Dangerous designs?

[usa2]

How much would a titanium alloy hull cost? Surely much more than a carbon fibre hull.

[Windvang]

[quote=Paul B]

The Canting Keel mechanisms are attached to the inner skins only via a secondary bond. Now you have to worry about core shear and tesnion/compression in addition to the bond itself. I am making an assumption here. Perhaps the builders remove the core in the area of the canting mechanism, making a solid ring frame. If so, the transition from the solid ring to the cores area might be the next weak link, since the flex in these areas would be so different.

The keel of the Volvo's is hinged between 2 ringframes, the ringframes are connected with stringer. The hydraulics are bolted to the stringers. The whole construction is independent of the skins

The next iteration of the VO70 rule should require the pivot to be normal to the outer skin. The whole notion of the bomber door/rotating drum arrangement has added far too much complexity to the program.

By the way, the photos of the bottom of Moviestar shows a bump at the keel/hull intersection. If this boat has the bomber doors why would it have the bump? Normally the bump houses the pivot. If the pivot is inside the hull there should be no reason for the bump.[

The small bump is the hinge between doors and keel, the keel slides up and down in it when canted. /QUOTE]

[Paul B]

[quote=Windvang]

Originally Posted by Paul B

The Canting Keel mechanisms are attached to the inner skins only via a secondary bond. Now you have to worry about core shear and tesnion/compression in addition to the bond itself. I am making an assumption here. Perhaps the builders remove the core in the area of the canting mechanism, making a solid ring frame. If so, the transition from the solid ring to the cores area might be the next weak link, since the flex in these areas would be so different.

The keel of the Volvo's is hinged between 2 ringframes, the ringframes are connected with stringer. The hydraulics are bolted to the stringers. The whole construction is independent of the skins/QUOTE]

At some point the mechanism need to attach to the hull. So the Ringframes you mention must be bonded via secondary bonds to the inner skins of the laminate. In composite construction all bulkheads and ring frames need to be bonded to the inner skin through secondary bonds. If not bonded to the hull what good would they do. They would simply float about inside the hull.



[quote=Windvang]

Originally Posted by Paul B

The next iteration of the VO70 rule should require the pivot to be normal to the outer skin. The whole notion of the bomber door/rotating drum arrangement has added far too much complexity to the program.

By the way, the photos of the bottom of Moviestar shows a bump at the keel/hull intersection. If this boat has the bomber doors why would it have the bump? Normally the bump houses the pivot. If the pivot is inside the hull there should be no reason for the bump.[

The small bump is the hinge between doors and keel, the keel slides up and down in it when canted. /QUOTE]

That may be true. I suppose the angle of the keel changes relative to the door surface as the keel cants, so the interface would have to rotate.

[wet feet]

The only sucessful titanium welding jobs I have ever seen have been done inside an enclosure from which all oxygen has been driven by purging the chamber with argon.You could probably build such an enclosure for a seventy foot boat.You could probably find welders,perhaps with diving experience,to work inside a glorified diving suit.You might find a wealthy patron for the project.Meanwhile,others will properly engineer a composite structure-and win.Take note of the increasing use of carbon in commercial aircraft.If Boeing and Airbus have reached this conclusion,why be different?

[D'ARTOIS]

Originally Posted by wet feet

The only sucessful titanium welding jobs I have ever seen have been done inside an enclosure from which all oxygen has been driven by purging the chamber with argon.You could probably build such an enclosure for a seventy foot boat.You could probably find welders,perhaps with diving experience,to work inside a glorified diving suit.You might find a wealthy patron for the project.Meanwhile,others will properly engineer a composite structure-and win.Take note of the increasing use of carbon in commercial aircraft.If Boeing and Airbus have reached this conclusion,why be different?

Well, if you are convinced that such is the reality, I shall not try to convince you that this is not the case. The fact is that the only case where titanium was widely used in aircraft was in the construction of the SR72 and those planes still fly - no one lost.

You have proved already by your remarks that the general knowledge of the metal is almost nil lest it's unpublished alloys.

What you say about composites is true. If Airbus or Boeing could use paper they would do it.

You should ask yourself if the search for light metals have ever stopped and if the qualities of the composites are that good.

A titanium boat goes forever; a composite one....well, please fill in....

New alloys are on the way....lighter that Ti and twice as strong.....

Ideal for high performance sailing yachts. Techniques at this time not available to the yacht designers, they never investigated the metal way and stayed with the plastic way...so let them go.

All the VOR boats of this generfation are junk boats. Even before they have finished.

Let's see what the 2nd generation will do.

[usa2]

I think switching to titanium would be a bit extreme. There are lots of composite boats out there that dont suffer any problems. Its just when you get people trying to get the most out of a rule that is accidently encouraging structural failure than you start to have problems.

[D'ARTOIS]

Of course, USA2 y're right. Basically a titanium hull will not cost more than a composite one, that's one...

Secondly, it will not end up as a junk bond like all the composite boats as the VOR's

Imagine a boat like Mari Cha, but engineered and build in titanium - a timeless ship that will last centuries......and will be as fast as ...name it!

Just like the SR73, 30 odd years old and still not beaten.....

[usa2]

sorry that this is not completely relevant, but wasnt there a version of the MiG25 that was just as faster(maybe faster) than the SR-71?

[Windvang]

[quote=Paul B][quote=Windvang]

At some point the mechanism need to attach to the hull. So the Ringframes you mention must be bonded via secondary bonds to the inner skins of the laminate. In composite construction all bulkheads and ring frames need to be bonded to the inner skin through secondary bonds. If not bonded to the hull what good would they do. They would simply float about inside the hull.

[quote=Windvang]

The ringframes are laminated in over a large area. On top of that I think the chainplates are integrated in the front ringframe so the skins are primarely to keep the water out.

When you post-cure the hull including the internals all bonding is as strong as the rest of the laminate.The thing to avoid in composites are peeling forces, this is solved with this setup.

Most of the problems seem to be related to the rams.

[wet feet]

Perhaps D'artois would be kind enough to guide me to any information about sucessful sailing boats constructed from titanium.I will then be able to learn a little about the process.It will be fascinating gaining some knowledge of the processes used to make this normally uncooperative metal conform to the shape of a boat and the manner in which the various panels can be welded together without the white crystalline surface deposits that indicate the presence of oxidation.As the unpublished material is by its nature unpublished,we will have to wait and see what comes along.

[usa2]

Windvang is right about the problems being mostly ram related.
Also, if Farr had calculated the forces on the supporting structure correctly than it would have been built strong enough. Composite materials are certainly strong enough, its just you need to have people who understand every force that will be transmitted through the structure.

I remember reading an article in Seahorse(?) about the MaxZ86's Pyewacket and Morning Glory. Jim Pugh mentioned how the boat builder was confused as to why there was so much structure in the center of the boat, around where the keel would be. This particular build was used to building IMS maxis which were of course all fixed keeled, and did not have the strong overbuilt structure in the vicinity of the keel.

Basically, if you dont overengineer this part of the boat, it will break.

[D'ARTOIS]

Originally Posted by wet feet

Perhaps D'artois would be kind enough to guide me to any information about sucessful sailing boats constructed from titanium.I will then be able to learn a little about the process.It will be fascinating gaining some knowledge of the processes used to make this normally uncooperative metal conform to the shape of a boat and the manner in which the various panels can be welded together without the white crystalline surface deposits that indicate the presence of oxidation.As the unpublished material is by its nature unpublished,we will have to wait and see what comes along.

frankly, your response learned already that titanium in it's alloyed state is totally alien to you. I cannot learn you what I have learned at high expenditure and similar remarks from people that do not know.

I would suggest to check on following issues in Google: SR-71/73; Titanium and its alloys; Akula class summarines etc.

There is a next generation metals that are even stronger than Ti, although not commercially available at the moment.

[wet feet]

Tried Google,unfortunately the search only led to obsolete aircraft and submarines.I was hoping to see sailing vessels.

[D'ARTOIS]

Wait and see.... or not

[D'ARTOIS]

that's why there is always a first......