Brodhead Pietenpol Association

Original Posted By: "Wayne Sippola"
Hello, folks;I won't jump in on the 'grain orientation' discussion except to add a little side-note to those using Douglas fir rather than spruce. In my experience (3 yrs. building a single-place wood-frame/foam/fiberglass experimental, and probably one more year to go!)- Doug fir tends to splinter and split a lot easier than spruce. Where fasteners (nails, screws, whatever) are going to go through the wood, it sure is easier to prevent problems when you are going across the grain (looking at the end of your piece, the "layers" are like a stack of pancakes, and you're drilling or nailing straight down through it). One other little thing is that the growth ring stuff will tend to deflect your screw/nail/drill bit to one side if you are not working perpendicular to the grain... it seems to be much harder than the wood between the rings. If your grain is angled (not either parallel or perpendicular) I can almost guarantee you that your nail/screw/drill bit will wander off on the angle that the grain/growth rings go... even out the side of your piece. Don't ask me how I know ;o)And, yes- I believe that the grain shown in the drawings is simply "artistic license" to show that it's wood. Technically inaccurate, but just fine for folks who understand proper use and selection of aircraft wood (like farmers in the 1930's in the Midwest, eh?)Oscar ZunigaMedford, Oregonmailto: taildrags(at)hotmail.comwebsite at http://www.geocities.com/taildrags/____ ... __________

Original Posted By:> Owen Davies
I still think the capstips are supposed to have the grain horizontal,although it is NOT a strength issue as the capstrips and longerons are allused in a truss framework and virtually all stresses on the individualcomponents are in compression or tension. The main stick of wood used as abeam are the spars (and the tail feather beams) and these are used with thegrain horizontal. But again as mentioned it is not for strength but forgreater wood stability. I would suggest someone check the grain orientation of some bentwoodfurniture that is not made up of laminations. I suspect it would be in thesame orientation as a leaf spring or deck of cards.Wayne Sippola, Winnipeg----------

Original Posted By: Wayne Sippola
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Original Posted By: "Wayne Sippola"
I remember reading from a reliable source that the grain is to vertical incapstrips so that when you have to nail the leading edge sheeting on, thecap strips will not bounce with each hammer blow.Chris BobkaTech CounselorMinneapolis----- Original Message -----

Original Posted By: "John McNarry"
> > > Doug Bryant observed:> > > The grain direction does not matter for any wood except for the sparsand> > that is because the wood expands the least across the grain. DougBryant> > I'd add one exception, which no doubt everyone knows already,> but it seems worth mentioning now, because some of the same> reasoning may apply to the longerons.> > Grain direction also matters for the long pieces of capstrip that> form the upper curve of the wing ribs. The wood layers that> make up the grain go vertically, in part because doing it the> other way would increase the risk of separating the "laminations"> that make up the grain and splitting the stick as it bends over> the tightest part of the curve.> > I'd think that same reasoning applied to the lower longerons.> Their curve is not as tight, but the splitting forces must be higher> in the thicker cross-section.> > Also, isn't the strength significantly different with or across the> grain? Either is probably strong enough, but for the strongest> possible airframe...> > Owen Davies> > > > > > ________________________________________________________________________________

Original Posted By: TomTravis(at)aol.com
> >> >> > Doug Bryant observed:> >> > > The grain direction does not matter for any wood except for the spars> and> > > that is because the wood expands the least across the grain. Doug> Bryant> >> > I'd add one exception, which no doubt everyone knows already,> > but it seems worth mentioning now, because some of the same> > reasoning may apply to the longerons.> >> > Grain direction also matters for the long pieces of capstrip that> > form the upper curve of the wing ribs. The wood layers that> > make up the grain go vertically, in part because doing it the> > other way would increase the risk of separating the "laminations"> > that make up the grain and splitting the stick as it bends over> > the tightest part of the curve.> >> > I'd think that same reasoning applied to the lower longerons.> > Their curve is not as tight, but the splitting forces must be higher> > in the thicker cross-section.> >> > Also, isn't the strength significantly different with or across the> > grain? Either is probably strong enough, but for the strongest> > possible airframe...> >> > Owen Davies> >> >> >> >> >> >>>________________________________________________________________________________