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Yes, and this is the main reason I'd like to retain the slats.

How about using outboard wing only ailerons (might need to make them bigger)
and keep the slats on the aileron portion, only?

-- Jim in NC

Back when I was MUCH younger I flew A3-B Skywarriors.
(http://www.soaridaho.com/Naval_Pictu..._12-Aug-64.jpg)
It had aerodynamically actuated slats. They slid in and out using rollers
on a track. When sitting on the deck gravity would cause them to extend.
At normal cruising flight speeds the air resistance would push them in.
They popped out at high angles of attack. The system worked pretty well;
however, heaven forbid that one of them got stuck in while the other
extended!

Wayne
http://tinyurl.com/N990-6F


"Paul Saccani" wrote in message
...

On Sat, 24 Sep 2011 16:32:53 +1000, "Jeff R." wrote:

Thanks for your reply, Paul.
Some comments below in context...


"Paul Saccani" wrote in message
.. .
On Sat, 24 Sep 2011 11:27:57 +1000, "Jeff R." wrote:



I'm inclined to trust Chris Heintz, as the engineer/innovator, but at the
same time he has (had - he's retired) a significant financial attachment
to L.E. slats. Not just on the 701, but right up to th 850.

Depends on your mission. The STOL performance of the 701 is such that
most don't even need to use the flaps. The slats do dramatically
steepen approach and departure, and if that's what you need....

Not so much need as "want".
Catch is, I also "want" a decent glide slope and fuel economy.
(yes, I know)

Indeed. VG are a good compromise.

I plan to cut the first stringers in about a year from now.

As I recall, the stringers are all in the forward cabin, and all need
solid rivets. You may find it worthwhile to buy those and the main
spars from Zenith, with the solid riveting done.

If you intend to build as per the edition 5, 7th revision, you will
find that some items, such as the spar caps, are non-standard custom
extrusions for Zenith. They will sell you a spar complete, but not
the components to make the main spar.

Still not decided on full kit or build from plans.
I rather fancy myself at metalwork, but the cost of the raw materials makes
the CNC cut kit awfully attractive.

IIRC, it was about four grand for all the aluminium sheet in my one.
But I suspect that ordinary prices would be a good deal higher.

Now, if the US dollar would just oblige my falling down again...

Better take a good look at shipping costs and duties.

Well, it has been done, but the company was bought out, I'm not sure
if they are in production again. PegaSTOL was the old company.

Yup. Saw that, and like the idea (lots) but the weight?

No idea. I don't know how their mechanism works. I've thought it
might be worth trying Tiger Moth slot style spring loading and cable
locking. They get pushed back at speed, but pop out as you slow down.
Locking is done to prevent accidental asymmetric extension - it
aggravates any tendency to a spin.

Most people don't know this, but at one time (late eighties), CH was
recommending that some CH701 use VGs attached to the slat!

!
Seems a bit greedy.
I take it that didn't work... (?)

It did, but it was only for some, which had a high drag at cruise
speeds. The VG was a quick fix, but the location of the slat was
changed as a general fix.

It's just an interesting piece of trivia.

What you lose if you use VG instead of slats, besides the steepness of
approach and departure, is the "stall" controllability. With the
slatted 701, you can go way on the wrong side of the lift/drag curve,
so you no longer have enough lift to stay up, but aileron remains
effective and there is no wing drop. It just gets "mushy". Sans
slats, with VG, you get a conventional stall, and wing drop. Nothing
nasty, but a little faster, with a little less control.

Yes, and this is the main reason I'd like to retain the slats.

Well, it is experimental, after all.... I'd stick with the slats
first off, though you might want to consider redesigning the slat
brackets so that they can be removed and re-instated, rather than
using the wing without slats but still with the brackets, as per CH
advice. I don't know if the brackets create a great mischief or not,
but going with his recommendation seems a safe bet. Myself, I plan on
keeping them and tuft testing to see how much of a mischief they
make. I might use them for fences, that way, if the mission needs it,
I can put the slats back on.


12kg.
Hnh.
I have main courses at dinner bigger than that.
(anecdote edited for the sake of propriety)

Baggage compartment is limited to 18 kg, it's a fairly significant
weight for a little aeroplane.

Still, the drag is a real bummer.
I still don't know how much long distance stuff I'll be doing - I hope a
lot - but then I suspect that good STOL will also be a significant factor
in my dream "trip-around-Australia".

It's a big country - plenty of space to land.

Endurance - economy - STOL?
Helluva balancing act.

Having said that, I'm leaving mine on for the moment.

With an EA81 and a 68" 3 blade warp drive at 16.5°, mine does 70 kts @
13 litres an hour, @4,000 RPM for the engine, 1,820 RPM for the prop.

Hmmm.
None too shabby.
75hp?

100 HP.

That enough for good STOL two-up?
How's the rate of climb?

I can't answer either of those yet. 600 fpm is the figure that comes
to mind.

In due course, I plan to fair my struts, but you could order the strut
material for the 750, which is in an aerofoil shape, and save yourself
a lot of bother.

Fair them rather than remove them?

Well, I do need them to keep the wings on....

Do you need the extra square feet, considering what you said above about
the slat's contribution to total chord?

Struts... The standard ones are round 4130 tube. The parasite drag
of each sides struts is almost as much as the whole wing. The 750
uses aerofoil section aluminium extrusions. For the tube, you put
thin fairings on them to reduce the drag.

For the other idea, I reckon foam inserts could be shoved in the slots
to reduce drag, either with or without VGs. Then you could remove
them after long distance cruising to investigate off the beaten track.
Less aggravation than taking the slats on and off, plus you could take
the slats with you on a long trip. That would probably weigh less
than a retractable slat and be less likely to create mischief.

Also, having the elevator bell crank bracket on the aileron torque
tube sucks. I have a part 35 engineered solution, where the bracket
is mounted on a fitting that is fixed to the airframe, and allows the
torque tube to rotate inside it. This gets rid of the elevator cable
tension issue, where the aileron and elevator interfere with each
other.

Thanks again for all that Paul.
It's good to toss this stuff around.
(just had a quick look at your page at Zenith...)

That saves me suggesting that you join Zenith Aero, though I don't
recognise your name on the new members list.

Those photos are pretty rough, I've taken some better ones, but
haven't put them up yet.
--
Cheers,
Paul Saccani
Perth, Western Australia.

On 9-21-2011 17:36, Wayne Paul wrote:
Thank you for the responses.


Maybe this is all a sign of the times and we are becoming a society
where people no longer develop the skills and self confidence to build
or repair thing.

Or maybe, things have gotten SO expensive and folks have changed hobbies
to something cheaper?

This is definitely true in the world of Amateur Radio
where homebuilt system were common and now seldom exist.

Not in my house! In the past 5 years or so, I've built transverters
for 222, 902, 1296 and 10 GHz for myself. Built transverters for 222,
902, 1296, 2304, and 3456 for others to help them get on the upper
bands. Build my own antennas as well. Last commercial rig I bought was
back in about 2003 or 2004.

Scott
N0EDV
http://corbenflyer.tripod.com



Again, thank you for the replies.

Wayne
HP-14 "6F" W7ADK
http://www.soaridaho.com/