re-waterproofing bimini

[capnjack.morton]

Picked up a 'new' used boat. The bimini's and a cockpit tent for it have been sitting in a garage for a long time. They are in very good physical condition, but when I had them up in the rain on a recent trip, I discovered rain came through them - not in torrents, but at an unacceptable level - drops at the seams, and occasional spatter elsewhere. Not sure what the fabric is, but feels like a light canvas. What have forum members found to be most effective product for restoring watertight performance? And where do you get it most economically?
In advance, thanks for your thoughts and experience.
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[sailorchic34]

Thompsons water seal works rather well.

[Ironman162]

Dont laugh! I used uv resistant concrete sealer on mine. Goes on white and dries clear.
6 months and still going strong!

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[JPA Cate]

In the States, Thompson's Water Seal would be my product for an unknown type of canvas. You can get it at discount hardware stores in gallon cans.

Depending on how looks conscious you are, I have seen people use latex house paint to paint old Sunbrella dodgers, but never an awning.

The concrete sealant sounds like a good idea, too, but I have no experience with it.

Ann

[Sea Dreaming]

If the water is coming in at the seams you might try using tent seam sealer. It come in a tube or as a tape. It's more effective at covering the gaps in stitching. Use Thompsons or silicone boot water proofer on b the body.

[capnjack.morton]

Thanks to all who have shared their experience. More ideas to consider.

[groundtackle]

I was at Home Depot today they have several choices for clear Thompson's water seal .
Any specific one...they have one that says wood, one that says multi surface including wood and concrete and one that says "super" or some such word and another that is low VOC.
too many choices!
Any particular one better thank another?
Nick


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[UNCIVILIZED]

Funny about the Thompson's, I'd heard that it's good for waterproofing maps & charts.

When it comes to seams, there are plenty of good waxes that'll do the trick. Albeit a fair number of them need to be either thinned out, or melted down prior to drizzling them into the seams & threads. In order to get them to wick & penetrate well.
Bees wax is a good one, & in a pinch, candle wax will keep things leak free for a while.

There's also the old school option of doing something akin to how sailors used to waterproof their Oil Skins. Via painting the seams, & or cloth, with a mixture of thinned out wax/oil.

About once a year, I do this to my around town/back country rain hat. Coating the cloth, & especially it's seams with whatever boot waterproofing agent that I have on hand.
And yeah, sometimes it takes the hat sitting for a day or three post treatment for it not to be oily & slippery to the touch. That, or a good going over with a hair dryer, in order to get some of the oils to either penetrate or evaporate. Leaving it with a nice, waxy, waterproof finish.
Much like the Filson oil cloth clothing.

As to fabric waterproofing, a friend who's a Material's Scientist came up with this one. Albeit I've yet to try it. But the theory is sound enough. Though I'd first make a small batch & try it on something unimportant first.
Anyway, here's the "recipe":

"If I want something really water proof, I mix clear RTV silicone with naptha to thin it to watery pancake syrup consistency, and then brush it on, and let it cure.
Once completed, you will have a flexible fabric/silicone composite structure.
It is cheap and easy. It works really well.

Here's how:
I buy the least expensive clear RTV silicone in caulking tubes at t the hardware store. Mix it with naptha in a polyethylene paint bucket using a battery powered (De Walt) drill motor or air powered drill with a paint mixer head attached. (you can also use deodorized mineral spirits but it takes longer to dry the solvent out)
Be sure to use enough naptha to thin it well enough to brush in easily.

Do not mix more than one caulking tube full at a time unless you are going to be working very fast, as you do not have a long pot life once the RTV hits the air. Applying it in cold weather (<50F) will prolong pot life for application, but you will need to move the treated part to a warmer area to effect the cure.

Apply with any clean nylon paint brush. Work it into the fabric a bit with the brush.
Works on sueded leathers too, but expect them to darken. Second coats are only necessary if you want excellent flame resistance.

Another tech note: Allowing surfaces to touch each other while curing means they will bond together, in case anyone had not already figured that out!
When doing a garment, I like to stuff the garment with newspaper or something that will help it maintain its form of use while the material cures. It also makes handling the garment while applying the silicone a little easier.

Do this process only in a well ventilated area. Use all appropriate solvent and RTV handling precautions.
Allow 48 hours at 70F for full cure and de-gas of all solvents."

[Ironman162]

Whaton earth is RTV Napta and deoderised spirits.. I feel asif im im time warp

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[capnjack.morton]

Uncivilized - very interesting process and product. It sounds like it will be heavier, and not soft and flexible as before at the end. Kind of like a newly waxed outback duster. Yes?

[tomtriad]

West Marine 303 worked great on my dodger which was made of sunbrella.

[Sailmonkey]

Originally Posted by tomtriad

West Marine 303 worked great on my dodger which was made of sunbrella.

It's 3M 303 fabric guard......not west marine....(they drive me nuts putting their name on stuff).


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[Cheechako]

The fabric guard works well. I've never tried Thompsons on sunbrella, good to know. Although on wood decks it's worthless.

[chuckr]

Our bimini is 12 years old - a number of years ago when we were in the Bahamas someone suggested we try elastomatic roof paint - white in color. Our bimini was leaking and we were using 303 and other stuff on a fairly consistent basis to prevent from leaking. Got the roofing paint at home depot and put it on during a very hot visit to the Cheaspeake Bay. We then headed down to Mexico and Panama and Colombia and the white really cut the heat and waterproofing proved itself more than once. The same thing in the Eastern Caribbean -- We sailed into the Med and the bimini began to show it's age and started to leak again so I repainted the other day. Two driving rain storms and not leaks. and looks good again -- oh some German boaters saw what we did at some port in Greece this past summer and told us what a great idea to cut the heat.

[capnjack.morton]

Thanks to all who are sharing ideas.
Chuckr - the elastomeric sounds like it would indeed be waterproof. Do you leave your Bimini up all the time? Mine goes up and down according to what's happening with the boat & weather. My guess is the elastomeric would make the fabric fairly stiff, and not nearly as flexible if the Bimini has to be folded up - true?