flat vs convex surfaces

[Rumars]

Let's try another way, the two most "squared up" boats I know of:
Banana Split, dory hull, Strongall construction, 12mm bottom, 10mm sides, no stringers just bulkheads. You can't get less welding unless you go to a deep V strongall hull.
Hermann Heinrich, plywood, shallow V (single chine) hull. No stringers just deck clamp and furniture stiffeners. Eigenbaukatamaran in Epoxy Sperrholzbauweise. Fotoalbum https://www.hermann-heinrich.net/foto/bau/index.htm

 

[gonzo]

In the delos video, they spend a significant percent of the hull time in bending and fitting the plates. A faceted design would probably have removed about 30% of the labor to date.[/QUOTE
30% of the hull building time is maybe 3% of the total build time. It does not pay to build a boat with little market appeal that will cost the same as the attractive ones.

 

[lucdekeyser]

the two most "squared up" boats I know of

Thank you for these finds. These are very interesting examples, indeed. The owners seemed delighted. Performance was not their priority. I am very curious about their weight, though, to compare with more traditional builds. Comments from 2009 on this forum did not clear that up.

From here, the theoretical exercise may be to consider how to get rid of the remaining curves, one by one, starting with those below the waterline. Like, cats need rocker, proas don't. How assymetrical can multihull bow entries be? Have one side flat and curve the other one doubly? Can this other side be an oblique flat surface instead? If the sides flare upwards, how to fit the single oblique flat side of the bow? How much is the penalty for not flaring the sides?

 

[lucdekeyser]

It does not pay to build a boat with little market appeal that will cost the same as the attractive ones

That is a given. Would you be so kind to comment on an earlier conjecture about the guestimated trickle down effect on the remainder of boat building costs

If flat saves 3-5% of total boat costs in the hull alone, flat may save the same proportion of the remainder that is 85-90% of the total boat costs, ranging the total saving between 18-30%.

 

[gonzo]

It is not a guestimeated trickle down effect, but an estimate based on the experience of building dozens of boats. The hull of a boat cost ranges at 10-15% of the total build cost.

 

[DogCavalry]

Okay, now it's getting useless. Mortgage your house, build a proper boat, and a flat surface boat, and come back with the financials in a spreadsheet.

And start a new thread, because I've unfollowed this one. DC out.

 

[lucdekeyser]

an estimate based on the experience of building dozens of boats

That is dozens more than I have. Point taken.

 

[gonzo]

The percentage of cost of the hull vs the total build diminishes as boats get bigger and more luxurious. For example, a megayacht may have several million dollars of artwork in it. Also, expensive items like gold plated hardware, fancy plumbing fixture, specialty marble, etc., far exceed the cost of the hull.

 

[lucdekeyser]

The percentage of cost of the hull vs the total build diminishes as boats get bigger and more luxurious

I was focusing on 40+ cruising multihulls which I guess range from about 350K - 1250K $. Even a good proportion of the higher ends is made in lower wage countries but still using off the shelve relatively expensive hardware and machinery from reputed manufacturers. Do we know how much cheaper these builts are, more or less?

 

[gonzo]

I can't think of any 40+ foot catamaran that sells for 350K. Do you have any examples?

 

[lucdekeyser]

examples

A Warrham 42' costs less than 100K in building materials + 2000 hours + equipment
Rumar's referencing to the Hermann Heinrich above

 

[gonzo]

Sure, but that is like trying to sell Model T Fords. There is no real market for them. Also, that would be possible in a reasonably well equiped shop and skilled labor.

 

[Rumars]

A Warrham 42' costs less than 100K in building materials + 2000 hours + equipment
Rumar's referencing to the Hermann Heinrich above

You can't compare costs between amateur builds and professional construction, in fact you can't compare them even between amateur builds. One guy will buy all new Festool the other use his grandfathers tools. Accounting is a joke with most amateurs, the true cost and time isn't usually known. How many amateur boatbuilders do you know that log the time, gas and vehicle depreciation they incurred going to the hardware store to buy some sandpaper because they run out? Or the hours spent online trying to find a deal on some hardware or asking advice on a forum?

As for material prices, what can I say. Imagine you're a small but successful yard, doing several boats per year. When your resin, glass, foam or ply orders each fill a semi-trailer the prices are different. Even the amateur can get significant price reductions if he orders a drum of resin or a pallet of plywood.

 

[lucdekeyser]

Let me share some of the conclusions from a similar discussion on another forum:
1/ faceted designs can approximate to considerable extent the drag with curved designs 2/ flat designs would not offer building efficiencies 3/ the double ender transonic hull idea was expertly debunked.
Thank you for your patience and indulgence. It was a good learning experience.