From time to time I have heard of idea of adding an extra wing bay to max (himax if I recall correctly). Although I have not contemplated doing so for current Eros build, I am curious as to the performance outcome and building experience of anyone who has made such a change. I.e., Did modification substantially alter/"improve"/meet performance objectives builder had in mind? Were any additional related changes made/required to accommodate the modification?

Any and all constructive comments are welcome. Intent is not really to re-hash general arguments for and against, domino effect, etc., of diverting from proven plans; but if anyone is willing to share their actual experience, or thought out perspectives of such a specific modification I would love to hear.

Thank you.

OK, nobody else has dived in, so here's my observations FWIW.

Adding an additional bay would increase the wingspan from 25' (no tips) to 27.5'. If you add tips as well, that would take your span to 29'. It would increase wing area by approx 12.5 sq.ft.

So comparing a square-tipped unmodified Max to a stretched wing with standard tips, the aspect ratio would change from 5.55 to 6.73, while the wing loading would decrease from about 5lb/sq.ft to roughly 4.7 lb/sq.ft (depending on your finished build & pilot weight, of course!).

Aspect ratio is a good indicator of glide performance. You can even very roughly equate an aircraft's L/D ratio to its aspect ratio to its glide angle, all other things being equal (which they never are). But crudely, you could expect to stretch your glide by up to 20%.

Your wing loading will keep the speed down, but the the increased area plus the improved aspect ratio will also improve your climb performance markedly.

So, on the positive side, you will have better glide & climb performance. You will burn less fuel as the wing is more efficient.

Now to the negatives. Structurally, you would need to recalculate the spar loads, which may also have a knock-on effect on strut dimensions & mounting points. You would almost certainly have to beef up the inner drag members in the wing. The ailerons might start to get a bit torsionally suspect (flutter?), & may not feel as nice. All this would increase the weight of your bird.

As to handling, the roll rate will be reduced, and you will be more susceptible to turbulence (lighter wing loading & longer span). Hangarage might be a bit more of a problem, as may ground handling, rigging, & transporting.

It would be interesting to hear how a stretched wing Max performed, but to do it properly could be more work than you'd expect, & you may end up with a rather lumbering beast as opposed to the very nimble bird that the Max is as drawn.

If you want to improve your climb & glide angle without changing the basics, you might do better to concentrate on reducing the 'D' part of the L/D figure with drag reduction mods on the standard  Max. Here's a few things I've done on my Eros to this end: http://www.lonesomebuzzards.co.....-Drag+Reduction+Mods

One other way I've reduced drag is by embodying a 6º reflex position for my flaperons. Helps on top speed & reduces fuel burn.

Bruce

Quoted from beragoobruce

OK, nobody else has dived in, so here's my observations FWIW.

Hey thank you for your insightful reply! This all makes very good sense, and is consistent with what I imagined might be someones rationale for doing so. I think someone on this board has actually built/flown such a bird, so I am hoping he might weigh in with his experience.

Thanks again for your great response Beragoobruce!

If you want a bigger wing that is already designed look at the old Tandem Airbike wing.

Quoted from radfordc

If you want a bigger wing that is already designed look at the old Tandem Airbike wing.

Good thought. Thank you. Are there any public domain plans for the airbike wing available anywhere? Would love to examine... Would also still love to hear from anyone who has flown max with extended wing.

Now if you put the old tandem airbike wing on a Hi Max, wouldn't it seem as if you're flying a tandem airbike, but without the extra passenger?

One Caveat, I think the mounts may be different.