(The comments on SAM technology are appreciated, and provide an opportunity to open a dialogue on this subject, to provide more detail and information, and to clarify some of the finer points. The first thing to note is that all of the SAM designs which have been published have been field tested, so far with good success. What happens over extended periods of several years is not yet absolutely certain. You will be advised of problems if and when they come to light.)
The following is the text of the technical concerns raised by robert.pogson@mwcs.mb.ca. (Comments in brackets are the reply of the developer.)
The FFFSAMn.GIF files are interesting but I do not believe they are universally applicable. I am a welder and shooter so I know a little of both technologies. The corrugated culvert material is not sufficiently waterproof in wet country. There are usually dry riveted seams which are not intended to hold back a head of water. At the least, these seams and rivets should be welded to reduce leaks.
(Use the rivetless culvert made by Spir-o-lok. This uses a folded force-fit seam which in most cases proves to be watertight. As mentioned in the SAM instructions, it always pays to check by filling the container with water, drying it out and sealing any leaky seam with silicone caulk, though in most cases this will not be necessary.)
Welding galvanized metal is dangerous as the zinc vapour is hazardous. The recommended procedure is to use E6011 or E6010 with a whipping motion. The blast of gas from these electrodes can scrub the metal free of zinc as you go. One pauses in the puddle, backs out to the edge of the puddle and pauses til the original puddle begins to freeze, then reenters the original crater but not all the way in. By repeating this cycle, the zinc is periodically scrubbed from the steel shortly before one welds the steel, advancing in steps of 1/8" or less. As you can imagine, this is tedious and requires skill for all the undulations of the culvert's surface and around rivets. I don't recommend it.
(Agree - but we didn't have to weld the long seam, just the butt plate and steel ring which didn't take that long. We used a hydrogen weld. All heated surfaces were then treated with metal primer, metal paint and auto-body undercoat, as mentioned in the instructions.)
While it may not be as readily available as culvert, I recommend steel pipe if you can get it.
(Agree. If you can get steel pipe, use it.)
For the seal around the top, I would recommend welding instead of sealing with caulk for very long term storage.
(Certainly a long-term solution. But various sealants of varying quality will last 10 - 35 years. Also, the particular SAM design you refer to is an operational design primarily for short term storage. If you are interested in long term storage, use one of the other designs that is recommended for this purpose.)
Most farmer-welders would be surprised how difficult it is to make a waterproof weld. Pressure welders practise for years before getting a trade ticket. Of course, most of these objections could be overcome by installing the SAM in a tarp and placing in very well drained soil.
(Site selection is important, in some areas more than others. Also, use the plastic oil barrel design if you are not able to weld. It is as good as any of the others, or better for some applications.)
Where I live, water tables rise to near the surface several times each year with spring runoff and thunder storms.
(Water tables are a concern. Careful site selection is advisable for a number of reasons, also for ease of digging. In your swamp, consider placing the top of your SAM near, at, or above ground level, then piling up the dirt and adding moss and/or brush over the top as camouflage.)
There is probably a military person on the net who could comment better than I how firearms should be stored.
(Already done. Plus gun dealer input. Commercial and military products are available. But quality common substitutes also are available, which was the intent of this particular project.)
I have seen many old firearms packed in grease that were as good as new, but I doubt any had been underground. Most would be surprised to learn that grease is not usually water proof.
(Proper desiccation is the key. The recommended desiccant works fine, but be careful not to spill any since it is a salt and could corrode gun metal if it comes in direct contact. Special purpose non-corrosive desiccants are available. See your gun dealer.)
It is usually a mixture of soap and oil. The oil excludes air and water to some extent and the soap renders the mess somewhat basic as opposed to acidic to prevent rust and binds the oil so it will not run off over time. Soap is commonly used to remove oil from hands by binding to both oil and water so I believe most greases will dissolve and separate in water, so a flood would be disastrous for a SAM unless the shell were perfectly tight.
(Agree. Perfect sealing is critical if there is any possibility of flooding. Don't use just any old grease, rather use the synthetic autolube as recommended in the instructions.)
Another problem is buoyancy. The SAM will tend to float unless packed tight with sand or earth. Frost heave (the phenomenon that makes stones appear to "grow" out of the ground) could lift a SAM, I think.
(As mentioned in the instructions, frost heave could be a problem, over time. If you make the bottom butt plate out of an oversize steel disk, it should help to anchor the SAM, if this is a concern. If anyone has experience with other approaches to anchoring against buoyancy or frost heave, let us know.)
Burial below the frost line for the bottom is essential.
(In most places in Canada, this would put the SAM too deep to be practical. Don't be spooked by frost heave. You might want to keep an eye out for its occurrence, and re-bury if and when it gets too bad.)
In the north this would be a problem. We have a lot of stones here, maybe I could do horizontal burial in a stone pile.
(You are right. The SAM designs you have are designed for vertical emplacement. Watch for more information on horizontal containers, to be made available as soon as possible.)
(You swamp rats want a Manitoba Missile Silo, not a Saskatchewan SAM Site. To convert a SAM to a SILO, you are going to have to overcome significant buoyancy and frost heave as you quite rightly say. The buoyancy force can be resisted with an anchor or counterbalanced by weight. The maximum buoyancy force can be calculated on the basis of the weight of water displaced by the volume of the container. For an operational container 12 inches in diameter, that works ou to about 48 pounds per foot length, or 260 pounds for a 5 1/2 foot container. The most secure solution would be to bury a 260 pound weight some 12 feet deep (ie. under the frost line), with a 6 foot chain or cable attached to the bottom plate of the container. This will counteract both frost heave and buoyancy. Or you can cheat to varying degrees, with varying degrees of certainty. For example, accounting for the weight of the container itself and the fact that it is underground and not underwater, you should be able to get away with a much smaller weight, say 100 pounds or so. The weight doesn't have to be metal, it could be a bunch of rocks in a cable net or similar net. The weight could be welded or attached directly to the bottom plate of the container instead of at the end of a deep chain or cable. The flatter the weight, the more it will function like an anchor as well as providing weight.
(The result of the above certainly would be satisfying. Who could ever find your guns in the swamp? But it could also be a lot of work. Careful site selection can save a lot of time and effort.)
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