More questions on screws and glues

I would appreciate your advice/opinions on the following: Frearson drive vs. square drive screws. ( The Frearsons are cheaper) If I use epoxy resin and hardener for my adhesive do I need to add filler such as cabosil or do I use it without filler? How important is it for the Southern Yellow Pine I am planning on using for framing to be quarter sawn rather than plain sawn. Thanks much!!!

 

Cab-o-sil is not used so much as a filler. Instead it's used to adjust the viscosity of the resin from a fluid to a tixotropic glue. In that regard you can use so much as it's needed to achieve the best results for the specific task.

 

I prefer square drive, though Frearson do much better then Phillips.

Epoxy can be use "neat" as an adhesive in some limited applications. Most of the time you'll need to keep it in the joint with a thickening agent(s). Cab-o-sil is a common one, but there are others.

SYP will cup, warp and expose internal stresses as flat sawn lumber. It's moisture gain rates will also be much higher. Quarter sawn stock is more stable and less prone to these issues.

 

I've been using both on my Silverton. If you drill a proper pilot hole either is OK. If I have room to work (decks for example) I use the less expensive Frearson drive. In tight quarters (interior spaces) I find that Robertson or square drive works better. You can drive the screw a bit off center with the square drive (if your working next to a bulkhead for example) and still get enough torque on the screw without stripping out the head. One thing I've noticed if the pilot hole is too tight the square drive in Silcon bronze will strip out the head of the screw much sooner than will the Frearson drive.
I learned quickly to be careful with the pilot holes.

Regards, MIA

 

Thanks and more questions about epoxy

Much thanks for your advice and opinions. Now a couple more questions on epoxy. PAR and others have said that cabosil and similar additives are mainly used to adjust viscosity of the epoxy. Is that really necessary, as I see (at least on the U.S. Composites site) that they offer epoxy in thin, medium, thick and extra thick viscositys. You would think that one of those would be correct as is. But...that's why I'm asking these questions; because it's all a learning experience for me. Let me ask it this way...scenario.....I am about to apply the epoxy on my frame prior to screwing on the plywood skin. Should the viscosity of the epoxy be like water, pancake syrup, toothpaste or putty? That will help me get a feel for it. As always, I can't thank you folks enough for yoour advice. What a wonderful forum!!!

 

You need to watch the yellow pine, I have had some perfect
boards and when you rip them to smaller widths, in a short
time they become cork screws!

One the good side, sometimes they fit on the boat frame
after they warp.

 

It's not necessary but it's more convinient having only one "barrel" in the boatshop which, by adding different additives, make a compound for the specific task in hand.
First wet both surfaces with "like water" then "majoynaise" on the other one..

 

That might have more to do with the way it was dried. Fast kiln drying can set up tensions in just about any wood, so that when cut, the tensions are not equal and it warps and twists an awful lot.

 

To answer your question on epoxy thickness........

I'm not familiar with US Composites (I use System Three Resins), but based on my experience you will need various "additives" for your epoxy so that you can achieve the results that you want.

I've never seen a resin that right out of the container will stay put on a vertical surface or an overhead. In these cases the user has to mix additives to the base resin in order to get the consistency that he wants. Silica, wood flour, plastic mini-fibers, microballoons are all examples of these additives. You'll want to make faring compounds and gap filling adhesives and will need additives to get the results you want.

Seems that many folks swear by a certain brand of resin. I think they all all good. I think it's a matter of personal taste.

West Systems puts out a good small book on using their products. System Three has available "The Epoxy Book". It's available on the System Three web site and is free for download. I'd suggest that you read these books. I'd also suggest that you order some of these additives and mix them up with your favorite epoxy so that you can see first hand how they work and what they do. Your boat will be all the better for it!

Good Luck, MIA

 

As a few have pointed out, you will need a variety of reinforcements (fillers) to use with your epoxy.

You can buy resin that has had the filler premixed, but you are paying 10 times more for the few ounces of material they add, then the actual cost of the fillers if purchased separately.

There is no set mixture that suits every need, nor every environmental condition. One filleting mixture used on a day that is 20 degrees warmer then the previous filleting batch, will require a different amount of reinforcement to be added to the epoxy. Just the amount of humidity in the air can affect the filler requirements for that epoxy session.

Most experienced users have several different reinforcement additives that will be used. I use every thing from regular wheat flour to coarsely ground up 'glass fibers. I have thickening agents, a few different densities of fairing fillers, a few different strengthening fillers, home made mixtures, literally a shelf full of different powders, granules, milled bits of stuff, all used with epoxy. Each imparts a specific set of physical properties to the cured resin.

Log onto the major epoxy manufacture sites and down load their "how to" manuals. Then practice on less critical parts, until you get a feel for the stuff. It's costly enough to not want to make big mistakes on structural elements, so get a feel for the stuff.