Turbo

With the stock setup, I can hold the plane stopped to about 4000 rpm, enough, I think, for a decent mag check.  Following Fred and RFPhntmfxr's thoughts, I am inclined to remove the toe brakes entirely, actuate a single master cylinder remotely with a bicycle's Bowden cable and brake lever on a highly curved stick, which would move the top of the stick back towards me, so I could still swing my leg over it for entry & exit.  Then I would cut the two rudder interconnect tubes and re-weld them together with the pilot's side pedals (minus brakes) clocked forward to give the same firewall clearance on both sides.  Will that buy me enough footroom?  I don't know.  Will the lost ability to use differential braking for sharp turns on the ground be a problem?  Also don't know.  Will that lost capability deprive me of a way to escape an impending groundloop?  I doubt it.  There's quite a discussion going on in another thread, but I know that some of the guys are not shorties, so thought I'd ping y'all for ideas.

P.S. that looks like a good idea.  How about headroom?  New slingseat with less padding?

I am 5'11", and have a hard time squeezing myself into the Avid C's confined cockpit.  It seems my legs are too long, as my knees are inches from the top of the stick, and the rudder pedals with toebrakes contort my feet to the point where my lower legs cramp up.  This is disconcerting to say the least, especially when contemplating an imminent landing!  My slingseat is all the way back.  So, you guys that are as tall as me or taller:  how do you do it?  Is the Mark-4 cockpit any bigger?  My bird doesn't seem to want to fly well with feet off of the rudder pedals.

So you 6'-plus guys:  how do you deal with this limitation?  Or is this airplane only for shorties?

I have often wondered why nobody has criss-crossed the space below the fuselage with slightly longitudinally offset gear legs, then use the kind of vertical spring-shock arrangement above the wheels.  The Just Aircraft SuperStol gear pivots about the centerline keel.  Criss-crossing the lower fuselage give even better geometry, with shallower angles, and hence even less squat as the gear compresses.  It puts more stuff out in the propwash, though.  Still, this concentrates virtually all the gear's force at the shock/spring attachment.

"Rimless" shoes make a huge difference, as they don't get stuck under the "V" bar in the middle.  I can't imagine how someone with large feet (size 11 and up) can safely operate the Avid with the stock setup.

Re-reading paragraph 5 of Ken Kelso's blog brings a significant issue to light.  This may well be why using differential braking to stop a groundloop with our stock toe-brake setup is so difficult.  The toe brakes exacerbate the problem instead of helping.  

While I was using premix, my plugs needed to be pulled then shaken & blown out prior to flying, or the engine wouldn't start.  Even going to the extended tip plugs didn't solve the problem.  After putting the oil injection system back in play this problem has totally disappeared.  I have the pull-start.  It saves weight, not only from the starter itself, but the battery as well.  I don't consider a restart while flying as feasible, however.

Drag is a myth!

Seriously, though, how about two flat screens: one is an efis with flt parameters and engine info, second is gps.  The second can be as simple as a tablet, as many have the gps chip built-in.

I'm not sure I have the skill to pull that off.  For this old man, things seem to happen faster.   I always land without braking, then try to apply them equally to slow the airplane down.  A single master cylinder would cure the issue of uneven braking and its negative effects under normal circumstances.  If the runway is sufficiently wide, one might consider landing diagonally on it to lessen the crossflow component.

I heard that the swept fin and rudder on the C-150 loses authority at high AoA, and that the TD mod really only works well on the older straight tail versions.  This loss of authority makes it hard to control on landing.

If you're unsure, make sure whatever prop you buy is ground adjustable, so you can play with pitch to make the engine happy.

Kitfoxes have more seatback recline and (I think) more legroom, with a more comfortable overall pilot position as compared with at least my Avid C.  But the Avid's foward visibility is much better.

Despite having to yaw your way along while taxiing, vs the Avid's superb forward visibility, the Kitfoxes I've seen look to have a more comfortable pilot position.  Maybe that's part of why they command a higher price on the used market.  Dean must have shorter legs than I do.

By-the-way, I have found that using the oil injection system my plugs stay oil-free, and I don't have to pull them out to shake and blow the excess oil off every time I go to fly!  The inverted engine is not so bad after all!  It's likely true for those premixing Amsoil at 100:1 also.

Yeah, sorry guys, that's me.  My legs are too long and prone to cramping.  Otherwise, I like the little bird.  Was contemplating a brake lever on the stick, then clocking the pilot's side pedals (minus master cylinders & toe brake levers) forward a smidge to buy additional legroom.  But there are other issues.  Oh well!

Interesting!  Counted cells in the brochure pic above, and yeah, it must be a 12" spacing!  Was thinking of a second wing tank on my C, but it would only be useful when I'm solo.  

O.K. but the 1150# gross is for the basic Mark 4 STOL, not the HH version (see above).  Like I said, assuming 4.4 Gs instead of 5.7 for the same wing gets you very close to the 1150# gross touted for the Mark 4!  My guess is the negative G requirement bumped it down to 1150# from the 1180# you'd get from just changing the positive G limit.  The bigger lift struts on the HH must be to maintain the negative G limit at the even higher GW of the HH.  It's all about column buckling in the lift struts at negative G.  If there were no structural changes to the basic STOL Mark 4 over the C model, the 1150# gross number should apply to the C model as well.  JimChuk, you're the best historian we've got!  What can you tell us?

This is all very interesting.  I wonder why the model C (stol) gross weight is only 911 lbs.  Was there additional structure added to the wing for the Mark 4 to bump the gross weight up to 1150 lbs? 

If I only claim 4.4 Gs instead of the 5.7 the original STOL wing was sandbag tested to, I get 1180 lbs for allowable gross.  Maybe the negative G requirement took a 30 lb bite out of this?  No mention has been made to my knowledge of any negative-G testing, though, although you'd think they would want to have done it.

Much less!  A forward-facing flat, at AR=1 has a drag coefficient of 1.1.  At high AR it asymptotes to 2.0.  Either of these can be cut in half by placing a rounded fairing on the windward side, such that the air flowing around it is able to leave the leeward edge in the outer-flow direction.  Forward-facing flats are an aerodynamic sin!

Who is Dana's mother, anyways?

One nice thing about moving the brakes to a hand brake on the stick is, at least on the earlier Avids, is the possibility of more legroom, and better ergonomics. With the brake components gone from the pedals, the pilot-side rudder pedals can be clocked forward maybe 10 degrees or so.  The passenger-side rudder pedals can't be clocked forward,, as there's no bulge for master cylinders.

Nick,

It's coming into focus for me, though.  More legroom, more speed, bigger gas tank(s).   My damn legs are too long!

Looking at my original post, it occurred to me that it's highly likely that in the cruise case the lower-surface flow, if it separates at all, re-attaches on its own as a turbulent layer, so it would make sense that nothing would help there.

Here's a suggestion:  Glue or sticky-tape a styrofoam block to crush when the TW spring compresses, then go out and make a few landings.  First, make sure the foam doesn't rebound, or if it does, by what fraction.  This way you can get the answer you seek, but nobody seems to have the answer to.  The foam block needs to be thick enough that it doesn't undergo column failure, though.

So, Manu, how is the new trim tab working out?

The one thing Trent did not do is reposition the VGs , so they probably ended up too far aft with the LE extension on.  Can't say I blame him though; moving them is a lot of work!  Then there's the question of where they should be placed with the LEX on.

My Avid STOL C climbs really well, in fact I just took it up to 8500 ft and it ran fine, even without leaning.  I agree with C5 that the 582 is a reliable engine if treated right.  In my view, though, the C model lacks adequate legroom, and the minimal seatback incline makes it ultimately uncomfortable to fly for long.  It looks like the Kitfox cockpit is better ergonomically.  And the stock 14 gallon tank is too small to really go anywhere.  I hate to always be worrying about fuel!  Love the viz over that inverted engine, though, and the oily plugs problem seems to go away when the oil injection system is used.  I'd also like more speed; seeing 50kts GS on the gps flying into a little wind is daunting!