Adding a low cabin to a 22ft open boat

[mugball]

I have a 22ft open boat pics attached, that am converting to electric inboard. It has very narrow beam of 5.5ft. Intended use is inland waterways in Ireland.

Ideally what I want to do is to add an element of shelter upfront for my young kids as we get as many wet days as dry here. I am trying to make it is low as possible, ideally to just above the top of stem post, which is about 35cm on top of the gunwhales.

Design I am thinking of is something along the lines of the Skiff America, photos attached. Low cabin open in the centre with fabric to allow a standing walkway to the bow. Can be covered in adverse weather for kids to shield from rain.

I have very little knowledge of boat design, geometry etc other than understanding that adding weight higher up can cause stability issues. Main other weight distribution is batteries (almost dead centre of boat), inboard motor just behind the batteries, and helm seat behind the motor.

Other weight in the boat I can be more flexible with the distribution.

Thinking of using 9mm ply for cabin.

Question I have is am I likely to cause significant stability issues with this idea?

 

[fallguy]

Just use a soft fabric bimini.

 

[Tops]

Hello, are you thinking of a squarish box or something that more follows the curves of the boat?
Is the hole in the front deck for a mast or sampson/bollard post?

 

[mugball]

Hello, are you thinking of a squarish box or something that more follows the curves of the boat?
Is the hole in the front deck for a mast or sampson/bollard post?

Hole is for a sampson post. What I am thinking is following the curve of the gunwhale on the uprights, and a slight curve to the roof. It will look rectanglish from the side I guess, but not from above. Similiar to how the curve on the Skiff America narrows towards the bow.

 

[Tops]

The cabin top on the skiff is basically the side chine panels, extended and captured by bulkheads fore and aft.
If heavy crew sat on the cabin top wales, all one one side, there could be consequences...
Chine Panels – The Building of Northern Cross, a Skiff America Design and other Cool Stuff https://hamnegger.wordpress.com/category/chine-panels/

I am having a hard time visualizing how the above concept might work with your boat (assuming that the basic deck and coaming on the launch are left intact).

PS I think the cuddy would be a nice add, just not sure how best to do it...

 

[mugball]

The cabin top on the skiff is basically the side chine panels, extended and captured by bulkheads fore and aft.
If heavy crew sat on the cabin top wales, all one one side, there could be consequences...
Chine Panels – The Building of Northern Cross, a Skiff America Design and other Cool Stuff https://hamnegger.wordpress.com/category/chine-panels/
View attachment 208004

I am having a hard time visualizing how the above concept might work with your boat (assuming that the basic deck and coaming on the launch are left intact).

PS I think the cuddy would be a nice add, just not sure how best to do it...

Thanks for images, that's useful visualisation.

The deck and coming will be left intact so I guess it will be quite boxy given the almost vertical line of the coaming. I won't be able to get splay outwards as on the skiff, so the top of the upright will be inside the side deck. Nonetheless there will be no crew sitting on the roof, never mind the tipping risk its understood that this will be not be capable of bearing weight.

The angle where the coaming meets the foredeck is not quite as harsh as it looks in the photos. Not far off it admittedly, but I am hoping it will allow a bend in the ply to the follow the curve of the coaming. If needs be I guess I could layer 6mm + 3mm to make the bend. Hopefully this will take the edge of the boxy look.

The distance where the coaming meets the foredeck is about 4.5 feet. Most common use case, the opening at the bow only needs to be sufficient to allow crew to reach through to foredeck to handle ropes etc. Occasionally it will be necessary to step through onto the foredeck. I am thinking an opening of 18 inches here will allow for that.

I will try and mock something up with cardboard so I can have a better visualisation.

 

[HelmutSheina]

Well Mug, because your dear old tub has sailboat sort of lines and this is a lot about aesthetics, I thought you might find some design inspiration by looking at some timber yachts of similar size, and found Duckworks has five pages of plans in one relevant category.

Good luck.

Also how about writing up your leccy conversion on here? It will help others and there are relevant experts around if you need any.
Plans by type - Sailboats - Cabin Sailboats 20' to 25' - Page 1 - Duckworks https://duckworks.com/plans-by-type/sailboats/cabin-sailboats-20-to-25/

 

[Tops]

@mugball I am glad the pictures were some use. One of my assumptions is the deck would have have a small crown from the centerline out to the sheer.
Mocking up in cardboard is perfect. Sometimes I cut the cardboard close and then hot-melt glue little 'ticks' to pick up the mating curve. Then the ticks are used to mark points to fair with a batten on the new material.
In the plans @HelmutSheina mentioned, page 3 or 4, the Highlander 23- shows a boat with the cabin sides rising from the deck like a coaming.
The SCAMP boats also have an interesting cabin top. I saw a picture online of a plywood top being bent into a curved shape with the webbing ratchet straps used to hold goods onto small trailers.
The 'consequences' I mentioned on the skiff were meant to be boat motion and sliding off into the water instead of failure of the cabin top.

 

[mugball]

thanks both. I took a look at the plans, including Highlander and Scamp and they do represent sort of what I'm thinking, like a catboat cabin.
The key for me is the the ability to walk down the middle to the bow. Hence the interest in the skiff design.
Marrying that idea to the lines of my boat I guess what I am envisaging is not too disimiliar in outline to the attached pic. I think that boxy shape kept low looks ok. I'm thinking of that approx shape, maybe a little softer but obviously also narrower, in timber plus an open middle with fabric roof cover strip.

 

[Tops]

Not seeing the picture, perhaps attach it again.

 

[mugball]

apologies, attached now

 

[willy13]

Regarding stability, converting to electric inboard with batteries allows you to add useful fixed ballast low to offset the additional higher weight of the cabin. So you have an advantage over the outboard powered skiff america you posted.

Cool project bt the way!

 

[Tops]

Are you thinking of bulkheads on the aft end of the cabin top?

 

[mugball]

Are you thinking of bulkheads on the aft end of the cabin top?

thanks again for the helpful images. Yes definitely plan to include bulkhead aft.