What a great site !!  Im new to this forum. I started building my plane approx. 5 yrs ago... two jobs and two relocations later i am finally settled down a bit and have time to start building again. i have a majority of the parts built. I am combining ideas from the HD and XL plans. my wing will have the HD airfoil less the center wing box (will increase span to equal orig.wing area) no flaps.   I had the alu.  spring gear made. I am using flush rivets (mostly solid) rather than the button head blind rivets.  this  requires dimpleing but end up with a "cleaner look"   I will use the 650 canopy design with the rollover protection. has any other builders combined ideas from other designs ?

My previous wood and fabric airplane was built from diferent designs as well. 




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Hey Mike .. I'm all for mods and I'm also not familiar with the 601 design in depth (so I don't know definitively the exact and specific components you're describing - but I do know the meaning of those components in general) ... I would just want to make sure you understand that a center wing box is a core structural component of the wing structure. If you make mods in this section by deleting wing box components (which provide both load bearing for the wing loads and also torsional rigidity for the wing itself) then you may require additional ribs, thicker spar web sections (or doublers), modified spar caps and the like. You would well note that wing loading is highest at inboard wing stations (closest to the fuselage) which is presumably where the center wing box section is placed.


BUT ... as long as you've done the wing loading and structural analysis (and/or are willing to build 2 sets of wings - one to load with lead-shot bags according to the appropriate values and distributions of wing load i.e. for ultimate load for testing ... and the other to fly - then go ahead! I'm reminded of Don Knuth (well known computer-scientist) "I have only proved it correct, not tested it" ... For a significant structural modification I would strongly consider empirical testing in addition to analysis!


At a minimum I'd recommend a review of Chris Heintz' excellent book "Flying on your own wings" (I just bought mine recently) which provides an excellent sweeping review of key aspects of aeronautical design, without getting bogged down in the details of specific areas (e.g. static analysis, aerodynamics, airfoil selection etc) where better single-topic references are available. It's a great book!


Of course, at the end of the day this is why we have the experimental category .. but make sure you're working on the basis of experiment, not blind faith ;) Go for it .. good luck If however you don't want to through the process above, I would strongly recommend sticking to one wing design or the other .. not a hybrid of the two. Your call :)

Hi and thank you for your insite. no I wont build two sets of wings and test one set to failure. really only one wing would have to be tested to failure....  I worked with a experimental kit designer/builder and we did stress testing with a structural engineer. so i have experience with that.I am not an engineer however with almost 30 yrs in aviation structures design and rework from ultralights to boeings new composite widebody 787. I have a widly diverse amt. of experience. Im not perfect and I dont know it all.  my reasons for doing these mods are strictly mine and are for my personal reasons. with the XL wing design  after studying the plans I wasnt too keen on the fwd spar being tiilted the way it is. I understand the thinking... keep the same web width allowing a overall thinner airfoil. but the spar when angled the stress loading is changed and transmitted to other parts of the wing. which I figured may cause a  bit more twist and flexing  than my likeing. which now we know may have been occuring. I like the HD wing. its a fatter airfoil a bit slower... but im not in a big hurry.  but a much more "traditional" design. the center box will be built as it is on the HD plans but will not extend out past the fuse.  With the HD design i wasnt too excited with the landing gear attaching to the wing.  Im not the worlds best pilot and sometimes plant down a bit hard....   I dont need to transmit those hard landing loads directly to the wing. so thats the reason for the spring gear option. there are more things that i will be doing as well. but again i must stress are my personal thinking and may not be correct but are merely based on my aviation experiences.    

take care!!






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