Nimbus 3, or not to be?

[Jono Richards]

All,

I am thinking of 'up-grading' in the not too distant
future, and have looked at the possibility of a Nimbus
3.

Now, although I have never flown one, I have seen a
couple and what to know the pros and cons...

By word of mouth I have heard of possible yaw problems/keeping
it straight..but is this statement founded? Also, I
have noticed from pics that some have wings a bit like
the new Nimbus's, with the upturned ends, and others
have 'normal' wings..whats the difference, and is the
newer one really better?

But yeah..are there any problems I should be aware
of with Nimbus 3's, either currently known, or that
are due to ageing?

Would appreciate a good response! And I know the pro...57:1
or thereabouts

JR

[g***@sbcglobal.net]

I have about 600 hours in my Nimbus 3. I have not noticed a yaw
problem. There are some techniques used to center thermals that are a
little different, pulling up, yawing and dropping the nose for
instance. You have to think further ahead then in a 15 meter ship, it
does not react as quickly. It takes about twice as long to put
together, but then you can often fly when others cannot due to the
increased search area.

I never use the shorter tips, always have used the "upturned" wings and
it climbs very well. As you pointed out performance is great. Some of
the older 3's don't have the fuselage wing fillet retro fitted, I think
these are important.

[jphoenix]

I have fewer hours than Gary in my 3, about 100 I think. I was flying a
1-26 before I transitioned into the 3, no problem. The wings are a bit
longer than the 1-26, so that took some getting used to. I left the
gear down on my first flight by mistake, but once I discovered the gear
handle it was no problem. I think it's easy to fly, others may not
think so. With the flaps in L and the big powerful spoilers, it lands
very well. Big disk brake, 500x5 wheel - it can take plenty of abuse.

Regarding yaw, the wings are long, so some turbulence can push it
sideways a bit, but the rudder straightens you out just fine. At 80
knots it is very stable, in my opinion. Because the wings are 10 meters
longer than normal, it doesn't have the same roll rate as, say, a 1-26;
but its glide ratio is much better. Take a look at the performance page
on my website to get an idea of what these things can do. All these
numbers were developed by Dick Johnson when he owned my Nimbus 3 and
he's provided a lot of good data for this model glider:

http://www.jimphoenix.com/jimphoenix2/pages/Nimbus/N3%20Data/N3%20Data.htm

No bad habits. I've heard that the wing fillet fairings are important,
but mine has always had them, so I don't know how they perform without
them. Most N3's have the 25.5m "eagle tips" as we call them now. No
aging problems that I've discovered, mine is a 1982 model so it would
be a fleet leader for aging. I did find the aileron mixer bolt loose
during the condition inspection last week, but I just tightened up the
nut and it's OK. No US AD's, they're all experimental over here. Some
TN's that should be done, like the elevator rod. Wedekind sleeves on
the fuselage L'Hoteliers are nice - speeds up rigging a bit. Mine has
two batteries. CG hook on mine, but I never had a problem with that.

I normally rig mine by myself using the Amazing Udo Dolly. Takes about
an hour to get it all together. Like Gary says, thermaling is no sweat,
once you get it wound up it just goes around fine. But the smart guys
that fly these don't turn much, I still have some learning to do in
that department so I spend more than 25% of my flight thermaling,
unlike most of the better pilots.

Cockpit is exactly the same size as Ventus B or Discus B cockpit.

Gary Kemp and Garret Willat did pretty well in the US Open Nats last
year, only Nelson Funston beat them in his Nimbus 4, but I don't think
those guys ever stop to thermal, they just go straight to the turnpoint
and keep going after that ;-)

More detailed photos here: www.jimphoenix.com

Jim

[Ian Strachan]

I have flown many hours in a Nimbus 3T and a Nimbus 3DM. Yes,
stability is slack directionally and you need lots of rudder to
counteract adverse yaw when aileron is applied. It is also rather
slack longitudinally and aero-tows in turbulence can be hard work.

The Nimbus 4 that I now fly is much better in these respects. But do
not let that put you off the 3, it is a magnificent glider. You just
push the rudder in proportion to the aileron (lateral stick) that you
put in.

Perfomance is much more important than handling, in my opinion. Many
years ago I was criticising a particular type of glider for lack of
roll response in thermalling and that guru of the time Nick Goodhart
simply said "but Ian, do you fall out of the thermal", "no", "then
that's all right then".

Nick was right.

Performance over handling, within reason.

I encourage amyone to upgrade to a higher performance glider than the
one that they are now flying. More glide angle always worth having.

And if I might be a mite biased, an outboard motor (as our friends in
sailing say) is even better. Personally, I do not any more like
landing in fields, or trailer retrieves. So self launchers or self
sustainers (often mis-named "turbos") give you the best of both worlds.
Good soaring and the probability of not landing "with the cows" as the
French say.

Gliding literature in the past was often about "herioc retrieves".
What we should be about is SOARING and again, SOARING. Not rigging and
derigging in fields surrounded by corn , cows or whatever.

[Robert Hart]

Post by Jono Richards
I am thinking of 'up-grading' in the not too distant
future, and have looked at the possibility of a Nimbus
3.
By word of mouth I have heard of possible yaw problems/keeping
it straight..but is this statement founded?

I'm a Nimbus 2c driver and have not flown a 'three', but have talked to
many who have.

From their description, it sounds like the 3 is as under-ruddered as
the 2, but this does not result in yawing instability, which is in fact
governed by the fin rather than the rudder. An aircraft with significant
yaw instability (as in having difficulties keeping it straight) would
not get a CofA - although most aircraft have a very slow yaw instability
(which most pilots never notice).

The lack of rudder authority in the 2 required me to learn a new thermal
entry technique, as my early attempts resulted in me rollling but not
turning until I was well past the thermal due to the adverse yaw from
the ailerons (aided by the huge moment arm) holding the glider straight
even if full rudder was applied.

I was clued into how to get into thermals by a veteran pilot who flow
Nimbus 2's when they were new.

Roll in as normal (which is slowly in a Nimbus 2), using full rudder.
When the right angle of bank is reached, keep the in to turn rudder on
and flick the stick across as if to roll out of the turn. The glider
turns into the thermal immediately (with the yaw string flapping wildly,
but down't worry about that), so you only need the opposite aileron for
a moment.

On blue days here in Australia, which can be really strong, you can hit
thermals in the cruise at 100 kts. Provided I am alone, I use a modified
entry under these circumstances to avoid flying through the thermal.

Pull up and roll, as if going into a Chandelle, feeding in flap as the
speed drops, but allow the speed to fall through the stall. As Nimbus 2s
won't spin unless the CG is well aft, the nose slides away into the turn
as the inner wing stalls and if you hit the core right (with the oomph
of a strong thermal adding to the airspeed) you end up at about 50kts
turning perfectly centred in the thermal (at least, I manage that about
once in three attempts at present).

If you don't hit the core, the nose slides away a bit more and you will
need to centre the thermal, but you won't have gone racing past the thermal.

I suggest that you practice your chandelle's before doing this so that
you are comfortable with the manoeuvre!

Again, do NOT do this if the thermal is occupied or you have other
gliders close by as the risk of collision is too great! If the thermal
is occupied, you'll have plenty of warning it's there and an aerobatic
entry is not required.

On a wider note, if you haven't flown open class gliders before, try one
out before you buy one. You may not like them (and certainly
rigging/derigging them is a way to find out who your friends are). Open
class pilots tend to be more solitary in their flying habits and if you
like going round in a gaggle with other 15m ships, you might not find
that possible to do on open class tasks!

I love my Nimbus 2c and have vowed to keep her until she (her name's
Alice) becomes the limitation in our flying rather than me. So far, we
have 600+ hrs together and I am thoroughly enjoying the learning process!

[Bill Daniels]

Post by Robert Hart

Post by Jono Richards
I am thinking of 'up-grading' in the not too distant
future, and have looked at the possibility of a Nimbus
3.
By word of mouth I have heard of possible yaw problems/keeping
it straight..but is this statement founded?

I'm a Nimbus 2c driver and have not flown a 'three', but have talked to
many who have.
From their description, it sounds like the 3 is as under-ruddered as the
2, but this does not result in yawing instability, which is in fact
governed by the fin rather than the rudder. An aircraft with significant
yaw instability (as in having difficulties keeping it straight) would not
get a CofA - although most aircraft have a very slow yaw instability
(which most pilots never notice).
The lack of rudder authority in the 2 required me to learn a new thermal
entry technique, as my early attempts resulted in me rollling but not
turning until I was well past the thermal due to the adverse yaw from the
ailerons (aided by the huge moment arm) holding the glider straight even
if full rudder was applied.
I was clued into how to get into thermals by a veteran pilot who flow
Nimbus 2's when they were new.
Roll in as normal (which is slowly in a Nimbus 2), using full rudder. When
the right angle of bank is reached, keep the in to turn rudder on and
flick the stick across as if to roll out of the turn. The glider turns
into the thermal immediately (with the yaw string flapping wildly, but
down't worry about that), so you only need the opposite aileron for a
moment.
On blue days here in Australia, which can be really strong, you can hit
thermals in the cruise at 100 kts. Provided I am alone, I use a modified
entry under these circumstances to avoid flying through the thermal.
Pull up and roll, as if going into a Chandelle, feeding in flap as the
speed drops, but allow the speed to fall through the stall. As Nimbus 2s
won't spin unless the CG is well aft, the nose slides away into the turn
as the inner wing stalls and if you hit the core right (with the oomph of
a strong thermal adding to the airspeed) you end up at about 50kts turning
perfectly centred in the thermal (at least, I manage that about once in
three attempts at present).
If you don't hit the core, the nose slides away a bit more and you will
need to centre the thermal, but you won't have gone racing past the thermal.
I suggest that you practice your chandelle's before doing this so that you
are comfortable with the manoeuvre!
Again, do NOT do this if the thermal is occupied or you have other gliders
close by as the risk of collision is too great! If the thermal is
occupied, you'll have plenty of warning it's there and an aerobatic entry
is not required.
On a wider note, if you haven't flown open class gliders before, try one
out before you buy one. You may not like them (and certainly
rigging/derigging them is a way to find out who your friends are). Open
class pilots tend to be more solitary in their flying habits and if you
like going round in a gaggle with other 15m ships, you might not find that
possible to do on open class tasks!
I love my Nimbus 2c and have vowed to keep her until she (her name's
Alice) becomes the limitation in our flying rather than me. So far, we
have 600+ hrs together and I am thoroughly enjoying the learning process!

I also fly an N2C and Roberts post seemed just a bit strange to me as I read
it. I fly a lot of different gliders from a 2-33 to a Duo Discus and I have
never thought of the N2C is under ruddered. Of course, like almost all
gliders, if you use a lot of aileron at low speeds, there won't be enough
rudder to oppose the adverse yaw.

I do use a trick to get a faster roll rate. Counter-intuitively, it's to
back off the aileron a bit. It seems to work with any glider if it has
appreciable dihedral. Slightly skidding the turn entry uses the dihedral
yaw-to-roll coupling effect to accelerate the roll. A dab of extra aileron
takes the skid out as the wings approach the desired bank angle. Now, I'm
not saying use a lot of skid. About 10 degrees of yaw string deflection is
enough to start and reduce that as the final bank angle approaches.

Using this trick the N2C will reverse bank 45 degree right to 45 degree left
in about 4.5 seconds which is about what most gliders do. Without it, the
bank reversal takes about 5.5 seconds.

All the big birds have thier quirks but you quickly get used to them. I
know this isn't about the N3 that you asked about but the trick probably
works fine. Jim Phoenix got out of a 1-26 into a Nimbus 3. That pretty
well tells the story.

Bill Daniels

[nimbusgb]

Remember 'There is no substitute for span!' If you are seeking the
ultimate in glide performance and you are operating on a budget then a
Nimbus 3 is the way to go.

If you are rigging every day it can become somewhat tedious unless you
have lots of friends. If you operate a '3 from a hangar you have almost
the perfect ship.

Ian
Ex Nimbus 3

[Craig]

I have about 4 seasons on my N3 and still can't stop grinning every
time I fly it. The biggest adjustment was learning to trust the flight
computer.. Looking out at the horizon you just won't believe you can
make the glide the computer gives you. Having such 'long legs" to go
between lift opens up lots of options for flights that might otherwise
be marginal.

I agree with Robert about using the adverse yaw to your advantage while
thermalling. The big wings have lots of yaw inertia and often full
rudder isn't enough to get things around quickly enough. Briefly
feeding in aileron opposite to the turn creates enough drag on the low
wing to swing the nose around nicely. It's a different animal than the
15m birds. Not worse, just different.

Most of the N3s have (or had) gelcote problems. It's probably worth
the extra money if you can find one that has been reprofiled and
refinished. We are looking at refinishing ours in the next few years
and will probably go with polyurethane to avoid the brittle cracking
problems that seem to happen with prestec refinishes.

Craig Funston

[Robert Hart]

Post by Bill Daniels
I also fly an N2C and Roberts post seemed just a bit strange to me as I read
it. I fly a lot of different gliders from a 2-33 to a Duo Discus and I have
never thought of the N2C is under ruddered. Of course, like almost all
gliders, if you use a lot of aileron at low speeds, there won't be enough
rudder to oppose the adverse yaw.

Interesting - I've yet to meet a Nimbus2c pilot that doesn't think the
way I do here in Australia (not that we have many such ships - even if
there are two at my club).

Post by Bill Daniels
I do use a trick to get a faster roll rate. Counter-intuitively, it's to
back off the aileron a bit. It seems to work with any glider if it has
appreciable dihedral. Slightly skidding the turn entry uses the dihedral
yaw-to-roll coupling effect to accelerate the roll. A dab of extra aileron
takes the skid out as the wings approach the desired bank angle. Now, I'm
not saying use a lot of skid. About 10 degrees of yaw string deflection is
enough to start and reduce that as the final bank angle approaches.

Interesting - I'll certainly try this the next time I fly her (hopefully
this coming weekend).

I wonder if the difference we feel could have anything to do with the
thermals we are used to encountering. Here in south east Queensland,
Australia, the thermals are quite strong (6+kts is an average day and
8+kts common) and down low they are narrow as well. Take off about
1.5kts for the standard winter day, although we still get 10kts to
10,000ft some days in the winter.

I suppose it depends on where in the US you are from as I would expect
the southern areas have at least as good conditions as we do here (and
possibly better in the desert areas).

Robert

[Bill Daniels]

Post by Bill Daniels
I also fly an N2C and Roberts post seemed just a bit strange to me as I
read it. I fly a lot of different gliders from a 2-33 to a Duo Discus
and I have never thought of the N2C is under ruddered. Of course, like
almost all gliders, if you use a lot of aileron at low speeds, there
won't be enough rudder to oppose the adverse yaw.

Interesting - I've yet to meet a Nimbus2c pilot that doesn't think the way
I do here in Australia (not that we have many such ships - even if there
are two at my club).

Post by Bill Daniels
I do use a trick to get a faster roll rate. Counter-intuitively, it's to
back off the aileron a bit. It seems to work with any glider if it has
appreciable dihedral. Slightly skidding the turn entry uses the dihedral
yaw-to-roll coupling effect to accelerate the roll. A dab of extra
aileron takes the skid out as the wings approach the desired bank angle.
Now, I'm not saying use a lot of skid. About 10 degrees of yaw string
deflection is enough to start and reduce that as the final bank angle
approaches.

Interesting - I'll certainly try this the next time I fly her (hopefully
this coming weekend).
I wonder if the difference we feel could have anything to do with the
thermals we are used to encountering. Here in south east Queensland,
Australia, the thermals are quite strong (6+kts is an average day and
8+kts common) and down low they are narrow as well. Take off about 1.5kts
for the standard winter day, although we still get 10kts to 10,000ft some
days in the winter.
I suppose it depends on where in the US you are from as I would expect the
southern areas have at least as good conditions as we do here (and
possibly better in the desert areas).
Robert

I doubt thermal strengths are the issue. Here in the mountain west of North
America, 8 - 10 knot thermals are common with occasional 10 - 15 knotters
and turbulence to match.

Try the trick and post what you think. The more the yaw string is displaced
in the direction of the roll, the faster the roll rate. To really get the
best result, use all the rudder available right from the beninning and not
quite enough aileron to center the yaw string. This may turn out to be only
about an inch of stick movement.

It's really important not to let the yaw string get to the opposite side of
the intended bank direction. If it does, the dihedral is fighting the
ailerons inducing the pilot to use more aileron than neccessary and
therefore require more rudder than is available just to oppose the adverse
yaw.

Lest I set of anyones flame alarm, I'm NOT advocating skidding turns, just
roll entries. I agree with Dick Johnson that the best thermalling turns are
with the yaw string 5 - 10 degrees to the high wing.

Bill Daniels

[Jono Richards]

Right well cheers for that guys...I will see what happens
in the future as to whether I can find the right one
(or the money!)

Couldnt give me an idea of how to much reprofile/refinish
the glider?

Thanks anyhow

JR

Post by Craig
I have about 4 seasons on my N3 and still can't stop
grinning every
time I fly it. The biggest adjustment was learning
to trust the flight
computer.. Looking out at the horizon you just won't
believe you can
make the glide the computer gives you. Having such
'long legs' to go
between lift opens up lots of options for flights that
might otherwise
be marginal.
I agree with Robert about using the adverse yaw to
your advantage while
thermalling. The big wings have lots of yaw inertia
and often full
rudder isn't enough to get things around quickly enough.
Briefly
feeding in aileron opposite to the turn creates enough
drag on the low
wing to swing the nose around nicely. It's a different
animal than the
15m birds. Not worse, just different.
Most of the N3s have (or had) gelcote problems. It's
probably worth
the extra money if you can find one that has been reprofiled
and
refinished. We are looking at refinishing ours in
the next few years
and will probably go with polyurethane to avoid the
brittle cracking
problems that seem to happen with prestec refinishes.
Craig Funston

[g***@sbcglobal.net]

I just did mine in 2004/05, did all the grunt work and had an expert
paint and direct me, still cost $14,000

[Stewart Kissel]

Post by Jono Richards
Couldnt give me an idea of how to much reprofile/refinish
the glider?

Well you oughta check Jim Phoenix's most excellent
site to see how much fun it is doing on your own...