Possible Steel Jet Setter?

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electric tug
Posts: 71
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Possible Steel Jet Setter?

Post by electric tug »

:D :D :D
decided to go with a smaller design instead...
Last edited by electric tug on Tue Apr 13, 2021 8:38 pm, edited 4 times in total.

Kevin Morin
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Re: Possible Steel Jet Setter?

Post by Kevin Morin »

electric tug,

My post is to mention the other side of welded aluminium boats, compared to welded steel boats. There are other points of view and there are some very strong market forces that reveal why the difference in the two metals' properties results in a huge market for aluminium boats- both formed and riveted as well as welded; while there is virtually no market for the same boats in steel.

I understand from your post that your don't care for aluminium and less for welding it! And as someone who's designed built hundreds of them, welded by my own hand, we have a point of view difference that may be a gulf that can't be bridged. I have built a couple of steel boats but at 43' and 52' they hardly concern our discussion about small boats here on Glen-L's Forum.

http://www.kastenmarine.com/alumVSsteel.htm this article is by a marine designer and would allow readers of the Forum to research some of your assertions about Alum V Steel and make a detailed comparison of the two metals.

The primary points to consider IMO are that all steel requires painting to a level that will require a decent sand blasted surface other wise; its just a steady march to 'rusting away'-and this includes ongoing maintenance- where Aluminium Oxide is 'self healing' "Ferric Oxide" is not. So the market builds in aluminium for the corrosion resistance provided.
electric tug wrote:
Mon Mar 29, 2021 3:16 pm
I think AL. is overrated. Many times I think its used just because it more exotic and novel.
Note that 100% of all jet sleds being mfg'd in the PNW that run rocky rivers; use welded aluminium and not steel? If the steel was preferable- why wouldn't the market of dozens of name builders reflect that? I think your assertions are not really as accurate as some web research might explain?

Cost of material and welding equipment? No question steel is cheaper and welding it can be done with 10X less skill and cost of equipment when compared to welded aluminium... no argument from me. And this is from someone who's owned (and owns) plural 10's of thousands of $ worth welding equipment to weld aluminium.
electric tug wrote:
Mon Mar 29, 2021 3:16 pm
And if the boat is not pro welded, I dont know if I would trust it under conditions which would stress the hull.
Skill in welding: No argument it takes more hours of practice to produce the level of beads required for a well built aluminium hull than it does for steel. Aluminium welding, both MIG and TIG are much more demanding skills than their steel alloy counterparts but.... I consider this just a matter of practice and skill development. I started in steel stick electrode welding and gradually moved my skills upward to produce acceptable beads on aluminium- anyone with determined practice can do the same.
electric tug wrote:
Mon Mar 29, 2021 3:16 pm
The welds can crack unless you heat treat them. Especially if running into white water or heavy chop.
As someone who's welded 20k hours of MIG and TIG aluminium on hundreds of small welded aluminium boats: I have never heat treated any welds and they have never failed! Most of my work still fishes commercially (when allowed by government!) and all of them go out in a surf, (bow on) and retrieve 4 to 10x their hull wt in salmon and land that load in a following sea on a gravel beach. All of them are still in service in various Alaskan waters and take whatever sea state is present to do their job. I can't say your quote above doesn't seem based on too much experience with a "heavy chop" as we'd define it here in the Alaskan waters?

Aluminium costs versus steel costs: Aluminium is not proportionally more expensive its out of proportionally more expensive. However, our 'feelings' about metal costs don't matter: the market wouldn't charge more for one metal over the other if people weren't willing to pay that premium. One metal provides a series of benefits over the other in regard planing hull shapes. So the market pays the premium to get the "superior" product for the benefits those properties offer the specific market niche of impact resistant, light wt. planing hulls.

E'Tug, I guess we'll just have to "agree to disagree" about the two metals? I think the market forces are very important to consider? Mfg's are in business to make money... if they didn't use the metal that was most profitable to their products they'd make less money... and the small metal boat business is 100% (figurative percentage; not exact) made of aluminium. The strength to wt ratio is not in steel's favour, the cost is higher for the "Miracle Metal" but there must be some underlying economic reason for the markets' decision?

I think that reason is that, all considered, marine alloys for welded planing boats, and stretch forming alloys for riveted boats are all more profitable and economically viable using aluminium over steel.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

electric tug
Posts: 71
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Re: Possible Steel Jet Setter?

Post by electric tug »

no point posting about this
Last edited by electric tug on Tue Apr 13, 2021 8:34 pm, edited 2 times in total.

Kevin Morin
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Re: Possible Steel Jet Setter?

Post by Kevin Morin »

E'tug,
couple of points that are not mentioned yet.

There is a rule of thumb in boat building that aluminium is roughly half the strength of steel at one-third the weight. This means that an aluminium vessel can be built at an equal strength that is only two-thirds the weight of ANY comparable strength steel boat.

This is a fact and it leads to lots of considerations for the metal boat owner- besides the builder.

Equal strength boats, one of aluminium and one of steel of equal "strength" :
the steel boat will weight 1/3 more forever; the steel boat will lift 1/3 LESS over every wave.
the steel boat will use more than 1/3 more fuel; we're discussing planing boats ONLY, where speed is the criteria for the hull's shape and function.
the steel boat will carry 1/3 less payload; it's like the material's density simply adds 1/3 the hull wt in 'concrete in the bilge' so: there's a 33% benefit to be lighter wt. in a small boat.

The steel boat will will cost more than 1/3 more to tow behind your truck on a trailer, remember those bags of concrete in the bilge every trip to and from the water!

Finally, the steel boat will have to be treated, coated, painted annually or bi-annually to keep from rusting into dust! In alternative the original hull can be sand blasted, primer coated, top coated - which essentially makes up the different in material costs. (You assert that blasting and coating is a "myth" but try to get a bank or credit union to buy support the purchase of a non-blast and painted steel boat!!)

As to abrasion resistance steel will stand up to regular dragging on a sand or rock beach better than aluminium, however I'm not really sure that is a design criteria for a small boat? If the same skiff runs on the rocks (one Al, one Steel) and they weigh the same... aluminium will scratch more but steel will hole more often due to less malleability.

As to interior framing? unless you propose an exact design, and show the exact plans- there's no possibility of any real discussion. (I generalized above about overall weight to find a common comparison) I've built lots of and lots of welded offshore skiffs (100's) and many of them used a series of framing but a few insisted on having thick plate hulls and and didn't have much of any framing.... but were still lighter to build, run, load, and land than their equal strength counterparts in steel.

Your complaint is (it seems) about cost not just materials but welding costs as well? The Great Lakes don't have any salmon fisheries of the scale in SC Alaska. Not everyone, but plenty of small boat fishermen do make 40 to 250k $ per 3-6 week season. So they're able to pay for the highest performance equipment that money can buy- to invest in the most durable, seaworthy and economic (for their equation) boats. And that is welded aluminium - not steel.

Your area has no commercial fishery of comparable return or scale, and perhaps no oil and gas (N. Slope) to support such and active wage/salary market as we see here. So I can understand why the cost of the investment is so critical.

This is like arguing that a steel air plane would be "stronger" than an aluminium plane! For the same wt air plane the aluminium plane will be stronger!!! by 33%!! Your post is about a planing hull. Planing is a combination of shape and Horsepower to Weight Ratio. Supercubs have steel tube frames but have to have cloth skins to compensate and Cessna's are made of all aluminium in order to get the Hp to Wt ratio to fly as well as they do.

Small skiffs that plane are more economically made of and have longer duration in, and return more for the investment in welded aluminium (or stretch formed & riveted ) alloys as compared to steel.

Another view and one supported, I assert, by the market offerings. Are there any small boat mfg.'s in the Great Lakes Region that offer a line of small welded steel boats? Regardless of shape? Jon boats, cambered bottom V-Bow like the Gregor or Lund? I'm not aware of one single mfg that agrees there is reason to produce these classes of boats in steel?

I just don't think the physics are there for a high density material, that rusts, to make small boats? But if there are builders offering these and they're not a one off shop (like me) - then I'd like to learn more about them.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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kens
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Re: Possible Steel Jet Setter?

Post by kens »

Reading the above I noticed there was mention of 16ga steel, and, stick welding with a $500 machine.
Now I am very much a rookie in welding, but somehow I doubt stick welding 16ga with said $500 machine.
16ga steel with MIG? maybe, but not $500 machine, and even IF you could, you would have as much experience as that of welding in aluminum.
16ga steel with TIG? Sure, you bet. But the time to fitup and time to weld would be painfully slow.
Just my .02 cents from an un-experienced welder.
Oak..........the juice ain't worth the squeeze :D :shock: :o :)

Kevin Morin
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Re: Possible Steel Jet Setter?

Post by Kevin Morin »

Kens, with the current models of both circular saws and jig saws, cutting thin steel is pretty easy- not quite as easy as plywood but... coming very close. And cutting small steel pipes, angles, or rectangular tube with slow speed (1300-1400 rpm) cut off saws is very nice! I bought one after using this version of a chop saw in another shop and have put up the bigger falling frame metal band saw in favor of the 14" metal cutting chop saw.

So, with fast cutting, even curves and cambers in steel- no longer confined to gas torch or plasma - I think that small steel boats could be a wash in labor compared to the Miracle Metal in hand layout and cutting the major hull components? But then comes the welding.

I agree that welding thinner metal is much harder than welding thicker metal. And using stick on 0.0625" sheet does sound pretty challenging!! Even automotive body fender MIG welders who work in pretty thin sheet have to adjust their welding techniques to that thin a metal. They just keep spot welding closer and closer together until there is a "weld"!!

Tig is more to scale in the smaller welds- I agree- but again as you note not exactly rapid paced welding. If the joints were designed with a larger rod- say a 3/8" round rod inside the chine (as heat sink or weld back up bar) and a 1" or so pipe at the sheer- then welding a steel sled with MIG wouldn't be too hard and might be done with stick too? However the welding time with stick ( about have to be 3/32" rod?) will surely be higher than other processes- about the time of TIG?

Overall, regardless of the metal when the hull material gets thinner than 1/8" or maybe 0.100" the welding required is going to require special joint designs, maybe fixtures and definitely longer hours practice to achieve those smaller welds if they're to be in proportion to the material being used.

On a similar note; I've seen lots of posts online over the years where the poster hasn't built in metal before- and states their desire to "start small" so "I think I'll build a little 12' boat" to practice!! And being the spoiled sport that I end up being.... I usually remark that the smallest welded metal (aluminium for sure) boat a new or first time builder should attempt would be 16-22' with the thinnest hull panels of 1/8" . Never did see a post of the 'begin smaller' skiffs so I'm not sure how many posters had to give it a try before they'd believe some random remarks on line!

I think it would be interesting to see E'Tug's jet sled if he decides to go for it? Just think there are some very major obstacles to overcome and then the wt will be pretty high!

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

electric tug
Posts: 71
Joined: Thu Feb 11, 2010 4:15 am

Re: Possible Steel Jet Setter?

Post by electric tug »

:D :)
Last edited by electric tug on Tue Apr 13, 2021 8:35 pm, edited 2 times in total.

Kevin Morin
Posts: 775
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Possible Steel Jet Setter?

Post by Kevin Morin »

e'tug, glad you 'rested your case'; it will be interesting to see your steel welded jet boat.

I did address every single point you made- and countered them and you seem (IMO) the one who misses what's been posted?

For a fact, two boats of equal strength aluminium will be lighter by 33% as I've already posted and explained and you've ignored!
For a fact, if two welded metal boats, one steel and one aluminium, were the exact same Wt. : the aluminium boat would be 33% stronger as I've already posted and explained and you've ignored.
Your assertions to the contrary are based on unconfirmed physics and your opinion of physical facts- might try using density, tensile strength, material yield and failure loading?

Your figures for the relative projects may play out- you build 'em and show us?

My example about manufacturing was to illustrate the error of your many, many assumptions and estimations about steel compared to aluminium; I was using economic facts of life to refute your unfounded assertions. To wit:" IF what you say is valid....then why aren't builders flocking to the steel version of their jon boats and jet sleds?" If there is a valid product to be sold... some mfg. concern WILL try to make one an sell it!

You seem to be interested in planing boats? But then resort to comparisons of displacement boats? Not sure your point? Yep 5 knot tugs are economic in steel. So are 5 knot 'log broncs' in a saw mill pond and so are container ships- none of which plane. (all up) Wt. is an overriding factor in design when (all up) velocity is the key priority in a mechanical system; therefore my air plane example(s). All missed by your response.

Yes, I do understand you're discussing a one-off- steel jet sled and I agree it could be done. But... as shown, your jet sled will be heavier than aluminium for equal strength and the labor, once coated, will be much higher. You assert (w/o evidence since you showed a painted boat!) that steel coating is a "myth"; so I'll assume your steel jet sled will be 'au-naturale' and left to the elements- like any comparable aluminium boat would be?

You've missed the point-on-point refutation of your assertions and (therefore) the proof will be in your 'pudding' : I look forward to seeing your (flux core!!) welded steel, unfinished, jet sled build and running. I know what the plural thousands of welded aluminium jet boats look like! I know what my few hundred small boats look like and the dozen or so larger boats look like too and understand "a little" about the misconstrued "facts" you've asserted.

Let's see your steel jet sled? I did mention that for equal strength you'll need 33% more power to push it and if you want to compete with a hp/wt ratio of an aluminium jet sled- you're going to need more power not just the difference in wt! Remember F=MA and in sprint boats A is a big, BIG deal.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

electric tug
Posts: 71
Joined: Thu Feb 11, 2010 4:15 am

Re: Possible Steel Jet Setter?

Post by electric tug »

lol a 2000 lb steel jetboat needs the same hp as a 2000 lb Aluminum jetboat :!: :!: :) :) :)

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