Another way to design & build in Aluminium boats

Kevin Morin
Hi Kevin the boat you have mentioned is showing the framework the way I build my boats.
Because back when I built most of my boats we did not have digital cameras so I don't have to many photos showing my framework.
The boat you are asking questions about was my prototype aerated racing hull.
WAS, Yes it went to the scrap yard as it was not giving the performance I wonted .
The concept will work just needs more air.
I have a new design and hope to build it one day.
The drawing that I have posted gives you an idea on how I use pressings to help reduce welding time and ease of fabrication.
The drawing and photo are of a 5.8m boat.

 

More Posts!

monomad,
almost every line in your post could become a full post IMO, and well worth the time to read and reread by me and others who design and build.

It was helpful to see the Body Plan section drawing, and to see the location of the bottom's longitudinal seam- I wondered where you'd found and then how you'd handled this very wide sheet into a break and then onto the frame?

I have no knowledge of aerated bottom concepts or design but its seems you do? If you'd care to take time (?) I'd sure like to learn more about the concept and your experimentation with this concept. I don't build racing boats, and don't think anyone will approach me for this class of boat, but the ideas involved are completely new to me; so they're of great interest.

The pressed forming I see doesn't seem to be small radii that I often see from current shops, can you remark about the radius of the forming shown?

I was glad to see that someone else considers it normal work technique to remove mill scale prior to welding- that seems to be a 'lost practice' in may online images of currently built boats. My welding tests have always shown me that this was imperative but in the US, there are large scale builders who don't bother to clean weld joints properly- IMO.

I hope circumstances allow you to build again, when time allows, since the work shown is innovative and well thought out, I do hope to see more and learn more from your posts here.

Thanks again,
Kevin Morin
Kenai, AK USA

 

HI Kevin
The bottom is 3 x 5mm sheets one inner two outer.
Aerated hull.
Designer- Boat builders try to get their boat as far out of the water as possible to get the max speed ( Less drag ).
Does not matter what method they use to this the problem they all encounter is what happens when they reach that speed then the rest of the hull hit the water whether it be the wash from another boat or a swell.The wetted area is increased very quickly and the drag slows the boat down causing much discomfort to the crew.
With a fully aerated hull I am looking at over comming this problem.
Have you ever played on a air hockey table.With the air turned off the puck does not move very good but when you turn the air on the puck flies around the table.
The concept is not just for racing but also for High speed pursuit boats.
Time and money all play a part in development work.
Pressings
All the plate that was used on my boat hulls was 5083 - H321 Structural from 3mm to 6mm.
I found by standardizing on one tooling saved cost in changing tooling.12mm Radius is what used, a good radius on the sides.
I don't clean all welded areas.Have you heard of Frronius welders, for welding aluminium with out cleaning they are very good.( Frronius TransPulse Synergies 3200 )
Kevin what types of boats do you build.

Mr Efficiency where are you based.

 

I live in Brisbane too !

 

The minimum bend radius with H321 is 4t, t = plate thickness. If you're using 6mm plate, then the min rad needs to be 24mm, not 12mm.

 

Hi Ad Hoc
Yes I agree with the formula on pressing 6mm but with the small amount of 6mm that we have pressed we managed with the 12mm radius.

Mr Efficiency would you be interested in catching up with a cup of coffee.

 

building details

monomad, thanks for the information, I don't work in high speed craft and wasn't familiar with the aeration methods, but it seems like the vents would let the air out? I mean if it were trapped or 'run over' by the hull's shape, where the strakes would conduct air below the running waterline then are the shaped vents intended to disperse the air to a wider region of the hull?

I think air hockey tables work on surface effect compressibility so that implies that a marine shape would have to be shaped like an inverted, shallow, U so there was some compression to retain the air cushion? The Hickman Sea Sled comes to mind, perhaps a rigid hover craft like arrangement?

I've heard of lots of technology that is supposed to remove mill scale or oxide but all of my own break bend tests have shown an increase in weld purity by mechanically removing oxides and then disturbing the reformed film just prior to welding.

I use the Lincoln 350MP with a pulse-on-pulse features supposed to be as well found an arc control as currently available for advanced MIG wave forms; but the welds are still better with mechanical removal and joint prep. I did notice you have some large vertical wire brushed areas at the intersections of your longs and xverse frames so I'd thought that work method typical?

I used to build commercial fishing skiffs and some larger inboard (w/shaft & forward engine) commercial fishing boats. Now I just build a skiff now and again for enjoyment and recreation.



25' open skiff with weather helm.



Most of what I built is still used to work. So I enjoy looking at the 'race boat' set of work in your posts. (racing boats to me)

Of real interest is the method of using the press brake to form entire longs, and transverse pieces, did your layout work happen by hand (lofting, marking, prep to cutting) or was this part of the computer technology now more commonly used?

thanks again,

Cheers,
Kevin Morin

 

Concur. That's the best practice we adopt when building our vessels. I should also point out that we are always building to Class and survey, not just local builds for pleasure.

 

Kevin, I love the pic of folks pullin' over the rail! Same for me, to have long term service is the best test. I've been bunched up with going to daughters grad in Minnesota and moving across the Bay. Start actual construction tomorrow after fighting the plotter that won't feed today, she gets bitchy when the roll gets smaller. Will post progress and look forward to comments.

 

Kevin, that is one lovely boat! I appreciate the detail of the gunwale - the alu tube bent into such a precise and complex shape reveals very much about the level of your workmanship.

 

hijacking the thread!

AdHoc, it find is so odd in today's highly informationally driven world that people who work in aluminum alloys don't pay full attention to the mill scale AND oxide properties of high melting points, porosity and water retention, and instead concentrate on high speed fabrication!

They are, without apparent awareness (?) building in their own boats' future deterioration by allowing substandard weld gaseous inclusions and surface quality deterioration, when for a little acid etching or mechanical abrasion that exact boat would last decades past the premature end they build-in! What a conundrum as these act are done by intelligent, skillful and otherwise knowledgeable people

I'm at at a loss to understand this, and exponentially so when the level of effort to correct these problems is so miniscule?

Yofish, I can only envy anyone who's life is so well organized as to live on the South side of the KBay in the summer months
yep, rolling reds over the rail is 'living the good life' and not everyone sees those slabs as 20 dollar bills; but they should.

daiquir, thanks for the kind remarks, I use a 1/2 pipe extrusion that we buy in the 2" (2-3/8" OD) or 2-1/2" or 3" ANSI pipe sizes. In 1977 when I first began skiff building I requested this 'half pipe' extrusion but was not aware of the potential to copyright the extrusion template and lost out on what may have been a financial boon!

Oh well, the pipe in that photo was applied to the sheer as a 1/2 pipe extrusion, that is 1/2 of an ANSI 2" (therefore 2.365" OD or 60mm OD) profile. Therefore, once the sheer line is cut on the topsides, and the guard deck or 'gunwale flat' is tacked to the topsides at the horizontal; an extrusion can be clamped and tacked on flush or even with the top most surface.

This will leave a three sides 'U' shape to fill with weld. The topsides upper most edge forms the bottom of this groove, the extrusion's inner most edge the outer side and the guard deck or sheer flat plate's outer edge forms the inner side of the U.

In this case, the welds can be placed very hot, since the bottom or support of the U is the upper edge of a sheet. That means that both sides of this U groove will be fully fused to the outer edge of the guard deck/sheer clamp plate, and the inner edge of the extrusion's 'pipe' cross section.

This method allows one weld to fuse all three elements of the boat AND the top of the weld can be sanded fair without reducing the overall welds' structural integrity.



This concept is shown here, but the drawing doesn't show the bevel that is used when the depth of the pipe or guard deck (flat plate at sheer, inboard of topsides) are thicker than the topsides. Then a router is run along both edges to open the U to a V- the reason being MIG will typically allow the arc to run on the two top edges instead of the needed arc in the bottom of this V/U groove formed by the three pieces.

After tack up, the tacks are dressed with a rotary burr mounted to a high speed air or electric hand piece so the weld is allowed to 'burn out' the tack and leave good quality continuous welds.



Without doubt, images of welded aluminum are not the best the coloration is so subtly different that most weld details are hard to 'see' and clearly understand.

IN this image the half pipe extrusion is tacked in the foreground. It is welded in the middle of the distance and in the after sections has been dressed with sanding and then finished (brushed) with the 3M ScotchBrite (tm) pads to the maroon or medium grade.

Also, the guard deck to topsides weld was already made and then dressed and chamfered using a 4" belt sander to provide a uniform (but beveled) seam on which to clamp and tack the half pipe.

The rough sanding only takes off the crown of the weld, which, because of joint designs and preparation allows a very deep penetration; giving up the crown is not a structural detriment to this hull seam.

(For the keen eyed photo interpreter; yes there is a Siberian Snow Springer Spaniel laying at the after starboard of this skiff in the photo and his head shows along side the gunwale.)



and another gray scale image of what the finish dressed seam can look like using this method.

Thanks again for the kind remarks.

Cheers,
Kevin Morin
Kenai, AK

 

Hi Kevin
It's good to see the different styles of boats used around the world and your boat building skills sure do show in your boats.What HP do you use in your boats.
It is interesting what professional fisherman won't in their boats because that boat on the water I posted here is the same boat the pro fisherman as moved the center cab right up the front and he still reckons the boat still handles the same.He shoots he's nets out the back.
The other photo is of a 7.5m Diesel / Jet for a professional fisherman.

The concept of the aerated hull is not to trap the air under the hull as this would only add to the slamming of the boat when hitting the water.
By allowing the air to escape freely right across the hull sets it up to ride on air bubbles thus reducing the drag.

 

Client is Always Right?

Monomad, the saying is that the boat's owner is always right may apply to good business but it does make for some serious differences in boats from one owner to the next.

I always wanted to build a single design (or several) and produce the boats as low cost as possible to keep working year round, but my market just wouldn't buy the same skiff over and over. I had to adjust the sides, the interiors and even the overall length and shapes to suit - so I ended up building hundreds of net skiffs, for salmon fishing here in Alaska, that were very similar but had countless variations of side lean out, gunwale heights and more interior details changes than I recall. Sure would have been less expensive for all concerned to have made them the same, I don't know that the differences made for better fishing but it made for better sales!

I agree that the cabin location is one thing fishermen all disagree with each other about. Of course, they're fishing so they should make that call.

I understand more about the aerated bottom idea now, and the notches, which I'd noticed are precisely laid out and cut make sense. I was going on my 'ground effect' or cushion idea of the air hockey table instead of looking the surface boundary effect of the drag reduction by bubbles.

Speaking of power for the boats I've built?


This one is just powered by oars! This dory was a 'metal copy' of a Gardener historical plan called the Chamberlain Gunning Dory, that I found in a book by John Gardener. I modified the planks a bit to make it of metal and built her with 0.100" (2.5mm) material. Low power.

In order to increase my feeble arm and back power I made hinged oar locks that swing outboard to increase my leverage and make the 8' oars more effective. In this picture she's rigged for tandem rowing which is a nice afternoon outing in tidewater Alaska, given some fair weather.

And one other little boat has an 8hp engine; not shown here; as she emerged from the paint shop.



This little 14'er, also in 0.100"(2.5mm) material, uses a little gear motor to drive it at displacement speeds, about 5 knots or so. The 2.8:1 ( I think) reduction allows the engine to move her at low speeds and not to worry about trying to plane.

So my building used to be commercial boats with more power but has dropped down to little boats with very little power. The 25'er, shown above, was originally powered with a 150hp I think, the owner did his own rigging and I'm not sure if he decided to stay with that power or moved up as is often the case.

Anyway, thanks for the reply and pictures.

Cheers,
Kevin Morin
Kenai, AK

 

Good gawd, do I know that one. BB and PWS set-netters were my bread and butter for years but lordy, lordy they ALL came in and said, "I really like the skiff you did for Billy Bob, BUT, BUT and BUT." As a side note, I'm experiencing an eerie similarity to the late 80's in the money flow and attitudes.

monomad, once again thanks so much for sharing your approach to the craft. You have introduced me to a way of thinking about the common problems we all face as a designer/builder that is so outside my ken that it's a short, sharp, slap to the senses. I use pressings, as you call them (I like that term and am going to use it now) as I can, and especially would more so if I could afford a press brake. Unfortunately, hereabouts it's an expensive process and sometimes with the time it takes to get it done, I don't do it and have in fact worked around the nicety of it to get the job done.

 

Yofish
I did not have my own press and like you having to get someone to press when and how you wanted it pressed was some times frustrating. Like you I wished I had my own 6m press.
Here's a simple 3m punt pressed out of 3mm structural plate with no ribs or stringers just seats, side pockets , front storage shelf. 50mm tube welded to the sides.