fill speargun barrel with some foam

It has to be dense foam that won't crush at depth. I think at least 4lb? You can buy it here Urethane Foam , Expanding Marine Polyurethane Foam. The dense foam will make your gun heavy. Plan your pour carefully as it expands fast.

You can also look into this stuff http://spearfishing.world/spea…un-building-material.html

So is the weight of the catalyst and the base the same as the resulting foam? I want to reinforce my tandem kayak but I don't want to add too much weight.

Any ideas?

You don't have to worry about a kayak being taken to depth, so I think the 2lb foam should be good.

You could fill the tandem kayak with empty water bottles if you want to avoid adding much weight, assuming you have a large enough access hatch of course. The money you save on expanding foam you could spend on stubby holders (Australian for Beer Cosy?) so that they don't make too much noise.
I imagine the kayak would be a write-off if the expanding foam were to become water logged.

It i closed cell foam so I don't expect it would ever water log. I have it in my lifeguard can and have not experienced any water

Thanks Dan. Great point.

Water bottles is a good idea too!!

Why a high density foam? At what depth will a barrel crush?
Why not just use a barrel plug (Speargun Tube Rubber Plugs) in front of the place where it will be drilled?
Let us know what worked

Quote from LunkerBuster

So is the weight of the catalyst and the base the same as the resulting foam? I want to reinforce my tandem kayak but I don't want to add too much weight.

Any ideas?

Pool noodles.

Seriously, they're very cheap and easy to insert into your kayak. Cheap insurance.
I know a lot of kayak fishermen who have their hulls stuffed with a bunch.

Undersea, when you ask for advice it's better if you explain what you're doing, so people don't waste their time giving you advice. Foam will not work for what you're trying to do. You'll need a solid plug or epoxy plug to hold a screw. And you'll need to seal behind it to prevent water from coming into the tube.

Quote from Undersea

ok hombre el problema es que me cuesta trabajo explicar en ingles lo que quiero hacer o decir ,es simple lo que quiero es fijar el tubo a la madera con tornillos tirafondos ,queria rellenar el tubo con espuma waterproof,lo que dices de sellar los agujeros con epoxy no se como hacerlo,podrias explicarme en españool si no te es mucha molestia?ya se que mucha gente no gasta su tiempo dando explicaciones o ayuda,bueno yo solo pregunto el que quiera qe me ayude y el que no bueno es su problema .

Bueno ahora los de habla hispana si te entendimos bien, y a ver que contesta Dan que por lo que te puso entendió otra cosa, tirafondo es de lado a lado (al final tuerca?).

Aun que por respeto/ educación lo mejor (apropiado) sería en los idiomas para los no hispano parlantes:)

Dan te comenta que el foam no es /sirve para fijar los tornillos y que tendrías que sellar el tubo antes de los tornillos con un tapón, si la espuma esa está garantizada para no absorver agua podría servir sin un tapón o sello de otra manera absorviendo agua, será jodido retirarla y reemplazarla por otra cosa.

Saludos y buen azul.