Good day all - some advice would be greatly appreciated. My plans are very old (circa 1976/77) so some of this may not make sense to those with more recent issues.
The spar pillar spacing for the centre section (Main Spar) varies - typically: FWD Spar Dwg 5 (from the centre out) - 7.5"; 7"; 5"; 10"' 10" = total 39.5" half-span. I assume this spacing was relevant to the mountings of the original retract gear. The same dwg also shows another view of the fwd main spar with a pillar spacing of 13.5" centres?? Question 1: What have the builders done that opted for the later fixed u/c? The overall spar length (Center Fwd) is given as 83" with (*65) in parenthesis? Could this be the KR1 wing dimensions? Similarly, the Outer fwd spar length 77.5" (*59.5"). The outer fwd spar the pillar spacing is given as 6" TYP. It has intrigued me for many years that the pillars are not all the same thickness (shear web to shear web). Is there an engineering reason for this or is weight reduction the reason? Maybe spar breathing? We all want the strongest and lightest spar - I am placing more emphasis on strong, so the main spar will be laminated from 6mm (1/4") or whatever it takes to make the bend to the dihedral angle at the fuselage (refer Mark Langford's notes on his mods). I was further encouraged when I saw that Riley Collins did something similar - a bent spar. Using full length spruce (14') allows the center spar to go up to half span (for better flaps). The WAF's move further from the cantilever pivot, so they carry less load. One-piece spars were considered (and designed) but if ever I had an off-field landing ...... Question 2 is: The KR plans call for no taper on the centre section and a double taper for the outer spar caps. That makes sense with a short carry through spar but in my case the centre section spar is much longer. I am making the spar caps nearly 30% deeper (66mm vs. 50mm) and would like to shed some weight by uniformly (proportionately) reducing the thickness all the way out. With a laminated spar it will be extremely convenient if it is OK to keep the same cap width and reduce the cap depth all the way out (through the joiners at half span). i.e. - a single taper in front view (no taper in plan view). Is there and engineering reason /principle that makes this a bad idea? As a matter of interest - I opted for the P51 wing section (BL17.5). I was stunned to see the similarity to the 16% AS5046 section - I will probably use the Ashok 15% for the tip. (Plus 2 degs with 2 degs washout) Regards Steve J Askies"AT"microlink.zm
