Overhead Epoxy Work

Hi All, First time poster, long time reader. I have a project coming up this spring I need some advice on. I am installing rolling chocks on my 32' bayliner and the attachment of the chocks to the hull is going to require some overhead work. What is a good method for applying fiberglass and epoxy overhead? The chocks measure 10' long by 9 inches wide, and consists of 2 layers of 3/4" marine plywood laminated together. Any suggestions on weight of material and application techniques would be appreciated.

I've attached photos of a sister ship to mine with the same modification that I am going to make to give an idea of what I'll be attempting.

 

Overhead work is messy. Good to have a few helpers.

The last time I did an overhead repair , I first impregnated the cloth on a table, rolled the impregnated cloth onto a PVC pipe and then with three guys helping....rolled the ply onto the bottom of the hull. Repeated this twice to get the correct thickness of glass then covered the glass patch with peel ply and compacted with a brush and bubble buster.

It worked OK.

Perhaps other guys who do alot of glass work can give you a better way.

 

Here are some tips that help:

* Layout shapes with magic marker on plastic sheeting, then wetout glass on sheeting and cutout shapes with shears (this is less stringy) and apply to surface with plastic backing, rollout and peel off plastic.

* A little cabosil mixed with the resin makes it much clingier to the over head.

* Wear wrist protection and I use three pairs of disposable gloves at once so if thing get too messy for me I just peel the top layer and continue.

* Take your time. A little practice helps. Some people are better with rollers, other like spreaders and rollers.

Good luck

 

Overhead work can be made easy using the method DGreenwood describes. I do it a little different.
I start by cutting the mat to exact size and put a marker on the hull where they are to line up.
The size of the mat you can put up each time depends on how many hands you have available
If you are putting the mat in corner I would limit the size to approx. 1´x 2´. On flat overhead surfaces you can do bigger peaces by bringing the wet mat on the plastic up to the hull on any stiff material that you gradually slide it to the side as you roll out on the plastic. You peel the plastic off right away and be careful around the edges of the mat, not to pull it down with the plastic. Have the plastic sheets at least 4" bigger than the mat on each side.
I have not done this with epoxy but i think it should be the same. Here is photo of wet-out mat on plastic sheet before it is brought up to the hull.

Hope you understand this.

Axel

 

OK great, I think I get the idea of using the plastic to bring the pre-wetted fabric up to the hull. Is there a limit to the thickness of the fabric being applied or number of layers of fabric applied at once? I would like to use thicker fabric of course to limit the number of trips under the boat. Does anyone have any thoughts about how many ounces of fabric there should be in this kind of application? I have several books and have looked online but have not found much in the way of guidance for this type of project. My initial thought is 4 layers of 1700 biaxial w/ no mat. Am I in the ballpark? Thanks!

 

Pre-wetting fabric is the hard way. Do enough dry runs with the fabric, so you know where the epoxy must go, then apply a light coat of straight epoxy with a roller, in the area the cloth will live. The next step is to wait until the initial coat goes tacky, which is temperature and hardener dependent. With the epoxy tacky, apply the fabric, which will stick nicely to the goo. Position as needed and continue the wetout of the fabric, with more neat epoxy.

Alternatively, you can use a very light misting of 3M-77 spray adhesive on the surface, where the fabric will live. Not much, as it grabs very well and let it flash off most of it's solvents and lose most of it's tackiness. Apply the fabric as described previously, into the slightly tacky 3M-77 and wetout the fabric normally with straight epoxy.

These two methods, will save you from using your bald spot as a squeegee, in the wet on wet method, described by others. No, the 3M-77 will not affect the bond, assuming it's a light misting, rather than a heavy coating.

Use peel ply, plastic sheeting or Mylar sheets to help control the finish if necessary.

 

Use a little Cabosil mixed with the resin ( thicking agent ) which works rather well and in fact i think you will be suprised , and depending on the fabric doing to many dry runs will and can distort the fabric .

 

You see everyone has a favourite method, and when familiar with the method it's pretty easy. I wet out the surface with caposil thickened epoxy and roll the pre measured piece of gf dry over the wetted area slowly sqeezing with plastic spattle..

 

My applause for this particular bit of info - this is going to be a big help .

 

For overhead work or areas that are hard to reach which required small pieces of shaped cloth , I find the Aircraft " poor mans Prepreg" technique to be handy .

Best to read to understand

http://www.dpdillon.com/cozy/tipstechniques/howtolayup/index.html

 

Several good ideas here. I think what I'll do is set up a coupe of test pieces with plywood and try different methods overhead to see what works for me. I can also get a better idea of how many layers of glass I'll need for appropriate strength. Thanks All!

 

That's the way to do it. A little experimentation and practice go a long way in anxiety reduction when you go to do the real thing. Please come back and let us know how you get on.

 

Bag it . . .

 

The local glass gang bags everything. The problem for a homebuilder is that the tooling up costs rapidly turn a 500 dollar repair into a 1500 dollar bag project.

 

FridgeNorth,
I've been building rolling chocks for quite a while now and would be more then happy to help you with any questions you might have. You can send me a PM here or email me at midnitmike <at> hotmail.com.

MM

You can check out this thread for pics of my last rolling chock.

http://www.boatdesign.net/forums/hy...rted-chines-strakes-question-oh-no-43908.html