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Old 05-11-2011, 10:16   #16
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Re: Epoxy Fillets and Screws

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Originally Posted by capt.bobfm View Post
you'll be much happier later when you're in 20 foot chop
I don't think it is called chop anymore when it reaches that height.

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Old 05-11-2011, 10:39   #17
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Re: Epoxy Fillets and Screws

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Originally Posted by GordMay View Post
IMHO, drywall screws are for drywall, and deck screws for decking.
I'd use Silicone Bronze (“Durium” or “Everdur”) wood screws for wood.
+1 .
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Old 05-11-2011, 10:53   #18
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Re: Epoxy Fillets and Screws

---or Iron nails
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Old 06-11-2011, 09:02   #19
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Re: Epoxy Fillets and Screws

Tip on filleting from a pro. Most people use tongue depressors or the like for structural fillet. This actually requires a lot of practice to get an even fillet, which can be an issue when fairing after the glass goes on. The fillet is the hardest part to fair, as it all has to be done by hand with a custom made block to get it really fair. The problem is that the angle at which you hold your tongue depressor or squeegee to the work surface has to stay absolutely constant to prevent wobbles in the fillet. This becomes impossible when you start hitting 3 way corners, or when hardware is in the way and you have to start/stop. It can make for much more fairing later if you want factory looking fillets. As someone who does a lot of industrial tooling, I became familiar with hot wax fillets long ago. This is how you make a naturally releasing fillet in a mold, and the system produces perfect fillets at any angle by using heated steel balls of the desired radius to melt the wax and shape the fillet simultaneously. So I just started to use hot wax fillet balls for making fillets in laminates. They give you a perfect fillet every time at exactly the size you choose, from 1/8" (which is much smaller than you could ever do any other way) to a special 2" fillet ball I had custom made out of a ball hitch. They cost a little, but in hours of sanding saved when fairing I can't think of a cheaper more sensible buy. Your fingers will thank you...

Wax Fillet tool set - East Coast Fibreglass Supplies
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Old 06-11-2011, 09:45   #20
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Re: Epoxy Fillets and Screws

My wife does lots of dessert variations. When I was building my stitch-and- glue dinghy she raised H*ll when I used the melon ball tool.
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Old 06-11-2011, 11:40   #21
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Re: Epoxy Fillets and Screws

Quote:
Originally Posted by minaret View Post
...fillet balls for making fillets in laminates. They give you a perfect fillet every time at exactly the size you choose, from 1/8" (which is much smaller than you could ever do any other way) to a special 2" fillet ball I had custom made out of a ball hitch...
Wax Fillet tool set - East Coast Fibreglass Supplies
Thanks for a great tip!
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Old 06-11-2011, 12:11   #22
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Re: Epoxy Fillets and Screws

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Originally Posted by minaret View Post
They cost a little, but in hours of sanding saved when fairing I can't think of a cheaper more sensible buy. Your fingers will thank you...

Wax Fillet tool set - East Coast Fibreglass Supplies
Awesome

(and a great Epoxy etc site that is also in the UK!)
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Old 06-11-2011, 14:38   #23
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Re: Epoxy Fillets and Screws

The balls do work good as long as you don't get too much filler forward of them. Here is 80' of fillets along the inside of the cap-rail. What a pain that was!


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Old 07-11-2011, 03:06   #24
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Re: Epoxy Fillets and Screws

Re: Epoxy fillets and screws from kwhitehead, posted on Tech support site. Thanks for all the advice. The jury still seems to be out on leaving screws in plywood epoxied to stringers, bulkheads etc. I did do a few tests with 42x21mm stringers epoxied to 12mm marine ply. Without screws a hard downward hammer blow on side of stringer will break it off, either the first ply laminate separates or a sliver of stringer. With screws its very difficult.
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Old 07-11-2011, 03:33   #25
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Re: Epoxy Fillets and Screws

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Originally Posted by KKat View Post
The jury still seems to be out on leaving screws in plywood epoxied to stringers, bulkheads etc. I did do a few tests with 42x21mm stringers epoxied to 12mm marine ply. Without screws a hard downward hammer blow on side of stringer will break it off, either the first ply laminate separates or a sliver of stringer. With screws its very difficult.
Sometimes a bit of hands on makes things clearer

I have never built a boat - but unless plans (designer) says otherwise I would lean towards also using Screws. Albeit not going mad on them. Got to remember though that if the force used is sufficient anything will seperate, whether epoxy alone or with screws......and on that you are in the hands of the designer (to have got his sums right). IMO you either trust the designer completely - or you don't get on the boat ......and as already said, "more" is not always better (and can be far worse) when it comes to building (especially where weight is an important factor - like for a Cat).

My big concern with Plywood is when it gets wet, as ultimately will end up with veneered papier maché. with a screw you get to have less of an expoxy plug, so unless also glassed over more possible that the plug will pop out and water / damp ingress......and I have seen the results of that, if (when) left unchecked

If you follow the advice on filiting in this thread, your mate is going to be as sick as a parrot when he sees the filets on your boat (and the time saved ).

So, what are you building? and where?
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Old 07-11-2011, 03:36   #26
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Re: Epoxy Fillets and Screws

Minaret- great idea. I'm sick of the wooden sticks too but had never thought of using a hitch ball....

Re. screws:

If they're going to be left in, use bronze. Stainless, drywall, deck, etc. will corrode through.

There are two different structural concepts that could be in play here.

One is a conventionally framed wood structure in which the fibreglass is just used to keep water out and to beef up some stress points. If the boat's designed this way (and, btw, it's not one I particularly care for), the screws serve a structural role. Use bronze and leave them in.

The other possibility is that it's a wood/epoxy composite structure that was engineered from the start to use the two materials together. If this is what the designer had in mind, he'll probably say to use cheap, temporary screws and to pull them before glassing. And there will be a detailed laminate schedule describing exactly how much of what kinds of glass should be placed in which direction along each joint. If it's properly engineered and executed, this method- with no mechanical fasteners at all- can be quite a bit stronger than a comparable structure that depends on screws. But it has to be engineered as such from the start.
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Old 07-11-2011, 05:10   #27
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Re: Epoxy Fillets and Screws

Lets think about this.
We have decided that we are going to use screws, and leave them in place in the plywood.
Any screw in plywood should only pull down flush with the surface veneer. If you go beyond the surface veneer, and tighten down, you compress the internal veneers and initiate seperation from the outer.
Standard countersunk wood screws carry their wedge shape to a sharp edge. Careful c/sinking to the gauge size will still only provide a max of about 1.5mm of sloped compression surface on the wood.
The splitstop screws I referred to earlier (with which I have no commercial connection) were designed to to be used in engineered wood life MDF,OSB and particle board.
The head is a convex underside surface, developing into a rounded extremity, which, if tightened carefully, will pull the outer veneer down gentley, without pulling through. I always c/sink one or two gauge sizes smaller.
I have used these screws in this way often, and IMHO, do a better job in engineered wood.
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Old 07-11-2011, 06:17   #28
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Re: Epoxy Fillets and Screws

I built a little Van de Stadt 6.5 from ply/epoxy using clamps (no screws). Worked well for the year I sailed it, and, from what I'm told, kept on working until a truck backed into it.

If the designer approved I'd dry fit the ply using 8g pan head screws with oversize 3/16 washers under the head. Then apply glue and rescrew (using pan heads and big washers) in place, with fillets.

After the epoxy had set I'd remove the pan heads (using a little heat as necessary). Depending on the designers advice they could be replaced with countersunk 8g SS screws, glued in place, or the holes could be filled with thickened epoxy from a syringe.

The countersunk screws could be put in with enough tension to reinforce the bond, but not enough to crush the wood.
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