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building a sailbox
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Author:  miralph [ Tue Apr 07, 2009 4:41 am ]
Post subject:  building a sailbox

Does anyone have plans/ideas for how to or not? I would like to build a sailbox on my trailer. I am thinking just plywood ,maybe triangular on the front.

Hobie 16
Hobie 18

Author:  srm [ Tue Apr 07, 2009 8:15 am ]
Post subject: 

In the long run, it's probably cheaper to bite the bullet and buy a plastic or fiberglass box that will never rot, but I usually have a tough time spending mucho cash on something that I can build reasonably well for significantly cheaper. So I built my boat box last winter out of plywood and ripped down 2x4s. All supplies were purchased at Home Depot. So far, it seems to be holding up nicely.

I made it rectangular on all sides to get the most efficiency out of the wood and maximize space - nothing fancy. Approximate dimensions are 10' long x 2' wide by 18" high. I have a hinged drop down door in the back and a hinged door on the side in the front. I specifically wanted to avoid a removable top or any top access as these always end up being leak points, and the less water you get inside, the better your chances of avoiding rotting.

The design is pretty simple, I ripped my 2x4s down to about 1-1/2" square and framed out the box using wood glue and bar clamps on the joints and then fastening with drywall screws. Since plywood comes in 8 foot lengths, there is one section of frame member that centers on the 8 foot distance to join the additional 2 foot sections. This also acts as framing for the front door.

After framing, I LIBERALLY coated all the framing with wood sealer. Then installed the plywood sides and bottom with wood glue, silicone caulk, and drywall screws. Plywood is only about 1/4" thick since the framing shares the load. Coated everything inside and out with wood sealer. Did the same with the top and installed that. Last the doors were built.

Also, it's important to look at the orientation of the edges. For example, I wanted to make sure that the top panel overlapped the edge of the vertical side (and not vice versa) so that water on the top would not seep into the joint. (There is a theme here, water is not good).

All in all, the box probably cost around $100 and about two afternoons of work in the shop. If it hold up for a few more years, I'll be happy. If the top or bottom skin eventually rots, I can probably replace with new plywood pretty easily.


Author:  miralph [ Tue Apr 07, 2009 8:54 am ]
Post subject:  thanks

Thank you for your detailed reply. It will be very helpful. I need to get this going before the sailing starts, then nothing gets done . Sail,Sail.Sail.

Author:  Harry Murphey [ Tue Apr 07, 2009 8:54 am ]
Post subject:  Sailbox

I built a box of almost the same demensions out of 1/4 Marine grade Plywood in June 1987 ..... still got it !!!!! Mine was designed w/ a one piece top that slides on and off, so I can get into it w/ the boat on the trailer. It's constructed w/ 3/4"x3/4" framing on the edges/corners and on the inside of the box lid in a grid pattern (I can actually walk on top of the box when rigging the boat). I used West Epoxy and coated the whole box inside and out ... then painted the box white ( keeps the box and contents cool) The box is mounted on my trailer in such a manor that my beach wheels can slide underneath and be secured to the trailer's front crossbar.

Author:  SailMore [ Tue Apr 07, 2009 10:46 am ]
Post subject: 

I was just going to post my piece that I've been assembling (mostly from previous writings) in between other tasks this morning and I see a couple of others have posted similar material. Seems we have much in common in our thoughts on this subject. I'd be interested to know about the wood sealer mentioned - brand and source…

Also, I'll comment that 'marine grade ply' (made from tropical hardwoods - that will not 'check') is now approaching $100 per sheet in the thin stuff and easily over that in many thicker dimensions, depending on variety. And while that marine ply (hardwood, not fir) will do OK with epoxy-only coating (then properly painted to prevent UV degradation of the epoxy) there is no use coating cheap pine ply, or even marine grade fir ply, with epoxy, without glass, as it will 'check' (open small cracks) and then you may as well have used cheap paint.

Glassing it quadruples the labor on the exterior, at least (and you must logically then finish the interior also) and by that time you have invested into a boatbuilding-quality system and it makes sense to use only expensive boat-grade primer and paint. The conclusion is that doing more than the standard prime/fill/caulk/paint on construction-grade materials, logically becomes an all-or-nothing proposition (one exception being the traditional 'paint & canvas deck' finish, described below).

And so I'll add my piece:

I've built, over the decades:

- An open trailer, 16' x 6', flatbed with 2' removable front & side boards with removable gate on the rear.

- Two larger (16') closed cargo box trailers with double doors on front and rear.

- A smaller cargo box trailer (8.5').

- And an 11'L x 6'W x 3.5'H windsurfing gear & 'sleeper' trailer with racks on top, welded from square steel tubing, that carry four boards, booms & masts on one side, and two mountain bikes on the other side. The interior has a permanent sail and gear storage on one side with full-length shelves holding maybe ten sails, multiple gear bags and boxes, and so on, accessible on the side through an 7' x 2.25' door that opens down and hangs on chains like a tail-gate for use as bench, gear table or spare bunk (with snap-on screened awning cover). There is also a completely separate enclosed section on the other side, with double doors on the front, side and back, that can be used as a tight double 'sleeper' section or, with the bed rolled up out of the way, steel racks that fold out from the wall and allow secure interior storage of the boards, booms and masts from the roof racks.

Some observations:

- You mention 'Triangular in the front'. If I understand the meaning correctly, that may not yield much, if any advantage for the work it would take, and having an opening rectangular door at each end may add a lot of advantage.

- Many people seem to tend to overbuild. For a garden shed it doesn’t matter if it weighs 4 times what it needs to, but for a mobile unit that is a problem. I've seen home-made windsurfing trailer boxes made from 2x4s and 3/4" ply that must have weighed a ton, almost literally, and certainly they weighed many times more than the gear they carried.

- Unless you get into welded metal framing, or boat building techniques like glass or epoxy/wood/glass composite, you will likely be making a painted box with a wood skin on a wood frame.

- The key to light construction is using less (thinner) materials and a 'smart' design.

- Light, strong and cheap construction is easy - its preventing rot without going to expensive and labor-intensive methods and materials that presents the problem.

- To demonstrate how I learned the hard way - my first trailer box (16'L x 6'W x 7'H) was built in 1985, and it was a good design, structurally and weight-wise, but I failed to use rot-proof materials: 2x4 floor and rim joists, 5/8" ply flooring, 2x2 (1.5" x 1.5") studs, 2x2 top and bottom wall plates, roof beams sawn from 1x8 pine (gave rounded box roof top), 1/4" pine plywood for siding and roof, with hot tar/membrane roofing. It was fastened with regular deck screws and none of the wood was treated. I got a lot of daily use out of it and earned a big stack of cash hauling my tools and materials around in it while it lasted, but in a few years it was structurally rotted to the point that I was afraid to take it on the road anymore, and many of the screws were structurally rusted as well. It was then taken off the trailer, put on blocks and used, after patching it up, as a storage shed for another ten years.

My lesson from that was to never use framing, flooring or structural fasteners that can rot or rust. Treated wood framing and treated ply floor, fastened with SS deck screws was the rule for all subsequent designs. Light-weight 1/4" pine plywood used for siding and roof decking is easily and sensibly the exception to the rot-free rule, and it is cheaply patched and eventually easily replaced as needed over the years - there is no real obvious rot-proof alternative available that is all at once as strong, light and cheap. This thinking went into designing and building the next trailer box, which after eventually getting an epoxy/glass exterior with some fairly spendy paint, lives today in good and mostly maintainance-free health and is used semi-regularly. The original painted ply siding and roof lasted about seven years before I finally replaced it and finished it like a boat.

- So, for a small box, use minimal treated wood floor framing, maybe 2x2 (1.5 x 1.5), with a 1/2" treated ply floor screwed to longitudinal floor framing at close intervals for stiffness, and maybe 1.25 x 1.25 treated wall framing and top plates, with slightly curved roof beams sawn from 1x4 or 1x6 treated wood, all fastened with SS deck screws, then skinned with 1/4 ply.

I glue the side and roof ply onto the framing with foaming urethane glue ("Gorilla glue" or similar), position the ply and hold it in place with deck screws (remove later) then fasten every few inches with air-driven narrow-crown staples. Allow the ply roof to overhang the sides, front and back by maybe an inch for best siding life (round the corners and edges prior to finishing).

Sand smooth, then paint (only the exterior) with a coat of Kilz Premium primer (water-based), working it into all the holes and cracks. After the primer is well-dried, fill staple and screw holes with 'water putty' or similar and caulk all long cracks (exterior only) with at least one layer of Alex Plus 35-year siliconized acrylic caulk.

Apply two more coats of Kilz - no other paint is needed as Kilz is very weatherproof even though it’s a primer - I once painted an old fiberglass fishing boat with Kilz and was amazed at how many years it lasted out in the full sun.) As with any common house-type paint over regular wood not protected by large overhangs, recoat once every year or two to prevent UV degradation and water ingress into micro cracks in the wood.

If you want a better roof (you do!) but don’t want to get into hot tar and membrane, or epoxy and fiberglass, an old 'painted canvas deck' style of roofing can be used with good success on plywood: After surface is smooth and initial primer is dry, roll down a medium-heavy coat of Kilz primer (water based). Its fast drying, so plan ahead and work fast (roll most of it, just use the brush for detailing). Then lay a pre-cut and pre-fitted piece of an old bed sheet on the wet paint, smooth it wrinkle-free with a squeegee if needed (drop squeegee, and any other paint gear that is in danger of drying for that matter, immediately in a bucket of water for later easy cleanup and reuse, and keep a wet rag handy in the bucket to immediately clean your hands and any drips as they occur - much easier than letting them dry even a little). Then, before any of this dries, roll and brush on another medium coat of Kilz Premium primer over and into the cloth so there are no dry or thin areas. After it dries, put on a couple more regular coats for good measure.

Many years of keeping windsurfing gear in a wood trailer box has taught the following:

- Put in plenty of vents (from Home Depot). Front and side vents should be closable for rain travel. Cheap aluminum louvered vents with screens can be installed on 'raised' wood flanges (1" x 1" stock) with a slight 'groove' around the edge, and then to close the vent a piece of plastic tarp or other fabric can be fitted over and secured with a round turn and square knot in 1/8" line (the cheap way), or a nice cover with a drawstring and cord stopper can be sewn from light, waterproof fabric. One could even make hinged hatch-type covers from wood, sealed with weather striping and secured with latches - essentially boat hatches - but I was never that ambitious…

- Don’t paint or caulk the interior wood - let the wood of the box continuously dry from within instead of trapping moisture within the wood and causing rot.

- Keep your sails and gear off the floor and walls of the box with some sort of wood or plastic grating or other spacing material to allow air circulation all around and prevent slime, mold and mildew from growing on your box wood and your gear - this is true even in a 'fancy' non-wood box… I've had good success making 'cheap and easy' (like a girlfriend I once had) 'grid lattice grating' from 1/2" square treated wood stock spaced 2", then other pieces placed on top of that at 90 degrees, again spaced 2", with a staple at each junction. This '2x2' grating is an inch thick and will let air flow in all directions between gear and interior box surfaces, protecting your gear, and also the bare wood surfaces of the box interior, if that applies. Orient the top layer of the lattice long-ways for easy sliding of gear in and out of a long box that accesses from the ends.

- To keep mildew and slime under control, kill the foundational 'early stages' by spraying box interior and exterior every few months with a pump-up garden sprayer with commercial deckwash (bleach based) diluted 50/50 with water (Armorall brand from WalMart, Behr #63 from Home Depot, or just 50/50% bleach/water solution with maybe a 1/4 ounce squirt of dish soap) Let it soak in for 15 minutes, rinse well with a garden hose, then dry with a fan blowing air through the empty box for as many hours as it takes.

- When not in use, keep the painted surfaces (and your whole boat, for that matter), under a shelter or tarp (not a tarp directly on the paint). This will limit weathering to the times you are actually using it and so will extend the life and minimize maintenance many times over.

Author:  srm [ Tue Apr 07, 2009 11:13 am ]
Post subject: 

SailMore, you put a lot out there. I was only able to skim it at this time. But I tend to agree on many of your points. I've seen beautiful boxs that are built of marine grade ply and fiberglassed/epoxied. Unfortunately the cost of such a project can easily approach or exceed a commercially available plastic product which will never rot or degrade (although home build does give you the advantage of being able to build exactly what you want). My goal was to relatively quickly build an inexpensive box with the understanding that I may only get a few years out of it and basically see how long it will last. So at this time, I'm satisified because as I said, the all up cost was around $100 and the box still seems good.

I belive I used Baer deck sealant (it is much thicker than basic Thompsons water seal). And I applied several coats. Also, the construction has proven to be virtually watertight (at least it was last year, I haven't checked on it all winter but it's under a tarp).

As to the overbuilding, I agree with you there as well. It is very easy but also quite unnecessary to go overboard, especially with today's gas prices every pound counts. I never weighed my box, but I would guess it is somewhere around 80 to 100lbs. Not light, but not real heavy either.


Author:  John Lunn [ Tue Apr 07, 2009 2:41 pm ]
Post subject:  Trailer Box

My H18 trailer came with a tube. Actually, it is a green sewer pipe, with hinged plywood ends/doors. Works great, and Harry M and others can share with us all their experiences with product like this. I've seen them at road building projects, so ask a site Foreman if they have any 'extra', do a 'deal'. I can tell you that it's weather proof, tough as nails etc. you may want to drill breathing holes in it. Email me off line, I'll send you pictures....lunnjohn at magma dot ca

Opening day is scheduled for April 18, but there is still ice on the river!


Author:  Karl Brogger [ Tue Apr 07, 2009 6:05 pm ]
Post subject: 

I have been really impressed with a couple of home-made sail box's. I'm just far too lazy to make one.

I bought a piece of 12" sch40 pvc pipe for the sails, boom, tiller x-bar and hot-stick. Came in a 12' stick, I used 10' of it. I cut two slots in the back. One goes half way down the width of the pipe allowing a piece of 1/4" plexi glass to slide in. The other notch is in the bottom of the pipe and allows a tab on the plexi glass to go through. Drill a hole in the tab, tie a short piece of line with a couple of stopper knots and it doesn't come out. PVC pipe is cheap, the caps and clean outs are rediculously expensive.

For the rest of the crap, rudders, boards, gear, tools etc. I just bought a aluminum tool box made for the back of a pickup. I got stupid lucky and a friend sold me one he no longer needed for $60. Its the style that sits on the floor of the pickup bed and goes flush with the rails of the box, not the type that sits on top of the bed rails.

The other option is Trey Brown has had some aluminum boxs built that are supposed to be really nice. I have no clue how to get ahold of him.

Author:  Harry Murphey [ Wed Apr 08, 2009 2:46 pm ]
Post subject:  Alum Trailer Box

Trey Brown posts on CatSailor all the time ... I believe he is "NCUTrey"

I believe "Jake", "Team Cat Fever"/Todd, or "Undecided"/Thad can also put you in touch w/ Trey.

Author:  ncmbm [ Fri May 15, 2009 1:06 pm ]
Post subject:  Re: building a sailbox

You have to catch Trey when he is having several of them made. His boxes are real nice and reasonable. I bought his galvanized box when he switched to aluminum. He fielded 5 teams for this years Tybee and was having boxes made last year for all of them. He is NCSUTREY on Catsailor. You can also contact him thru www.velocitysailing.com.

Author:  h16bill [ Tue Jun 30, 2009 12:59 pm ]
Post subject:  Re: building a sailbox

Are those aluminum boxes the ones I saw in Tampa many years ago made out of aluminum diamond plate? I would like one of those.


Author:  RobBartz [ Fri Jul 03, 2009 9:59 pm ]
Post subject:  Re: building a sailbox

Inexpensive, Weather Resistant, Lightweight Sailbox:

Similar to one of the other replyies on this topic, I used a 12" X 10' plastic corrogated culvert pipe as sailbox. You can probably buy this at Menards, Home Depot, Lowes, or whatever home improvement superstore is near you. When rolled up, the sails slide in together very easy.

The corrogated pipe will trap water in the low ripples. Simply drill holes in each of the ribs so the water drains out. Because the sail only contacts about 50% of the bottom surface, this sailbox completely eliminates puddling water below the sails and lets the air blow through.

For covers, I used a large plastic pot from trees I planted and drilled a hole through both sides of each and stuck a 18" 1/4 steel dowel with hairpin cotter pins through.

I used common steel straps with holes to strap it down to the trailer at every junction it crossed steel.

The only thing I don't like is the pipe sags a little between where it is supported. However this also serves to secure the sail so it doesn't slide back and forth while trailering.

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