The DeeperBlue.net Gun Building Extravaganza - The Build

Hello spearos!

Firstly let me say what a pleasure it is to have been invited to take part in this venture. I believe that this is the first time a spear gun has been built in this way. When I was first asked about this I wasn't sure it could work but you gang look to proving me wrong yet again. Your imagination is the only limit to what we shall end up building together, so I hope to see plenty of discussion to come. Please if you have any ideas that might be built into this new gun then speak up early so you all may discuss them together. It does not matter how small and idea or how insignificant it may seem, from small acorns do mighty Oak trees grow. Remember I am only the hands controled by your collective input.

Let us begin then: I have been informed that you all decided on Burmese Teak and Brazilian Purpleheart as the timber of choice. This is quite a good choice, the Teak and the Purpleheart have quite similar physical properties so they will expand and shrink at similar rates. This is good if we are going to mix woods, otherwise we will end up in the future with steps along our gun or even worse in extreme cases total de lamination. Armed with this knowledge I took the drive out to a lumber yard where on a normal day is held a huge stock of Teak as well as a small selection of other tropical timbers. As luck would have it on this day we were faced with a tiny stock of teak on the racks as shown in the photograph below. The boards that were available unfortunately were much to big to buy just to make one gun. They also displayed some very erratic figure which is not what we want for our gun. After some time moving and inspecting these boards it became clear that things were not getting off to a good start. At this point in time I was feeling a little despondent, Teak is not the easiest timber to find and not the cheapest of timbers either. The lumber yard owner was unwilling to rip off half a board for us to use the best half of the board so it was beginning to look like we would have to go further afield to source our material.

If we had been building furniture then that timber would have been just what we would hope to find, large clean boards of attractive Teak. Our gun needs the exact opposite, very plain straight figured wood, simply put, very boring. Why is this we may ask? To explain why we must think about the tree from which the timber came from. It grew from its small beginnings having to put up with a prevailing wind, it had to grow differently in places to support heavy limbs. All these things define the tree itself, all these things are held in the tree's memory when it is cut. We must imagine how much strain was put on the trunk while supporting that heavy limb. When we cut that tree into planks or strips some of those stresses will be released, mostly very quickly but some will be released over time. From this we can see that straight figure in the wood generally will mean less stresses and a straighter finished product.

This was my dilemma, the wood was not good and at $250 £128 €165 a cubic foot it was a disaster. Never one to dwell on things like this I turned on my heels toward the doors only to come face to face with some thin strips of 3/4" x 2 3/4" x 98" or 20mm x 70mm x 2500 very straight grained quarter sawn Teak, exactly what we were looking for! This had by the account of the yard owner been there for some time, excellent news for us as it means that all the stresses that would have been released at the cut have now dissipated and we do not have to wait for this which moves on the build very nicely by a few weeks. See the second picture for the Teak as I found it. The wood was too long to fit in my car, so I had it cut into 1500mm and 1000mm pieces as can also be seen below. Also to this we have acquired a nice piece of Purpleheart more than enough for our needs. Again this is very straight figured.

Now for the next week this timber will be allowed to acclimatise to my workshop before we proceed with the next step which of course will be the machining and gluing into our fledgling gun.

See you all next time spearos!

Hello spearos!

Thank you very much for your warm welcome to deeperblue.net.

Blaiz this is a very important consideration when making any construction in timber. A symptom of modern life is the loss of the very basic knowledge due to the new ways we are finding to learn new skills. We might consider the huge advantages of modern adhesives when we construct something. Without careful consideration however we might tend to ignore the simple fact that out timber will move in one direction through atmospheric changes quite considerably but hardly at all in another. This could or possibly more accurately terminate the masterpiece through catastrophic failure. Something the most lowly village carpenter who learned his craft from an experienced master would have known to avoid and consider a better method of construction.

Moving back to your question I shall try to explain. Yes we shall we reversing the patterns of the timber in every direction. Once the timber has settled down and de-stressed it can be finally machined straight, usually this is done over many stages to let the stresses fully dissipate and allow us to keep our components straight. So if we rebuilt our laminates in the same order as they were cut from the tree we might well be lucky and the gun keep straight. This is more possible with very straight figured timber such as we have been lucky enough to find. With some of the more decorative timbers it is less likely to be this way and mixing up our laminates disperses any small stress points evenly over the job or even to reverse them.

Something perhaps I could have explained better in my first letter would have been the choice of grain cut on the timber. If we consider a simple plank of wood, over time as it either dries out or gains moisture from the environment it will breath so to speak and change size much as our chest does as we breath. The wood does not move evenly in every direction, along the length of the plank or it's long grain it will hardly move at all. Referring to the drawing below I have tried to show the possible views of the end of our plank. Can you see how here on the end grain of the wood that the major direction of movement is in line or following the growth rings of the tree not in the radial direction which is somewhat less. This is why if a freshly cut log will split if left to dry. Hopefully you can now see why the quarter sawn plank or board is less likely to warp or cup than the through or plain sawn plank. Holding this information fresh in our minds I will explain more carefully the choice of our timber. Teak actually changes its dimensions at a greater rate than the Purpleheart in a given direction. It so happens that the movement of Teak radially is very similar to that of purpleheart in the direction of the growth rings. I was lucky enough to find a piece of Purpleheart that must have come from a very large tree and its growth rings are almost in a straight line along the end of the plank. So our lamination will now take a form similar to =||=||=. I hope this will prove to be a very stable arrangement.

Now to continue with some questions for you. This weekend we will be machining our laminates to size for gluing. There is information I need to know before this is done.

What do we know?

1. The gun will be made up from 5 main laminates.
2. The gun will have an enclosed track
3. The gun will be a 90cm model

I would like the finished blank to be 50mm x 50mm x 1500mm

This is what I need to know: As we are having the enclosed track, how are we going to make this track?

• Do we use some Derlin and make our own?
• Do we incorporate some metal or plastic tubing into the blank?
• Do we cast our own Graphite/epoxy track?
• Do we machine it straight into the Teak centre laminate?

I would like to read some discussion of this if you could help me out on this. Try to think how these options will look from above and about the practical merits of each. Any other ideas you may want to put forward feel free.

See you all next time spearos!

Hello again spearos!

Lockedin, your point about using grain opposed at 45º is again a good one. If we had chosen a single timber then yes this would be a very good solution that would help disperse stresses evenly. In our gun here we have a very different situation. This has been my attempt at solving the problem of mixing different timbers, by using them in such as way to avoid different rates of movement that would eventually be the cause a step in the join between the woods, or even worse future de-lamination. Timber that has its growth rings running in such a way is also at its most stable which is another of those desirable attributes of a speargun.

I like your signature Lockedin, it is a true statement indeed.

See you all next time spearos!