Pietenpol-List: spiral grain definition

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Pietenpol-List: spiral grain definition

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Original Posted By: Darrel Jones
The wood I brought home is difficult to examine at the lumber yard because it is rough sawn. What I thought was a nice piece with vertical grain appears to have "spiral grain" on the edge. The ends are nearly perfect vertical grain. What I don't understand is if the vertical grain meets specifications (1" slope in 15") do I even need to worry about edge grain? In theory=2C if the end grain on both ends are perfectly vertical through-out the length of the piece=2C shouldn't the edge not really have a grain? Don't know if this makes sense or not. On the other hand=2C if the grain does slope (even 1" in 15")=2C the grain on the edge should also have a slope or (spiral grain) which is the point you work the formula for spiral grain??? Sorry=2C I'm just confused and cautious on what to be using for spar material and one of my board is in question now that I've planed it down and jointed the edge.Tom B.________________________________________________________________________________Date: Sun, 23 Aug 2009 14:44:30 -0700
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RE: Pietenpol-List: spiral grain definition

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Original Posted By: owner-pietenpol-list-server(at)matronics.com
Tom,The "1 in 15" grain slope cannot occur at any place in the board, not justthe ends. If it does occur at the end, and if you can cut it off, you have agood board. Viewing the end of the board shows two things, that the boardwas "quarter sawn" (no flat grain), and that you have the minimum 6 growthrings / inch. Without a doubt, your spars need to be the very best wood onthe whole plane! If you have any doubts, get a replacement. Best of luck toyou..Gary BootheCool, Ca.PietenpolWW Corvair ConversionTail done, Fuselage on gear(13 ribs down.) _____
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Pietenpol-List: spiral grain definition

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Re: Pietenpol-List:

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Original Posted By: Oscar Zuniga
Subject: Re: Pietenpol-List: For all we experimental aircraft builders, fliers and would be designers a little something to wet the whistle of creativity.EnjoyJohn_Rare Aircraft - United States_ (http://rareaircraf1.greyfalcon.us/UNITED%20STATES.htm) ________________________________________________________________________________
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Pietenpol-List: spiral grain definition

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Original Posted By: Jeff Boatright
I know it's not rainy and cold outside and it's not theright time for theoretical discussions, but I'll startone just the same.Regarding the spacing of growth rings (tightness ofgrain), we want a minimum number of rings per inch sothat we have the minimum required strength. When therings are too far apart, the wood is not uniformlystrong because the wood between the rings is too soft.No problem understanding that.Regarding grain orientation, my understanding of thestrength of wood relative to the grain is that the woodhas essentially the same strength parallel and perpendicularto the grain but not the same dimensional stability. Thatis, changes in moisture content tend to deflect the wooddifferently parallel to the grain as perpendicular to it.Thus, with nice tight grained wood that is aligned with the axes of our spar (or longeron, or whatever), the wooddoes not tend to twist or kick when its moisture contentchanges with changes in humidity, or if it does, it isuniformly in the direction of the long axis and does nottend to twist or warp the wood or pull apart the glue joints.With spiral grained wood, or wood that does not have thegrain perpendicular to the direction of loading, changesin moisture content will warp the structural member andintroduce distortion or tend to pull glue joints apart.Is this the only reason we care about the grain orientation?As I understand it, it's not about strength.Thanks for any enlightenment any of you can add. And, ifI may state relative to Bill Rewey, "there but for thegrace of God go you or I". Bill did not lose his flyingskills overnight; no, not at all. Circumstances ariseduring flight that call for our best judgement, but sometimesthe circumstances win. Not a reflection of the pilot's skills,in many cases. Bill will need the support of his pilot friendsto help him evaluate his next move. There will be plenty ofthe "other kind" of people trying to make that move for him,like they are with Pieti Lowell. Let's stand by them.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Sun, 23 Aug 2009 21:58:31 -0400
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RE: Pietenpol-List: spiral grain definition

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Original Posted By: gboothe5(at)comcast.net
Gary and others=2CThanks for the responses on spiral grain=2C but I'm not sure you're understanding my question - By no means am I trying to shortcut anything or use substandardmaterial - I'm just confused about the requirements - hopefully the following will clarify my question.Both boards I purchased have well over 6 grains per inch. The both have vertical end grain (1 has grain about 15-20 degrees from vertical - anything under 45 deg. is within specifications). Both have met the 1 in 15 runout rule (more like 1 in 30 worst case) - this is the grain slope as measured on the face (widest part) of the board. So based on this=2C all is good. Where I get fuzzy is reading the EAA book "Wood". They show an example piece which has end grain nearing 45 deg. and due to this=2C it also has an edge grain. This is the first time I mentioned edge grain. This is where they say something to the affect of 'if the face grain runs out 1 in 20 and the edge grain runs out 1 in 16=2C then you must use a formula to determine actual slope because this is a spiral grain condition'. The point I'm trying to make is where the grain is near perfectly vertical - Does it also need to have edge grain? If so=2C I don't see how this is physically possible except at the point where the face grain runs out. I don't know if this makes any sense - Tomorrow I can try to clarify with pictures or drawings or something.Thanks=2CTom B.
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Re: Pietenpol-List: Re: spiral grain definition

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Original Posted By: Robert Ray
Regarding the wedge blocks, I believe they are only required at the two locations shown, as reinforcement for landing gear attachment. Some builders have opted to use lightweight balsa filler wedges in other locations, to avoid water collection in the pockets (not a bad idea).-Regarding plywood, one important feature of Aircraft grade plywood is that it is manufactured using waterproof (actually boilproof) glues. This will prevent the plies from delaminating, should the wood somehow become soaked with water. An economical alternative to Aircraft grade plywood for the fuselage sides is the use of BS1088 or BS6566 Okoume Marine Ply (Okoume is a mahogany-like tropical wood).-While it is not quite as strong as Aircraft ply made of Birch, it is apparently strong enough for this purpose, and is manufactured using waterproof (also boilproof) glues. In addition to the lower cost, it is also lighter (in weight, as well as color) than Birch, and available in 4' x 8' sheets.-A couple of sources for Okoume Marine Ply:--http://www.noahsmarine.com/http://www.b ... .com/-Bill C.//mail.yahoo.com ________________________________________________________________________________Date: Tue, 25 Aug 2009 01:13:12 -0400Subject: Re: Pietenpol-List: Re: spiral grain definition
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Re: Pietenpol-List: spiral grain definition

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Original Posted By: Ryan Mueller
Mike - on Props for the O200Check the "Legend Cub" website. Sensenich is making 2 experimental props for themand would be right for the Pietenpol.Jack - on the Engine mount dimensions. A65-8, C85-8, C90-8 all have the same enginemount footprint as the C85-12, C90-12, and O-200A except the O200A is riggedup for the "Lord" rubbers. The -12 and O200A engines all have a larger accessorycase to allow use of the Starter and Generator.If you are trying to run a Starter and Generator on the back of an O200, it mightbe a problem trying to use an A65/C85-8 mount. I am not sure - need to makemeasurements. But if you are planning to block off the starter and generatorplates on the back of the O-200, the A65/C85-8 mount should work just fine. Also... If the mount already works for a C85-12 with accessories, it will workwith an O200 with accessories. You do not have to convert the O-200 to use those machined conical bushings. Theywill work on the A65/C85 mount. But if you already have a cowling made tofit the A65 / C85-8, you will have to deal with the engine being located about3/4 inch farther forward when using the "Lord" mounts. Thats where the machinedbushings are most helpful. You can use them to upgrade an A65 airplane toan O-200 with minimal trimming on the cowl, etc..--------Terry L. Bowden254-715-4773http://terry-bowden.blogspot.com/Pietenpol A-75 "HopGrasser"Taylorcraft BC12-D N95598Curtiss Robin C-1 NR82HRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Mon, 24 Aug 2009 13:02:10 -0500Subject: Re: Pietenpol-List: spiral grain definition
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Re: Pietenpol-List: spiral grain definition

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Original Posted By: rmueller23(at)gmail.com
Subject: Re: Pietenpol-List: spiral grain definition
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Re: Pietenpol-List: spiral grain definition

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Original Posted By: rmueller23(at)gmail.com
Thanks for the info - I have used the info from AC 43.13 which is summarized in the EAA Wood book. Hopefullythese photos will clarify what I'm getting at. Inphoto #1=2C you can see vertical end grain and face grain - really thereis no edge grain unless the face grain runs out (slopes) and then therewould be some funky shaped portion of the end of the grain (where I noted "nograin here"). Does that make sense? If so=2C then the question I haveis about the funky shaped portion on the edge where the face grain runsout. Do we have to measure the slope of it? To me this would be atotally ridiculous expectation but I'm just trying to get clarification.Inphoto #2=2C you can see grain which is 20 deg. from vertical (stillvertical by definition up to 44 deg). Due to this end grain variation=2Cthere is now edge grain which needs to be measured for slope. This isthe only place I believe the spiral grain rule applies is when the endgrains aren't perfectly vertical and you have some edge grain. Doesthat make sense?Thanks for all your comments - I'm probably reading too much into this spiral grain thing but I'm just being cautious.Tom B.Date: Mon=2C 24 Aug 2009 13:02:10 -0500Subject: Re: Pietenpol-List: spiral grain definition
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Re: Pietenpol-List: spiral grain definition

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Original Posted By: TOM MICHELLE BRANT
Be carefull you guys, what looks like grain sometimes is not. I have experienced this first hand working with some lovely fine grained douglas fir. If you split a piece the crack will not nesecarily follow the aparent grain. The best way to determine the grain direction of both faces is to drag a sharp needle along the surface it will follow the actual grain or (I have not tried this one) drop a little ink on the wood and see the direction it runs as it soaks into the grain. If in doubt cut a few inches off the end of a board and split it with a sharp chisel.regards Mike T. Covering tail feathers. ----- Original Message -----
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Pietenpol-List: Re: spiral grain definition

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Original Posted By: "Bill Church"
Okay Tom, now I understand what you're getting at. The Ol' picture's worth a thousandwords, once again.I remembered an article that used to be on the GN-1 website (no longer active),and was looking through my files for a copy, but then I remembered that all theold Sport Aviation articles are available online (to EAA members), and I trackedit down. This article explains exactly what you're asking about. As yousaid, if the wood has true vertical grain (quarter sawn), there won't be any grainvisible on the long, 3/4"-wide faces of the board (top and bottom of thespar). So, don't worry about the "funky shaped portions". That will only becomean issue when the wood isn't truly vertical grain. The article explains howto calculate the "effective slope".To make things even more clear, they provide an example.This is a really good, useful article - so I hope the EAA doesn't mind that I'veattached a copy.Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/1966 ... ___Subject: Pietenpol-List: Re: spiral grain definition
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Original Posted By: jorge lizarraga
Okay Tom, now I understand what you're getting at. The Ol' picture's worth a thousandwords, once again.I remembered an article that used to be on the GN-1 website (no longer active),and was looking through my files for a copy, but then I remembered that all theold Sport Aviation articles are available online (to EAA members), and I trackedit down. This article explains exactly what you're asking about. As yousaid, if the wood has true vertical grain (quarter sawn), there won't be any grainvisible on the long, 3/4"-wide faces of the board (top and bottom of thespar). So, don't worry about the "funky shaped portions". That will only becomean issue when the wood isn't truly vertical grain. The article explains howto calculate the "effective slope".To make things even more clear, they provide an example.This is a really good, useful article - so I hope the EAA doesn't mind that I'veattached a copy.Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/1966 ... ______Date: Mon, 24 Aug 2009 21:37:02 -0700 (PDT)
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Re: Pietenpol-List: Re: spiral grain definition

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Original Posted By: "Jack Phillips"
Take a towel. One end in each hand. Stretch it out.Twist it up a few turns. This is what a spiral growntree looks like. Picture a board cut from that tree.I've seen trees with one complete spiral in a hundredfeet and others with a complete 360=B0 twist in 8 ft. There's an old four foot diameter log on WreckBeach just like that right now.And then there's trees that grow out the side of a hill.When you cut a board from such a tree in half it'll doone of two things. Those halves will either spread apart or the kerf will close up.Another thing to watch for is a very fine jog in the grain,kind of like daisy the dog in Dagwood. That comesfrom a tree falling on another log. If it hits just right itwon't break in half but will slightly shift the grain. Thisis a definite cause for rejection. Your not going to seethis often but it does happen as one hapless laddercompany found out.Oh, the vagaries of wood. Just like people.ClifRemember, no effort that we make to attain something beautiful is ever lost."~ Helen Keller There is an Austrian site that explains spiral grain pretyy simple explanation, also shows the correct way to lay quarter sawn wood in relationship to load bearing. On Mon, Aug 24, 2009 at 11:43 PM, Bill Church Okay Tom, now I understand what you're getting at. The Ol' picture's worth a thousand words, once again.________________________________________________________________________________
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RE: Pietenpol-List: Engine question

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Original Posted By: brian.e.jardine@l-3com.com
Hi Brian I bought an engine that spent many years on an airboat and what I learned from it ( the hard way) is that mostly unairworthy propstrike engines end up on airboats AND that airboat guys are brutal to their engines. I'd say 80% of the bolt threads that were excessable from the outside of the engine were stripped or damaged in some way. The crank failed a magnaflux test and needed to be replaced. The cylinders had so many broken fins that I had to replace them all and was very lucky to find someone who would even take them as cores. The engine had two Chevy pistons in it when I tore it down=2C it had been over reved so bad that all the pistons had baddly broken skirts. I did all of my own work and still could have bought a low time A65 for what I have in parts and machine work. Soooo be careful=2C I know I will never buy another airboat engine. Ed Grentzer
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RE: Pietenpol-List: spiral grain definition

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Original Posted By:
Tom=2CThe =931 in 15=94 grain slopecannot occur at any place in the board=2C not just the ends. If it does occur atthe end=2C and if you can cut it off=2C you have a good board. Viewing the end ofthe board shows two things=2C that the board was =93quarter sawn=94 (noflat grain)=2C and that you have the minimum 6 growth rings / inch. Without adoubt=2C your spars need to be the very best wood on the whole plane! If you haveany doubts=2C get a replacement. Best of luck to you=85.Gary BootheCool=2C Ca.PietenpolWW Corvair ConversionTaildone=2C Fuselage on gear(13 ribs down=85)
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Pietenpol-List: Engine question

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Original Posted By: Dan Yocum
Group=2CI have been debating on the type of engine for my Piet. I need something with horses since my field elevation here in UT is 4700ft. My neighbor has been over to visit and see my project as well as my T-craft project. He told me he has an old 0-235 on an airboat that he would sell me for $1200. It runs but leaks oil like crazy and needs new mags and who knows what else. It has a carb=2C not sure which type and the junker boat. I could turn and sell the boat for $600 and have a certified engine for $600. My fear is buying an old engine with no logs and an unknown history and having to pay big money to have it gone through to be able to put it on my Piet. Any suggestions from experienced fliers would be appreciated.BrianSLC=2C UTBrian JardineL-3 CommunicationsOperations Project Engineer640 North 2200 WestP.O.Box 16850Salt Lake City=2C UT 84116 L 801-594-3482brian.e.jardine@L-3com.com_________________________________________________________________Hotmail=AE is up to 70% faster. Now good news travels really fast. http://windowslive.com/online/hotmail?o ... ______Date: Wed, 26 Aug 2009 13:37:39 -0500
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