KR>Spar lamination direction - Oops
My main reason for stating that you should not drill through the glue joint was because it is very hard to keep a drill bit going straight + Good point - could ruin an expensive spar if the drill bit goes walkies. >>>. If I build another one, it'll be just like you built yours. + Thanks - that gives me more confidence. Still bothers me that Don Reid did not like the idea - I was expecting a boffin (like him) to step up and declare this to be as good as (or better). My instinct is to stagger the WAF bolt holes so as to void having them on the same line - anyone have any thoughts on that. Holes in a row offer images of the perforations in toilet paper. What size bolt holes are required for mounting the Diehl type u/c? (I have old KR plans with retracts). I presume that the Grove rendition has bolts all the way through the spar from the bottom up? Thanks for the input Steve J Zambia
KR>Spar lamination direction - Oops
At 09:58 AM 6/10/2004, you wrote: >Thanks - that gives me more confidence. Still bothers me that Don Reid >did not like the idea - I was expecting a boffin (like him) to step up >and declare this to be as good as (or better). > >My instinct is to stagger the WAF bolt holes so as to void having them >on the same line - anyone have any thoughts on that. Holes in a row >offer images of the perforations in toilet paper. You should notice that in my original answer, I said "should not go through the glue line". I did not say "must not". If I were in that situation, I would try to align the laminations so that the hole misses the glue line. If I could not, then I would make darn sure that the hole is well drilled, perpendicular and also reamed to size. In the traditional construction, it is also acceptable to do a lot of different scarfing and inlaying techniques. Larger pieces may be scarfed with smaller. Cross banding (high density overlay, like birch plywood) can be inserted into the interior of the bolted joint area. This is tough to describe, but think of a mortice and tenon joint. The tenon is made of high density wood or plywood and glued into the mortice. This high density insert is trimmed flush with the end of the spar. The bolts then go through the tenon and spar material. As long as the spacing is greater than the allowable minimum, it makes no difference at all whether they are in line or staggered. Don Reid - donreid "at" erols.com Bumpass, Va Visit my web sites at: AeroFoil, a 2-D Airfoil Design And Analysis Computer Program: http://www.eaa231.org/AeroFoil/index.htm KR2XL construction: http://users.erols.com/donreid/kr_page.htm Aviation Surplus: http://users.erols.com/donreid/Airparts.htm EAA Chapter 231: http://eaa231.org Ultralights: http://usua250.org VA EAA State Fly-in: http://vaeaa.org
KR>Spar lamination direction - Oops
In a message dated 6/10/2004 9:59:54 AM Eastern Standard Time, ask...@microlink.zm writes: What size bolt holes are required for mounting the Diehl type u/c? (I have old KR plans with retracts). I presume that the Grove rendition has bolts all the way through the spar from the bottom up? Steve, The bolts supplied for the attachment on the diehl gear are 1/4", I did replace mine with 5/16 due to the gross weight I am anticipating. I also floxed the attachment to the spar and the legs to the bracket. You need to do some planning as to where to drill these to place the holes as close to the centerline of the spar caps as you can. The spar will have an upward dihedral angle and the brackets need to be level to maintain the correct geometry. On my bird this also caused the bracket to protrude from the bottom of the wing on the front corner of the bracket. (new airfoil) no problem as the fairings will cover it I think the grove gear mounts on a 90* angle bracket that would be mounted to the spar in a manner similar to the diehl. I don't know if any of the KR plans show anything other than retracts (about 1/3 of book) I bought my plans in '96 or '97 Hope this helps Riley Collins Rutledge, Tn
KR>Spar lamination direction - Oops
I was expecting a boffin (like him) to step up and declare this to be as good as (or better). You should notice that in my original answer, I said "should not go through the glue line". I did not say "must not". .. And then gods came down from the heavens and the gods spoke. Listen to what I say my son and don't utter what I have said lest you do it as I did it an no other way. Now go forth and spread the truth to brother Langford. Amen ___ALL-NEW Yahoo! Messenger - so many all-new ways to express yourself http://uk.messenger.yahoo.com
KR>Spar lamination direction - Oops
His take on it is exactly that, it doesn't matter either way, but don't put a bolt through the glue line. +++ This would otherwise be my reaction as well - but I am forced to give the matter more thought. My centre section spar caps comprise 6mm (1/4") laminations to allow the dihedral bend - so there is no way to avoid the WAF bolts intersecting glue lines. If I use the RR design WAF - all the bolts will intersect the same lamination. I plan to have a longer centre section, so the spar is substantially thinner (in front view) at the WAF location - not much room to move around. I opted for 1/4" laminations as I figured this would be about right to accommodate the dihedral bend. My first reaction on seeing this post was to consider thicker laminations and resort to steaming as a means of achieving the radius. My second reaction was to re-read all my material on glue joints. Every indication is that a properly done glue joint is as at least as strong as the host material. A scarf joint is allowed in a wing spar (cap) according to AC43 - at an angle similar to the minimum spec on grain run-out within wood, suggesting that a glue line is at least as strong as nature's own laminations (wood-grain) - is this not the very reason that a laminated beam is seen to be stronger than a single piece of lumber (of the same size and wood)? The topic should be a head up in other ways as well when we drill holes in the spars for various other reasons - this will influence the main undercarriage location (under the spar or in front of the spar) to avoid drilling even larger holes through the laminations. These holes offer an even greater moment arm than the WAF's. Steve J Zambia
KR>Spar lamination direction - Oops
Steve Jacobs wrote: > My second reaction was to re-read all my material on glue joints. Every > indication is that a properly done glue joint is as at least as strong > as the host material. A scarf joint is allowed in a wing spar (cap) > according to AC43 - at an angle similar to the minimum spec on grain > run-out within wood, suggesting that a glue line is at least as strong > as nature's own laminations (wood-grain) - is this not the very reason > that a laminated beam is seen to be stronger than a single piece of > lumber (of the same size and wood)? Personally, I agree 100%. I'd still do it the way you are doing it, and have no reservations at all. If I build another one, it'll be just like you built yours. I'm not sure it's necessarily the glue that makes a laminated beam stronger (although is probably a contributor), but the fact that if there is a hidden knot inside a large monolithic beam it goes undetected, whereas in a lamination it would be culled out and replaced with good wood. Also, the wood grain isn't perfectly aligned between laminations, so there's a certain amount of "crack-checking" that goes on, like in plywood, which I would consider to be a good thing. Mark Langford, Huntsville, AL N56ML at hiwaay.net see KR2S project N56ML at http://home.hiwaay.net/~langford
KR>Spar lamination direction - Oops
There are production planes with laminated bent spars made of a lot of thin laminations. I am sure that a lot of them have bolts through the glue joints. My main reason for stating that you should not drill throught the glue joint was because it is very hard to keep a drill bit going straight through the softer wood and the harder glue. You will need to be very carefull and use a good drilling jig to make sure the bit comes out where it is supposed to. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -Original Message- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Mark Langford Sent: Thursday, June 10, 2004 7:20 AM To: KRnet Subject: Re: KR>Spar lamination direction - Oops Steve Jacobs wrote: > My second reaction was to re-read all my material on glue joints. Every > indication is that a properly done glue joint is as at least as strong > as the host material. A scarf joint is allowed in a wing spar (cap) > according to AC43 - at an angle similar to the minimum spec on grain > run-out within wood, suggesting that a glue line is at least as strong > as nature's own laminations (wood-grain) - is this not the very reason > that a laminated beam is seen to be stronger than a single piece of > lumber (of the same size and wood)? Personally, I agree 100%. I'd still do it the way you are doing it, and have no reservations at all. If I build another one, it'll be just like you built yours. I'm not sure it's necessarily the glue that makes a laminated beam stronger (although is probably a contributor), but the fact that if there is a hidden knot inside a large monolithic beam it goes undetected, whereas in a lamination it would be culled out and replaced with good wood. Also, the wood grain isn't perfectly aligned between laminations, so there's a certain amount of "crack-checking" that goes on, like in plywood, which I would consider to be a good thing. Mark Langford, Huntsville, AL N56ML at hiwaay.net see KR2S project N56ML at http://home.hiwaay.net/~langford ___ to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
