after he has already heated and twisted the blade to where he wants it... He then heats the prop again, after that step, the prop will hold the pitch for a long time.......
JZW
I have been trying some new things, high point forward, less of a sharp leading edge, different tip shapes and so on...
There are so many variables going on at the same time, its hard to know how it all works together, but of the research I have done, one of the most important things is having consistant airfoil sections where you want them... That means you must be pretty good at making straight edges, angles and all the things that come into play when shaping wood... I have never been real good at those things and I am sure this is why most of my props are down from blackie... Someone that is good at this, say a craftsman, should be able to make the airfoil exact and consistant...
PS... the blade has to be hot, but charcoal.... That is too hot, try again, it does not take that much heat to twist them up, I can still hold the tips after I have heated them, you want it hot enough to twist, but not so hot you cannot hold it... Shoot you can twist up some props with no heat and they will hold for about a minute... Do it with heat and it will relax a little, then stop and stay...
MDP uses a relax heat step that heats the fibres after he has already heated and twisted the blade to where he wants it... He then heats the prop again, after that step, the prop will hold the pitch for a long time.......
JZW
