Building my first boat.

[Aquatek]

He didnt sound like someone who was skilled at boatbuilding, more like someone who had a dream and had no idea of how to fufill it.
I was mearly ensuring that he had the necessary boatbuilding groundwork covered before he rushed into it without any prior knowledge or experience of the engineering fundamentals required.
And I have nothing against aluminium, its my favorite engineering material but I dont like the idea of using it in boats.
I have an aerospace background and I am used to working in aerospace alloys, not marine grade aluminium so perhaps my fears are unjustified?
As for aluminium narrow boats, I know you need to be very rich to afford one!

Regards

Aquatek

[kmorin]

Aquatek, in air frames; aluminum and water don't mix- to use the phrase. On the other hand mixed with a tad of magnesium and a dash of manganese the stuff becomes a veritable 'fish in water'.

Beginning by building a row boat, outboard powered boat or other 16' design in welded aluminum is logical; but unless there is a hidden set of long canals in ihallenius' neighborhood a narrow boat still seems a bit out of place.

About the relative costs- Aquatek you're falling for the "materials cost comparison as indication of cost of ownership" and that syllogism is disproven again and again in the market; not to mention this and other posts online.

What is the relative cost of aluminum versus oak? The metal is generally more expensive- and by 3 or 7 times. What is the relative cost of the EXACT same design boat made in both materials? (lets just take a 70' x 7' canal boat?) When the exact same design is made in both; the cost of the metal hull comes out several times less COSTLY. What's up here? The cost of ownership is NOT determined by the cost of materials alone.

When the oaken boat was fully complete in the exact same design as the metal and at higher cost, what would be the term of service? What would be the results of collisions of each hull? What would be the relative displacement to move about for the lifetime of the vessels? What about the countless other considerations to ADD to the value comparison of the two vessels? If the two can be assigned market value based on the relative cost of the two materials why aren't there as many wooden boats built today as alloy?

When you move into the planing- higher hp/wt ratio boats- less than 30' long- in 'one-off' designs- welded aluminum OWNs the market because you can buy this relatively expensive metal and lift it by hand, cut with common tools and fit it together with simply learned skills.

If you buy a home handyman grade circular saw with a 2 amp motor for 25$(US) and it gives up in the second month's service I assert you've saved nothing in buying for less. The 250$(US) dollar model that is still running after 20 years is the correct value for costs. While it cost 10 times as much its still reliable after 100's of more months of service. The cost of ownship of the latter is 10 times LESS expensive even though the original costs is 10 times GREATER. By the end of the life of the "less expensive" saw you'd have spent several thousand ($US) to have the cheap saw in service for a comparable time.

If you buy materials that are the least expensive you will STILL add 200- 2000 or 10,000 hours of your effort- (your lifes' span) to achieve the the finished boat. When you're through - will you constantly return to the working stage of repair, replacing and maintaining -or will you have done the job with the BEST you can find and be done with it? If you're going to spend your life's time building and then trust your life's breath to the result, wouldn't you want the best you can find?

I've built welded alloy boats for about 30 years and with a quick wash of acid they're almost "new" but the few steel boats in that period have degraded to become full time maintenance projects and they were blasted and epoxied in build.

Surely, as an engineer/engineering type, you are instantly at the conclusion of my implications about the relative value of the results of effort being ASSOCIATED with the materials' involved but not determined by the materials costs alone?

Cheers,
kmorin

[Aquatek]

It depends how long you plan to have the boat and how much you are going to use it.
If you build a boat, and in this case its a small fast sports boat, not suitable to live on, the sort of boat that lives most of its time out of the water on a boat trailer, gets trailed down to the local slipway occasionally at the weekend, and one that gets launched and hammered for a few hours just for the hell of it....Who cares how long it lasts, its never in the water long enough to start corroding so it can be built of the cheapest and easist material available.
Aluminium may be lighter than Steel but its harder and more expensive to weld and because its only half as strong as Steel you need to use thicker sheets, bars, tubes and rods to get a similar strength hull to a Steel one, pushing the price of an Aluminium hulled boat up even more over the price of a Steel one.
Sure an Aluminium hulled boat may be a more attractive option than using Steel at first glance but at 5 times the price or more, that attractiveness quickly dissipates.
For a large full displacement commercial workboat then that much higher cost can be justified but on a small occasional use sportsboat as ihallenius has stated he wants to build I simply dont think its worth it.

Regards

Aquatek

[kmorin]

Aquatek,
sorry that you've so thoroughly missed the relationship between the metals, the forum's search function is useful in this regard, as well as a course of examination in properties of materials- best of luck with your steel boats.

Cheers,
kmorin