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Old 08-31-2012, 04:03 PM   #1
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Bimini Advice

I am in the process of extending the bimini on my flybridge. The photos show the existing cover, and a Photoshopped version of how I hope it'll look when the extension is complete. The black line indicates the projected position of the new bow I already have, and the white line will be straps to the aft rail. The approximate length of the extension is 56". My question is this: Do you think I need a short center bow in the extension, like the one in the original cover, or should the single bow be sufficient? Is there a rule of thumb regarding how far a cover like this can extend without center support?
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Old 08-31-2012, 04:39 PM   #2
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I would think it would depend on how much you're willing to let the fabric sag and how much rainwater you are willing to let puddle up there. And how much you are willing to have the canvas flap in the wind. If it was me I'd probably want the extra bow based on your illustration. But I don't think it would be needed for strength. Just to control sag and flapping.
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Old 08-31-2012, 05:38 PM   #3
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Art,

I had a separate bimini made for the aft section. 3 bows, and it seems to need the 3rd bow in the middle. In the Spring and Fall we usually have just the forward bimini up, but in the Summer it's scorching hot without the aft one providing shade.
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Old 08-31-2012, 06:29 PM   #4
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If it's not pretty tight, it will collect rain water. It will also flap in the wind and might damage itself. I would think support every two to three feet would be appropriate.
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Old 08-31-2012, 08:03 PM   #5
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Are you looking to have it up all the time or just rain/sun protection when at anchor/dock, etc?

I'm going to have an extension to mine for at anchor dock...zip it to the existing bimini, corners to halyards on the mast and a topping lift to a enter strap in the middle to shed water/wind.
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Old 08-31-2012, 10:59 PM   #6
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Here's how I did it.
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Old 09-01-2012, 07:17 AM   #7
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For folks going to the Bahamas , any thing that will collect rain water is a plus.
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Old 09-01-2012, 08:50 AM   #8
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For folks going to the Bahamas , any thing that will collect rain water is a plus.
That, mixed with the bird poop will be great!
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Old 09-01-2012, 08:53 AM   #9
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On my boat, the rear section zips to the front section but the reat has two bows. There is a bow every two to three feet from front to back when they are both deployed.

If you call in an experienced boat canvas person or shop, they will know what you need. They do this all the time and have to stand behind their work.
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Old 09-01-2012, 02:39 PM   #10
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Thanks for the inputs. I'm going to add the middle support bow. Ron, the reason I'm forgoing professional advice nad tackling this myself is to hopefully do itt on a budget. I already have about 10 yards of matching blue Sunbrella I picked up on eBay a couple of years ago, so the hardware, seam tape, etc will be my only expense.

I've tackled a few other canvas projects, so I am OK with the challenge. I've learned that if it doesn't look quite right the first time, you can always pull out a seam or two and redo it... or just get used to it!. One of the advantages of working on a nearly 40-year-old boat is that nothing's perfect, and so my home-made efforts blend in well anyway.
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Old 09-01-2012, 06:04 PM   #11
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Glad you're adding the extra bow for all the reasons stated above.

I'd give serious consideration to using aft support poles in lieu of the straps. The top will be much stronger and they will help resist flexing. They can be hard mounted to the top of your rail on a bracket with clevis pins to allow for easy removal. (see pic below marked "brace kit.")





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Old 09-01-2012, 07:11 PM   #12
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Sunbrella is much easier stuff to work than sailcloth - more like folding thin aluminium. The secret is to use the very sticky seam-tape specially made for acrylic cloths. Sunbrella is so hairy that the ordinary sail-cloth seam-tape doesn't stick very well. An electric or butane hot-knife is worth buying. It cuts cleanly and all your edges are sealed, even though you are going to hem them. Sailrite and Sailmaker's Supply are good sources of everything you'll need. Do you have a sewing machine that can handle 3 or 4 layers of Sunbrella?
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Old 09-25-2012, 07:04 PM   #13
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Well, it's pretty much done. A few details to work out on tying the corners of the two bimini pieces together, (maybe Velcro, or a couple of snaps?) but overall I am pleased with the result. That old Kenmore sewing machine managed to get thru the max of 3-4 layers of fabric I needed for this project with no problem. One thing I wasn't counting on was that the radius of the bows I added was different from the existing ones.. required a little fiddling to bring it all together.
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Old 09-25-2012, 07:21 PM   #14
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Nice job! Well done!

Shade is a good thing
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Old 09-25-2012, 08:43 PM   #15
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Sunbrella is much easier stuff to work than sailcloth - more like folding thin aluminium. The secret is to use the very sticky seam-tape specially made for acrylic cloths. Sunbrella is so hairy that the ordinary sail-cloth seam-tape doesn't stick very well. An electric or butane hot-knife is worth buying. It cuts cleanly and all your edges are sealed, even though you are going to hem them. Sailrite and Sailmaker's Supply are good sources of everything you'll need. Do you have a sewing machine that can handle 3 or 4 layers of Sunbrella?
My "cutting knife" is a little 30 watt soldering iron with a fat tip that holds heat but has a sort of knife edge as well. Set a straight-edge against it, and it'll cut a great non-fraying edge thru Sunbrella for a whole lot less$$ than buying a hot knife!. I have found that Walmart "denim needles" in my sewing machine will punch thru a whole lot more Sunbrella than you'd think. It'd be nice to have one of those walking foot machines.. keeps the stitches way straighter... but for my needs, my 40 yr old Sears machine works.

...and yes, I use that seam tape from Sailrite. . Never could have done the project without it.
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Old 09-25-2012, 08:43 PM   #16
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Looks really great, ARoss. I'm saving pics of this for when I am motivated to extend my FB bimini. If I do it, it'll be in retirement when I have the time and inclination to learn how to sew and build it. What a great skill set to have as a boat owner!!
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Old 09-25-2012, 08:48 PM   #17
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Just out of curiosity what type of thread did you use to sew it all together? The seams are generally the first thing to let go on a boat's canvas and once they go unless they are repaired immediately the canvas itself will start to come apart with the flapping. There is thread made specifically to prevent this sort of thing from happening.
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Old 09-25-2012, 08:59 PM   #18
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Marin, I used this stuff from Sailrite. Not only is it "sunproof" but it really slides thru my old machine.
Thread V-69 Derby Navy Polyester UV 4oz (1400 Yds) (1400 Yds)

Not a commercial, I hope, but anyone who isn't familiar with Sailrite should visit their site if you are thinking of doing canvas work. Loads of interesting instructional videos... and all the stuff you will need for any project.
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Old 09-25-2012, 09:10 PM   #19
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Marin, I used this stuff from Sailrite. Not only is it "sunproof" but it really slides thru my old machine.
Thread V-69 Derby Navy Polyester UV 4oz (1400 Yds) (1400 Yds)
On the advice of our canvas shop my wife uses Gore Tenara thread on the canvas on our boat. From what we've been told it's the best thread on the planet for outdoor use. But..... it is staggeringly expensive. The best price we found on-line for it several years ago was $125 for a spool. Tenara spool prices at that time were ranging from that on up to almost $400 for the same size spool. She first started using it some six or seven years ago I think and the seams she did then look like she did them yesterday. It's a little tricky to use, however as it requires a specific type of needle and the tension on the machine has to be set specifically for it.

Other than the canvas pieces she has made since we acquired the boat, the bulk of the boat's canvas came with the boat. Some of it was old when we bought the boat 14 years ago. I've been amazed at how this stuff has held up but it's only because my wife is diligent about replacing any deteriorating seams or weakening spots in the canvas. Considering we've gotten estimates as high as $10,000 to replace all the canvas currently on the boat her efforts are well worth it.
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Old 09-26-2012, 10:50 AM   #20
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Well, it's pretty much done. A few details to work out on tying the corners of the two bimini pieces together, (maybe Velcro, or a couple of snaps?).
A zipper will work the best. And if you have a flap over the zipper, it will keep water from leaking between the two pieces. The flap should be sewn to the front piece and lay over the back when they are zipped together.
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