Bestevaer 49ST

[Snowpetrel]

Originally Posted by Seaworthy Lass

A few shots of this for you. They are all high definition, so just click the top bar for full size and zoom in.

The front of the watertight bulkhead at frame 4:




The rear of the watertight bulkhead at frame 4:




The rear of the watertight bulkhead at frame 16. You can see the rear of the bulkhead at frame 9 in the background:

Thank you for these photo's SW. It shows the system nicely. It looks like the longitudinals are actually cut to shape from plate rather than extruded flatbar forced to bend around the hull?

A very interesting and a logical way to go if the whole boat is CNC cut anyway. If this is so then they are propabaly not 6061 but the same base aluminium as the hull which has corrosion benefits as well.

The big cutout will make full length welds much easier do between the bulkhead and the hull plate.

I am impressed by the forethought and detail evident in the construction. She looks great. :thumbup:

[Seaworthy Lass]

Originally Posted by Snowpetrel

Thank you for these photo's SW. It shows the system nicely. It looks like the longitudinals are actually cut to shape from plate rather than extruded flatbar forced to bend around the hull?

A very interesting and a logical way to go if the whole boat is CNC cut anyway. If this is so then they are propabaly not 6061 but the same base aluminium as the hull which has corrosion benefits as well.

The big cutout will make full length welds much easier do between the bulkhead and the hull plate.

I am impressed by the forethought and detail evident in the construction. She looks great. :thumbup:

That's precisely how it's done .

Longitudinals are in 5083 (as is the hull), CAD cut to the shape of the hull.

[avb3]

Originally Posted by Seaworthy Lass

A few shots of this for you. They are all high definition, so just click the top bar for full size and zoom in.

The front of the watertight bulkhead at frame 4:



...

I am surprised at how thin the ribs and stringers are. It looks like it allows for a lot of flex, and that raises the question of needing to redo welding.

My only experience with aluminum boats is my friends jetboat, and it would need re-welding at least once every 3-4 trips. I can only assume that the cycles of flex would be much greater in a sailboat than on a river, although we did go up some serious rapids.

So, a couple of questions.

1.) How would you know if welds are deteriorating? Are there inspection plates that one can check periodically.

2.) One doesn't hear welds being an issue as a result of flex with aluminum sailboats, yet physics are physics, and I can't image that going away.

3.) Have you had any repairs needed that you are aware of on your current boat?

Again, I can only reflect on the number of times we dropped off my friend's jetboat at the welders after a weekend out on the river.

[Panope]

avb3, The hull scantlings for this Bestevear are more than twice that of my boat (granted, it is a bigger boat) and I have had no hull cracking (except where someone botched the old motor mounts by welding them to the skin only ).

Also, I notice that the Bestevear frames are flanged whereas mine are simple flatbars.

I cannot image this boat suffering from routine cracking.

Steve

[avb3]

Originally Posted by Panope

avb3, The hull scantlings for this Bestevear are more than twice that of my boat (granted, it is a bigger boat) and I have had no hull cracking (except where someone botched the old motor mounts by welding them to the skin only ).

Also, I notice that the Bestevear frames are flanged whereas mine are simple flatbars.

I cannot image this boat suffering from routine cracking.

Steve

Steve, it is the welds I was wondering about, as the welds is the issue we had with the jetboat. It was only 22', and the bottom was protected with a 1/2 inch of teflon plate to deal with rocks and sandbars.

At any rate, it is just a question I have, as it is clear that aluminum sailboats do very well in the real world.

[Seaworthy Lass]

Originally Posted by avb3

I am surprised at how thin the ribs and stringers are. It looks like it allows for a lot of flex, and that raises the question of needing to redo welding.

I have been on New Zealand jet boats and they are very lightly constructed to minimize weight and allow skimming over shallow water. Flex is inevitable, so welds give. It has been a problem with some high speed ferries too. Flexing is not generally an issue with well designed alu cruising boats.

Our "thin" stringers on the Bestevaer are 8 mm thick. The ribs are T sections with 6 mm and 8 mm components (100 mm x 50 mm ). The hull is 8mm with thicker sections at the front and around the keel. No significant flex will occur.

I will respond with the rest later. We are just driving back from an afternoon with Willem-Jan, the person responsible for the design work done at the yard (as opposed to the earlier design work by the naval architect). Such a fun afternoon . He is brilliant to work with.

SWL

[Pelagic]

Originally Posted by avb3

I am surprised at how thin the ribs and stringers are. It looks like it allows for a lot of flex, and that raises the question of needing to redo welding.

My only experience with aluminum boats is my friends jetboat, and it would need re-welding at least once every 3-4 trips. I can only assume that the cycles of flex would be much greater in a sailboat than on a river, although we did go up some serious rapids.

So, a couple of questions.

1.) How would you know if welds are deteriorating? Are there inspection plates that one can check periodically.

2.) One doesn't hear welds being an issue as a result of flex with aluminum sailboats, yet physics are physics, and I can't image that going away.

3.) Have you had any repairs needed that you are aware of on your current boat?

Again, I can only reflect on the number of times we dropped off my friend's jetboat at the welders after a weekend out on the river.

You cannot compare the weld stress forces of a high speed racing hull repeatedly grounding in a shallow river to the heavier scantlings of a slow moving displacement hull in deep water.

Heavy weather pounding may cause some stress cracks if the original welds had some contamination or flaws, but the malleability of the metal easily compensates for vibration stresses on the welds if properly done.

[DDabs]

Woah woah woah, avb3, are you saying the stringers on the Bestevaer are not BLUEWATER CAPABLE?!?!?!?!?!?!



....jk

[avb3]

Originally Posted by DDabs

Woah woah woah, avb3, are you saying the stringers on the Bestevaer are not BLUEWATER CAPABLE?!?!?!?!?!?!



....jk

Absolutely not! I am just relaying my experience with my friends boat, and wondered how this application dealt with it. It's a beautiful design, and no doubt the naval architect and builders are capable, but as we know, all boats are some kind of compromise. SWL has explained how thick those stringers actually are. My real question relates to flex and welds.

[Seaworthy Lass]

Originally Posted by avb3

Absolutely not! I am just relaying my experience with my friends boat, and wondered how this application dealt with it. It's a beautiful design, and no doubt the naval architect and builders are capable, but as we know, all boats are some kind of compromise. SWL has explained how thick those stringers actually are. My real question relates to flex and welds.

I have not heard of any issues with welds on alu cruising boats. All the welds under the floorboards can generally be easily inspected. And in answer to your earlier question, we have never had any problems with our welds.

I simply doubt flexing is an issue given the thicknesses using in cruising boats if the welding technique has been good to start with.

SWL

[weavis]

Impressed with the professionalism and build quality.
Shame its only for one hull...

[avb3]

Originally Posted by weavis

Impressed with the professionalism and build quality.
Shame its only for one hull...

Thou ist stirring up fecal matter. Tsk. Tsk.

[Snowpetrel]

Originally Posted by Seaworthy Lass

I have been on New Zealand jet boats and they are very lightly constructed to minimize weight and allow skimming over shallow water. Flex is inevitable, so welds give. It has been a problem with some high speed ferries too. Flexing is not generally an issue with well designed alu cruising boats.

Our "thin" stringers on the Bestevaer are 8 mm thick. The ribs are T sections with 6 mm and 8 mm components (100 mm x 50 mm ). The hull is 8mm with thicker sections at the front and around the keel. No significant flex will occur.

That boat is a tank! I would have absolutely no worries about hull flex or cracking. Looked after she could still be sound and oceanworthy in 100 years or more.

It is however a valid concern with aluminium boats, especially lightly built racing hulls, some of which have used 3.2mm plate on the hulls of 60 footers. An old sixty foot racing boat I skippered used (hard to be sure exactly) mostly 4mm plate and survived with no real issues many years of hard antarctic service. She was considered overbuilt for racing. And had lots of full watertight bulkheads that added lots of rigidity to the structure. While I was on it she did show some minor cracks in the internal keel structure, which I monitored very carefully. And previously the welded chainplates failed due to fatigue cracking. But I never saw any issues or cracks in the plating, or frames/stringers.

David Adams reported issues with the ULBD Boc racer Innkeeper popping welds in the stringers and frames fwd during a nasty blow down south near the Horn. (See his excellent book 'Chasing liquid mountains' for details) I dont know what sort of scantlings innkeeper had but my guess is 3.2 plate.

I think (from memory) stiffness goes up to the square of the plate thickness, so doubling the plate from 4mm to 8mm gives four times the stiffness for only twice the weight.

My own alloy 40 ft 8 tonne boat has been raced very hard for 35 years and shows no cracks in any of the hull welds or frames. There is evidence that the 5 and 4mm hull plating has very slightly deformed inwards between the frames and stringers after fairing in the fwd sections due to pounding, but I think that this is a one off event, and now it has happened I dont think it is a further issue. Like a minor dent.

The 3mm deck has a few fatigue issues in one or two spots due tobthe light framing in a few areas and the locallised weight of a heavy bowman bouncing in the foredeck, or jumping into the cockpit. Easily fixed with a few intercostal stringers.

[Seaworthy Lass]

Work is proceeding rapidly on the boat. Each day we visit there is something new to "ooh" and "ah" over . Yesterday it was the bow thruster tube.

We are heading back to our current boat on the weekend for a week of antifouling before splashing for the summer, so I will try and add a few more images before we leave. New photos will probably be arriving next week .

This is the day fuel tank (upside down). The plan for the fuel system is pretty much as was sketched back in post #359.

The capacity is around 60 litres. It has a large inspection port, sump, and can also be filled manually from the top:





Fuel system:

[Seaworthy Lass]

A few hull plates have now been bent into shape.

The rolling process:




A completed plate with capping added: