Aluminum Boat Cabins

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Kevin Morin
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Location: Kenai, Alaska

Re: Aluminum Boat Cabins

Post by Kevin Morin »

North the idea of essentially making your own windows of the type you've described is a real challenge with welding equipment.

the reason is; as you're already aware, welding very thing sections is increasingly difficult as the sections get thinner. SO getting a window on the side of a cabin- lets say of 1/8" sheet using 1/8" angle extrusions is very challenging. MIG is almost out of the question due to the welding access and positions and the corners mitered or bend would be a serious challenge to weld- into anything that looks like finished work.

Then attaching a thin frame like that to the sidewall would require very small fillets, probably using 0.030" wire- or 0.035" but.... the resulting distortion would be very difficult to control the outcome desired- a flat cabin side.

There is a rubber extrusion that will cold install that has a trough for sliding hardware- used it a few times, mixed blessing at best. But other than (uber expensive) aluminum frame windows screwed in as a flange and bezel - getting sliders is hard to do.

Using Lexan or other plastics has shown to be a problem- first dust cloud or dirt road you trailer down? the haze comes onto the plastic- safety glass in fixed rubber is about the best solution for a boat this size- and keeps the entire design build in the lower cost range. Depending on the weather during your boating season? A side vent/tip out or round plastic vent fitting forward with draft aft, is a better solution to cooling a hot cabin on a warm day.

not sure if you'll have an after bulkhead w companionway? or just a three sided 'weather helm' design; but either way sliders, while nice, are not that simple to do without TIG.

If you're willing to do the work, take the time, you can build a set of bolt in/screw in mounted sliders for the sides by building then on the bench. Then using a two piece (frame and bezel) method, sandwich the cabin sides between the frame and bezel ring and you'd avoid trying to weld thin angles and keep the cabin sides straight.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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kens
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Re: Aluminum Boat Cabins

Post by kens »

Have you seen the cabin plans from Glen-L?
There is several versions in the same purchase, although written for wood, it still gives you something to go by.
I believe version D is the original for Double Eagle.
https://www.boatdesigns.com/Dory-Cabin- ... ducts/534/
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
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Location: Nova Scotia

Re: Aluminum Boat Cabins

Post by North »

Hi Kevin - you make some good points and yes, it would be hard for anyone, let alone me to keep the side straight while welding angle/sliders on to the cabin sides.
I would be interested in seeing more of how you would build the sliders on a bench!

I am not planning on having any back wall/ door on it, so yes it will be a 3 sides wind/rain/splash protection rather than a full cabin.

Although we do boat into the fall, where a warm cabin would sometimes be nice... the majority of our boating is on quite hot summer days with some cooler and windier days thrown in. The main reason I want the cabin is to stop the wind driven spray from soaking guests (and me) as a typical summer day here has 15 to 20 kt winds and we are always having the wind on the beam at some point. When we hit the 2-3' chop the spray rails knock it down a bit, but the wind drives it across the mid and stern sections of the boat.

That said, I am very leary of having a cabin that is too warm, if I cant open or remove a significant portion of the glass on the hot days.
I will put up with a less refined look (especially on the inside)if it means I can slide or (even better) remove panels and store easily when not needed.

What if the areas of the cabin where angle / slider tracks are to be welded were very close to more structural/ stiffer components like in the attached pic? I would think that the top of window is so close to the roof and to the transition just below it, where the cabin side changes shape (and I assume has some plate or similar welded into it, or it would be press bent/ formed to make the edge on the top of the lower cabin wall) that one might get away with more welding than you would on merely a 1/8" cabin side by itself?

Kens - I hadn't thought of, or been aware of the separate cabin designs. I only knew I did not really want the traditional Double Eagle cabin..
I do like the look of the B version but where it is made for wood, and on a smaller boat ( I believe) I am not sure how much value it would be for me.
I will consider it at least.. I see that plans are for a 5-6' cabin and I plan on using 8'long sheets to make mine, giving a little more room inside. Not sure how easily the dimensions of the plans would scale to suite it at 8' long..
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26-x-85-surf-pierce-hull-1305.jpg

North
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Re: Aluminum Boat Cabins

Post by North »

Hi Folks - question for Kevin or Yofish.. I am hoping to buy the two 4'x8' x 1/8" sheets for my cabin top in the next month or so.
I measured today roughly where I would like the forward edge of the cabin to start and it is about 6 feet from the bow stem.. just aft of where it really starts to become skinny..

My biggest question, which Kevin may have answered before, but I got confused in the process a bit... In plan view, should the cabin top (sheet pieces welded together) and therefore the cabin space underneath, be a perfect rectangle or should the forward edge be say 4" less wide than the aft edge, to reflect the decreasing width of the beam / measurement in between the sheer guards as it moved forward?
Note . I have looked on line at numerous images of cabins but not seen one in plan view yet...

The metal shop closest to me now bends on site so I want to be clear on measurements to give them and the number of bends I will ask them to do.
I will not be having any panels bent for the cabin sides at this time..only for the top. Once the top is in place temporarily, I will measure for cabin sides and may have some bending done.

- I will have one side (inner side) of each panel bent at 90 degrees , with about 1.5"?? turned up (to weld together in the method Yofish suggested and Kevin illustrated as well on cabin sides)

- As well, I am considering having one or two bends made on the outside edge of each panel, perhaps:
- one downward turn at 45 degrees, perhaps 3-4 inches from the edge of the cabin top, and another 45 degree bend about 1-2 inches from the edge. I would then likely weld my cabin sides up against the inside of this edge as a lap joint..
- or, again near the outside edge, perhaps a couple of 45 degree bends, only about an inch apart, leaving perhaps a 2-3 inches more at the outside edge, and the last inch would be turn back inside at 90 degrees, and I would then place my cabin side up against this edge and mating with the roof as well, so I could weld in a couple of spots...

I also have a question on the best/ potential/easiest way to bend the perhaps 1" x 1" square tubing which will be welded up under the cabin top to support it, running side to side and with a slight curve to have the roof higher in the middle.. I could build curved wood forms and pull the roof down to get the shape I want, and then perhaps use a cutting wheel to make relief cuts in the tubing every few inches and then weld in once it fits.. but is there an easier or better way? I assume metal shops will bend tubing at 90 degrees.. but will they put a slight bend on it for me, consistent over a 6- 7 foot section?

I would really appreciate any help and feedback on my ideas above or better ways to do these tasks!

Kevin Morin
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Re: Aluminum Boat Cabins

Post by Kevin Morin »

North,
lots of info there... and many expressed and implied questions. I'd try to give some replies but... they won't be in one four page post. I'll have to try to digest all you've posted, and reply in parts (incrementally)

Otherwise, the volume of information you've requested is more than I could try to supply at this time.

First is to discuss the plan view house design.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

North
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Location: Nova Scotia

Re: Aluminum Boat Cabins

Post by North »

Sounds good Kevin - yes, the plan view design is my biggest question or concern.
thanks

Kevin Morin
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Re: Aluminum Boat Cabins

Post by Kevin Morin »

North,
if you accurately draw the plan view of the boat, or built accurately to the plans then you could use them for your cabin plans.

Looking at the plan view- the sheer clamp/guard deck/gunwale plate that attaches to the sheer is either a curve following the sheer in Plan View OR its a line ? In either case that is the basis on which a side to side full width cabin is based. If the inner shape is a curve then a curved base to the cabin sides is implied. IF the inner line of that horizontal plate is a line- then you could use it for a single sheet side to the cabin.

In both cases, Curved inner sheer clamp or Straight inner sheer clamp edge; that is the basis for the cabin to weld to the existing hull so... that's what you need to know first?

In the case of the curved inner edge, I'd mentioned that an approx 1/2 ht (of the overall cabin side) could be cut to follow the curve and tacked edge to edge for a nice inside and outside weld. The inside weld will be overhead, (inverted) outside corner joint and the outside weld a down hand fillet.

Once tacked but not welded, then the top edge of this pc is curved like the bottom edge. Since a flat surface is needed to mount glass windows (not sure if you're using glass or acrylics?) the upper half of the window band needs to be flat.

To leave a flat surface on the upper cabin sides and a curved surface along the lower cabin side panels- a very narrow, horizontal strip will have to fit to the outer curved edge of the lower cabin side panel- while the inner edge of this strip is fitted to the upper, flat panel's lower edge.

This is easiest accomplished by press braking the upper cabin side panel's lower edge for a few inches and then cutting the outer, lower edge to the curvature of the top of the lower side panel.

This leaves only one weld at the middle of the side panel of the cabin. This weld would be fairly easy to do in 1/8" 5086 or 5052, as it is an outside corner, horizontal and is supported on edge by a bent corner only an inch or few inches away from the weld. So weld contraction, which might otherwise wrinkle the side panels would be minimized by this 'step' jog, ledge, horizontal member down the length length of the side.

NOW we can talk a little about the cabin's overall shape in Plan View. Once the lower parts of the cabin sides are decided and planned- then sloping the cabin sides inward - say an inch in 2 feet? Or 1-1/2" in 4' - not much slope but 'some' ... Then you could plan for the top of the cabin.

While planning the dimensions of the top- you'd need to make some decisions about the overhang/handrail/edging of the brow if you'll have any of these features. It is a decision to have them and a follow on decision fork as to what they look like, how they're attached as part of the structure and how will the be welded?

So, beginning at the sheer, there's a width at each point along the side of the cabin, and from that point the sides of the cabin go up and have some lean-in. From that you'd know the top of the cabin's outer roof measurements. Most cabins are vaguely trapezoidal in Plan View where the after transverse is the base and the two sides angled in (by some degree) toward the keel as the cabin top runs forward.

Hope this helps your planning, and clarifies some past remarks. The sketches posted some time ago, above, do show examples of a few ways of building or designing and planning to build cabins- and some of the details can easily be applied to a larger cabin but were drawn as related to a little dog house or skiff's weather helm.

Incidentally, in Dave Gerr's "The Nature of Boats" he shows a removable glass window frame type that could be adapted to work in metal.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

North
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Location: Nova Scotia

Re: Aluminum Boat Cabins

Post by North »

Hi Kevin - Yes, that does clear up a lot for me.
The inner sheer guard on my boat does curve with the sheer. It is NOT a line. It is effectively a piece of pipe (slit down the middle) welded over the topsides at the sheer, and then has a piece of about 5" flatbar welded horizontally on the inside (curved with relief cuts where needed and then welded back up). Then the inside of the flatbar has another split pipe welded over it's edge, so this pipe is the inner most feature of the sheer guard.

I understand your build method and descriptions. In my ignorance, I had planned on doing the math to try and find the dimensions of the top without actually building the cabin sides first... I had planned on using the measurements between the sheer guards, for and aft, then adjusting for slope, curvature in the top panels, etc. This way I had planned to build the top first and then move it slightly fore and aft until I was happy with its placement.. then tack it into place using some scrap pipes/ angle to hold its weight before building the sides..to fit at that time..

I will abandon my naive plans and try and follow your advice, at least until I have lower curved sides tacked in place and get a feel for the shape and size of the cabin.
Thank you for taking the time to help!

North
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Location: Nova Scotia

Re: Aluminum Boat Cabins

Post by North »

Hi Kevin - I am planning to start on the first panel, the vertical bottom one which would be welded to and follow the curve of the sheer guard.
Rather than the 1/2 height as you had suggested, I would like to keep this bottom panel as low as reasonable and therefor have a higher top panel, allowing larger windows.
I thought I had some scrap pieces big enough but it looks like i do not..
please see the attached pics of where i am proposing to place this bottom section. The white boards would be the top of this section.
The aft 8 ft of the white boards, between the red funnel and the can of wd40 aft would represent the cabin and the approx 3-4 ft ahead of this would represent the line where the cabin trunk top would be joined.
As it is about 12ft in total I could get a 4x12 sheet of 1/8" 5052, so there are no seams. Alternatively, I could just go with an 8ft length and do the cabin section only and fill in the forward portion for the cabin trunk later, once the cabin takes more shape..

Does this look decent of if not please advise what you would do instead?
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20201025_140746.jpg

Kevin Morin
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Location: Kenai, Alaska

Re: Aluminum Boat Cabins

Post by Kevin Morin »

North, I'd draw the project in its entirety before I bought or cut anything.

Decent is in the eyes of the builder/beholder- so a bit subjective. I don't design based on sheet sizes, I buy to whatever is needed to build my designs. So, what I'd do is draw the project, and make my adjustments to the drawing(s) and then build what I've drawn.

I don't see the cabin from these photos' implications, and so I'm not clear what you're planning? Drawings, by tracing over the plans, or redrawing the outboard profile view are how I've always done work like this.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

North
Posts: 308
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Aluminum Boat Cabins

Post by North »

Thanks Kevin. The plans and the boat are an hour away from me, so I will dig out the plans next time I am up there.

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