Pontoon small building

[catfishhoward]

I have a 1990 Bass Buggy DL, I want to get rid of the hard top and all the seats and seal the floor and build a small bldg with bunk beds and was worried about the correct location to put it so it rides the best and if the boat would even hold the weight with the 21" toons. I figure it would be built with 2" x 3" studs, 3/8" shed wood siding and a flat rubber roof and would be be 8' x 8' which with the bunk beds the bldg would be about 750lb's. With the bldg, 3 people, batteries, gas, flooring, handrails, 60 hp Johnson and everything else around 2300lb. I think the 20.5' x 21" toons are rated to hold 2700lb's +/- half immersed? I've attached some sketches of what I've come up with and would like your info If this could be done structurally safe or if you see a better way of doing it. I plan on using for weekend trips camping and fishing on calm lakes in Georgia, no tubing, just 2 mile trips from the boat launch to drop anchor.

I ran the numbers using 1.5" aluminum square tube for the main structure and it was only about 100lbs lighter since I would have to L bracket and bolt everything together and it would cost about $700 more than the 2" x 3" wood, so I'm not thinking aluminum.

The hard top coming off is about 60lbs, railing coming off is about 20lbs and I'm not sure what the seats all weight but at least 300lbs so I'll have at least 350lbs coming off, so from the picture water line I've attached I would only be adding about 400lbs and also I will be shifting the building towards the front 2.5' to give me a fishing platform in back and try to level out the weight. I figure I can move the batteries to the front as well.

 

[Scott Danforth]

I would use aluminum myself. when the wood gets wet, it will weigh twice as much.

weight will be your enemy here.

Have you thought of simply building it out of rigid foam covered in a layer of fiberglass?

 

[catfishhoward]

I planned on using Rust-Oleum Restore from Home depot to go over the outside siding so the wood should not hold water and it should last a while also and it will be dry inside as I planned on having air vents as well. I thought about rapping the outside in aluminum just like a cargo trailer but am having a hard time finding 49" wide flat panels in white. After I cut out for the 2 doors and 8 windows the 3/8" siding with the Rust-Oleum should only weight around 150lb which is not that much weight vs the cost of the aluminum rap but I will try to get some pricing.

 

[catfishhoward]

The foam and fiberglass is out of my wheelhouse and I don't have a welder either. Thanks

 

[catfishhoward]

Anyone know how to seal the flat roof that will last the longest, figure just a rubber liner?

 

[Woodonglass]

2x2's would be adequate for framing the walls. Ext. grade 3/8" plywood sealed with this...

Seal the framing wood too!!!

After you soak the plywood let it dry for 2-3 days then apply 2-3 coats of Rustoleum Pro Paint. The "Restore" product is NOT good. Used it and it's a PITA and WILL peel off. The Sealer/Paint combo will last a Long Time!!! I'd HIGHLY recommend a minimum of a 5 degree pitch on the roof. Easy to accomplish by using 2x4 ceiling joists and beveling them to the middle. Any roofing material will work.

 

[DeepBlue2010]

What is the height of the structure, it it 8 feet?

I am certain 2 x 2 will not be nearly enough to support this structure with the expected wind load and constant rolling and pitching over the water. These are structural issues that need to be very carefully considered. If you are going for wood, it should be pressure treated framing lumber to avoid worrying about rot and moisture.

There are some aerodynamics issues you need to think about and take into consideration as well specially the sheer force of the wind. This 8 foot high structure will act like a sail, don't underestimate the power of wind.

Bunk beds makes me a little nervous because of the height. The torque load generated on the base by a person sleeping in the upper bunk will be the weight multiplied by the height of the bunk. A 200 Ib person sleeping 5 foot high is generating 1000 Foot/Ib of torque on the base when the boat roll on the bed side; this could be significant. With a little creativity, the beds could be designed in such a way that the height of one of them is adjustable so that it can be stored and secured on top of the of the other and detached and put next to it at night.

Also, your design must provide a way to equalize the pressure inside and outside the cabin. I am not sure if you chose the flat roof based on any calculations of the wind load or it was just an arbitrary selection. Just trying to think out loud with you here.

 

[catfishhoward]

Thanks for the replies, I plan on driving this on the road some so I planned a flat roof to clear wires and I was going to using 2"x4" for the front wall and all the walls will be bolted through the wood flooring and aluminum frame and I'll use 2"x3" for the other 3 walls and roof and I will have 2 columns to help support the roof when I make the bunk bed frame, I'm also worried about being top heavy with a 200lb man up on the top bunk and 200lb on the bottom, I was going to put all 3 batteries and coolers on the right side to help offset the wieght (200lb's), I might be able to design it with a pull out sofa on the other side instead. I'm thinking about using a 1 part apoxy paint on the inside to protect the wood and Deck Restore or Safe-T-Deck elastic paint on the siding, I think pressure treated would add a lot of weight and I'm not sure it the treatment of the wood should be used in close sleeping area. I figure I would also treat the wood under the bldg on both sides to keep the floor sealed. I think I more worried if the 21" toons will keep me a float?

 

[gm280]

Thanks for the replies, I plan on driving this on the road some so I planned a flat roof to clear wires and I was going to using 2"x4" for the front wall and all the walls will be bolted through the wood flooring and aluminum frame and I'll use 2"x3" for the other 3 walls and roof and I will have 2 columns to help support the roof when I make the bunk bed frame, I'm also worried about being top heavy with a 200lb man up on the top bunk and 200lb on the bottom, I was going to put all 3 batteries and coolers on the right side to help offset the wieght (200lb's), I might be able to design it with a pull out sofa on the other side instead. I'm thinking about using a 1 part apoxy paint on the inside to protect the wood and Deck Restore or Safe-T-Deck elastic paint on the siding, I think pressure treated would add a lot of weight and I'm not sure it the treatment of the wood should be used in close sleeping area. I figure I would also treat the wood under the bldg on both sides to keep the floor sealed. I think I more worried if the 21" toons will keep me a float?

catfishhoward, before going and buying everything, make a diagram of your construction methods and layout. Yes a construction diagram. Then weigh out one 2 x 4 to see what the weigh will be. The do the same with the 2 x 3. Then figure out what the total weigh is going to be before sawing the first piece of lumber. I say all that to say this. That sounds like a great project, but for a backyard tree house or utility shed. I think the weigh is going to make your boat iffy and loaded. There are other products you can select to limit the the total weigh. I would research those options before proceeding. However, this is your project and boat and you can do whatever you think is proper and right. I just offered some mental suggestion to consider. JMHO

 

[mickyryan]

this would be a pretty simple job if you used aluminum , foam cored solid aliuminum roof system from screen porches, you would easily keep the weight down while having a strong project and materials would last forever on the water here are a couple I found for ideas too
http://ocala.craigslist.org/boa/5752443294.html
http://staugustine.craigslist.org/boa/5768881106.html
http://treasure.craigslist.org/boa/5773797232.html
http://cfl.craigslist.org/boa/5747458980.html

 

[catfishhoward]

The project with wood will weight around 750lbs, I figured the weight using 1.5" aluminum square tube and since I cant weld I would have to use a lot of aluminum L brackets and a lot of stainless steel bolts and nuts so the weight difference would only be around 150lbs, didn't figure it was worth spending another $1000 to save 150lb's. I'm not familiar with foam filled roofing, I'll look into it and see if they sale it in my area, I'm just not finding a lot of aluminum paneling options in Atlanta or companies making it easy to buy this kind of stuff, wish there was a kit. After cutting out for the windows and 2 doors I will only have 160'lbs of 3/8" siding and paint so I can't see using aluminum for the price their asking. roof with 1/2" plywood and wood joist would be around 150lb,

 

[catfishhoward]

As far as the toons 21" diameter and 20.5' long I believe they will hold 2700lb's +/- half immersed? So is that the safe weight the toons will hold (flooring, rail, seats, motor, cables and everything else?

 

[DeepBlue2010]

The project with wood will weight around 750lbs, I figured the weight using 1.5" aluminum square tube and since I cant weld I would have to use a lot of aluminum L brackets and a lot of stainless steel bolts and nuts so the weight difference would only be around 150lbs, didn't figure it was worth spending another $1000 to save 150lb's. I'm not familiar with foam filled roofing, I'll look into it and see if they sale it in my area, I'm just not finding a lot of aluminum paneling options in Atlanta or companies making it easy to buy this kind of stuff, wish there was a kit. After cutting out for the windows and 2 doors I will only have 160'lbs of 3/8" siding and paint so I can't see using aluminum for the price their asking. roof with 1/2" plywood and wood joist would be around 150lb,

The difference of 150 Ib will pay you back in spades in terms of fuel saving and reduced maintenance nightmares. Non-encapsulated wood will absorb moisture no matter what you do. Even with the formula posted above, it will slow down things a little but it will not stop them. You will have to renew your protection coat regularly and frequently (that is why wood ships need to be crewed by a large crew) or rot will start to eat it away. With wood being inside the walls, this makes this process unpractical to say the least.

If you go the aluminum route, don't use stainless steel fasteners without physically isolating the two metals from touching one another or corrosion will each the less noble metal (aluminum in this case) away

 

[sphelps]

How about metal studs and track for the structure ? You care about looks ? Corrugated galv panels for the walls and roof .. A little trim around the edges ... Maybe some ridged foam in between the studs ... You could also use the FRP Panels on the inside or outside ... That would wipe down easily . Would have to be lighter than wood ... Studs come in 2.5" or 1.5"
Just a thought ....

 

[Government cheese]

As far as aluminum panels, have you looked at the way semi trailers are built? Steel studs riveted to aluminum rails... There is a thin mylar strip similar to packing tape that is used to insulate the two metals from each other. Three posts per panel, or maybe better said two posts per panel, with one post shared by the next panel. Use buck rivets (two person job) and it would be extremely strong. If you stick with trailer style construction you could go with a flat roof. IMHO I would use the translucent fiberglass so you wouldn't need extra lights. Then make it simple and use camper doors and windows.

Speaking of campers, What about a small popup placed sideways?

 

[mickyryan]

should look at those rv plans they might give you some ideas rv are always worried about weight so they use construction methods that would work in a lot of cases on your boat.

 

[catfishhoward]

Thanks for the reply sphelps, I'm not worried at all about looks but it need to be safe while towing down the road and last a long time. I'm trying to stay away from galvanized steel due to rusting in the future I hate rust, it's easier putting a fresh coat of paint on wood when needed and I'm kind of scared of using the stuff from Home Depot they don't look like their stiff enough for wall support and driving down the road at 60mph (not sure though), heavier gauge needed would probably be the same weight as a 2x3 wood and more expensive?. I just bought some Kiln Dried Whitewood from Home depot and a 2x3 is .98lb per foot, 2x2 is .42lbs per foot, so using the 2x3 for the bunk and bldg would be around 750lb's, I will try to use the 2x2 wood if I can around the window to save a little weight.

Anyone know where I can buy FRP Panels 4'x8? I think I would need at least 1/4" thick for the siding so it doesn't blow apart on the road. A 4'x8' wood siding sheet of 3/8" thick I figured weights around 35lbs? I would have around 150 lbs of wood siding, if the FRP panels would save me 100lbs I would consider using it.

Thanks again, sphelps.

 

[catfishhoward]

As far as aluminum panels, have you looked at the way semi trailers are built? Steel studs riveted to aluminum rails... There is a thin mylar strip similar to packing tape that is used to insulate the two metals from each other. Three posts per panel, or maybe better said two posts per panel, with one post shared by the next panel. Use buck rivets (two person job) and it would be extremely strong. If you stick with trailer style construction you could go with a flat roof. IMHO I would use the translucent fiberglass so you wouldn't need extra lights. Then make it simple and use camper doors and windows.

Speaking of campers, What about a small popup placed sideways?

I have thought about a 8' wide popup but not sure of the weight after pull off the suspension, I would have to move my steeling wheel to the front about 10' so I could center the camper in the middle so it doesn't get to heavy in the back and I would have to add a back door? But I will look into it just dont think it will be lighter than 750lbs, I've found some nice ones around $2000.