Woodenspeargun - crack in stock, looking for advice

[Fisherik]

Hello spearos. I recently finished my third speargun build, where i used African Mahoganny with an oil finish.

Little bit info about the gun.

Its a litlle 80cm gun, with a laminated stock (only 2 pieces).

Used G-flex 650 for my blank.

I gave it 3 initial coats of oil, and oil every now and then if been used.

Everything has been fine, and it preformed well during first dives.

But under my inspection (i was admiring my creation), i noticed a crack, which seems to be paralel to the fibers.


Here are some pictures of the culprit:

The crack is about 1-2mm deep (eyeballing with a needle...)

I have been looking in the forum about solutions for similar problems, and found a few recommendation.

So at the moment i am considering:

1.
Sanding it down. But i doubt wether that would solve the issue? Or would it just be purely cosmetical to sand the crack away? I would be afraid of the crack maybe developing again later.

2.
The other option i have seen used, was to fill it with glue? I my case i only have some G-flex avaiable atm. which is very thick and could imagine it being difficult filling the crack completly.

I dont know if heating the glue prior to aplying it could solve that issue.

And i am by no means an expert in woodworking and usage of different glue - thats why i am hesitant to start, as i am scared of just removing the visible problem, but not actually stop the wood from falling apart

3.
Measure it and wait to see if it actually is getting bigger or if i'm being overprotective.


Hope somebody has been dealing with this problem before, succesfully that could share his/her insights.

Best regards

 

[Vitaly]

Not sure completely, but possible epoxy resin can be used to fill the crack

 

[musubi]

I'm no gun builder, but it doesn't look too bad to me. I would think using epoxy to fill would be fine, then monitoring after that. I'd be interested to hear what other gun builders suggest. Carbon fiber would be another way to strengthen the area if you can make it blend nice.

 

[Kodama]

As an experienced woodworker I can say that the options you propose are not great.
It is impossible to sand uit the crack. It probably is at least 10mm deep. Glue is a poor choice to fill it with.

As mentioned above epoxy is the way to go. Epoxy is thin and will run down to the deepest point in the crack. Fill it up completely.

However keep the following in mind. The fact that your stock cracked means there are residual stresses in the wood. Either it was not properly dried prior to finishing the gun or moisture enter the wood despite using oil.
If the wood is susceptible to developing cracks there is a chance it may happen again.

Make sure you always store it in a place that is not too dry. When the gun has been in the water best to make sure it doesn’t dry too quickly. Abrupt changes in moisture content will develop stress And the wood will either bend or crack. Always keep it away from direct sunlight.

Next time you build a gun use at least 3 layers. 5 is even better.

 

[Fisherik]

As an experienced woodworker I can say that the options you propose are not great.
It is impossible to sand uit the crack. It probably is at least 10mm deep. Glue is a poor choice to fill it with.

As mentioned above epoxy is the way to go. Epoxy is thin and will run down to the deepest point in the crack. Fill it up completely.

However keep the following in mind. The fact that your stock cracked means there are residual stresses in the wood. Either it was not properly dried prior to finishing the gun or moisture enter the wood despite using oil.
If the wood is susceptible to developing cracks there is a chance it may happen again.

Make sure you always store it in a place that is not too dry. When the gun has been in the water best to make sure it doesn’t dry too quickly. Abrupt changes in moisture content will develop stress And the wood will either bend or crack. Always keep it away from direct sunlight.

Next time you build a gun use at least 3 layers. 5 is even better.

Thank you for the informative answer. But sadly that is what i was afraid to hear - the wood being ssusceptible for further cracks.

I'll try filling the crack with some expoxy as you all recommended and probaly leave it hanging in the garage for a while. Maybe the oil finish wasnt deep enough since i did it during the winter time with temperatures around freezing point - dont know if that influences the penetration into the wood.

And definetly will try laminating with more layers next time - but as a poor student i probaly cut the corner at the wrong places.

Thank you

 

[mad mat]

Hi,
You might find epoxy will not bond well with the timber because it is oil soaked. I’ve tried repairing 3D bread boards that were constructed using epoxy and then soaked with butcher block oil. The repair never last. Cant quiet see from pic, but appear crack is in the middle of the gun. As previously mentioned, the flex of the gun might be exposing a defect in the wood. there are some flexible epoxies out there. Standard epoxy I recon will fatigue quickly and the crack will open up again.
An option might be to cut out the offending area completely with a router/drill and make it look like you designed it that way to lighten the gun. Just remove bare minimum. No one has said it yet, but you just might need to start again or you just made you first 500mm gun
Cheers
Mat

 

[Longhunter]

As an experienced bow builder I can tell you that, that crack is a recipe for disaster. Glues or epoxies will not hold, as has been mentioned before, the wood grain has absorbed oil. Almost all cracks are like icebergs, you just see a very small part of the problem. Failure will happen under stress and it's usually not pretty. Your best bet for both safety and looks is to start over. Experienced bowyers know that this is just part of the game and adds to knowledge. There is one upside, and that is that there is little uneven compression when loaded that takes place on a speargun like on a bow, so your gun could last for years, but it's a gamble. Best to do another build and enjoy the process. Good luck.

 

[blaiz]

as mentioned before, the epoxy will likely not bond to the crack due to the oil saturation... Does the crack run clear through to the other side? or is it a surface check? One option you might explore is cutting in a dutchman... Basically route out the crack and a little further each way, try to stay within the confines of that center laminate... (make a template and use either a pattern bit or collar on your router). Most of the tension and stress is going to be on your bottom and top lamanates, and by the looks of it you have plenty of meat to handle the two bands, even with the crack... the main thing will be stopping it from getting bigger.

 

[Gunsmoke58A]

As an armourer I suggest reinforcing the area with some threaded brass rod or stainless steel screws. It's how we fix cracks on rifle stocks and how my bowyer repaired my recurve bow. Food for thought.

 

[Longhunter]

Gunsmoke, what you say is true, and I have repaired one of my own guns the same way, but, a gun or a bow does not have to contend with being submerged and working in that enviroment. Excess moisture content is the enemy of both the gunstock and the bow. A speargun must live submerged and work that way, and under sometimes extreme external pressure from the water trying to penetrate. A repair would not be the best choice. Not impossible, but not the best.

 

[Fisherik]

Finally an update, life gets busy.

Thank you for all the following suggestions. I tried filling in some casting epoxy (only thing i had avaiable without spending alot of money). So fare the crack has been stationary after several trips. So fingers crossed.

Before filling the crack i tried to to som sanding and removal and used some mineralspirits, but it has soaked plenty of oil, so probaly not so effective. Anyhow we'll see if it

Might be worth to mention:

When making the blank i fitted af 50-60cm threaded stainless steel rod in the center - don't ask me why. Thought it was clever for stability at the time. (turned out almost neutral balanced - which i guess was a bonus ).


But as some of you suggested - i got a gun build in oak ready for coating and got my hands on some burmese teak - hopefully they will turn out better.

Cheers.

 

[mad mat]

The metal rod could have caused the crack. Wood swells and shrinks. It’s possible that the wood shrink Ed onto the metal until the grain popped. Just a thought.

 

[Fisherik]

The metal rod could have caused the crack. Wood swells and shrinks. It’s possible that the wood shrink Ed onto the metal until the grain popped. Just a thought.

Might have and if using stable wood it would be obselete anyway, so wont be trying anything fancy in next build. Just sticking with basics.