Bestevaer 49ST

[paulanthony]

Originally Posted by noelex 77

We are planning a new boat. It will be a custom designed aluminium boat, which makes no economic sense, but why not

The Bestevaer range of yachts are designed by Gerard Dykstra:
Dykstra Naval Architects

Why did you not opt for the Bestewind 50? Because of your preference for Aluminium or something else?

[noelex 77]

Originally Posted by paulanthony

Why did you not opt for the Bestewind 50? Because of your preference for Aluminium or something else?

There is no perfect boatbuilding material, but after owning both I think aluminium is a better option.

The Bestewind 50 is essentially the same hull in fibreglass.

Hull cost is only about 1/3 of the total cost. If you approximately double the cost of building the hull and deck it only adds around 30% to the total build cost.

I think investing in the fundamental construction of the boat is critical.

[Dockhead]

Originally Posted by noelex 77

There is no perfect boatbuilding material, but after owning both I think aluminium is a better option.

The Bestewind 50 is essentially the same hull in fibreglass.

Hull cost is only about 1/3 of the total cost. If you approximately double the cost of building the hull and deck it only adds around 30% to the total build cost.

I think investing in the fundamental construction of the boat is critical.

Is that the actual relationship between the cost of alu and the cost of plastic? Double?

[Polux]

Originally Posted by Dockhead

Is that the actual relationship between the cost of alu and the cost of plastic? Double?

The Bestwind 50 is pretty much a semi custom boat and I bet that they can make it in different types of "plastic". Some types would probably not be cheaper than aluminium and probably not less strong to impact. For instance the last voyage boat from Comar has a kevlar hull reinforced with carbon and that probably is not cheaper than an aluminium hull.

The Comet Explorer 46 has a swing keel with all ballast on the keel (1.6/3.50m) and offers the same advantages of a deep keel boat and a centerboarder (it can be beached).

Comet Explorer 46 EX - Comar Yachts

[Polux]

Here, a decent image that is not available at the site (cannot edit the post):

[noelex 77]

Originally Posted by Dockhead

Is that the actual relationship between the cost of alu and the cost of plastic? Double?

The exact numbers are hard. Painted, unpainted insulated etc. Fibreglass also gets much cheaper if you can build many boats from the same mould.

Overall, I think for round build aluminium construction double the cost for the hull and deck (compared to polyester cored fibreglass) and therefore about 30-40% extra for the total build cost is about right, but the details will produce considerable variation.

[noelex 77]

Originally Posted by Polux

The Bestwind 50 is pretty much a semi custom boat and I bet that they can make it in different types of "plastic". Some types would probably not be cheaper than aluminium and probably not less strong to impact. For instance the last voyage boat from Comar has a kevlar hull reinforced with carbon and that probably is not cheaper than an aluminium hull.

For the fiberglass Bestewind, K&M do offer the option of Kevlar reinforcement in the hull. It is not an expensive option and adds little to the price (Kevlar from the mast to the bow it is only slightly dearer than curtains in the pilothouse, or cheaper than screens on 4 of the hatches for example).

A full epoxy/ E-glass/carbon fibre hull will be more expensive than aluminium construction, but production boatbuilders do not (generally) offer this option. Even expensive boats like HR are built with "conventional" polyester fibreglass structures.

I have not had a look at Comar's construction, so I not directing this comment at their yacht, but some boatbuilders add a small amount of Kevlar, carbon fibre etc because it looks good in the brochure rather than achieving much from a structural point of view. You need details of the layup schedule to make the distinction.

There are specialised companies that do produce sophisticated and expensive to build composite structures. Shipman yachts are an example. Unfortunately, they are aimed at reducing weight and improving sailing performance. There is nothing wrong with this goal, but for a cruising boat personally I would prefer something of a similar weight that used the superior layup to increase impact resistance and reduce the risk of structural hull problems. Full time cruising is tough on a boat.

[estarzinger]

The major difference(s) in construction cost between metal and glass is that glass boats require tooling (a Mold) be built, while metal ones do not. So it makes sense to make series boats in glass to amortize the cost of the tooling, and to make one-offs in metal.

The cost of actual materials is trivial in both cases. And the cost of labor can be high or low in both cases depending on care and quality, but generally the metal boat requires somewhat more skilled labor (offsetting the lack of tooling costs).

[paulanthony]

Will you apply a vinyl wrap or something above the water line or keep it bare metal?

[Polux]

Originally Posted by noelex 77

For the fiberglass Bestewind, K&M do offer the option of Kevlar reinforcement in the hull. It is not an expensive option and adds little to the price (Kevlar from the mast to the bow it is only slightly dearer than curtains in the pilothouse, or cheaper than screens on 4 of the hatches for example).

A full epoxy/ E-glass/carbon fibre hull will be more expensive than aluminium construction, but production boatbuilders do not (generally) offer this option. Even expensive boats like HR are built with "conventional" polyester fibreglass structures.

I have not had a look at Comar's construction, so I not directing this comment at their yacht, but some boatbuilders add a small amount of Kevlar, carbon fibre etc because it looks good in the brochure rather than achieving much from a structural point of view. You need details of the layup schedule to make the distinction.

There are specialised companies that do produce sophisticated and expensive to build composite structures. Shipman yachts are an example. Unfortunately, they are aimed at reducing weight and improving sailing performance. There is nothing wrong with this goal, but for a cruising boat personally I would prefer something of a similar weight that used the superior layup to increase impact resistance and reduce the risk of structural hull problems. Full time cruising is tough on a boat.

Yes there are plenty of brands that have kevlar reinforcement on the most probable impact zones on the hull (including Bavaria) however is not that what they have on Comar 46 explorer but a full kevlar hull: Vinylester as resin (an epoxy resin), Kevlar as glass.

Regarding impact I don't know what is more resistant, kevlar or Aluminium but kevlar has a great resistance to impact and is why it is used as a bullet prof material for some military and police applications.

[paulanthony]

Originally Posted by Polux

Yes there are plenty of brands that have kevlar reinforcement on the most probable impact zones on the hull (including Bavaria) however is not that what they have on Comar 46 explorer but a full kevlar hull: Vinylester as resin (an epoxy resin), Kevlar as glass.

Regarding impact I don't know what is more resistant, kevlar or Aluminium but kevlar has a great resistance to impact and is why it is used as a bullet prof material for some military and police applications.

In tensile mode Kevlar is not fibre per fibre stronger than glass. It is much weaker in fact. The benefit of kevlar is that it weighs less so its strength to weight ratio will be better and also its compression values are stronger.

However on a hull you need high tensile strength with a low modulas rating(less brittle) so that impact force can be absorbed.

The use of kevlar is best suited to a localised one where you need high levels stiffness and also anti abrasion resistance.

I dont think kevlar conducts electricity also which is another reason why you would use it on the bottom.

I am not sure what the benefit would be of kevlar and glass as a laminate because to my logic they would undermine each other. I will have to find out. Maybe its added to stem and stern but can't see it being much use else where because it would fail under impact before glass would.

[noelex 77]

Originally Posted by paulanthony

Will you apply a vinyl wrap or something above the water line or keep it bare metal?

The hull will be bare aluminium above the waterline.
Many people dislike the patina that bare aluminium develops, but it is a very practical surface.

It can of course be painted. There are also some clear alternatives that just keep the aluminium oxidation free.

Has anyone used these clear coatings? Some first hand experience would be great.

[Polux]

Originally Posted by paulanthony

In tensile mode Kevlar is not fibre per fibre stronger than glass. It is much weaker in fact. The benefit of kevlar is that it weighs less so its strength to weight ratio will be better and also its compression values are stronger.

However on a hull you need high tensile strength with a low modulas rating(less brittle) so that impact force can be absorbed.

The use of kevlar is best suited to a localised one where you need high levels stiffness and also anti abrasion resistance.

I dont think kevlar conducts electricity also which is another reason why you would use it on the bottom.

I am not sure what the benefit would be of kevlar and glass as a laminate because to my logic they would undermine each other. I will have to find out. Maybe its added to stem and stern but can't see it being much use else where because it would fail under impact before glass would.

I confess I don't know almost nothing about the use of kevlar in hulls but I assume that the composite engineers that work for Comet, Bavaria and other brands that use kevlar reinforcements for increase the ability of the hull to sustain impact damage know what they are doing. That's their job and they are professionals.

On case of the Comar we are talking about a full kevlar hull that is rare on production boats but used on hard duty boats, like military Patrol boats.

Here is what Dupont, one of the main produces says about Kevlar and its maritime use:

"DuPont™ Kevlar® fiber helps deliver lightweight strength, stiffness, and impact resistance for the composites industry....Kevlar® in marine composites and maritime vessel composites helps provide an ideal balance of strength, stiffness, and lightweight properties for many marine applications. In patrol and service boats, higher speeds can be achieved by increasing engine power — this option has the potential to be prohibitively expensive. Another way is to reduce weight by incorporating Kevlar® reinforcement in existing laminate constructions or in new designs. DuPont helps hulls reinforced with Kevlar® be lighter yet tougher and more damage-tolerant, and perform better under hydrodynamic fatigue loading."

http://www.dupont.com/products-and-s...omposites.html

From another source:

"When woven, Kevlar® forms a strong and flexible material. If layers of the woven Kevlar® are combined with layers of resin, the resulting ‘rigid’ material is light and has twenty times the strength of steel. It is also superior to specialist metal alloys. However, Kevlar® is expensive due to the demands of the manufacturing process and the need for specialist equipment."...
Kevlar® 49 is used for specialist boat hulls and in the aerospace industry. It is popular as a material for boats because it is lightweight and can withstand a considerable amount of force (torque - twisting force), tensile stress and impact. Hulls manufactured from traditional materials, such as fibreglass, are limited in their resistance to forces and stress. ...

Eurofighter is relatively light compared to other similar fighter jets, due to the selection of Kevlar ® 49 as a material in its manufacture. This means that it can fly faster and further, before in-flight refuelling is needed. It is more agile than its rivals due to excellent force (torque - twisting force) and tensile stress resistance. The plane is more likely to survive being hit by small arms fire, compared to other fighter planes, as Kevlar ® 49 has excellent impact resistance.


WHAT IS KEVLAR? TYPES OF KEVLAR

[poiu]

Originally Posted by noelex 77

The hull will be bare aluminium above the waterline.
Many people dislike the patina that bare aluminium develops, but it is a very practical surface.

It can of course be painted. There are also some clear alternatives that just keep the aluminium oxidation free.

Has anyone used these clear coatings? Some first hand experience would be great.

I don't know about the clear coating, but how about anodising the hull? It should give better protection than bare aluminium. It is done with masts for that reason. Also, you can anodise in a huge variety of colours to create maybe a dramatic effect or design and it should last much longer than paint.

[dannc]

Originally Posted by monte

That's great SWL. I'm sure he could have done the same with duct tape and fencing wire if forced . We recently had a sloppy mix of bread in the breadmaker and Jen accidentally threw the lot (including breadmaker paddle bit) over for the fishes. Ok, that's what I have epoxy putty on board for I thought, so fashioned a replacement paddle. All seemed good till the cooking phase. I guess the epoxy putty didn't like the extreme temperatures because we ended up with paddle bread.
Innovation fail!

At the risk of derailing this discussion, get rid of the bread maker.

Years ago I saw a cooking show that used a no kneed bread recipe. I did some reading of other recipes on the Internet and started making no kneed bread. I stopped using the bread maker years and years ago and would just kneed the bread but with the no kneed recipes there is, well, no need to kneed.

The no kneed recipes basically use more liquid than normal and time to create the gluten. I mix up the dough incredients, which takes only a minute or so, throw a towel or plastic wrap over the bowl and sit it aside for a few hours. Even over night. One trick I learned was to use cast iron Dutch ovens or cast iron bread pans. Pre heat which ever container that will be used to bake in and just dump in the dough when the dough is ready. The Dutch oven with a lid seems to make crunchier bread but I use the open top cast iron bread pans as well. Bake the bread to an internal temperature around 190-200 degrees F. Maybe more. It ain't rocket science.

Later,
Dan