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Old 03-09-2008, 16:13   #1
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PVC Bimini Frame

I know PVC will die over time from the sun exposure and is "weak enough" that in any big wind I will want to drop the canvas but I am still thinking about it. The thing is the entire frame, corner units and all, would be less than 40 bucks. I can replace a lot of cracked tubes before I even begin to approach the cost of a "real" one.

Any thoughts? Anybody done it?

I am basically thinking a big reinforced box with a 45' peak like a house on top. It would run from just forward of the backstay to a bit forward of the stern end of my dodger...
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Old 03-09-2008, 16:48   #2
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PVC frame every 6 months, stainless frame maybe every 10 to 15 years if you take care of it. Now, how much does that cost on a yearly basis.
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Old 03-09-2008, 16:51   #3
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'maybe every 10 to 15 years if you take care of it.'


More like 20-25 years, IMO.

The PVC frame is a bad idea for a dodger or bimini. Fine for a winter cover with shrinkwrap, though :-)

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Old 03-09-2008, 16:53   #4
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Yep, Bill you are correct, I was just being conservative.
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Old 03-09-2008, 16:58   #5
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The thing is the entire frame, corner units and all, would be less than 40 bucks.
One storm and it's gone. It's fine if you live in a marina but not if you sail. The structural difference is unacceptable for anything but a marina based boat where losing it is not a big deal. At sea something like this loose and broken could be enough of a hazard to kill you or at least delay all your required reactions.

More like more than 25 years for stainless. It might have some surface rust but still better than PVC. Maybe 2 by 2 pine lumber with teak stain might be cheaper than PVC. Some clear plastic and you have a green house.
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Old 03-09-2008, 17:23   #6
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On a 30 footer, you might want to check around on marina boards, craigs list, and used boat equipment stores. A lot of Bimini frames are lying around and your boat should take a pretty standard one. I know the local store up here usually has 3-6 of them. I recently bought a Bimini (10' X 10') off of craigs list. Complete 1" stainless frame with the heavy SS fittings. It's a 4 hoop frame, with the sunbrella top in good shape AND a zip on cover for when it's folded. $150 Seek and you shall find.....
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Old 03-09-2008, 17:28   #7
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That is a spanky deal Chuck!

I saw a lot of 250ish ones that came off bayliners- but they didn't look like they would work well and were still pretty expensive.

And, for what it is worth, I never start cheap. I always dream big then whittle down until I find a sweet spot where form, function, and price meet.

I am mostly concerned with "at anchor" down south- not coverage while sailing so much. Do you think painting the outside would extend the life? I am assuming the shelf life we are discussing is UV related?
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Old 03-09-2008, 17:37   #8
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If you are talking about a cockpit cover while moored, have at it with the PVC. A cruising bimini might be better made out of stainless. Ours is 23 years old and going strong.

In most cases the mooring cover doesn't really need a frame however. You use the rig as the frame..
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Old 03-09-2008, 17:40   #9
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The other problem is attaching the Frame to your rails or...? One alternative is the bolt together aluminum railing. The fittings are cheap if you buy them in lots on e bay etc. But in the end.... find a used one!
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Old 03-09-2008, 18:00   #10
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Never really thought about doing that, but don't see why it couldn't be made to work. Low tech... but why not?

A little brain storming:

Might build what you want out of PVC and wrap it in a few layers of finishing cloth and resin. If you cut the strips so they butt together and put the gaps 180 and 90 degrees away from each other, it'd be easy to fair out and paint... and you'd have a hard time breaking it.

A really tough time breaking the straight sections, fiberglass tubes over forms really don't flex. I'd actually use polyester, because it shrinks enough to really grab hold of PVC pipe. (Does this sound like the voice of experience? Grin) Add a few extra wraps in the corners... Add some more where ever the pivots are. Use shoulder bolts, and add compression sleeves to keep the ends from failling. Actually... you could glue dowels inside. Or press a piece of clay or bit of cardboard in there and pack it full of thickened resin.

You'll want to use street elbows for the corners though... glass doesn't conform to 90's. Plus PVC breaks easiest at those corners. I'd use streets anyway just for that, could do the same clay and drill two little holes to fill up the corners full of thickened epoxy too.

Given its got some paint on it, PVC will last a long while in the sun. Rustoleum makes some paint for plastic that is actually half decent.

Good luck!

Zach
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Old 03-09-2008, 18:26   #11
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Doing anything like you are talking about woud be dangerous. First conside the wind in your cruising ground, which I assume is SF bay.

PVC is brittle. Imagine having your body, or you and a crew member, thrown against the frame. It instanly cracks in the form of a dagger. And you are still moving...

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Old 04-09-2008, 01:44   #12
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Zach- run with me for a bit and lets see if we get somewhere.

Witz- I hear your concern but I am not sure its correct. PVC isn't all that brittle. A long piece has a LOT of flex. If I can't imagine a scenario where it would snap into an impaling device that didn't also involve me going overboard. At that point we may be dealing with a gunshot or stabbing sort of scenario. Maybe you mean with the fiberglass wrap? In which case...

I don't think I would do any stiffening work. I think for the application I have in mind the structural properties of PVC would be okay- my main concern is degradation from the UV. I would love a bimini frame that I could hang and monkey around on. Failing that, my goal is shade. Heavy winds pulling on the cover could certainly represent a problem but I don't think light and medium winds would be too much trouble- just like sail I would reef early and often. And it would be cut-away-able.

What I am thinking is a three piece design. Blue is the PVC pipe itself.

The first piece is a cage where each of the verticle posts has two "T" fittings and a 3-way fitting. I would use the 3-way fittings to create a square shape with 4 legs. The two "T" fittings would brace the legs together to add lateral strength. This contraption would be held to the boat with some lines tied around the 3-ways and going down to the deck. Green are 3-way fittings, yellow is "T" fittings, purple is line.

The second and third would be two simple rectangle pieces that are the same length as the cage but each slightly more than 50% of the width. I would tie these together and then to the frame to create a peak. Red is a standard corner fitting.

The black lines show canvas draped over the whole thing then tied to something on the deck. If the wind did come up it could take the canvas and leave the PVC. If there is enough wind to snap PVC based on its own resistance I've got WAY bigger problems.
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Old 04-09-2008, 02:12   #13
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Make a permanent double hoop at the rear of permanent material, set about a foot and a half apart at the bottom (fore and aft) and tapering upwards to nine inches at the top and cross brace with smaller tube sections.
This is the rear frame. Rope each corner to fixings on the back of the cockpit, a post if you need the height. This is the front frame.
Stretch any material to hand, bed sheets to tarpaulins depending on weather.
Safe, sound, solar mountng on the rear hoop, or wind noise generator.
Springy intermediate hoops can be added as needed. Good Luck.
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Old 04-09-2008, 02:19   #14
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"Make a permanent double hoop at the rear of permanent material"

Lets start with "what is permanent material" and then I will ask what a double hoop is.

What do they make tent poles out of? Maybe I could get some of that?
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Old 04-09-2008, 04:21   #15
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The idea is to create a strong frame across the stern, hopefully clear of rigging and travellers, that will ake the rear of the bimini. If it's soundly mounted and a firm structure it can support all the other stuff like wind/solar power/aerials et al.
It also supports the rope forming the for and aft edges of the bimini roof and provides fixings for the back edge of the bimini, and side covers if required.
If it was designed into the boats structure it would carry the traveller as well, and the dinghy hoist etc etc.
If it's not it has to be compromised but does have benefits, can't damage bouncing crew, and if the bimini gets blown away it's easily replaceable.
It's something I sketch into my designs as clearing the cockpit of clutter and freeing the mast of multiple duties and providing dinghy hoist.
just an idea.
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