Surfing School - Shaping - Blanks
Choosing the right surfboard blank is an important part of your design. They are made by pouring a stirred resin mixture into a form. As the mixture cures, it expands to fill the form. Stringers are placed in the foam after the blank is cured by cutting the blank down the middle and gluing.
Blanks are available in various grades, sizes, and weights. First blanks used by most manufacturers are usually perfect as far as consistence of foam is concerned, and contain no air holes. Seconds may contain small shotgun pellet size holed or may have a thick spot in the foam. Rejects usually have large air bubbles or many small holes.
Rejects are considerably cheaper than first or second grade blanks, and the finished board probably won't look as nice, but functionally it will perform the same. Since many people can't tell the difference between blank grades, lesser grade blanks are sometimes sold as a first to the unwary.
Holes are found by holding the blank in front of a strong light. Move the blank back and fourth and note if small shadows or dark spots can be seen. Holes appear as dark spots. The background light method is used by manufacturers in initial grading. If you find a hole during shaping, you can still shape around it, but will need to fill it (if it's large) with foam dust during your initial glassing.
Classic, ultralite, superlite, etc. refers to the weight of the blank. Heavier blanks are slightly more expensive since more foam is used, but they are also the hardest and most difficult to ding. They are the easiest to shape. Big wave gun boards use heavier blanks since the extra weight is needed for stability and momentum when paddling into waves, especially on off-shore days.
Blanks are rated as follows.
Superlite - lightest and weakest
Ultralite - very light
Blue - light
Super Green - light but strong
Classic - heaviest and strongest
The blank's rocker (usually referred to as nose kick or tail rocker) is also important in wave catching and turning. Generally, the flatter bottom blanks are used for faster boards while natural rocker boards are used more for small wave contest and general recreation surfing. Rocker is placed in a blank when the stringer is glued. This is also true of nose kick. Natural rocker with a slightly flattened tail is the best bet for inexperienced surfers or shapers who are not certain of what they want to design.
Stringers add weight and strength to a board. Center stringers are normally 1/8 inch redwood for regular boards or 3/16 inch for guns. Balsa wood stringers are the lightest, but generally more expensive. Pressed paper or glue lines are also common for stringers, and are inexpensive. Stringerless boards are very light and also easily broken. They are not recommended for use in large surf.
A quick note on tail blocks for longboards. Tail blocks were used in the early days on longboards primarily to prevent the constant problem of dings on square tails which needed to be repaired. A longboard has more weight that a shortboard, so any points seem to get hammered much easier than those on a shorter board.
The key to a good tail block is to use hardwood such as oak, teak, or mahogany. Any hardwood that doesn't absorb water is fine, just remember that hard woods are also hard to shape. I prefer teak since it is very colorful when resined.
If you only need an 8" wide tail block, shape the end of the 8" wide by at least 1" thick board. Cut the outline with a hand saw then, using first an electric sander then a sanding block slowly whittle the edges to the desired shape using finer sandpaper. Finally, using a small tooth hand saw, cut the board straight across about 1 1/2 inches back from the formed area. After your board is shaped, cut the tail off at the proper thickness using calipers, glue on the block, and then glass over the completed board.
Making a Balsa Board
Balsa boards are much more difficult and take longer to make than traditional foam boards. This is because there are some additional shapes involved, and also because they take longer to plane and sand. Glassing, discussed in the next chapter, is just about the same with a foam board except that you can use lighter cloth. With balsa or redwood, you start with a plank rather then a blank. Foam blanks are really "blown planks." You buy wood in a plank then make a larger plank to shape the board from. Below are the steps involved and what you need to do. Since working with the balsa plank is the main concern, I'm only going to outline the steps at this point with more in-depth coverage later on in this chapter.
- Find The Blank
You need to find a balsa plank. Usually you need at least several 4" by 4" by 10' + planks, or at least four 6" by 6" planks to make up one larger plank. Some planks are available in 12' lengths, but a 10' plank can usually be found. These aren't readily available and usually must be custom ordered from some remote dealer. Make sure the blank is both long enough to allow for at least 1/2" to be cut from each end, and also thick enough to allow for both the thickness of your board and also any rocker you add. Many balsa boards didn't have rocker because the original blank wasn't thick enough to allow for it.
- Glue The Wood
In the early days we didn't always hollow boards much so the initial glue was the final glue. A good waterproof wood glue such as Elmer's wood glue will work. Use a squeege to evenly spread the glue on each side before connecting together. Use at least three large clamps to hold the wood tight while the glue sets.
- Rough Shape The Blank
Rough shaping is what you can do with an electric planer and rough sandpaper. Unlike a foam shaped board, you make vary shallow cuts with only slight angled cuts on a balsa plank. This means you need to constantly check the level of the deck and bottom with a straight edge to ensure uniformity. You also must slowly cut the rails to the shape you want as a small dip will become immediately visible.
- Saw The Board Apart At The Glue Joints
This step is tough and must be done very carefully. Nowadays, you rout out the inside of the board to make it lighter. This means that the board is shaped first and then hollowed out later. Since you have already glued the board, and since you want to minimize the effect re-gluing has on the board's finish, you need to make the new cuts along the glue lines with a fine tooth hand saw. Cut very slowly with the saw near horizontal to keep your cut line straight. If you were lucky and used 6" by 6" planks, only a few cuts are necessary.
- Hollow Out The Planks
I suggest you use a hand held router to do this. Solidly fix the balsa board with the side to be hollowed up using clamps. Use a small diameter cutting blade on the router unless you really know what you are doing. If you have 4" planks, set the depth of the cut to about 1/2 inches. The plank is 4 inches thick so this will allow about a full 1" strip for strength running down the plank's middle. If you have 6" planks, you can only cut to 2" before you need to worry about keeping your router blade cutting straight down. This means you will have a 2" inner strip. If you haven't shaped a hollow blank before, don't cut closer than 3/4" to the outer edge of the plank or you will have a problem with deck pressure dings.
- Re-Glue The Planks
Again, this is a slow process and must be done with care. Some builders like to add thin redwood stringers at the previous glue joints, but this also changes the surface color. It's also harder to keep the edges well aligned when a stringer is added. I glue the cut lines the same way as initially but put them back together by aligning their bottom edge on the flat surface of a table. You also need to be careful the blank's rails aren't depressed when you clamp. I suggest you use some thin boards against the clamp and rubber foam against the blank itself to prevent depressions.
- Complete The Shaping
This is done mostly with a hand plane and sandpaper. Make sure you always take long passes.
- Glass The Board The Same As Any Other Board
- Attach Fin
Fins for a balsa boards are usually custom made. Never use a fin box or a solid glass fin if you can help it as these detract from the boards worth. Most fins are made from redwood strips. Glue the strips together and then shape to the desired form. You need a wider base fin since turning the board requires more momentum transfer. Two to three layers of cloth on the outside of the fin with the edges pinched and cut after drying will do fine. Attach the fin in the same way any other fin is attached.
- Fill Coat, Sand And Gloss
This is done the same as for any other board (see the next chapter).