Today's Message Index:
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1. 02:13 AM - Re: Re: Slats (JC Gilpin)
2. 03:04 AM - Slats or no? Willis and Suzuki ... (Coen van Wyk)
3. 03:40 AM - Re: Re: Slats (Joe Spencer)
4. 06:14 AM - Re: Re: Slats (Roy Szarafinski)
Message 1
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Gday Roy,
That's a real good question.......
We tested many times with several aircraft, and couldn't detect any pitch
trim change with slats or slats removed. Which would indicate that the
slats weren't contributing much, if anything, to lift at cruise. More
recent experience of an aircraft with an already hose heavy tendency (early
model 701 with fuel tank in the cowl and battery mounted on the firewall)
noticed an increased hose heavy feeling with the slats removed.
In 1990 I carried to Sun'nFun, one of the first reduction drives for a
Subaru EA81 from a local manufacturer looking for a market over there.
When I showed it to Chris and said that the installed weight of the Sub
would be about 200lbs, he immediately said, "...too heavy, too heavy..."
That was the first year that Zenith had a 912 on the 701, and even with
that engine I noticed that they had a lump of lead wired onto the tail skid
(this would have been an early model 701 with the fuel tank in the cowl).
Hans' 701 with a Rotax 912s weighs in at max forward 20% (only pilot and
min fuel), and fully loaded at 26%, referenced from the leading edge of the
wing itself, without slats. It balances very well at all speeds. This is
already right at the forward end of the recommended range, so if you are to
have an engine that weighs considerably more that the Rotax, it would
certainly be too nose heavy.....
You mentioned John Boldings 65018 nose profile. I think that'd be a good
way to go to help that heavy engine. I did calculations long ago and can't
find them now, but as I remember, it appeared that extended leading edge
would move the center of lift forward about 3%. You might still need to
put the battery right in the tail, but hopefully not add extra weight.
This is getting a bit experimental, but not radical, and you seem to be
cautious and aware of the issues, so it should be an interesting
experiment. I look forward to hearing the results.
JG
*
From
Roy Szarafinski
I would like your considered opinion in regards to using the full 65018
nose rib and leading edge. The CG range being 20-35% in the original
configuration, from front edge of slat to rear edge of flaperon. Does or
did you notice any aft CG tendencies without the slat? My reason for asking
is that my firewall forward weight will exceed 200 poun ds and I do not
want to create a compounding situation running slatless.
*
*
*
Message 2
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| Subject: | Slats or no? Willis and Suzuki ... |
I have been reading the discussion re slats and vg's with interest, as I am still
far from that point. Present thinking is to build to plans, and later do some
experimentation.
But I must take up the "Willis vs Suzuki' argument, with a dose of good humour!
I had a Suzuki, did some amazing off road thinks with it, put some Land Rovers
to shame, and then got a Willis, albeit the 'modern 1964" CJ3B model. And there
is just no comparison, unless you run on the road a lot! over the rocks in the
mud, through the ditches, the Willis will be absolutely boring, it goes where
you point it, while the Suzuki has to work really hard.
So it boils down to the mission, and as far as flying is concerned, I want to be
as slow as I can when I get near the ground. Which is why I bought the CH701.
Now, if the difference is as small as it seems to be from the data, the VG's
must be considered. I will operate at hot and high, so I was wondering how the
figures work out under those conditions?
Message 3
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>>>So, slat-less and using a heavier engine means more rear ballast for
me, which
I'd rather avoid as much as possible
Hi Roy
The slats weigh 13# and even tho close to the CG range help move the CG
aft when removed.
Message 4
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Thanks Joe, JG and of course John B.
This project has been sitting on top dead center for too long now, I've been
looking at half skinned wings for close to 5 years and your inputs have cle
ared up some of my confusion.
I'll gain back some of those 13 pounds by upping the leading edge skin to .0
20, the .016 is pretty fragile. I substituted 2024 material for the wing att
ach points long ago, that's the only other change on the SP wing.
What I want to end up with is a cruiser version of a 701 since the mission c
hanged and I'm already so far into it. I am leaning toward picking up a set o
f 750 cruiser plans, the single strut and tail group have appeal.
It's time to cut some forming blocks, maybe.
Roy Szarafinski
www.roysgarage.com
roy@roysgarage.com
rvickski@yahoo.com
On May 13, 2013, at 6:40 AM, "Joe Spencer" <jpspencer@cableone.net> wrote:
>
>
> Hi Roy
> The slats weigh 13# and even tho close to the CG range help move the CG af
t when removed.
>
>
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