BYYB Forums

Timo, go to the www.westsystem,.com and www.systemthree.com web sites and down load their user's guides. They will have an over view of epoxy fillers, types, what each can be expected to do, etc. On the "Tips and Techniques" sheet of your plans epoxy use is discussed, though more detail can be had with the user's guides.

In a nut shell fillers are reinforcements, used in the resin matrix, just like 'glass cloth. They help control viscosity, density, tensile strength, etc.

There are thixotropic agents and the normal suspects are: fumed (colloidal) silica, chopped 'glass fibers, shredded cotton fibers, milled 'glass or plastic fibers and wood flour.

Then there are bulking agents, such as micro balloons (phenolic), qcells (quartz microspheres) and wood flour. This are typically used to make a light weight fairing paste (except wood flour) and offer little structural reinforcements.

You can also mix in pigments and other materials (like graphite) to change the look or surface qualities (graphite) of the cured goo.

Generally, you'll use chopped or milled 'glass fibers, wood flour and silica in structural applications, where gap filling, gluing and bonding are necessary. Micro balloons or qcells are reserved for fairing (body putty) and I see no reason for you to fool with pigments or graphite.

Thixotropic agents will be used sparingly as they have a dramatic affect on the resin viscosity once added (a little goes a long way). The reinforcement fibers will be the stuff you use the most, like silica, wood flour, and the other fibrous materials.

These will be incorporated into three basic thicknesses: slightly so, which is about like a heavy cream or catchup, moderately so, which feels like mayonnaise or fully thickened which is about the consistency of peanut butter.

Of course the thicker stuff is intended to adhere to vertical surfaces, but is also used for gap filling, bonding, fairing, etc.

Again, download both user's guides from West System and System Three, for a better overview then I can provide.

I checked the ´West web site and the videos were really good. A picture is more than a thousand words and video is even beyond that. I realized that my epoxy needs to be way thicker.

I have made some progress with the gaff jaws. The pieces are roughed out of the blanks


and were dry fitted to the gaff. Everything seems to fit OK


Routing the slot to fit the hexgonal spar was a fun excercise. I never really liked the router before, too much dust and too much noise to my old school mind. But I have to admit that this would have been a pain without it.

Very beautiful work!

Timo, don';t show those pics around too much. They will scare all us newbies off! Just kidding, very nice.

Greetings Paul,

I have wondered about this more than once ...

(04-05-2010, 02:40 PM)Paul Riccelli PE,NA link Wrote: [ -> ]All the stuff you learned with glue and cabinetry, must be forgotten with epoxy. You want ooze out, you want slightly sloppy joint fits, etc. Epoxy requires some bulk present to work, so less then perfect joints are then norm, not the exception. Ooze out all around a joint insures the joint isn't glue starved and also provides a handy supply for starting a fillet (if necessary).

The construction details in the Weekender (et al) plans for joining hull bottom to hull side, hull-side to deck, etc, involve the use of a roughly one inch cross section stringer that runs the full length of the boat.  After you apply the plastic resin glue to both mating surfaces and assemble the joint we then drill, countersink, and drive one inch wood screws through the joint into the stringer every three inches.  Even on the tighter bends around the front of the cabin, the every three inch spacing of the wood screws provides enough clamping pressure to assure a cabinet grade tight joint for the glue.

So the question is, if I switch to epoxy and use exactly the same methods for attaching the stringers, do I risk squeezing out too much epoxy an compromising the strength of the joint?

Sincerely interested,
Tom

Well, I'd have to say that, from my experience with the wood's behavior (not using epoxy, so I'm waiting to hear yea-nay on this), the spacing of screws is also pretty necc. to help torture the wood into place. If you start spacing too far, you run the risk of splitting stringers and having a less-than-fair shape to the ply.

Mike

Leaving the surface rough and not planing it will help keep some epoxy in the joint. And you don´t need to drive the screws very tight, just enough to get the pieces together.

Timo's correct, just bring the two pieces in contact, no more when using epoxy. On a 1" square (roughly) piece of wood, driving screws on 3" centers will easily compromise the integrity of the 1" square piece. Too many penetrations, on too close of centers will limit the ability of the piece to load up at all, without ripping internal fibers and splitting or breaking, let alone tolerate cyclic loading.

Timo, is your gaff tapered?

Yes, it is tapered as per the plans.

After looking at my picture again it is true that it is not that obvius. Maybe because I stepped back and zoomed in, it has a tendency to remove the perspective. If you look at the previous pictures the tapering is more obvious.

Shocked to see how long it is since my previous post :o

Other things have required my attention and not much has happened in the workshop. I also lost some pics taken a couple of weeks ago when I was dry fitting the jaws  ??? 

But here´s how the jaws look after applying epoxy to them. It works like varnish showing the grain nicely. I decided to not use ring bolts and you can see the things I will use to keep the strops in place. What would you call those thingies in English?


Today I glued and bolted the jaws into the gaffs but no pics yet.