Aluminum Boat Cabins

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

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Kevin Morin
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Location: Kenai, Alaska

Re: Aluminum Boat Cabins

Postby Kevin Morin » Sun Feb 28, 2016 3:38 pm

So far, we've looked at the brow in detail because I've argued it was a very important little piece of metal. I've shown lots of versions of this shape, and stated I think its shape is so influential for the cabin's look in regard the boats lines. IF you review the Glen-L catalog you'll see lots of different cabin lines; if you view anyone's design catalog you'll find different brow lines; and if you online and search you'll find a wide variety of this design element employed by designers.

Now, we'll look a bit at the layout or scribing and marking of the cuts. Not the only way to do this work, certainly, and as most one off home builders don't use software to develop surfaces; I'm showing here some rudimentary methods of marking so that cuts with hand power tools could result in clean lines and finely edged welds.

Image

By holding a plate/sheet piece to the cut arc on the top of the cabin, the edge of the brow can be marked reaching behind or below the intersection of the two pieces when held in this position. I've drawn the top edge cut, but in previous views you can see that any material thin enough to bend without rolling and extending above and below the cabin top will work as a blank.

A means to get the angle or rake correct is to put a set of temporary 'sticks of aluminum' tacked to the top- where one stick is at the angle in Profile View the other holding it up like a leg. Or; cut ply wedges and hold them to the brow blank while its in place. All work related techniques depend on the 'crews' size 1 set to lots of sets hands means different methods make sense.

Image

Once the blank is cut and tacked up... if the cabin is built on the shop floor, which may not be the case, its possible to strike the lower brow curve using a straight edge and several ares shown here. The image illustrates the method of striking the lower line by holding the aluminum bar extrusion at differing distances (width of the brow vertically) and when this is held in place the bar may be vertical or raked slightly and again these intersecting cylinder will create a VAST , large number, huge amount of different curves of intersections.

If the reader wanted to correlate this very unassuming image to the work done to build the boats in the photos above, then click back and forth and the relational geometry will hopefully start to emerge? Some of the brows we've seen have nearly horizontal lower edges, but others have a echoing curve upward in the transverse sweep. This is where some of the beauty of this shape becomes a subtle set of interrelated intersecting curves.

Regardless how refined the shape- these ideas shown are the basic building blocks for laying out and building your own version of an attractive (to you) cabin brow.

Image

While not an exhaustive exploration of this windscreen covers' shapes, we've explored the three main contributions to the brow and cabin top shape. First is the camber of the cabin top as it could contribute to the brow's shape. Next is the combinations of the Plan View radius of the brow and the Profile View rake so the brow. These elements are the main influences on this functional but aesthetically pleasing piece of metal that shades the windscreen, sheds water and stylizes your cabin.

but what about some corners and hand rails?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
Posts: 612
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Aluminum Boat Cabins

Postby Kevin Morin » Sun Feb 28, 2016 4:00 pm

We're getting closer to having a full cabin design build method shown here at the Forum, where it belongs. Let's continue with some more details and start by finishing the brow's outboard corners.

Image

IN a few of the boat photographs posted above, the brow is mitered or butted to the side brow plates, and that is not unattractive but also isn't quite as elegant as the forward curved surface curving into the side surface.

This image summarizes the geometry: a segment of a cylinder of tighter/smaller radius. All the curved corners we've seen are is this segment of another cylinder. Often in small cabins this piece can easily be cut from a piece of pipe, as I show here- 6" pipe.

Image

This image just shows the pipe surface in its finished orientation as part of the two adjoining surfaces but leaving the entire pipe visible so the origin of that piece is recalled in this sketch. In the image (next) above I left the two plate surfaces (browns) to show how all three intersect on tangents to the pipe's wall.

Image

Back to our cabin overall from different points of view, the added detail of a curved brow corner transition from the side to forward surfaces is shown here, and the blend of these three surfaces seems a nice refinement to me.

Image

Here is one such pipe wall segment used in the brow of a 25'er's cabin top. Note the brow extends down from the top but there is a lower lining or 'sub cabin top' structure in this design as well? I hope this corner image helps to show the sketches in real life construction?

Image

The upper edge of the pipe wall segment is not trimmed in this progress photo of this cabin's brow construction. One important point to make about this cabin design- the lines are subtly curved fore and aft- for the most part. This implies a vast increase in work, laying out and cutting the curves (#1); Fairing the cuts, and tacking up long sweet seams that could be bent :doh: (#2); and welding a lot of seams in relatively thin materials that is a major time contribution if you're coming to this work for the first time.

I'm not suggesting that this design is appealing to the wider boating audience, my Skipper (here) had lived on the water for his entire life, was very esoterically concerned about every design detail and was vocal and influential about every curves' nature and extent. He was a pleasure to work for in design and building as he would spend time considering and responding to the aesthetics of the work, making my work for him a nice challenge to meet. Not all owners are as concerned with the overall look of their craft and therefore lots of work was done in this cabin that might be considered too expensive for other boats?

(Generally you will not find this kind of one to one design build from the major builders as they need to keep to a schedule to stay in business, I'm not in business and only did this project for the enjoyment of building so I'm not saying that the extra level of effort shown would be economically realistic unless the owner wanted to pay for that extra time.)


I agree with anyone who says " it took lots more time" ( Read: Mo' $$$$ !!) but I'm personally pleased with the results of the extra effort and if you're building your own cabin; I think its worth your time to explore these details to consider if they're worth your time.

Let's keep going by finishing some other details of cabin building.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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kens
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Location: Coastal Georgia

Re: Aluminum Boat Cabins

Postby kens » Sun Feb 28, 2016 5:11 pm

This is a good thread, keep it going.
it is nice to read about how things work together to get a proportional correct lines on the boat.
I know a guy that builds in steel, and he built a custom workboat, had hard square transom corners, then he took a section of pipe as you similar mentioned above, and made a rounded corner transom. What a big difference that made in the looks.
How a small change can add so much to the general lines is amazing at times.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

twaite
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Re: Aluminum Boat Cabins

Postby twaite » Mon Feb 29, 2016 4:50 pm

Your just to good.. hope all is well... nice thread
Capt. Travis

Dillon
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Re: Aluminum Boat Cabins

Postby Dillon » Thu Oct 12, 2017 9:57 am

Great job covering the cabin building and design. Any chance you could do something similar on building doors and door jams? I have spent a lot of time on boats and all the boats I have been on look like they have had the doors rebuilt a time or two.
Thanks Dillon

Kevin Morin
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Re: Aluminum Boat Cabins

Postby Kevin Morin » Thu Oct 12, 2017 11:45 am

Dillon, I'm working on a drawing project right now, no time to spend drawing for cabin post. Maybe later this winter- not sure on my free time.

Doors and windows are often purchased as complete units because of the complexity of the smaller details required to do a good job on them. For example, very specific extrusions are used for aluminum window frames and those extrusions are usually 'owned' or exclusive to a given window manufacturer's purchase. They've invested in tooling to bend, shape and a procedure to combine metal and glass into a 'drop in' product.

That is true of doors as well, in fact many of the window vendors sell doors as well.

We'd like to see photos of your work? Not sure if you have a build thread going? Looking forward to seeing your project.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Dillon
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Location: Kenai Alaska

Re: Aluminum Boat Cabins

Postby Dillon » Thu Oct 12, 2017 12:12 pm

I don't have any pic right now. I am a slope worker and I just got back to work today so it will have to wait 2 weeks to post some boat pics
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Dillon
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Re: Aluminum Boat Cabins

Postby Dillon » Thu Oct 12, 2017 12:14 pm

Pretty cool how I got all my boats on the ceiling. Hmm. Not sure why that pic posted upside down

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mrintense
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Re: Aluminum Boat Cabins

Postby mrintense » Thu Oct 12, 2017 12:49 pm

These postings are such a wealth of information. Thanks again Kevin!. I've been pondering how to transition my wooden cabin with curves and I think this will help immensely. Thanks again.
Carl
a.k.a. Clipper

Crafting a classically styled Vera Cruise named "Some Other Time"

Clipper's Vera Cruise Build

Kevin Morin
Posts: 612
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Aluminum Boat Cabins

Postby Kevin Morin » Fri Oct 13, 2017 1:11 pm

Mr. Intense, I'd be happy to help explore any details shown - in a wooden version- if that might help in planning. Took a project recently that requires most of my day's work so while I may not be able to answer in a day's span? I will try to watch the site, and field suggestions of how the shapes may be constructed or planned to be built in wood- as a part of replies?

I'd help if I can- done a bit of wood work in the past, so its possible I may be some assistance- likely not much!!

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin


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