Removing Bench Seats & Adding Front & Rear Decks

I have an old 11' aluminum semi-V that I am in the process of modifying and I'm looking to install a front & rear fishing deck. I have 2 bench style seats (one on the rear and one in the middle) that are hollow underneath. One side of the bottom is riveted to the floor then there is an angle brace mounted to the wood seat & to the side of the boat on each side. Then I have a "floating" wood seat in the bow that is only mounted with the top angle bracket.

The question I am looking to have answered is - can I cut those bench seats out (leaving the riveted piece in the floor) and rebuild the seats where I need them in order to accommodate the deck(s) and the new floor? Or, am I committed to their locations because of stability reasons or something?

In a perfect world, I would like to cut the middle bench out and move it forward a foot or so to use it as part of the front deck or just remove it all together. The back one I can probably live but would like to bring that one forward some to allow enough room for a deck without the motor interfering.

Any insight would be appreciated.

PHOTOS will help the gallery help you.

drill a 1/4" hole into the sides of the seats and see what is there

use the search feature of the forum for REMOVING BENCH SEATS

Giving it the old tap test they sound hollow. In looking through some old threads it seems very doable to either move or remove, just making sure that there is some type of "brace" to keep the boat from flexing while under power and such, which is somewthing I was planning on doing anyway.

Seems like a green light.

When I removed the seats from my old 12', they sounded hollow from the "tap test".
Upon removal, I found blocks of polystyrene foam just free floating inside the seats.
Probably been that way since day one.
Use the search feature about "replacing foam" for some excellent pointers.
good luck in your build

Sorry it took me a day to get pics, but here's what I am looking at. Notice that there is a space underneath the seat(s), both middle and rear. The seats are only attached to the floor on one side of the seat.

What in the world would a seat need to be filled with foam for? I'm new to all of this modifying stuff, so I have to ask. Doesn't seem to make sense looking at it from a novice point of view...

SD Fishing said:

What in the world would a seat need to be filled with foam for? I'm new to all of this modifying stuff, so I have to ask. Doesn't seem to make sense looking at it from a novice point of view...

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To keep it from sinking to the bottom should it get swamped. You wouldn't like that.

If you're a novice it would really be worth your time doing a lot of reading here. Better to learn from other's mistakes than make your own - particularly when it comes to watching your boat sinking to the bottom.

bobberboy said:

To keep it from sinking to the bottom should it get swamped. You wouldn't like that.

Click to expand...

Now that makes total sense there.

bobberboy said:

If you're a novice it would really be worth your time doing a lot of reading here. Better to learn from other's mistakes than make your own - particularly when it comes to watching your boat sinking to the bottom.

Click to expand...

I have been. Not a total new'b to it. I have owned or been in boats all my life. All sorts and styles, but never decided to start gutting & modifying one until this one came along. Seemed like a nice winter project, and a small Bass boat is great for the times you don't care to haul around a 16' XPress, or 20' Champ by yourself. It gets tire some. Plus, I get to leave the wife at home when I take this one :lol:

Problem with the foam (if there is any) in that center seat is I was hoping to move it and make it a livewell and tie it into the front deck. So essentially the boat would be more like a U shape on the interior if that makes sense. But, if a boat needs foam and I have foam in a seat I am looking to hollow out, then I better get to figuring out how to replace that foam around the boat somehow.

Thanks for the replies guys. I'll keep ya'll updated. I'll probably get to work on taking that center seat out and mocking up the front deck tomorrow.

I also ran into this while browsing. It's the info for my boat. Over on the right hand side it says "AIR" (column next to the Max HP column) but I do not know what the lettering is or means in the column title. It looks like it says "Type F.of."...

Anyone knows what that means? In the PT-12 model from 1955 (below) has "Styro" in that same column. Is this in regards to the foam/air flotation stuff that is discussed in the "HOW MUCH FOAM DO I NEED" thread? I haven't gotten into those seats yet so I am not sure what's in them.

Just looking to get some addition insight on what exactly this piece of paper is telling me.

The overall thing to remember is that, if any boat gets filled with water (waves; leak; some nut swamping you by driving too close; etc.) that boat is going to sink.

UNLESS, it has something inside of the hull that will DISPLACE some of the water that has found its way inside of your boat. Foam does that displacing job.

When you remove foam, you are removing your life line. You can reposition that foam into a nearby space and all will be well again.

You can put a sealed empty live well in place of the foam. However, remember that if you fill the live well with water, it is no longer empty. If the live-well isn't totally sealed, then intrusive water will find its way into the "empty" space and you have more problems than you wanted.

I often read about people pulling foam out and not worrying about it. Doesn't make me sleep very well.

regards, richg99

A boat that's built like yours relies heavily on the seats and knees (the angled brackets) for keeping the boat from flexing when in rough water. as long as you replace that same degree of structure tying the sides together with your new decking you should be ok taking the seats out... just add floatation anywhere in the dead space you don't use under the decking and you'll be fine. Calculate the number of cubic inches of floatation you take out and be sure you put that much back in somewhere.

Air means your seats are probably just hollow aluminum not filled with foam. Doesn't matter.. just figure out how many cubic inches there is in the seat.. length x width x height.. and put that much foam under the decking.

The seats are completely sealed w/ nothing in them. I took the center one out and shook it all to hell and it didn't make a sound. My guess is, is it is a sealed cavity that's used for flotation, rather than one filled with foam.

With that being the case, my livewell project will be put on hold since I can't (don't want to) use the seat. What I did is I pushed the center "seat" back against the back seat to use for the back deck. I trimmed the top board that was used for the seat to sit flush against the aluminum seat box, slid it into place and attached it to the back seat so that it stays put.

I cut down the aluminum seat support to match the height of the support brace in the front part of the boat. I will attach angle to both sides of the support in order for the floor braces that are to come. The floor will run from the back seat box (the one I just moved) to the floor support brace in the front of the boat (pictured). In between the floor braces will be the foam panels, topped with 1/2" ply.

To revamp the flexing issue caused by removing the center seat/brackets, I was planning on adding side storage boxes that will be attached in the same fashion using those same brackets, so I should be in good shape there.

This way I am not removing any of the factory flotation, just rearranging it a little. I was planning on foaming the floor anyway since I have a ton of the pink board around here from a remodeling project in my basement. I was just going to use it to help deaden the sound of the boat, but since it helps in flotation - BONUS!

That all sounds good.

It may be a bit late to even bring this up...but....11 feet doesn't make for a very big boat. Have you temporarily put a piece of plywood on top of the seats and then tried walking around on it, while the boat was in the water?

Now, I am old and clumsy. I know I'd have a problem with "tippiness".

richg99

No, I haven't. I gave it a water test once I went through and resealed everything prior to getting to work on the modifications. I have a little 9' inflatable that I use for a couple small lakes around here that do not allow motors and I stand in that all the time.

On this particular build, the front deck will be my primary fishing deck. With the location of the floating seat where it is now up front I think I will keep that same location specifically for the reason you stated. The existing seat sits about 7"-8" below the bow of the boat so the new front deck will be the same. That way I am not fishing off the "top" of the boat.

The back deck is a different story, but that will not be used for fishing off of very often, if at all. I am making it primarily for storage - gas can, fire extinguisher, life jackets, bait boxes, etc. The back deck will only be a couple of inches below the top of the boat, so for stability reason it most like will not be used as a fishing deck - but never say never, haha.

I did get the floor in today. Need to do some sealing & tightening, but overall it's ready for foam & ply. That will most likely be my secondary fishing "deck" as it will have plenty of room to stand & move around without getting too tippy, even with the storage lockers I plan on installing along the walls.

My absolute BIGGEST fear in all of this is that I get this all made up, done exactly how I want it, and find out it's too heavy :shock:

re "too heavy"...I did that once. Built a full stern deck for a 16 ft. El Pescador.

The El Pescador was kind of underpowered (40 hp Suzuki 2-cycle) in the first place. That boat was also built too skinny since it sported a tunnel hull.

My heavy 2x6 and plywood decking overwhelmed the poor little thing. The only good thing was that I didn't fasten the deck down until after I sea-trialed it.

I was able to pull it off; set it next to my van, and go fishing. I dismembered it as soon as I got it back home.

There are probably very few dumb boating things that I haven't done, once or twice....

richg99

Well, if this little turd is rated for 4 persons, I am guessing it has a weight load of about 8oo lbs. The boat itself, naked, is 105 lbs. I added about 25lbs with the new transom. I haven't even thought about a motor yet, but lets say 150 lbs or so for motor and fuel. The aluminum I have added probably isn't munch more than about 10 lbs, but I still have some framing left to do and still need to add the ply (which is heavy enough as is). So lets say that, in total, I will be adding about 250 lbs to the boat with everything built, batteries, trolling motor, gear, etc. That leaves me around say 500 lbs. I'm 240 lbs, and my dog is about 90... so theoretically, I should have a 200 lb tolerance in there. This is a speculation at this point. I really have no idea.

Well, one thing that might help you is a number of five-gallon buckets of water. Water weighs around 8.34 lbs per gallon. So, a five-gallon bucket would come in at 41 lbs or so.

If you put X number of five-gallon buckets in the boat, full of water, and with lids fastened on tightly...you could try the boat out before going through a lot of work building things that might be too heavy.

I wish I had done that before doing my "improvement" on the El Pescador. I was younger and far more stupid then.

regards, richg99

I posted this info in another thread about weight limit concerns but the info seems relevant to Rich posted above.

I did a float test on the boat with the new deck, seats, etc. the other day and it was fine. I had a total weight load of 835-850 lbs (way more than I will ever haul) but I wanted to see what my limit was.

At that weight the boat was completely fine. The water never came up over the waterline ridge. It wasn't any more "tippy" than it was without all of the weight. I would never recommend adding 800+ lbs to a 12' tin, but at the end of the day mine handled it fine.

My final ride weight will be around 550 lbs (additions, motor, dog, myself, gear, etc) so everything will be within a safe operating weight limit.

Sounds good. Amazing what our little boats can handle.

richg99

richg99 said:

There are probably very few dumb boating things that I haven't done, once or twice...richg99

Click to expand...

...or that I'm in the middle of doing right now...



For that boat if you're using wood for the decking you're going to end up making it too heavy. If plywood weighs 20~25lbs per 1/4" of thickness per 4x8 sheet, your typical 5/8 decking material weighs ~1.75lbs per square foot...your boat is 11' long by ~3' wide average? the horizontal decking surfaces alone would weigh 58lbs, not to mention the weight of foam, hardware, vertical faces, bracing, livewell plumbing, wire etc. - it all starts to add up fast. You'll easily add 100lbs to the boat or more. Being a V-hull you're probably starting at 130 lbs +/- finished product will be well in excess of 200lbs.

You want a cubic foot of low density (2lbs per cu.ft. & less) foam for every 60lbs of weight you plan on putting in the boat including the weight of the boat, spread evenly around the boat so that the buoyancy is distributed to keep the boat relatively level in the event that you swamp. If you plan on attaching a motor then you'll want more foam in the rear of the boat to support the extra local weight there.

More weight = less free-board = dangerous combination in a small boat as any tipping and you're that much more likely to take on water making your foam placement that much more important.

Just saw your comment about the motive from not having room for the wife...that explains why you don't care if you still need to trailer a tin-boat to the water, so long as its NOT big enough for company to join it's good - renders most of my earlier comment irrelevant.