Thursday, January 31, 2008



Because of my limited space, my plan is to make all the flat parts for floats and main hull before I start planking.

I transfered the full size patterns to MDF using carbon paper.

To support the panels while I cut them, I put a sheet of insulating foam on the floor and then shortened the saber saw blade. To conserve material I followed the cut plan shown in the plans. I will save main hull #1 and 2 for later, as they will come out of my setup table and vacuum table.

Since the main hull forms use the factory 90 degree corners and parallel edges, alignment is easy. Since the floats come from some odd shapes, I decided that I would run them through the table saw so the top and bottom were parallel and uniform, and then align them so the deck was flat. I cut the area for the deck flange perpendicular with the miter saw, extending it so that the form for the flange could extend the length of the float without having to be cut different widths.

I then began building the strong back. I chose to use 2x6 cross pieces and 3/4 ply ripped to the same height for the sides. The braces are 2x4. It's a three dimentional trick to get everything aligned.

After construction I confirmed that the cleats were parallel to each other and perpendicular to the center string. It's raised on feet, and level was accomplished with a laser level.

Placing the forms with clamps began to give the whole thing shape! I used the deck edge for alignment.

The final step was to brace the forms plumb. Straight, level, plumb, perpendicular, parallel . . .

For battens I used Paulownia wood that is finger-jointed to remove knots and comes in 20 ft lengths. It produced a nice curve, though it's 'soft' (hence the low expense) so you could drive a screw head right through it if you over-tighten. The battens were 'artistically' placed: it seemed best to position wide for simple curves and narrow for compound curves. I usually started in the middle and worked towards the ends.

The only difficult area seemed to be at the keel near the bow, where the curve also required a twist (I ripped these square, which helped). Since the forms are not faired and sometimes have limited contact with the batten, I found the direction of the screw to be important -- perpendicular to the batten, not form, and off-center to counter any twist.

The transom overhangs form #11. Looks like a lot of battens. I guess I'll only put screws through if it helps shape the foam. Luckily I get to reuse them with the main hull.

At Jeremy's advice I decided to use the strong back/forms as my table legs for the vacuum table. Originally I was going to alternate back and forth, preparing one while the other was curing and vice-versa . . . of course I could never work fast enough to make this worthwhile. And I found that one waxed surface and one clean surface for prep work was the best.

It's all about physics: VI

As I have mentioned, I followed Henny (and then Tor), long before I committed to building a boat. 
Consequently, I always knew I would have to try Vacuum Infusion (VI). I do not plan to outline the details of the technique from start to finish (as they are outlined many other places and my advice would be to start with Henny's Kit) but I will mention some of my personal experiences.

I say 'personal experiences', because while this is the case with many techniques, likely it will be more so for those experimenting with VI.

I became very attached to the 'dry' lay up -- both sides, multiple layers -- that VI allows. Below you can see the disposable layers and a 2x4 foot foam panel with three parts outlined. (Note: the bulkhead shown below has a locating dowel used later for positioning the deck and beam. As Jay notes in his blog, the central position of this should be double checked before assuming you've put both bulkheads in correctly.)

Trying to control the variables (and finding out what they are) is most of the fun.

Resin. Although the resin I am using has been used for VI of large parts and vessels according to the manufacture, it is not designed specifically for VI (I accepted this as I knew I was not going to attempt VI of the whole boat). Hence its viscosity is a little high, especially for the temperature of a garage in winter. And it's open time is short, ~1 hour at 70 deg. F.

Vaccum. My system only pulls ~27.5 -- more is likely better (given the above).
One measure of a 'successful' session (besides a good product) is limiting resin waste. I think the volume that cures in the tubes and resin distribution media are fixed losses based on the size of your part package (though low viscosity resin might decrease this -- I might touch on this later). That leaves resin in the waste trap. Basically, a perfect session would have the top and bottom resin front reach the outflow at the same time. If one beats the other, you have to waste resin while it catches up.

My first issue was 'race-tracking' along the edge, which I cured by not allowing the resin distribution media (RDM) to go over the sides (the sides paralleling the direction of resin flow) and having a strategic pleat in the vacuum bag (VB). Second, my experience was that the bottom resin front was fastest. I suspect that the wax surface and fixed (larger) space in the RDM accounted for this. I am using a 'stretchy' vacuum bag material and this seemed to be sucked into the space of the RDM on the top layer, slowing the resin advance. By accident, I discovered that when I used two pieces of RDM and overlapped an edge, the resin would move faster in this area. So, I placed a second sheet of RDM on the top, whose shape countered the above tendencies. (I say 'shape' because it was not uniform. The counter current effect of the placement of the inflow and outflow, which should make this less of an issue, was not as efficient in my system.)

There were may more lessons -- but enough of that. To understand the picture below: inflow is far right corner, with a tube coming towards you (it ends early to help slow down the near side of the resin front). The outflow exits near left with its spiral tube going to the far (a little past) left corner. The dark green is the second layer of RDM. The goal is to have the top and bottom resin fronts get to the near right corner at the same time. You can see the beginnings of the foam showing through the now wet/transparent glass and the markings of the future aft-cabin hatch.

And a while later. You may be able to see that the bottom is catching up to the top.

Almost done. You can see I have blocked off the new section of garage with its glass 'heat sucking' roof, and have been heating the area (I had to take off my fleece). The heat did decrease the viscosity of the resin and speed up the process. I found I could clamp off the resin intake before the far edge was 100% and it would continue to finish. I picture the resin layer being wedge-shaped, and the extra resin to finish comes from the final 'flattening' of this layer. This was also how I also explained that even when I 'won the race' by having everything perfect, the waste trap would have excess resin in it the next morning.

It's always fun to open the package! What a great product VI can produce.

Another technique: VB

Read Henny and Tor's experiences and you will know that I still have a lot to learn. But I was running out of parts to efficiently fill my quarter sheets -- and I knew that was the reliable limit given the above observations with MY variables. It was time to learn something new -- tried and true wet lay-up vacuum bagging (VB).

I began marking out the area that I would wax -- moving up to bigger parts. I thought that the VB tape might not like the wax, but have since found that the tape I'm using will stick even on waxed surfaces.

Wet out the peel ply (PP) first. If the part has multiple layers of glass in specific areas, I trace this location onto the bottom PP with a pencil. Glass is next.

Then foam. At first I wet both sides -- but that was too much work and didn't seem to make a difference after the VB'ing. I started out using a thin foam roller, but while it may have a role (no pun intended) I have found a squeegee to be much more efficient.

More glass, peel ply, resin release film, two layers of breather, VB . . . and presto -- another great product.

You can see I have experimented with placing some strategic rebates for taping in an attempt to minimize faring later.

A sneak peek shows the nice matte surface under the peel ply.


My first VB panel was a repeat of my last VI panel. The weight of the final product was approximately 5% less for the VB -- sucking too much resin into the breather? -- though they don't look different and the thickness is the same (it might also be within the error of my scale). The difference in resin usage was significant -- about half as much, which was confirmed by weighing the RDM, etc. -- a significant cost in the garbage, not including the increased disposables.

So, my experience and variables supported continuing with VB'ing. Would I choose to avoid VI having come to this conclusion? NO. Like everything in life, additional skill and experience is a valuable bonus.

I do want to pass on something that might be useful. When researching VI, I came across a company that produces sticky fiberglass tape, which is designed to hold fabric in place dry before the VI is started. (Henny has been using synthetic staples, I believe.) The thin, open weave tape is incorporated into the laminate. I was going through a steep learning curve about cutting and handling stitched fabric when it came to me: I have some sticky fiberglass tape for repairing dry-wall!

It takes a couple of seconds to apply. Cut down the middle and both edges hold together without any fibers coming off. It also reduces snagged or twisted fibers from an inadvertent fold while handling. The roll stays neat -- and odd-shaped pieces keep their shape. This is especially true for 45/45 which seems to be very finicky. Originally I was thinking of leaving the tape in the part (hard to feel, at least after VB'ing) since if you take it off dry, it begins to pull at the loose stitching and causes a problem. If you wet it out with resin, though, it lifts off and the glass stays right where it was.

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