Laminating question

[JCooke]

Has anyone ever entertained the thought of laminating under vacuum or under pressure for penetrating the wood?

 

[Old Man Dave]

I used to make skate boards by laminating in a vacuum press. Have used a few vacuum bags as well. Never tried it on a gun. Laminating wood in a vacuum is usually reserved for working with thin laminates (2mm or less). They can be hard to clamp especially in a curve. Vacuum applies even pressure. Vacuum bags are sometimes used in carbon fibre construction but never tried this. As guns are made from a few relatively thick laminates glued more or less straight i don't see much need for a vacuum system but there is no reason why you couldn't use one.

Dave

 

[JCooke]

Well just thinking that on my first build im guessing there might be mistakes so Im opting to use oak ($ and availability)and go with more and thinner layers. Im playing a few ideas solid wood or wood upper section with a V shaped aluminum support truss on the under side running the length with a few bells and whistles attached that might help. Looking at 60" big water gun.
There are so many comfiguration..it endless.

 

[JCooke]

Is there a golden number when it comes to laminates layers.

 

[Old Man Dave]

Huge amount of info on homemade spearguns but to get you started this is one I had a hand in and although it's a few years old it still has some good pics. http://forums.deeperblue.com/homemade-spearguns/63452-teak-80-part-one-stock.html

Dave

 

[blaiz]

Is there a golden number when it comes to laminates layers.

I dont think there really is a golden number. Just depends on how much time you want to put into it. Some builders dont like laminating at all. I just built a gun with 5 laminates. My original plan was to put a t-laminate on it as well but opted out of it. Ive seen plenty of guns built with only 3 laminates as well. I think the odd number is best that way you have solid wood in the center of your track though im not sure that even makes a difference.

 

[JCooke]

Thank for the info, this leads me to the next question. For just a base referance (square stock laminate to make it easy)has anyone ever tested the size,type,and number of laminates of wood=to number and size of bands to safely have enough strength in the barrel. I want at least 3 or 4 5/8 bands on my big water gun.

 

[settingsteel]

Lot of variables in your question. Foremost is type of wood- at 3-4 bands a 2X2 block should suffice. As for the vacuum lams as already mentioned its overkill as most poxies will penetrate via chem. reaction anyways. I've been tinkering with "thinness" of guns and have noted after 1.5" you need to consider adding another material (in my case Carbon fiber) to prevent flex, then again the guns I make have a double taper which also has a great influence. Good luck on the build!

 

[Old Man Dave]

Thank for the info, this leads me to the next question. For just a base referance (square stock laminate to make it easy)has anyone ever tested the size,type,and number of laminates of wood=to number and size of bands to safely have enough strength in the barrel. I want at least 3 or 4 5/8 bands on my big water gun.

I wouldn't worry about strength. It's far less relavent in a big gun. Small guns are often made thin for good tracking and even though only single band strength is an issue. However, big guns need mass to absorb recoil. If you make your gun too thin and light you'll never control it, so make it "massive" and kill 2 birds with one stone (strength and mass-defeating recoil).

A good base for your project would be to have a look at the book Blue water Hunting by Terry Maas. Theres quite a bit of info on big gun design and its a great read as well.

Dave

 

[foxfish]

Well just thinking that on my first build im guessing there might be mistakes so Im opting to use oak ($ and availability
There are so many comfiguration..it endless.

Oak will work but a 5' long gun will be heavy & oak is not the easiest wood to work with either.
I know you said teak is not readily available but what about something slightly less dense than oak..mahogany or mahogany substitutes like utility, perhaps you can find out what other hard woods are available?
However if oak is the only one at least it glues up nicely & is very strong.
I have built a couple of guns with a backbone made from 2mm T section ally,I note you are an engineer so working with metal might not be a problem for you?
Would i be right in thinking those big halibut will be lying on the bottom when you shoot them? If this is the case then long range wont be an issue just the power needed to penetrate the fish?
What happens to the gun once you shoot the fish, is it attached to a float?
You will definitely get plenty of support from us if you need it as there are only a couple of gun build going on here on db at the moment.

 

[settingsteel]

Small guns are often made thin for good tracking and even though only single band strength is an issue. However, big guns need mass to absorb recoil.

I agree, but if you get to the nitty gritty idealy a gun that is narrow, that will also absorb recoil is the BEST gun...unfortunately attaining this design in an all wood gun is tricky, I add carbon fiber both b/t the lams and in the belly, this lets me trim size off while maintaining rigidity, seconldly I taper it (front to back & side to side). I ballast it correctly, and add 2 small narrow "wings" along each side...this allows me a very accurate (enclosed track), fast tracking (narrow), shock absorbing (ballast/wings) BW gun...food for thought- if your making it, might as well tweek it right:martial

 

[JCooke]

Thanks everyone.... another thought I haven't seen anyone use the water to absorb the recoil.... optimize fluid drag and keep necessary movement. Or evan a second handle maybe a power drill configuration.