The more I read about the KR-2S the more it grows on me. However, I have also read that, like the VP-2, it makes a better fat single seater than a cruiser for 2 adults.
+++++++++++++ Hi Sean I have been through the very same thought process and frustrations for a year now - including spending loads of time designing my own based loosely on a KR. Maybe my thoughts and observations will save you some time, so for what it is worth. I prefer to work with wood and I do not have the budget to throw $25k at a kit that is headed for $50k plus. There is little doubt that RR offers the basis for a great airplane with a low budget and costs that can comfortably be spread out over the build period - particularly if you live in the US where you have immediate (overnight) access to everything at really good prices. Construction can start with a small budget - just enough spruce, ply and adhesive for the fuselage, so $500 will keep you busy for months (the entire spruce / ply / foam package is only $1500). There is also little doubt that it can be built as a competent and safe airplane that will last just as well as any glass slipper or spam can - Dan Diehl's KR2 (N4DD) will be 30 years old this July and still going strong (and looking good) - there are many others. Consider the improvement in technology over 30 years, the ease of communication and the advent of refined engine conversions - it becomes clear that it has become easier to build a stunning, reliable and safe airplane. The important part of your question is really about changes to the original design. The short answer is to keep these to a minimum and the build will be much faster (there are KR's that have been completed in a few months) but in order to have a realistic two seat bird - some changes are necessary. There is enough data from completed airplanes to know that this in entirely possible provided you understand that each change has the potential to enforce other changes etc. and will substantially increase the build time (and weight). The KRnet is a super source of info, along with many well documented builder web sites. It is like having 10 different step-by-step construction manuals. I have researched all the airplanes where info is available - this is my advice. Refer Mark Langford's site (Miscellaneous Stuff) for the fuselage stretch (not what he did but what he says he wished he had done). Redraw the side and plan view incorporating the new length and moving the wide-point (plan view) back closer to the wing trailing (better aerodynamics and cockpit width were it is required). Any stretch over the stock KR2S will soften the effect of widening the fuselage - some have added up to 10" (34+10=44"). As a guide, the older C172 is 39" at the shoulder (inside width), so anything over that will be nice. The 2S already ads an inch or two to the fwd fuselage and that should make for ample leg room. If you are going to use a larger (heavier) motor - don't add any more length to the front. One other mod that may be helpful for tall people (refer Larry Flesner) is to lift the turtle deck / canopy an inch or three if necessary. No more than necessary, this directly affects frontal area. Resist the temptation to "beef things up" - rather do a really good job of building to plan with good materials. It is unlikely that you will build out at anything like the weight suggested by RR, so here are my thoughts on accommodating a higher MOTW. I know that MANY KR's are happily flying around at 200 and 300 lbs over weight - the KR that I flew weighed in at 1200lbs with myself and the builder on board. I believe that the wing loading at 1200 lbs is still perfectly acceptable, particularly if you have enhanced the stability (CG envelope) by stretching the aft fuselage (increased tail moment / tail volume). I don't believe that it is clever to totally ignore the fact that the spar was designed for less - even if it appears to work for others. If nothing else, they have a reduced safety margin for the day the bird encounters abnormal loads from severe turbulence or whatever - sh*t happens. We know that the AS 5048/15 results in a deeper spar, so we know that the spar is meaningfully stronger if made exactly according to plan (except for the extra depth) - so that takes care of that. I have read that the WAF,s are more than adequate, but to my mind these are so critical to the integrity of the wing and difficult to control (quality of the metal / treatment) so I did some extra reading. Search the KR archives on "WAF" and look for input by Don Reid. He discusses the topic and makes some suggestions for improving the existing arrangement - he provides the rationale and arithmetic that convinced me. Also visit his web site and look at "some older pictures" - his rendition of the main spar WAF's are visible in the pictures (single row of larger bolts). I would discuss (with a structural engineer) the impact of using the next size up 4130 (maybe 25% thicker). The pre-fab wing skins are great and must save a great deal of time - pity they are only available for the RAF48. The Diehl skins offer extra wing span that appeals to me - not so much because of the lower wing loading, but because of the higher aspect ratio that has a positive effect on efficiency / performance. Take care Steve J
