Maxim Magazine soaring article

On Thursday, March 30, 2017 at 7:50:40 PM UTC-4, Bob Kuykendall wrote:
On Wednesday, March 29, 2017 at 8:54:45 PM UTC-7, Eric Greenwell wrote:
The Perlan II was ... just molds at the time of Fossett's death...

Ah, but they were the best molds a crap-ton of money could buy!

I tried to interest Einar in a soft-tooled approach that would have cost about 1/20 of the CNC-cut, resin-infused molds that Windward eventually made, but he went with Greg's approach instead. We're currently using that soft-tool tech to make racing airplane wings, and it's working fine.

--Bob K.

soft tooling would have been a really good approach, given that P2 is a one-off. why did they elect to go with much more expensive mold materials?

On Friday, March 31, 2017 at 9:05:57 AM UTC-4, ND wrote:
On Thursday, March 30, 2017 at 7:50:40 PM UTC-4, Bob Kuykendall wrote:
On Wednesday, March 29, 2017 at 8:54:45 PM UTC-7, Eric Greenwell wrote:
The Perlan II was ... just molds at the time of Fossett's death...

Ah, but they were the best molds a crap-ton of money could buy!

I tried to interest Einar in a soft-tooled approach that would have cost about 1/20 of the CNC-cut, resin-infused molds that Windward eventually made, but he went with Greg's approach instead. We're currently using that soft-tool tech to make racing airplane wings, and it's working fine.

--Bob K.

soft tooling would have been a really good approach, given that P2 is a one-off. why did they elect to go with much more expensive mold materials?

Possibly the materials and methods of construction may have made use of those tools unworkable. If they used autoclaved prepreg, the molds may have needed to be less economical.
UH

On Friday, March 31, 2017 at 7:25:29 AM UTC-7, wrote:

Possibly the materials and methods of construction may have made use
of those tools unworkable. If they used autoclaved prepreg, the molds
may have needed to be less economical.

I ran the numbers on that, along with a bunch of other stuff. Prepregs have a lot of advantages, especially in strength, but they offer only a relatively modest premium in stiffness per unit mass. Stiffness is a lot more critical than strength when it comes to glider type structures.

I think that the main issue was that my Indigo Skye proposal was for a glider about 15% larger and 25% heavier than Greg's, predicated on space suits as backup for a pressure cabin, and also predicated on a 12 hour nominal mission profile as opposed to Greg's 8 hours. I think that that more conservative approach to the aero design did not adequately compensate for my agile RP approach to the fabrication.

--Bob K.

wrote on 3/31/2017 7:25 AM:
On Friday, March 31, 2017 at 9:05:57 AM UTC-4, ND wrote:
On Thursday, March 30, 2017 at 7:50:40 PM UTC-4, Bob Kuykendall wrote:
On Wednesday, March 29, 2017 at 8:54:45 PM UTC-7, Eric Greenwell wrote:
The Perlan II was ... just molds at the time of Fossett's death...

Ah, but they were the best molds a crap-ton of money could buy!

I tried to interest Einar in a soft-tooled approach that would have cost about 1/20 of the CNC-cut, resin-infused molds that Windward eventually made, but he went with Greg's approach instead. We're currently using that soft-tool tech to make racing airplane wings, and it's working fine.

--Bob K.

soft tooling would have been a really good approach, given that P2 is a one-off. why did they elect to go with much more expensive mold materials?

Possibly the materials and methods of construction may have made use of those tools unworkable. If they used autoclaved prepreg, the molds may have needed to be less economical.

Because the Perlan II is almost entirely autoclaved prepreg, the molds are also of
carbon fiber (and also pre-preg, as best I remember). The oven is huge because the
wing panels are so long.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

At 16:52 31 March 2017, Eric Greenwell wrote:
wrote on 3/31/2017 7:25 AM:
On Friday, March 31, 2017 at 9:05:57 AM UTC-4, ND wrote:
On Thursday, March 30, 2017 at 7:50:40 PM UTC-4, Bob Kuykendall
wrote:
On Wednesday, March 29, 2017 at 8:54:45 PM UTC-7, Eric Greenwell
wrote:
The Perlan II was ... just molds at the time of Fossett's death...

Ah, but they were the best molds a crap-ton of money could buy!

I tried to interest Einar in a soft-tooled approach that would have
cost about 1/20 of the CNC-cut, resin-infused molds that Windward
eventually made, but he went with Greg's approach instead. We're
currently
using that soft-tool tech to make racing airplane wings, and it's working
fine.

--Bob K.

soft tooling would have been a really good approach, given that P2 is
a
one-off. why did they elect to go with much more expensive mold
materials?

Possibly the materials and methods of construction may have made use
of
those tools unworkable. If they used autoclaved prepreg, the molds may
have
needed to be less economical.

Because the Perlan II is almost entirely autoclaved prepreg, the molds
are
also of
carbon fiber (and also pre-preg, as best I remember). The oven is huge
because the
wing panels are so long.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg.../download-the-
guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...in-sailplanes-
2014A.pdf


Sorry to blunder on to this thread with less knowledge than the other
contributors.
As I understood the problems when you approach "coffin corner " the stall
speed and vne meet,so the trick is to raise vne ,but flutter control is way

beyond me ,but it's not just a case of making the wing stronger.
Intresting isn't it.

This thread is getting pretty far from the original post. Not nearly a record for RAS, but still impressive drift.