Speargun Building 101: Making Blanks.

I remember back to when I was planning out my first gun build. I had all my parts, which included a beautiful teak blank made by Dean Koutras  from "Addiction Spears." As I was doing general research on speargun building I kept coming across forum posts related to making speargun blanks. I gathered as much information as I could on the subject and made the decision to put the blank I had purchased to the side (I still have it 4-years later) and dive into making my own speargun blank.

I started looking around for places to buy hardwoods, specifically teak. I came across a supplier in my area who was selling some reclaimed teak from the USS North Carolina, a famous battleship from the US Navy. The boards they had were deck planks. I thought it would be so cool to make my gun from reclaimed battleship wood. I headed over there and bought a couple pieces. I should have purchased more, he had a huge pile and the price was very reasonable. While at the hardwood supplier I also purchased a large piece of 8/4 padauk because I knew I would be making more guns after the first one was done. 

Fast forward to now and I have made somewhere in the neighborhood of 50 blanks. If you haven't made one yourself and are reading this let me start by saying that there are multiple ways you can get the job done. To illustrate this point, you may read that after the glue-up, lams should be clamped together stacked on top of each other so the epoxy between the lams remains evenly distributed. I clamp my boards together in a vertical orientation, I find it easier to keep them aligned sitting vertically. Some will argue that clamping a blank this way will cause the epoxy to run downward between the lams. I have observed an equal amount of squeezed out epoxy at the top of the blank and the bottom of the blank after curing and have not yet encountered a problem using this method. That is just one example I can think of where one person does something one way someone else another, and both methods work. That said, there are some basic "rules" that should always be followed. I will do my best to point these out as I describe my process.

Locate some wood!
Depending on where you live this might be the most challenging part of making your blank. If you don't have a hardwood supplier locally do a Google search for "Hardwood supplier."  Do that same search on eBay. Craigslist is another place you should check if you don't have a local supplier. Even if you do you just might find a good deal by searching around for used (reclaimed) hardwood.

The most common woods being used these days for spearguns are: Teak, Padauk, Mahogany, Sapele, and to a lesser degree Purpleheart. Technically you can use any wood if you will be sealing the gun with an epoxy finish. Beware, if you use a hardwood like maple be meticulous. Make sure every hole is completely sealed before taking your gun in the water. Certain woods just do not do well when exposed to water. Woods with a high oil content like teak and padauk can be finished with tung oil and will hold up well lasting a very long time. Personally my favorite woods to use are teak, padauk, mahogany and sapele. A great source of information on wood properties is the Wood Database.

When I'm purchasing wood I will look at as many pieces as possible until I find the one with the straightest and tightest grain pattern. Boards with this grain pattern have the tendency to be more stable and are less problematic when it comes to wood movement. Wood movement can happen every time you cut or mill a board. You will see this happen occasionally when you cut thin strips of wood off a larger straight board. You cut a nice thin straight strip on your tablesaw only to see it turn into a banana shape within a matter of seconds. 

Wood preparation, milling etc.

The wood I buy from my supplier is "Rough sawn."  The edges and entire surface of rough sawn lumber is rough! The boards are not perfectly flat or square either. To prepare a rough sawn board you must flatten each face and make sure the sides are straightened.

The first step to get wood ready for use is planing and flattening. Before planing I always let the wood sit in my shop for a few weeks so it can acclimate to the environment. Changes in humidity levels can cause wood movement (warping, bending etc...).

I'll start by cutting my board to a length that is a couple inches longer than what I want my final blank size to be. Next, with a straight edge I check to see which side of the board is flattest. I look for imperfections like twisting or bowing. Normally you would use a jointer to flatten one face of a board and then run that board through a planer to flatten the opposite side. My jointer is only six inches wide and the table isn't quite long enough to handle the heavy hardwoods I've been working with making spearguns. Luckily my planer, used with an adjustable sled can handle the job. I made my sled from a plan in "Shop Notes" magazine (now going by the name Woodsmith). The sled is a torsion box with adjustable supports. When set up correctly the flat surface of the sled is transferred to the top of the board passing under the cutter. I take very light cuts on the board checking it every few passes. When it is flat I run it through the planer with the flattened side down taking light cuts again until both sides are flat. If you think you might want to go this route and don't have the time or materials to build an adjustable sled you can do it on the cheap by using a melamine shelf and some shims hot glued below your board so the pressure rollers from your planer don't push the board down while cutting. See here.

Above: Planer, sled and 8/4 padauk being flattened.

After flattening the faces of the board I straighten the sides with my tablesaw and a sled. This is normally done on a jointer but I prefer using the tablesaw/sled combination for this task. The sled is very simple. I use a long melamine board which has a nice straight edge on it and secure my lumber to it with hold-down clamps. These knuckle clamps from Woodpeckers are great for this job. The straight edge of the melamine sled rides against the tablesaw fence and is then transferred to my lumber. I take a super thin rip off the edge to waste as little wood as possible and then remove the board from the sled to take a thin rip off the other side to complete the job.

 Above: several pieces of hardwood after straightening and flattening.

Cutting Laminations (lams)

The next step is to cut the thin strips which will be glued together to make the speargun blank. Laminating can give the wood assembly more strenghth and durability than that of a non-laminated wood stock. Below you can see a bunch of lams I cut from the boards I flattened. Ripping thin boards creates a lot of dust. Even with a dust collector hooked up!

I have more shop time in the winter months so it's usually around the end of the summer and early fall when I make a bunch of blanks to keep me busy during the winter. The temperature is better this time of the year. I live in the northeast and while my basement stays at an ok temperature during the winter (mid-60's) there are times when we get super cold and it can go a bit lower than that. I like to have my blanks fully cured before those really cold days arrive.

As far as how wide or how tall to make the laminations there are no hard and fast rules, obviously you will want to consider the dimension of the blank you will be making and then figure out how to make your cuts. Also consider how much wood you have to work with. For me I usually shoot for a lam width of 5/16" to 1/2" thickness that is 2 to 2.5 inches tall. 

One important rule to follow is the orientation of the grain. When cutting the lams be sure that the grain is running vertically. The picture below is a slab of 8/4 padauk that was flattened and straightened. What you wouldn't want to do is lay this board flat on the tablesaw and start cutting strips off it to glue back together. If you did that the grain on your lams would be running east to west instead of north to south.

What I would do first is rip a section off of this board (width determined by the height I want my lams to be) and then rip the lams from that board making sure I have positioned it with the grain in a vertical orientation.

After a bit of time pushing wood through my tablesaw I have a nice supply of lams; teak, padauk and mahogany in the photo below. I use a thin rip guide on the left side of my blade to speed up the process of cutting lams. The guide allows me to cut a lam, then position the fence without stopping the saw and taking measurements.

I will be making mixed wood blanks for single and double roller guns. These guns have a "cuttle" shape. Narrow at the front tapering to wide in the back. The blanks will be in the neighborhood of 3.25 to 3.5 inches wide 2 inches tall, and 55" long. How I assemble the blanks will be based on grain direction and the direction of any bowing that may have taken place after ripping. The images below illustrates some of the do's and don'ts of laminating.

This image is showing the correct way to orient grain direction and how to offset tension in the wood that causes bowing.

The below image illustrates how not to glue your wood together!

Now that I have a bunch of lams cut up I will let them sit for a day or two so they can stabilize. After the short wait I start sorting through them. There might be some I don't use at all if they are severely warped or twisted. Once I've picked through them I start to organizing the lams into blanks orientating the lams in the position that I will glue them in. 

Making Blanks!

Now that I have the configuration of each blank all set I will get to gluing the lams together. The first thing I do is take a permanent marker and label each lam on one end of the blank so I know exactly how to assemble it once I've mixed my epoxy.

Before the glue-up there are two more things I like to do . The first is to take some heavy grit  (60 or 80) sandpaper and lightly go over each surface that will be glued. If there are any saw marks I like to sand them down just a touch. Some guys will send the lams through their planer taking a very light cut from each side. This most definitely does a better job than the light sanding I do. Some guys don't sand or plane. This is another one of those things where if you get the important stuff right probably won't make a difference in the longevity of your speargun.

After lightly sanding each lam I take a rag or paper towels soaked with acetone to remove any oils or sanding dust that may remain on the wood. A cleaner surface will help the epoxy adhere and bond properly.

With the lams cleaned up I let them sit for a little while to make sure the solvent has fully evaporated from the wood. I then get them organized in the proper layout according to the numbers I labeled them with.

The Glue-up

I glue my blank together on my workbench. My bench used to be perfectly flat 5 years ago when I made it. Over the years it has developed some uneven spots. There are high spots created by glue and epoxy drips that need to be scraped off, the whole top needs to be flattened again. To avoid the several hour job of flattening my bench I now just put a piece of melamine on the bench top so my surface is totally flat and when I tighten my clamps. The melamine board is covered in wax paper to prevent the blank from sticking to it after the epoxy cures.

I use two pieces of angle aluminum, one on each side of the outer lams. These metal pieces are also covered with waxed paper. After the blank is glued up the angle aluminum is used like a clamping caul holding the blank together as clamps are tightened every six to eight inches or so along the length of the layup.

West Systems epoxy is what I've been using exclusively to glue up my blanks. 

Make sure to follow the mixing ratios on whatever epoxy you decide to use for your glue up. I use a scale for this purpose and mix by weight.  With the West Systems epoxy I also use an epoxy thickener which helps to fill voids and create a better mechanical bond between the lams.   

Once the epoxy is mixed I will have my blank on the wax paper ready to be glued. I do two surfaces at a time. I'll start by running a bead of epoxy poured from a dixie cup along the length of each board.

Next I will use a disposable paintbrush to paint the entire surface with an even coat.

I continue with this method stacking lams in the correct order of my layout

Once all surfaces have a layer of glue on them I turn them on side and clamp them up

I'll usually start with one clamp dead center

then, systematically start adding more clamps gradually tightening. I use the small mallet and a piece of scrap wood to gently tap across the top of the blank. As clamps are tightened sometimes a lam will get raised slightly. The clamps do not have to be excessively tightened but you don't want them loose either. If you have good coverage with the applied epoxy you will see epoxy squeezing out between the lams. This is normal.

Once all the clamps are tightened and in place the blank sits for a minimum of 24 hours while the epoxy does it's thing.

Final steps:

After the epoxy has cured and you have released the blank from the clamps it will look like the blank on the left side of the image below. At this point I install a small hook in the end of the blank and hang it for no less than a week.

Hanging the blank is important because it eliminates any external stress on the wood. If you were to unclamp your blank and then lean it at an angle against a wall, or leave it sitting on an uneven surface the weight of the blank itself could cause deformations while the epoxy was still curing. Hanging it reduces the chance of warping etc. 

Referencing the photo above, there are a couple of ways you can get the blank on the left to look like the one on the right. All that squeezed out epoxy must go. On small blanks I will put the blank on the same sled I used previously to straighten the edge of my rough cut lumber. It's quick and does a really good job of cleaning up the edge of the blank. One pass on the tablesaw usually does the trick. The opposite side is done without the sled since the first side is now straight. You can use this same method to straighten a blank that has warped while curing. Blanks like the ones in the photo above are too tall for the sled so I run them along the fence without the sled and then flip end over end making a second pass on the same side.

The blank will look something like the one below after the first pass because the saw blade is not tall enough to reach the top of the blank.

After flipping and taking a second pass you will have a surface like the one below.

I'm sure there are guys who would use their planer before using the method I've described but for me in my small shop it's just more convenient to go this route. Once I've cleaned up the cured epoxy squeeze-out I use digital calipers to take measurements along the length of the blank to make sure there are no drastic variations in thickness that need to be corrected. If correction are needed I will usually repeat the process described above taking a very light cut off the blank and then re-measuring. If you ever get into a jam and things got so bad to where you had to remove more material from the blank than you would have liked you can always add a horizontal lam and make a "T-Lam" blank.

The photo below shows a smaller blank. This was the first blank I made from the battleship wood. Notice the horizontal lam across the top. This is what is referred to as a "T-lam." Adding this horizontal lam across your vertical lams will create additional stiffness in your blank. It's also a way you can salvage a blank that has become too thin if too much material was removed during the final cleanup phase. 

Blanks that are waiting to be turned into guns stay hanging from the ceiling until I decide to use them.

I hope this write-up helps you formulate a plan of attack towards making your first blank, or gives you some ideas on how to improve your blank making endeavors. Feel free to comment or eMail me with any suggestions on things you think I could do to improve my process as well.