Stemme S12 in Michigan this Saturday, May 20th (KOZW) @ 4 pm

On Tuesday, May 23, 2017 at 11:31:44 AM UTC-4, Sean Fidler wrote:
Arcus overheating: I understand that one cannot run at full power
for more than a few minutes with the ArcusM (or 32?).
Sorry if I'm mistaken.

You are mistaken; ArcusM (unlike 32) has no time-limit on max power.
Max RPM is limited to 5 minutes 6600-6700, but max power is 6600 anyway.
Range in the manual (with 3 tanks) is listed as 135nm.

As I understand it, the ArcusM and others like it are designed for
self launch over an airfield and immediate soaring, not cross
country cruising under power.

Yup. Absolutely not optimized for XC cruise under power.

The only downside I can see is that landouts in fields are not a good option
(flipping over forward in soft ground is a risk) and once in said field
getting out would be a major undertaking.

And field landings are prohibited in the manual IIRC.
So Stemme owners I know must be much more conservative about getting low.
As in any motorglider, landing is plan A. Plan B is when the motor starts.

I also wish to fly at an airport where the Arcus or 32 would be very
impractical (likely impossible). I would need to integrate with moderate
regional airport power traffic and there is no grass parallel for
glider operations.

I fly my ArcusM at a regional airport with plenty of power traffic.
No problem to assemble solo in the AM and taxi (to and from runway).
You've seen me taxi to runway and back to your hangar at your home field.
Its a different machine than Stemme, but perhaps not as limited as you imagine...

Maybe I'll get the boys to bring the Ionia Arcus over to the Howell airport and see how it taxis. No question that the ArcusM is a phenomenal sailplane.

Thanks Dave.

On Tuesday, May 23, 2017 at 1:26:01 PM UTC-4, Sean Fidler wrote:
Maybe I'll get the boys to bring the Ionia Arcus over to the Howell airport and see how it taxis. No question that the ArcusM is a phenomenal sailplane.

Thanks Dave.

The only issue for these big birds is availability of wide taxiways. I am lucky that from the hangar to a runway I have probably 150-200 feet wide path. I have a wing tip wheel so all of my wing needs to be on the taxi way. Some airports don't have taxiways wide enough for a 21 m ship like mine. So there is always a reason to put on the 18 m tips. Arcus has a wing wheel a few feet inboard from the wing tip and that will probably solve the narrow taxiway problem. The wankel will also easily cruise to a destination at low power settings with no heating up issues at all. You don't need full power for cruise. You would exceed speed limit for the airframe if you tried to maintain a level flight with full power.

On Tuesday, May 23, 2017 at 5:11:11 PM UTC-4, Andrzej Kobus wrote:
On Tuesday, May 23, 2017 at 1:26:01 PM UTC-4, Sean Fidler wrote:
Maybe I'll get the boys to bring the Ionia Arcus over to the Howell airport and see how it taxis. No question that the ArcusM is a phenomenal sailplane.

Thanks Dave.

The only issue for these big birds is availability of wide taxiways.
I am lucky that from the hangar to a runway I have probably 150-200 feet
wide path. I have a wing tip wheel so all of my wing needs to be on the
taxi way. Some airports don't have taxiways wide enough for a 21 m
ship like mine. So there is always a reason to put on the 18 m tips.
Arcus has a wing wheel a few feet inboard from the wing tip and that
will probably solve the narrow taxiway problem. The wankel will also
easily cruise to a destination at low power settings with no heating
up issues at all. You don't need full power for cruise. You would
exceed speed limit for the airframe if you tried to maintain a
level flight with full power.

All true. Antares at 20m gives me less than 1" extra space to edge of
taxiway (standard USA size) so requires some care, but tailwheel-in-rudder
and heavy tail weight gives precise steering so this is doable.
Arcus with inboard wing-wheel or Antares at 18m make this less critical.

Stemme has a different issue: it can get "rocking" (in roll) and hit a tip.
I know this has happened more than once (on grass fields) - damage results.

Always trade-offs!

See ya, Dave

I thought I read where the S-12 wheelbase was wider than the S-10, so the rockinrollin might be less of an issue.

On Tuesday, May 23, 2017 at 8:18:42 PM UTC-4, Duster wrote:
I thought I read where the S-12 wheelbase was wider than the S-10,
so the rockinrollin might be less of an issue.

I don't know, but also span is bigger....

Yes, the main gear track is wider in the 12 than the 10.

On 5/23/2017 6:47 PM, Dave Nadler wrote:
On Tuesday, May 23, 2017 at 8:18:42 PM UTC-4, Duster wrote:
I thought I read where the S-12 wheelbase was wider than the S-10,
so the rockinrollin might be less of an issue.
I don't know, but also span is bigger....

--
Dan, 5J

The 12 is 6 inches wider than the 10 and they say that makes a big difference. I was told that in certain circumstances the 10 could start a rolling motion in taxi that would not stop (or worsened) until the pilot slowed or stoped the glider and let it settle. At Howell airport (6/10 taxiway for smoothness) it was never that bad but there was only a 18 inch to 2 foot clearance on some taxi lights. A big roll at the wrong time and it might have been possible to get a light. Most thought I was being to cautious and it was almost impossible to hit a light if near the centerline while taxiing. This is no different than towing a pure glider down a taxiway with taxiway lighting I suppose except the trailing edge is exposed and damage is far more severe.

For what it's worth...

Sorry, I heard 6 inches wider gear. I'm not sure if that's each side from center or total increase. Again the taxi was amazingly easy in Howell, and it was windy, and the taxiways are not perfect by any means (lots of elevation change on the airport), and it was blowing 20 knots all day.

That said, I wasn't used to 82 foot wings. Few are. They were both well over the taxi lighting and it was a 3/4 mile taxi to the runway. So maybe 100 sets of taxi lights along the way. If it was my 369k on the line I would have be very cautious taxiing at first. I'm sure eventually I would get more comfortable. Even a slight dip in the pavement caused eye opening movement in each wingtip. I have witnessed 2 sailplanes towed into runway lights (trailing edge first) and it still makes me nervous. But in this case I think it was unnecessary.

After a weekend which saw a significant number of pilots with no experience in the Stemme taxi out to the runway themselves, roll was clearly not an issue. I think that point says great things about the stability of the glider with its new increased landing gear width.

Sean

On 24/05/2017 09:28, Dave Nadler wrote:


Stemme has a different issue: it can get "rocking" (in roll) and hit a tip.
I know this has happened more than once (on grass fields) - damage results.

Always trade-offs!

See ya, Dave

I walked interestedly around the first Stemme I saw some years ago with
an aeronautical engineer friend. As we chatted about it he ran one hand
under the trailing edge of the wing tip and suggested I do the same.
The aileron bottom was heavily abraded for the outboard 4 feet or so.
Same on the other side.

'Every aeroplane touches the edge of the envelope somewhere' he said.

--
GC