---------------------------------------------------------- Pietenpol-List Digest Archive --- Total Messages Posted Mon 02/02/04: 19 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:43 AM - Re: more airfoil talk (Robert Haines) 2. 07:44 AM - walnut shells and airfoil talk (Robert Haines) 3. 08:04 AM - Re: walnut shells and airfoil talk (del magsam) 4. 08:11 AM - Re: walnut shells and airfoil talk (Christian Bobka) 5. 08:22 AM - Re: walnut shells and airfoil talk (del magsam) 6. 09:03 AM - Re: walnut shells and airfoil talk (Christian Bobka) 7. 09:12 AM - Re: walnut shells and airfoil talk (Robert Haines) 8. 09:20 AM - Aviation Wisdom (MacklemAW@aol.com) 9. 09:27 AM - Re: walnut shells and airfoil talk (Cy Galley) 10. 09:38 AM - Re: walnut shells and airfoil talk (Cy Galley) 11. 09:43 AM - Recommended Reading (MacklemAW@aol.com) 12. 09:52 AM - Re: Re: walnut shells and airfoil talk (Jim Vydra) 13. 09:52 AM - Re: walnut shells and airfoil talk (Robert Haines) 14. 10:52 AM - Re: walnut shells and airfoil talk (Larry Ragan) 15. 11:04 AM - Re: walnut shells and airfoil talk (Robert Haines) 16. 11:19 AM - Re: walnut shells and airfoil talk (Deon Engelmann) 17. 12:08 PM - Re: walnut shells and airfoil talk (walt evans) 18. 01:35 PM - Re: walnut shells and airfoil talk (Robert Haines) 19. 04:27 PM - Re: Re: walnut shells and airfoil talk (walt evans) ________________________________ Message 1 _____________________________________ Time: 07:43:44 AM PST US From: "Robert Haines" Subject: Pietenpol-List: Re: more airfoil talk --> Pietenpol-List message posted by: "Robert Haines" Well, yea, that's the exact attitude you should have with any unproven aircraft, even one with the FC-10 airfoil. There are hundreds of things that can go wrong, you should always try to completely understand all the risks and develop plans to mitigate them. Yes, one would be to use a proven airfoil, that would be one less risk, no argument there. But let me ask, how exactly did Bernie develop this airfoil? Did he pour through endless wing section diagrams, did he develop remote control models, did he run computer analysis or do wind tunnel test? As I understand, he made several sets of wings and tried them all out on the plane, and then decided on the one he liked best. As the story goes, he spent all of 10 minutes drawing that one out. I am not advocating any unsafe methodology to procede with the design, development, and construction of an aircraft. I also think to many people foolhartedly proceed with an existing design and just "burn-off" the flight hours required in the initial testing phase. Simply because this design is proven over and over, does not mean that your new aircraft is free from the scrutiny required for any new experimental aircraft, and I would strongly suggest that you initially fly the plane as if it were about to experience any sort of catastrophic failure. Regarding the comments to wing flutter: yes, flutter is a likely event when increasing the speed of an aircraft with unbalanced control surfaces. Although, how many who have considered that putting in more powerful engines, providing covers over the wheels, or streamlining any other area would increase the speed of the aircraft to a point that the control surfaces would flutter? I haven't heard one word. Not to say that it would or wouldn't, and I hope I don't sound like I'm lecturing, but my point is that changes in design always have to be taken with a strong consideration to the consequences. Changing the airfoil is just simply another one of those things that you must provide a concious effort to seek out the results of said change and that's how you proceed with an EXPERIMENTAL aircraft. OK, getting off soapbox now. Thank you for your support. Robert Haines Du Quoin, Illinois > From: BARNSTMR@aol.com > Subject: Re: Pietenpol-List: Re: more airfoil talk > > Have you ever read about Jimmy Doolittle's test flight of a highly modified > Travel Air Mystery ship? The airplane, owned by Shell Oil Company, was taken > to Parks College in St. Louis for refurb.... I think in 1931 or 1932. They > did an aerodynamic clean-up adding sweeping wing filet fairings, and other > changes, including an airfoil mod. The first flight lasted about 30 minutes with > > Jimmy Doolittle at the controls. He climbed to approx 5000ft. and joined up > with a camera ship. One in-flight picture was taken as far as I have ever seen. > > Jimmy claimed the "Shell 400" was performing so well that he decided to do a > high speed pass over the field. At an altitiude of less than 50 ft, aileron > flutter set in so bad that Doolittle had no choice but to pull up and bail > out. His Parachute flight was said to be the lowest on record up to that time. > > Lucky that the canopy opened in time. The second picture of the "Shell 400" > that I know of is of the mangled twisted wreckage. > > I don't know about you guys, but I feel that its going to take some biig > cahoooonas for me to climb into the Piet for that first flight. I would wear a > > 'Chute, but I doubt I could fit in the cockpit with it, much less pry myself > loose to bail out if anything happened. Go ahead and do your research and > experiment with another airfoil if you must. But I'll pass. I'd much rather test > > my airplane with the known FC-10. > > my $ .02 > > TLB ________________________________ Message 2 _____________________________________ Time: 07:44:50 AM PST US From: "Robert Haines" Subject: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Robert Haines" Just sent my rant about airfoils, caught three misspellings after the fact, I hate that. To all those who are building a Corvair engine, it's been suggested that abrasive blasting with walnuts shells is a great way to get the surfaces clean and bright. As I have a sandblaster, I started looking for a supplier of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for $45 plus $30 shipping, I about choked. That seemed to be the same price for all the traditional suppliers. Fortunately, I found a food producer that sells walnut products and sells the walnut shells, ground to several different sieves, as a byproduct. They are Hammons (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 plus about that for shipping. They took a phone order by credit card, and the bag arrived four days later. I had to explain to the wife when she saw the receipt what the heck I needed 50lbs of walnut shells for. Robert Haines Du Quoin, Illinois ________________________________ Message 3 _____________________________________ Time: 08:04:59 AM PST US From: del magsam Subject: Re: Pietenpol-List: walnut shells and airfoil talk great info Robert, what grade did you buy? and please post on how they work for you, or if a different grade should be bought. Del Robert Haines wrote: --> Pietenpol-List message posted by: "Robert Haines" Just sent my rant about airfoils, caught three misspellings after the fact, I hate that. To all those who are building a Corvair engine, it's been suggested that abrasive blasting with walnuts shells is a great way to get the surfaces clean and bright. As I have a sandblaster, I started looking for a supplier of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for $45 plus $30 shipping, I about choked. That seemed to be the same price for all the traditional suppliers. Fortunately, I found a food producer that sells walnut products and sells the walnut shells, ground to several different sieves, as a byproduct. They are Hammons (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 plus about that for shipping. They took a phone order by credit card, and the bag arrived four days later. I had to explain to the wife when she saw the receipt what the heck I needed 50lbs of walnut shells for. Robert Haines Du Quoin, Illinois Del-New Richmond, Wi "farmerdel@rocketmail.com" --------------------------------- ________________________________ Message 4 _____________________________________ Time: 08:11:43 AM PST US From: "Christian Bobka" Subject: Re: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Christian Bobka" If you use industrial grade baking soda, it does a good job and is water soluable so that you rinse the engine out with water when you are done and all the abrasive is gone. Chris Bobka ----- Original Message ----- From: "Robert Haines" Subject: Pietenpol-List: walnut shells and airfoil talk > > --> Pietenpol-List message posted by: "Robert Haines" > > Just sent my rant about airfoils, caught three misspellings after the fact, > I hate that. > > > To all those who are building a Corvair engine, it's been suggested that > abrasive blasting with walnuts shells is a great way to get the surfaces > clean and bright. As I have a sandblaster, I started looking for a supplier > of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for > $45 plus $30 shipping, I about choked. That seemed to be the same price for > all the traditional suppliers. Fortunately, I found a food producer that > sells walnut products and sells the walnut shells, ground to several > different sieves, as a byproduct. They are Hammons > (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 > plus about that for shipping. They took a phone order by credit card, and > the bag arrived four days later. > > I had to explain to the wife when she saw the receipt what the heck I needed > 50lbs of walnut shells for. > > > Robert Haines > Du Quoin, Illinois > > ________________________________ Message 5 _____________________________________ Time: 08:22:00 AM PST US From: del magsam Subject: Re: Pietenpol-List: walnut shells and airfoil talk where is a source of industrial grade baking soda? Del Christian Bobka wrote: --> Pietenpol-List message posted by: "Christian Bobka" If you use industrial grade baking soda, it does a good job and is water soluable so that you rinse the engine out with water when you are done and all the abrasive is gone. Del-New Richmond, Wi "farmerdel@rocketmail.com" --------------------------------- ________________________________ Message 6 _____________________________________ Time: 09:03:57 AM PST US From: "Christian Bobka" Subject: Re: Pietenpol-List: walnut shells and airfoil talk Del, Try this website for info: http://www.transportandconstruction.co.za/rasmech.html I know, I know they are in New Zealand. But there was a guy in Winona marketing this stuff at Oshkosh about ten years ago. His name is Mike Thern. I think he was a teacher in the aviation tech school down at the winona airport. I would contact him at the airport at 507 864 2705 or at home at 507 454 2705 and ask him where it can be had. These phone numbers a current as I just got the info from the Luscombe association newsletter that came in saturday's mail. I know the soda is cheap. He may be out of the business becuase it is so easy to purchase hence everybody bought it elsewhere. Please let the piet list know what you find out. chris bobka ----- Original Message ----- From: del magsam To: pietenpol-list@matronics.com Sent: Monday, February 02, 2004 10:20 AM Subject: Re: Pietenpol-List: walnut shells and airfoil talk where is a source of industrial grade baking soda? Del Christian Bobka wrote: --> Pietenpol-List message posted by: "Christian Bobka" If you use industrial grade baking soda, it does a good job and is water soluable so that you rinse the engine out with water when you are done and all the abrasive is gone. Del-New Richmond, Wi "farmerdel@rocketmail.com" ________________________________ Message 7 _____________________________________ Time: 09:12:42 AM PST US From: "Robert Haines" Subject: Pietenpol-List: Re: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Robert Haines" I've got no experience here, but I chose the 20/30 (they mentioned it was one of the more popular grades), it appeared to be middle of the line medium abrasive. Now that I have it, it has the size of coarse sand, just for comparison, but I'm sure walnut shell sieve and sand sieve do not correspond as far as fine/medium/coarse grading. I haven't used it yet, I can't comment yet. Also, baking soda, I've read somewhere at sometime and may or may not be right (how's that for a disclaimer?) attacks aluminum. Again, I don't know for sure. Although, I do know that walnut shells pose no chemical danger. :) I do have a copy of the CORSA magazine that has the proceedings from a CORSA presentation that the plant manager of the engine factory gave (November 1997?). It was interesting but I wished there was more technical details on how they did what they did. He mentioned that the heads and cases were low pressure die cast with sand cores. They had problems getting the core sand out of the heads until they figured out about abrasive blasting with walnut shells, and so that's how they were cleaned at the factory. He mentioned that they bought walnut shells by the rail car load. So, if it's good enough for the guys who built them in the first place, it'll be OK with me. Robert Haines Du Quoin, Illinois ________________________________ Message 8 _____________________________________ Time: 09:20:16 AM PST US From: MacklemAW@aol.com Subject: Pietenpol-List: Aviation Wisdom Only a portion of this applies to Piets. But I hope you enjoy the Addenda For Fliers: "Though I Fly Through the Valley of Death ...I Shall Fear No Evil ... For I am at 80,000 Feet and Climbing. (Sign over the entrance to the SR-71 operating location Kadena, Japan). There is no reason to fly through a thunderstorm in peacetime. (Sign over Squadron Ops desk at Davis-Monthan AFB, AZ, 1970). Advice given to RAF pilots during WW II. When a prang (crash) seems inevitable, endeavor to strike the softest, cheapest object in the vicinity as slowly and gently as possible. You've never been lost until you've been lost at Mach 3. (Paul F.Crickmore, test pilot) From an old carrier sailor - Blue water Navy truism; there are more planes in the ocean than submarines in the sky. Navy carrier pilots to Air Force pilots: Flaring is like squatting to pee. When one engine fails on a twin-engine airplane you always have enough power left to get you to the scene of the crash. What is the similarity between air traffic controllers and pilots? If a pilot screws up, the pilot dies; If ATC screws up, the pilot dies. Never trade luck for skill. The three most common expressions (or famous last words) in aviation are: "Why is it doing that?", "Where are we?", and "Oh S#!+!" Weather forecasts are horoscopes with numbers. Airspeed, altitude, and brains. Two are always needed to successfully complete the flight. A smooth landing is mostly luck; two in a row is all luck; three in a row is prevarication. Flashlights are tubular metal containers kept in a flight bag for the purpose of storing dead batteries. Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it. When a flight is proceeding incredibly well, something was forgotten. Just remember, if you crash because of weather, your funeral will be held on a sunny day. The Piper Cub is the safest airplane in the world; it can just barely kill you. (Attributed to Max Stanley, Northrop test pilot) If you're faced with a forced landing, fly the thing as far into the crash as possible. (Bob Hoover - renowned aerobatic and test pilot) If an airplane is still in one piece, don't cheat on it; ride the bastard down. (Ernest K. Gann, author &aviator) Never fly in the same cockpit with someone braver than you. You know that your landing gear is up and locked when it takes full power to taxi to the terminal. Basic Flying Rules: Try to stay in the middle of the air. Do not go near the edges of it. The edges of the air can be recognized by the appearance of ground, buildings, sea, trees and interstellar space. It is much more difficult to fly there. Allan W. Macklem Elkhorn, NE TEL: 402 880 6559 // 402 289 2298 FAX: 402 289 3474 Personal growth comes from being surrounded by highly talented people. ________________________________ Message 9 _____________________________________ Time: 09:27:34 AM PST US From: "Cy Galley" Subject: Re: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Cy Galley" What is the difference between baking soda and industrial grade BS? More for a cheaper per pound price? ----- Original Message ----- From: "Christian Bobka" Subject: Re: Pietenpol-List: walnut shells and airfoil talk > --> Pietenpol-List message posted by: "Christian Bobka" > > If you use industrial grade baking soda, it does a good job and is water > soluable so that you rinse the engine out with water when you are done and > all the abrasive is gone. > > Chris Bobka > ----- Original Message ----- > From: "Robert Haines" > To: > Sent: Monday, February 02, 2004 9:44 AM > Subject: Pietenpol-List: walnut shells and airfoil talk > > > > > > --> Pietenpol-List message posted by: "Robert Haines" > > > > > Just sent my rant about airfoils, caught three misspellings after the > fact, > > I hate that. > > > > > > To all those who are building a Corvair engine, it's been suggested that > > abrasive blasting with walnuts shells is a great way to get the surfaces > > clean and bright. As I have a sandblaster, I started looking for a > supplier > > of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for > > $45 plus $30 shipping, I about choked. That seemed to be the same price > for > > all the traditional suppliers. Fortunately, I found a food producer that > > sells walnut products and sells the walnut shells, ground to several > > different sieves, as a byproduct. They are Hammons > > (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 > > plus about that for shipping. They took a phone order by credit card, and > > the bag arrived four days later. > > > > I had to explain to the wife when she saw the receipt what the heck I > needed > > 50lbs of walnut shells for. > > > > > > Robert Haines > > Du Quoin, Illinois > > > > > > > > > > > > > > > > > > ________________________________ Message 10 ____________________________________ Time: 09:38:21 AM PST US From: "Cy Galley" Subject: Re: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Cy Galley" What grit size did you buy? ----- Original Message ----- From: "Robert Haines" Subject: Pietenpol-List: walnut shells and airfoil talk > --> Pietenpol-List message posted by: "Robert Haines" > > Just sent my rant about airfoils, caught three misspellings after the fact, > I hate that. > > > To all those who are building a Corvair engine, it's been suggested that > abrasive blasting with walnuts shells is a great way to get the surfaces > clean and bright. As I have a sandblaster, I started looking for a supplier > of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for > $45 plus $30 shipping, I about choked. That seemed to be the same price for > all the traditional suppliers. Fortunately, I found a food producer that > sells walnut products and sells the walnut shells, ground to several > different sieves, as a byproduct. They are Hammons > (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 > plus about that for shipping. They took a phone order by credit card, and > the bag arrived four days later. > > I had to explain to the wife when she saw the receipt what the heck I needed > 50lbs of walnut shells for. > > > Robert Haines > Du Quoin, Illinois > > ________________________________ Message 11 ____________________________________ Time: 09:43:17 AM PST US From: MacklemAW@aol.com Subject: Pietenpol-List: Recommended Reading I very much enjoyed these and recommend them to you. Unlocking The Sky (Glenn Hammond Curtiss) by Seth Shulman, Perennial, Harper Collins Publishers, 2003. Wings of Madness (Alberto Santos-Dumont) by Paul Hoffman, Hyperion Publisher, 2003. First World Flight (Billy Mitchell) by Spencer Lane, U.S. Press, 2002. Allan W. Macklem Elkhorn, NE TEL: 402 880 6559 // 402 289 2298 FAX: 402 289 3474 Personal growth comes from being surrounded by highly talented people. ________________________________ Message 12 ____________________________________ Time: 09:52:16 AM PST US From: Jim Vydra Subject: Re: Pietenpol-List: Re: walnut shells and airfoil talk I bet the walnut standards are identicle to sand standards...The American Standards Institute (ASI) sets all standards...I live near Stockton, MO where Hammons is located. They sell to many industries. Can't imagine an industry that would buy an abrasive without knowing what standard grade it is Robert Haines wrote:--> Pietenpol-List message posted by: "Robert Haines" I've got no experience here, but I chose the 20/30 (they mentioned it was one of the more popular grades), it appeared to be middle of the line medium abrasive. Now that I have it, it has the size of coarse sand, just for comparison, but I'm sure walnut shell sieve and sand sieve do not correspond as far as fine/medium/coarse grading. I haven't used it yet, I can't comment yet. Also, baking soda, I've read somewhere at sometime and may or may not be right (how's that for a disclaimer?) attacks aluminum. Again, I don't know for sure. Although, I do know that walnut shells pose no chemical danger. :) I do have a copy of the CORSA magazine that has the proceedings from a CORSA presentation that the plant manager of the engine factory gave (November 1997?). It was interesting but I wished there was more technical details on how they did what they did. He mentioned that the heads and cases were low pressure die cast with sand cores. They had problems getting the core sand out of the heads until they figured out about abrasive blasting with walnut shells, and so that's how they were cleaned at the factory. He mentioned that they bought walnut shells by the rail car load. So, if it's good enough for the guys who built them in the first place, it'll be OK with me. Robert Haines Du Quoin, Illinois ________________________________ Message 13 ____________________________________ Time: 09:52:59 AM PST US From: "Robert Haines" Subject: Pietenpol-List: Re: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Robert Haines" Industrial grade BS?! (oh, you meant baking soda...) RH ________________________________ Message 14 ____________________________________ Time: 10:52:22 AM PST US From: "Larry Ragan" Subject: RE: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Larry Ragan" I think if you were to use regular baking soda (sodium bicarbonate) you could purchase it through swimming pool suppliers. It is used to balance ph and can be purchased in 50# bags. Don't buy it at the local pool supplier because they repackage it in 5#containers....rename it....and jack the price up. Larry Ragan Jacksonville, Fl. lragan@hotmail.com ________________________________ Message 15 ____________________________________ Time: 11:04:08 AM PST US From: "Robert Haines" Subject: Pietenpol-List: Re: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Robert Haines" Apparently I didn't do a good job making my point. What I meant to say was that walnut shells at 20 sieve (U.S. Mesh at approximately 0.030" in diameter so says Hammons) and sand at 20 sieve may not be considered in the same abrasive category; where a 20 sieve sand is considered "coarse" (I'm pretty sure about that), 20 sieve walnut shell may be considered "medium" (or "coarse" or "fine"). I'm not sure of this gradation, but this is the point I was trying to make. They could be graded exactly the same, I just didn't want to assume this to be true considering they are somewhat different materials. What I want is a "medium" walnut shell abrasive since my parts are not covered with mud, crud, paint, rust, etc. Also, most abrasives get smaller with use, so eventually (no telling how long) I would likely end up with "fine" anyway. Since Hammons, in their FAQ section, noted that 8/12, 12/20, and 20/30 were their most popular, and my assumption was most applications use "coarse" and "medium", I concluded that 20/30 was probably "medium". Just a guess. Robert Haines Du Quoin, Illinois ________________________________ Message 16 ____________________________________ Time: 11:19:11 AM PST US From: "Deon Engelmann" Subject: RE: Pietenpol-List: walnut shells and airfoil talk Hi This company is actually in Alrode, Johannesburg, South Africa (.co.za ). It is about 25 min from where I stay. Deon Engelmann EAA322 Midrand # SA12055 Pretoria South Africa -----Original Message----- From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Christian Bobka Subject: Re: Pietenpol-List: walnut shells and airfoil talk Del, Try this website for info: http://www.transportandconstruction.co.za/rasmech.html I know, I know they are in New Zealand. where is a source of industrial grade baking soda? Del ________________________________ Message 17 ____________________________________ Time: 12:08:40 PM PST US From: "walt evans" Subject: Re: Pietenpol-List: walnut shells and airfoil talk --> Pietenpol-List message posted by: "walt evans" In my line of work, over the years, when we wanted less destructive blasting we always used ground corn cob. It comes in the consistisy of corn meal but it's the cob. Think places like Grainger or McMaster Carr stocks it. walt evans NX140DL ----- Original Message ----- From: "Robert Haines" Subject: Pietenpol-List: walnut shells and airfoil talk > --> Pietenpol-List message posted by: "Robert Haines" > > Just sent my rant about airfoils, caught three misspellings after the fact, > I hate that. > > > To all those who are building a Corvair engine, it's been suggested that > abrasive blasting with walnuts shells is a great way to get the surfaces > clean and bright. As I have a sandblaster, I started looking for a supplier > of walnut shells. Eastwood (automotive products, etc.) had a 50lb bag for > $45 plus $30 shipping, I about choked. That seemed to be the same price for > all the traditional suppliers. Fortunately, I found a food producer that > sells walnut products and sells the walnut shells, ground to several > different sieves, as a byproduct. They are Hammons > (http://www.black-walnuts.com/) out of Missouri and the 50lb bag was $15 > plus about that for shipping. They took a phone order by credit card, and > the bag arrived four days later. > > I had to explain to the wife when she saw the receipt what the heck I needed > 50lbs of walnut shells for. > > > Robert Haines > Du Quoin, Illinois > > ________________________________ Message 18 ____________________________________ Time: 01:35:01 PM PST US From: "Robert Haines" Subject: Pietenpol-List: Re: walnut shells and airfoil talk --> Pietenpol-List message posted by: "Robert Haines" My Granger catalog only had glass bead. However, my McMaster-Carr catalog had a number of choices, including walnut shells and corn cob. Walnut shell was $25.00 for 50lb at 20/30 (the cheapest) and cob at $18.35 for 50lb at 20/40 (also the cheapest). The heavier grit get slightly more expensive. Shipping is not known. Thus, my recommendation for Hammons at $15.00 per 50lb bag of walnut shell. Frustrating thing is that I'm in the middle of corn cob country. You would think that I could get all I wanted for free if I was willing to pick through the fields in the Fall and grind it myself. :) Walt - what were you using cob blasting for and what were your experiences? Robert Haines Du Quoin (located between this corn field and that one), Illinois ________________________________ Message 19 ____________________________________ Time: 04:27:08 PM PST US From: "walt evans" Subject: Re: Pietenpol-List: Re: walnut shells and airfoil talk --> Pietenpol-List message posted by: "walt evans" Robert, I didn't personly use it, but in talking with our engineering P.E. (who has since left and is with EASA) The sand grit actually hits and leaves a "barb" since the sand is much harder that the steel/alum. And it could short out the laminations on an AC motor. Where the corn cob is softer and either doesn't touch/flattens the surface on the steel. {{We are one of the largest electric motor/pump facilities in the northeast (only one ISO 9001 certified first time out)}} But actually now they've switched to using a high pressure water blaster that can also add backing soda to the mix for action. (the one where the operator wears "tim man" shin and foot covers to limit cutting off toes.) Don't know where cob, walnut shells, and baking soda compare, but just wanted to bring up another option. I imagine that if baking soda does the job ( and since it's not an acid,but a base?) Like Chris Bobka suggested, it's probably the best way to go. Besides, when you're done, you can make buscuits. : ) walt evans NX140DL ----- Original Message ----- From: "Robert Haines" Subject: Pietenpol-List: Re: walnut shells and airfoil talk > --> Pietenpol-List message posted by: "Robert Haines" > > My Granger catalog only had glass bead. However, my McMaster-Carr catalog > had a number of choices, including walnut shells and corn cob. Walnut shell > was $25.00 for 50lb at 20/30 (the cheapest) and cob at $18.35 for 50lb at > 20/40 (also the cheapest). The heavier grit get slightly more expensive. > Shipping is not known. > > Thus, my recommendation for Hammons at $15.00 per 50lb bag of walnut shell. > Frustrating thing is that I'm in the middle of corn cob country. You would > think that I could get all I wanted for free if I was willing to pick > through the fields in the Fall and grind it myself. :) > > Walt - what were you using cob blasting for and what were your experiences? > > > Robert Haines > Du Quoin (located between this corn field and that one), Illinois > >