Re: letting buoyancy chambers breath?
- I have only seen the need to vent air chambers on 1 type boat, the Olympic Class Tornado built by the Gougeon Brothers in the mid 1970's. In the first Tornado they build there was an expansion failure when the air in the hull heated up and broke/sheared a piece of blocking at some cross bracing deep inside the hull. These boats were built so precisely no inspection ports were installed at the factory because they didn't leak. The solution was a very small aluminum vent alum tube, 1/16 ID, installed and hidden inside the front beam so the air pressure could equalize. The tube was considered so small that in the event of capsize the hydrostatic pressure could not overwhelm the air pressure inside the hull.
When inspection ports were installed later we took to "burping" the hulls by opening the inspection ports to equilize the air after the boat was launched. We were carefull to do this when the boat had been sitting in a hot parking lot and then getting tossed into really cold water like Lake Ontario. This "burping" helped the air chamber vent do it's job faster.
As for my homebuilt Goat Island Skiff and Hapscut where my hatches are homebuilt and are nowhere near as tight as a Gougeon built boat, I don't worry about it.
--- In Michalak@yahoogroups.com, Curran Bishop <curranb79@...> wrote:
> I was talking to a guy who was admiring the AF4 and he said he had built
> fiberglass johnboats and warned me to make sure the buoyancy chambers had a
> means of breathing. He pointed out that with the way I have mine set up
> with pop-out deck-plates to keep them water-tight the sun hitting the sides
> of them can heat the air inside and make it expand, compromising the seams
> of the chambers. While I store and transport the boat with the deck-plates
> open, there is still opportunity for heating when the boat's in use - how
> serious a concern is this?
> I've been thinking something along the lines of a 1/8" hole on the boat's
> centerline, above the deck-plates, running at an upward angle as it enters
> the chamber (so that water splashed on the hole will run out and not enter
> the chamber) would be the simplest solution...
> Thanks all,
> Curran Bishop
> " 'Round our boat be God's aboutness,
> 'er we try the depth of sea,
> egg-shell frail for all her stoutness
> unless Thou her helmsman be."
> -- Old Scottish Prayer
> [Non-text portions of this message have been removed]