Why have a buoyant dinghy hull?

[poiu]

I had always thought it was a bit pointless. My Avon 4.0m dinghy has a buoyancy chamber in the hull and a three chamber tube. I didn't see the point thinking the tubes were enough, but now I get it. One of the chambers burst recently and it turned out that the internal baffle had failed, so the second chamber emptied too. Luckily this happened in flat water very near the main yacht. I didn't even get my feet wet and I was able to get to safety. If the hull had not been buoyant then I would have only had one side chamber to keep the dingy afloat. The hull would have sunk, the weight of the engine would have rotated the hull and the engine under water and I would have been sitting on a single tube section drifting and needing rescue. A real mess and potentially it could be realy dangerous.

I'm going to seriously think about getting a replacement with a buoyant hull or maybe with 5 tube chambers instead of 3. Ideally both.

[poiu]

It looks like there is no one doing a 5 chambered dinghy in small sizes. I can have new tubes made for just a little less than the cost of a new dinghy, which will have 5 chambers, but with the work to fit them it doesn't make a lot of sense. I think the buoyant floor will be enough extra security, so that's what I'm going for. An AB Navigo probably.

[KD8NPB]

Originally Posted by poiu

I had always thought it was a bit pointless. My Avon 4.0m dinghy has a buoyancy chamber in the hull and a three chamber tube. I didn't see the point thinking the tubes were enough, but now I get it. One of the chambers burst recently and it turned out that the internal baffle had failed, so the second chamber emptied too. Luckily this happened in flat water very near the main yacht. I didn't even get my feet wet and I was able to get to safety. If the hull had not been buoyant then I would have only had one side chamber to keep the dingy afloat. The hull would have sunk, the weight of the engine would have rotated the hull and the engine under water and I would have been sitting on a single tube section drifting and needing rescue. A real mess and potentially it could be realy dangerous.

I'm going to seriously think about getting a replacement with a buoyant hull or maybe with 5 tube chambers instead of 3. Ideally both.

Most inflatables are designed with a 10 year serviceable lifespan in mind.

Material doesn't last forever. UV / general degradation can lead to rupture and seam failure, which was probably the main source of the issue. The concussion of the sudden loss of pressure is likely what caused the baffle to fail (would not happen on a newer boat).

A much newer inflatable of quality construction would likely not have this problem.

[poiu]

Originally Posted by KD8NPB

Most inflatables are designed with a 10 year serviceable lifespan in mind.

Material doesn't last forever. UV / general degradation can lead to rupture and seam failure, which was probably the main source of the issue. The concussion of the sudden loss of pressure is likely what caused the baffle to fail (would not happen on a newer boat).

A much newer inflatable of quality construction would likely not have this problem.

I am sure you are correct. This is my understanding of the problem. The dinghy is 15 years old. I was surprised at the internal baffle failing as that sees no UV. The external failure was because the outer coating of the material had worn down and exposed the central fabric to UV. I expect it was UV damaged as the exposed fabric tore. If I had protected that area with a patch I would not have had this failure.

The main point I was making though was that the air chamber in the floor is a valuable thing. It saved my engine from potentially being destroyed by a dunking and me from needing a rescue.

[KD8NPB]

Originally Posted by poiu

I am sure you are correct. This is my understanding of the problem. The dinghy is 15 years old. I was surprised at the internal baffle failing as that sees no UV. The external failure was because the outer coating of the material had worn down and exposed the central fabric to UV. I expect it was UV damaged as the exposed fabric tore. If I had protected that area with a patch I would not have had this failure.

The main point I was making though was that the air chamber in the floor is a valuable thing. It saved my engine from potentially being destroyed by a dunking and me from needing a rescue.

Heat, oxidization of the adhesive, oxidization of the material, as well as hydrolysis from ambient moisture. Hydrocarbon fumes too. All things play in to the life of the boat.

Did the baffle unglue, or tear? On my 27 year old Zodiac FC470 that had been rode hard and put away wet by the US Military, when I lost a baffle, it unglued on the top (heat permeation through the topside), then when it reached a strongly glued spot, it tore.

FYI though, your boat is totally fixable once dry. It takes about 3-4 hours to do a baffle, and another 2-3 to do a large inside/outside patch, plus probably 0.5L of adhesive and a half square meter of material.

[poiu]

Originally Posted by KD8NPB

Heat, oxidization of the adhesive, oxidization of the material, as well as hydrolysis from ambient moisture. Hydrocarbon fumes too. All things play in to the life of the boat.

Did the baffle unglue, or tear? On my 27 year old Zodiac FC470 that had been rode hard and put away wet by the US Military, when I lost a baffle, it unglued on the top (heat permeation through the topside), then when it reached a strongly glued spot, it tore.

FYI though, your boat is totally fixable once dry. It takes about 3-4 hours to do a baffle, and another 2-3 to do a large inside/outside patch, plus probably 0.5L of adhesive and a half square meter of material.

I don't know what happend to the baffle. I took the view that if it had failed I had been sent a sign of imminent demise, so I patched up the tear to get me going until I could find a new one, which I have done, just a short trip away.

I agree the thing is fixable and I have repaired the main tear, but I have no confidence in it now. I have done several smaller repairs over the last two years and there are more than half a dozen bare patches to repair, plus after the baffle fail, I suspect the main seams are on their last legs. I don't want to ride like I am walking on broken glass. That's no fun. Hasta la vista baby. A 4.0m dinghy is going for cheap in Guadeloupe/Martinique.

[Bean Counter]

I wish Walker Bay (hard dinghy with inflatable tubes) would make one that could plane and take a 20 HP, and sail too