----- Original Message ----- From: "Peter Stockdale" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, September 22, 2006 3:36 PM Subject: [canals-list] Re: Drydocks for canal boats
> --- In [email protected], Adrian Stott <[EMAIL PROTECTED]> wrote: > > > >. > > > > > > > Steve, a Frenchman beat you to this idea by about 150 years. > > > > Exactly this system was used in the Pouilly-en-Auxois tunnel on the > > summit of the Burgundy canal. This tunnel was too low for unladen > > peniches to pass through, so such peniches were navigated into a > > floating caisson, which was then sealed behind them. Flotation > tanks > > in the caisson were then flooded , making the caisson float lower. > The > > caisson was then towed through the tunnel by an electric tug. The > > flotation tanks were pumped out, and the peniche released, at the > > other end. > > > > When I went through the tunnel about a decade ago, the caisson, and > > the tug, were still moored there, but I think they hadn't been used > > for many years and that the power cable along the tunnel roof > (power > > was picked up by the tug via a trolley-bus type arrangement, using > a > > rather worrying and low-hanging bare wire) probably was no longer > safe > > or workable. > > > > There's (almost) no commercial traffic over this summit any more. > > > > However, the system worked well, and may well be worth considering > for > > Froghall.. > > > > But is Froghall tunnel sufficiently deep enough to allow a caisson > to > > float low enough to make this work? And is it wide enough to > accept a > > caisson at all. > > > > Worth investigating, IMHO. > > > > Adrian > > > > Adrian Stott > > 07956-299966 > > Ah - yes - the concept develops . > Pump water IN not > > Quoting Steve - > > Suppose your boat floated into a tank which was quite > deep, say 5ft draught or so. The door is closed and the water pumped > out. The whole lot will stay afloat as some of the water has been > replaced by air, but the roof of your boat will be maybe 18 inches > lower, depending on draught as it sits on the bottom of the tank. > > Would this work...? > > not OUT ! > > The French method obviously worked and obeys Archemedes. > In the Froghall situation it would be expedient to sort out a > solution that requires negligible maintenance and no operatives > involved. > Doityourself caisson opetation not on !! > Only a change of tunnel height or tunnel water level seems to solve > the problem. The reason I gave a tongue in cheek reply last night was because Steve didn't mention Archemedes or ballast/flotation (sorry Steve). I can see the principle behind the French method, as stated by Adrian, which makes sense. However, that wouldn't work at Froghall, with water ballast, due to restricted depth and width. But, if the caisson was ballasted at the bottom with steel (8x denser than water) and with narrow side tanks tanks built in for flotation/ballasting fine tuning I could see it working in theory. However, as Peter hinted at, the whole arrangement might require a fully trained BW operative to work the paddles/pumps/valves etc. I have a fully functional drawing in my head - but no time to put it down on paper. Also, the only evidence I have of my last passage through Froghall tunnel is a broken aerial mount. Maybe it might be a cheaper option to have a crane at both ends and a supply of steel ballast adjoining the towpath. This could be hired out on a price per ton/daily rental basis :-) The next time I go to Froghall I will first check the stoppages list to make sure that no trials are taking place :-) Phil nb Lowcabin and loads of tumblehome Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/canals-list/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/canals-list/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
