Vacuum Forming

If you've been following along with the 'bagged construction you've probably noted that most of the bottom contours have been nonexistent As Dennis and I were discussing, I was doing some flta bottoms because it was easy. James' TWP bullet has a single concave that he likes...I built a single to double concave that was seriously fast and so I wanted to be able to vacuum form some bottom contours.

I started by shaping a single concave into the blank that has the wood perimeter stringers and d-cell rails. This picture shows the concave under the level, it is about 5/16".

that's some serious concave jeff. cool!

Hey Matt,

Yeah, it's fairly deep.

In skinning the bottom, I wanted to wrap the rails a bit. The Surftech Tuflite construction, as well as, Lost Placebo Flexlite construction uses d-cell wrapped around an EPS core, however, they use heat to shape the d-cell around the rails. I don't have that ability with my bag and hotbox arrangement, so...I have to limit the wrap on the rails.

If you look closely this is the bottom of the rails shaped. The d-cell that I skin with will wrap a portion of this.

In a discussion with Jerry Price of Shred Stixx he was saying that one of the reasons that Epoxy boards seemed to be faster was that they are stiffer by nature. The Inland Surfer boards all seem exceptionally fast to me also, so I know there is some truth to this.

We want this board to be very stiff, I intended to cover it with 5.7 oz carbon and the sandwich layers will be 4 oz e-glass. To make the boad as stiff as possible, I am using extra resin and doing all the resin work on the outside layer. I also didn't seal the blank so that the resin would work into the EPS core and create a stiff section close to the skin. The stiffest epoxy that I can find, readily available, is the TAP super hard.

I used d-cell as the skin, evn though I prefer corecell as a skinning material. The d-cell is more flexible than corecell and will more readily adapt to the contours of the bottom shape. With a stiffer lamination schedule, I believe that the underlying skin material won't be as important.

I cut the outline of the board from a sheet of 1/8" h-80 and then also matched the fiberglass. As noted earlier, I did the resin work on the d-cell (which sucks resin) rather than wetting the glass and applying it. Again, I'm looking to stiffen this board up.

Once the glass was wetted out, I fliped the skin on the the upside down blank and aligned. I find that squaring the rear first and rolling out towards the nose makes it easier to align.

The concave is present after the skin is attached.

This board has wood perimeter stringers, d-cell h-80 rails - 1/2" thick and the bottom rocker was hotwired in. What this allows me to do is BAG the bottom skin on to the prepared blank without losing the rocker or deforming the blank. In my previous bagging I have always bagged to a rocker table to insure the rocker remained consistent. Having already bagged the wood stringers ON that rocker table, I won't lose the rocker by bagging just to itself.

This opens up the potential to bag any sort of bottom contour, after the blank is hand shaped. So we'll gain the custom shaping with a hard exterior.

One last point. When bagging without a rocker bed, it requires a tube. The tube encase the entire board and will form to the bottom contours. However, the bag if used with a rocker bed is usually substantially longer than the board. You need to be careful that you don't seal the bag on the pull, before you have applied pressure to the skin. SO...make sure the vacuum port is fairly close to the board inside the bag. If you leave 12" of bagging material it's easy to seal of the vacuum before there is adequate pressure on the skin. Trust me on this one

When this one comes out of the bag it will have a single to shallow double concave. Hopefully with an adequate rocker to maintain release. What we want to take away from this exercise is that complex bottom contours can be vacuum formed without expensive molds nor are we relegated to old methods of glassing without a tough exterior skin to create the contours.

(Message edited by surfdad on December 26, 2007)

Out of the bag and you can see the start of the double inside the single concave.