Dean Allen wrote: > Does anyone have any thoughts on the tandem seating arrangement? > Is this a minor inconvenience of having your passenger in > the back seat? Or, will this bird handle differently in the air? > I am a low time student pilot.
Below I've pasted in two messages that I found in the KR archives at http://www.maddyhome.com/krsrch/index.jsp by keying in the word "tandem". The bottom line is make sure the CG is under control, but my guess is that it's going to move quite a bit, and will be a handful to land with two aboard. You could always consider it to be a one seater with lots of baggage area. You'd have yourself the ultimate KR1.5T! As for the 51% rule, the interpretation that I've heard is 51% between you AND the guy previous builder is just fine, so I wouldn't worry about that one bit. And in reality it's probably only 30% done anyway! Who's to say, and nobody's going to question that. Below are the tandem comments that I made earlier... ------------------------------------- List-Post: krnet@list.krnet.org Date: Mar 11, 2001 7:08 AM From: Mark Langford <langf...@hiwaay.net> Subject: Re: KR> Lengthen a KR-2S? Steve Robinson wrote: > Question for you that are knowledgeable on the KR-2S design. I'm about to > order the plans and join your community (been passively reading net traffic > for some 2 years). My thought is to avoid the cramped two-side-by-side > concept and build a two-seat tandem taildragger. What issues do I need to be > mindful of? Widening the KR2 or S fuselage requires about 5 extra minutes of layout time as opposed to following the plans, and that's about the extent of the "redesign" effort required to widen one. If you can add the number 4" or 6" to the two or three dimensions given in the plan (top) view, you've just done the work. Maybe you don't have the plans yet and don't know it, but it's not like every piece of spruce is laid out on a measured drawing. Except for those few layout dimensions in the plan view, it's all "cut to fit". Even the instrument panel is a matter of "gee, what's that supposed to look like?", because you'll get no clue from the plans. The only other real potential construction time penalty is that you can't use RR's premolded top deck and canopy frame, which you obviously aren't going to be able to do with your tandem version either. Weight and balance is almost completely unchanged, since you've added maybe 2 pounds of extra material, right on top of the CG. For the tandem version, besides basic weight and balance and stability issues created from moving the wing and tail around, you'll have the problem of structure for the passenger and pilot. With the stock side-by-side seating, you have a real case of FREE LUNCH. The seating structure is provided with the spars. Just stretch a little canvas, composite, or aluminum between them, and you've got yourself a very light, structurally sound seat-for-two that is going to be there as long as there's enough plane left to fly. In the tandem, everything changes. Now you've got to support both a pilot and passenger. The KR2 structure is simply not up to that. If I let my 42 pound 6-year old daughter climb into my plane, I have to make sure to tell her not to step on the bottom ANYWHERE, or I'll be headed to ER and then fixing the resulting hole in the floor. Supporting a 180 pound passenger (times 4 for 4g flight=720 pounds) anywhere other than between those two spars is going to demand some serious structure somewhere, and some serious weight gain (and weight and balance shift, as well as performance degradation) is going to come along with it. ----------------- List-Post: krnet@list.krnet.org Date: Mar 11, 2001 7:08 AM From: Mark Langford <langf...@hiwaay.net> Subject: Re: KR> Lengthen a KR-2S? Steve Robinson wrote: > Question for you that are knowledgeable on the KR-2S design. I'm about to > order the plans and join your community (been passively reading net traffic > for some 2 years). My thought is to avoid the cramped two-side-by-side > concept and build a two-seat tandem taildragger. What issues do I need to be > mindful of? You're definitely talking total redesign here, with some very careful attention paid to CG. I'd think it would be a whole lot easier to just make it a little wider rather than re-engineer the whole airplane. The tail would end up being larger to handle the larger CG range, trading off some of the wetted area increase of a widened fuselage. Your idea of putting the passenger on the CG is good, but that almost certainly puts you behind him, and now your poor visibilty over the nose just went to NO visibility over the nose, with or without a passenger. Dual controls for a tandem are more complicated and heavier. And then there's the problem of talking to your passenger. I plan to spend a lot of time flying with wife and kids, so I'd rather not have that, but you may not have that "problem". I'd like to use the right seat to give my kids lessons on flying and navigation. It's your decision, but if you are determined to do this, I'd start with a weight and balance spread sheet (you can borrow a generic one I stole from the internet at http://home.hiwaay.net/~langford/WB.xls ) to get an idea of what you're up against, and the tradeoffs involved between tandem and side-by-side. The problem is that you probably don't know enough about the final weights to really even start this, which is going to end up being yet another excercise in aircraft design. I could go on, but you get the picture. I don't mind changing things that cry out to be improved, but I don't think side-by-side seating is one of them. Probably not what you wanted to hear... --------------- Mark Langford, Huntsville, ALN56ML at hiwaay.netsee KR2S project N56ML at http://home.hiwaay.net/~langford
