Floating "dock" platform - will this design work?

[firstmatedavy]

I live on a sailboat, and I'm trying to make some space for a container garden of vegetables in 5 gallon buckets. I want to add a triangular floating platform in the space between the bow and the dock, so that the plants won't be in anyone's way.

I looked at some floating dock designs that use barrels for flotation, and then drew up a version using additional 5 gallon buckets, with lids sealed on and some foam put inside so they won't sink even if they leak a little. Barrels would have been too large (and visible to the marina staff, who say we can't add anything "tacky"), and purpose-built floats would cost $190 for two in the smallest possible size, which seems like a lot.

I'll consider this a success if it can hold a bunch of plants without sinking, and doesn't fall apart in the weather. It doesn't need to support a person's weight; I'm planning to pick the buckets up with a boat hook when I need to reach them.

Does this basic design seem sound?

[ixtap]

I would surprised if this were to meet your marina's standards. I have seen people make a similar garden in a simple inflatable raft, which you can usually get for ~$25. I would also consider a more attractive container or paint the plant buckets to look plucky, rather than tacky.

As to your dock design, I would be concerned about the stability left to right in what you have shown. Might it make sense to orient the buckets the other direction so that they can be placed along the edge?

[cool7hand]

Fresh or saltwater? Is seasonal ice a factor?

[uniwelder]

I'm trying to get a sense of the dimensions.  From the size of 5 gallon bucket and your sketch, it looks like you have a triangle 8 feet long with 4 foot base.  Is that about right?

I'm confused about whether the buckets exist just for flotation (seems to be the case if they're sealed and you put foam inside) or if these hold plants somehow as well.  Just seems like if I were incorporating buckets into the design, I'd want them to hold plants and soil.

Could you buy a piece of 2" thick foam board, cut across the diagonal, and screw together?  It would degrade in the sun, so you'd need to paint or cover it with something, but would provide an excellent flat base.  It would take about 300 lbs to sink.

[Fishindude]

I've yet to see one of these homemade barrel docks that looks nice or holds up very well.   Most wind up with a leaking barrel or two, float on a list, then become an eyesore.
They make some very nice floating modular dock systems you could purchase.

It made sense to build a raft like this 30-40 years ago when you didn't have options.
With all of the good quality stuff available today, I think this would be a mistake.

[lthenderson]

My concern wouldn't have anything to do with the floating platform but what your liability would be is someone were to use it as a shortcut and fall through or tip it over and bang their head on the dock or boat as they flipped.

[firstmatedavy]

Fresh or saltwater? Is seasonal ice a factor?

Brackish water. Doesn't freeze.

[firstmatedavy]

I'm trying to get a sense of the dimensions.  From the size of 5 gallon bucket and your sketch, it looks like you have a triangle 8 feet long with 4 foot base.  Is that about right?

I'm confused about whether the buckets exist just for flotation (seems to be the case if they're sealed and you put foam inside) or if these hold plants somehow as well.  Just seems like if I were incorporating buckets into the design, I'd want them to hold plants and soil.

Could you buy a piece of 2" thick foam board, cut across the diagonal, and screw together?  It would degrade in the sun, so you'd need to paint or cover it with something, but would provide an excellent flat base.  It would take about 300 lbs to sink.

Correct, it'd be 4 x 8

The buckets in the picture are just for flotation. Once the platform is put together, I'd flip it over, float it in the water, and set down some additional buckets on top to put the plants in. I was going to buy plain white ones to help keep it looking nice.

Foam board is a good idea! I'm worried about whether it would hold up to being in the water, though. I'd rather not let a bunch of tiny styrofoam bits come off in the water. Maybe I could wrap it in a plastic sheet of some kind? I like that this sounds easier and cheaper than having to build a wood frame.

[firstmatedavy]

My concern wouldn't have anything to do with the floating platform but what your liability would be is someone were to use it as a shortcut and fall through or tip it over and bang their head on the dock or boat as they flipped.

This is a good point! I was aiming to have it float lower than the level of the dock so it doesn't look like part of it. I should probably add some kind of "fence" or edging so that it doesn't look like a shortcut when no plants are on it. I'd been thinking of doing that anyway to help prevent plants from falling off on windy days.

[firstmatedavy]

I would surprised if this were to meet your marina's standards. I have seen people make a similar garden in a simple inflatable raft, which you can usually get for ~$25. I would also consider a more attractive container or paint the plant buckets to look plucky, rather than tacky.

As to your dock design, I would be concerned about the stability left to right in what you have shown. Might it make sense to orient the buckets the other direction so that they can be placed along the edge?

For asthetics, I'd add some trim along the sides like a fence to cover the non-submerged part of the buckets and some of the visible part if the buckets. I'm hoping the buckets all being plain white would help with the look some, too. If they don't like it I'll figure something out.

I think I don't understand how turning the buckets would affect stability by much. Are you thinking to avoid a lever type effect if there's weight put on the edge and nothing to balance it out in the middle?

[firstmatedavy]

I've yet to see one of these homemade barrel docks that looks nice or holds up very well.   Most wind up with a leaking barrel or two, float on a list, then become an eyesore.
They make some very nice floating modular dock systems you could purchase.

It made sense to build a raft like this 30-40 years ago when you didn't have options.
With all of the good quality stuff available today, I think this would be a mistake.

I had a design using real dock floats designed to be dock floats, but the cost makes me hesitate. The smallest, cheapest floats are $85 each, and I'd still need to DIY something to hold up the pointy bit at the end.

[firstmatedavy]

Thank you everyone for your feedback! I appreciate your help with thinking through how this will work.

[mntnmn117]

Floatation: Soil/Dirt/Saturated dirt is very heavy.  I would calculate assuming saturated soils with a unit weight of 100lb/CF or something. You don't want it to sink the first rainstorm you get. Each 5 gal bucket only provides 42lb of buoyant forces. Including all the framing you would want at least two submerged buckets for every garden bucket. Not worth it on this scale but they actually make lightweight garden soil for rooftop gardens with pumice sand/high peat content. For this just get something with a high peat moss content.

Gardening: Not sure how much experience you have bucket gardening, but I would go with more area, less depth. Like I would plan to soil the entire top of your dock with 8" of soil evenly distributed. Reason's being the smaller the pot, the more trouble I have keeping the plant evenly watered. Most garden annuals don't grow that deep.

[lthenderson]

I was going to mention that after years of trying to raise things on a deck in buckets, I finally gave up. Like the previous person said, plants don't grow that deep and the top soil where they do grow roots dries out incredibly fast and if I don't water them everyday religiously, they tend to bake and dry out quickly. We went to a shallow but wider planter and had more luck as long as we stay back from the edges.

[sealab2021]

I have lived on a sailboat for 6 years in the past, a cold wind came one day and all the leaves on my plants died and it turned into a twig almost overnight. It depends on your climate if this would work. Your idea is not going to be good, between tide swings and it bouncing off your hull it’s not worth it. Also, every marina I have been to would not permit that design you have. I can’t even have a dinghy tied to my boat at the slip. Maybe turn to guerilla gardening or make a Chinampa offsite. Or, focus on things the marina can’t see, fish and crab traps also you can cultivate oysters.

[mntnmn117]

I was going to mention that after years of trying to raise things on a deck in buckets, I finally gave up. Like the previous person said, plants don't grow that deep and the top soil where they do grow roots dries out incredibly fast and if I don't water them everyday religiously, they tend to bake and dry out quickly. We went to a shallow but wider planter and had more luck as long as we stay back from the edges.

Too lazy to post a photo but for example we've planted tomatoes in the large barrel planters and also put some from the same starts directly in the ground (raise beds).  Raise beds plants grew easily twice as big during the season. All plants like consistency of moisture and temperature. 

I would hunt around for a community garden you can join or maybe there's some brackish water hydroponics.  Or a small planter of herbs & chives on the boat itself might be the fix you're looking for without the hassle.

[firstmatedavy]

Floatation: Soil/Dirt/Saturated dirt is very heavy.  I would calculate assuming saturated soils with a unit weight of 100lb/CF or something. You don't want it to sink the first rainstorm you get. Each 5 gal bucket only provides 42lb of buoyant forces. Including all the framing you would want at least two submerged buckets for every garden bucket. Not worth it on this scale but they actually make lightweight garden soil for rooftop gardens with pumice sand/high peat content. For this just get something with a high peat moss content.

Gardening: Not sure how much experience you have bucket gardening, but I would go with more area, less depth. Like I would plan to soil the entire top of your dock with 8" of soil evenly distributed. Reason's being the smaller the pot, the more trouble I have keeping the plant evenly watered. Most garden annuals don't grow that deep.

I've been looking into foam sheets more. I realized I could layer some together and then shrink wrap over them (the thick white wrap used for storing boats in winter) so it would look nice and not degrade in the elements too much.

One 2"x4'x8' foam sheet is about 5.4 cubic feet of area. Assuming water is 60lbs/cuft (it's a bit more but varies by temperature), 326lbs of water is displaced by submerging it.

Each bucket holds about 1cuft of soil, 100lbs when wet. (I looked it up, it's 80-110lbs so 100 seems reasonable for estimation.) So I'd need 1 sheet of foam for every 3 buckets. This assumes complete sheets are used, but if I cut them on a diagonal I can probably get two layers out of each sheet, so that's just fine. So for 9 buckets, 3 sheets of foam, and the raft would be 12 inches thick.

(Cost: $90 for 3 foam boards, $20 worth of shrink wrap, plus some kind of mat for the top. So $110-$130 or so. I'm expecting actual cost to be a little more because projects always blow up somehow.)

I'll see what other containers can be had cheaply. If I find a way to go wide and shallow, maybe just setting them on the dock will work, since they'd be less vulnerable to getting blown down in the wind then. We're both working from home for the foreseeable future, so frequent watering needs aren't too much of a problem.

[firstmatedavy]

I have lived on a sailboat for 6 years in the past, a cold wind came one day and all the leaves on my plants died and it turned into a twig almost overnight. It depends on your climate if this would work. Your idea is not going to be good, between tide swings and it bouncing off your hull it’s not worth it. Also, every marina I have been to would not permit that design you have. I can’t even have a dinghy tied to my boat at the slip. Maybe turn to guerilla gardening or make a Chinampa offsite. Or, focus on things the marina can’t see, fish and crab traps also you can cultivate oysters.

We've been here a year, got a good feel for the climate and space to bring plants inside occasionally when weather happens. The dock floats and the raft would be tied to the dock so it can't bump the hull.

There definitely is a risk of the marina saying no, but it'd be in a spot where it can't damage any boat but ours and won't look too obvious, so it seemed worth a shot.

[firstmatedavy]

https://norfolk.craigslist.org/for/d/mannboro-wooden-oak-barrels-food-grade/7269937345.html

As a possible alternative, I could get a couple of these barrels and cut off the top and bottom to make 4 planters that'd look a lot like the barrel planters the marina already uses for flowers. I think that's about the most I could fit on the dock without them getting annoyed, or making it hard for us to use the boat. A downside is that these are probably too heavy to bring inside if we get a cold snap. I wouldn't want to use them on the float because they'd be too big to lift.

Wide plastic planters would work similar if I can find ones that are a good shape and not inordinately expensive.

Edit: just discovered fabric planters, which come in wide flat sizes without being ridiculously expensive (2 foot radius for $20 https://www.amazon.com/gp/aw/d/B0055F5OOM/ref=ox_sc_saved_image_1?smid=A3TVGJT7NY2ZAO&psc=1 ). They also look lightweight and easy to move. One if the main reasons I was considering buckets, was that the planters I'd seen in stores were usually small, expensive or both.

[lthenderson]

Each bucket holds about 1cuft of soil, 100lbs when wet. (I looked it up, it's 80-110lbs so 100 seems reasonable for estimation.) So I'd need 1 sheet of foam for every 3 buckets. This assumes complete sheets are used, but if I cut them on a diagonal I can probably get two layers out of each sheet, so that's just fine. So for 9 buckets, 3 sheets of foam, and the raft would be 12 inches thick.

This would be to hold your buckets as water level. I'm assuming you want to hold your buckets somewhat above water level. It also doesn't count for any structure used to contain the foam sheets which have mass and add to the weight counteracting buoyancy.  It would also assume that you are referring to closed cell foam and not open cell foam which can absorb water and lose buoyancy.

[firstmatedavy]

Yes, definitely closed cell foam, probably from insulation boards. With a foam built the additional structure would be pretty lightweight, just shrink wrap and some kind of top layer like a rubber garage mat. I should probably use 4 foam boards and 10 buckets or something like that to have more margin of error. I'd actually prefer the platform not float very high - if it floats way lower than the real dock, that's a good visual indicator to people not to try to walk on it.

[Wintergreen78]

How will shrink-wrap or home center buckets hold up to UV? I’d be concerned with those getting brittle in just a year or two, then breaking down and getting bits of plastic everywhere. I thought most plastics made specifically for marine use were made to be more uv-resistant, which is part of the cost difference.

Every time I’ve seen people try to do boat stuff more cheaply by substituting materials, it seems to fall apart and look horrible.

[NaN]

https://www.liveaboardhq.com/how-grow-garden-liveaboard-boat

[firstmatedavy]

How will shrink-wrap or home center buckets hold up to UV? I’d be concerned with those getting brittle in just a year or two, then breaking down and getting bits of plastic everywhere. I thought most plastics made specifically for marine use were made to be more uv-resistant, which is part of the cost difference.

Every time I’ve seen people try to do boat stuff more cheaply by substituting materials, it seems to fall apart and look horrible.

The typical material for buckets is hdpe plastic, which is UV resistant. Shrink wrap is supposed to hold up to UV for a few years, so I was planning to replace it every few before it gets too degraded.

For now I found some attractive cloth planters that I can just put on the regular dock. I was mostly looking at the platform because I was having trouble finding affordable planters, and thought floating the buckets at a lower height than the dock would make them look less obvious. The cloth planters are affordable for the size (vs hard planters which seem to be really expensive for anything other than a disposable-looking plastic pot) which I hadn't expected to be able to find.