Seat Modification

I just purchased a 16' Aluminum Lund. There is no floor in the boat and looks like its always been that way. I want to add a floor and remove seats. I know that the seats our structural but I have an idea that I would like to know what you all think. What if I cut the center section out of the seat (middle seat) down to the hight I want my deck at. Then just leave a foot or so of the seat in tact on each side. Would that keep enough structural integrity. Take a look at my attached photo to see what I mean. Its very crude and not to scale so dont judge

Thanks,
Josh

 

Hi Josh,

What you're proposing is not unheard of, but it is not simple.

Firstly- why do you want to add a sole? (In boat speak- what landlubbers call a "floor" becomes a "sole", and the term "floor" is used for the frames under it.) There are a few notable disadvantages that this would create in a boat like yours- mainly to do with the tendency of the space between hull and sole to collect water, gunk, rot, corrosion, etc.

The bulkheads under your seats- and the seats themselves- are important for keeping the proper shape of the hull. Taken together, the bench seat, bulkhead and hull form a stiff, I-beam-like structure. If they are to be cut down, additional reinforcing needs to be added to maintain the same stiffness and strength as the original structure.

I'm not sure how much of an engineering or metalworking background you have. If the answer is "none of either", you're probably in over your head. But if you're OK with working aluminum (bolted or riveted, you won't be welding the thin sheet your Lund is made with) and can see from your drawing where the added reinforcement needs to be, your project might be possible.

Hint- really beef up any areas of potential stress concentration, and you want to make sure the upper corners of the bulkhead stay the same distance apart, and don't forget the bulkhead's rigidity in the fore/aft direction (currently very good, thanks to the bench seat securely fixed on top of it).

 

Thanks for your reply Matt. I'm an architect so I understand a bit about structure (although building structure, not boat structure.) As far as metalwork goes I'm somewhat familiar with what is going on. I'm not super concerned about making it pretty, just safe. If you saw what I'm starting with you would get why it doesn't have to be pretty. How do they say...you put lipstick on a pig, but its still a pig.

As far as my reasoning, there are a couple. In this boat is really hard on my 12 year old dog to hang out on the floor. Flat surface is much easier on him. My wife enjoys coming with, but doesn't like those sloped floors. Last reason is I'm not a big fan. I like to fly fish sometimes and I'm not very good at casting so the flat floor to stand on is easier.

With all of that being said, I'm not really sure where to start. Any thought on how to reinforce the seat area if I did take it out? In an aluminum boat are the seats like that always structural? I have attached a photo of my new boat. What do you think, are these structural, I"m guessing they are.

What I was thinking was to only take out a small section of the seat. Big enough to walk through. Just dont know where to start.

Thank,
Josh

 

It's hard to tell from one small photo exactly how everything's fastened in. But my guess is yes, those bulkheads and seats are structural. They most likely have beefy riveted angles to the hull at each side of the bench, and will also be securely riveted to the bottom of the hull.

Have you given any thought to building a "drop-in" sole to fit within each bay? With the addition of supporting cleats on the bulkheads and hull sides, you could build a slatted wooden deck within each bay, that would be sufficiently high and flat for your needs, but wouldn't compromise the structure or the budget. Or if you want to do it on the cheap, cut plywood to the exact shape of each bay at the height you want the deck, add some stiffening and supporting members underneath, add cleats on the bulkheads, and some good anti-rot treatments (and maybe astroturf, if you're into that sort of thing) finishes it off.

With a flat, raised deck I think you'll find that stepping over the benches isn't nearly so big a deal. And with simple panels that fit within the existing structure, you can still take them out to clean the bilge (or retrieve lost lures).

 

Yeah, I think that might be the way to go. Originally I had an uncle that could weld aluminum quite well, so we were going to engineer something. But he no longer has access to a welder. Now I was just wondering if there was anything else to do. I'm thinking I might just do the way you said. You keep saying bulkhead. What does that refer too?

So I have another one for you. In this picture there is a top over the bow(?) of the boat. Do you think this could be safely removed?

 

The deck (this is what the top over the bow is called) you mention looks to me like a structural part too. This is normally the case (it gives a lot of stiffness to the boat), I wouldn't just remove it.

 

There is another bench seat that sits just behind the deck. I was thinking about adding a small casting platfrom from seat up to the very front. So I could reinforce the front somehow, but I dont know how. I'm open to suggestions.

Thanks!
Josh

 

Hi, I'm a newbie and don't know a boat from a bathtub (lol, yes I do) but I have seen what I think you want to do. The deck on the bow is structural, if you cut that out you'll need to beef up the gunnels, perhaps with a yoke like a canoe, IMO, never saw that done, the deck is really nice to get older huys on and off the boat. Anyway, to the seats, I have seen these cut out and boxed in at the sides. From the far sides at the floor/sole, the seats were cut out going straight up. This kept a wedge shaped piece along the sides. The seats were cut down about a third, maybe half. A stringer board ran from bow to stern on the inside where the sesat was cut away. A sole was put in butted up against the bttom of that stringer (like a 1X8) and then plywood was set on top of that stringer and top side of the seats where they had been cut down and scribed to run along the sides. So, It had smaller inner walls along the walk through that came up a few inches then back out to the sides. At the front and and where the seats had been, spay foam was used to fill that void. Compartments were along the side access from a hinged top. The plywood was continious running back for an 8 ft. run and top hatch was cut out with piano hinges. All covered in indoor/outdoor. Look nice. I have a cabin at Tablerock Lake and a neighbor up the road I have coffee with did this to his boat.
Running stringers and plywood top was stiff enough to brace the sides where the seats supported the boat, IMO, since he had no problem on that lake...and it gets some pretty good wakes out there!

I'd suggest you call the manufacture and discuss it with the guy in the engineering office. Lund is made up the road on I-44, Lebanon, Mo. They will talk to you and get you on the right track. Good luck!