 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsBoatsPaddle BoatsSailingCruisingBuildingElectronics Related Topics CarsMotorcyclesMore Topics ... |
Boat Forum / Cruising / October 2004better RO water system for cruisers
Most RO systems work by pressurizing water against a membrane that only passes fresh water. Pressurizing and the pumping is done either electrically or mechanically from the engine. This involves running the engine. I imagine you could do it by having the prop turn your alternator as you sail or use a towed generator behind the boat but the efficiency of turning motion into electricity and then into motion to produce pressure may be low. I propose to use a variation on the old hydraulic ram pumps to directly produce pressure from the boats motion. HYdraulic ram pumps use the momentum of falling water to force a small part of the falling water to a higher level than the water falls. In other words, if your water falls 20', you can pump a very small portion of it to say 50' higher without any electricity or engine. Used on a sailboat, the momentum is not produced by falling, but simply by the boats motion produced by the wind. This directly produces pressure in a small portion of the water against the RO membrane. Of course this produces drag but with proper design the drag can be varied thus enabling the user to produce more fresh water in a lot of wind. Havent done th ecalculations yet but it may be reasonable. >in a lot of wind. >Havent done th ecalculations yet but it may be reasonable. Tell me again why you are hesitant to go long-term cruising again... With all the clever if untested notions you come up with I would suggest a 45 footer pilot house. The pilot house will be the saloon. The saloon will be the work bench/test bed/micro-foundry. All socializing will be on deck as you...Captain Frankenstein...build the perfect labour-saving gadgets for budget-conscious cruising. The V-berth will hold 500 lbs of tools. And you and the missus can sleep in the back. Now, you can't tell me that's not an attractive plan. R. >The pilot house will be the saloon. > [quoted text clipped - 5 lines] > >And you and the missus can sleep in the back. ====================================== Don't laugh, I once saw a 60 footer that was rigged out just about like that. The welder was in the pilot house and all construction material too large for the V berths was under a tarp on the foredeck. Not pretty but very functional. >Don't laugh, I once saw a 60 footer that was rigged out just about >like that. The welder was in the pilot house and all construction >material too large for the V berths was under a tarp on the foredeck. >Not pretty but very functional. Except for the raised CG, I would imagine. Actually, that layout has some appeal. November's Cruising World has an 83 foot pilothouse cruiser that just sleeps four, because the owner is realistic about how many crew he's ever going to have and because he's rich enough to have a skipper and mate as permanent employees. The workshop is to drool over, I swear. Although I would likely design something in the 40-45 foot range for myself (if I won a lottery, say), I find the idea of a larger work/cargo space and a more compact saloon appealing. "Cozy" is safer, too. R. > >in a lot of wind. > >Havent done th ecalculations yet but it may be reasonable. [quoted text clipped - 17 lines] > > R. That actually crossed my mind a while back. I have a Prazi jewelers lathe/mill that I considered putting in a Gulfstar 42 and cruising and just making weird things. However, then I realized that I am really terrible at making "pretty" things. Everything I make has lots of duct tape, hose clamps and gouge marks all over. In real life, I have realized that it pays to pay people who do that sort of thing so i have two very good machinist/instrument makers. They look at me like I am crazy when I explain what I want, but I think they like the challenges. My designer walks away shaking his head but returns a few days later with a way to do things. My engineer and physicist joke that they will lock up the electron microscopes for fear I turn em into "Frankenscopes". It would be tough to have this sort of great relationship with these people long distance and working with them is a real joy. However, then I realized that I am really >terrible at making "pretty" things. Everything I make has lots of >duct tape, hose clamps and gouge marks all over. Same here, although I managed some nicely symmetrical woodworking on deck this year <G> I think you can justify a nice workspace if your cruising plans include providing a small business service on board. People who do sail repairs are always popular in remote anchorages, and converting the V-berth to a sewing room makes a lot of sense. A machine shop, albeit a small one, is doable on board, with the biggest obstacle likely power, not space. I believe there is one cruising dentist who pays for his continuing travels by tooth care for both cruisers AND locals. He apparently has the full dental chair bolted in his gutted V-berth! Now, that's a type of genius, although you'd have to be very careful about stowage. I have no idea what he does for X-rays. R. This might work from an engineering perspective, but from a usability standpoint it misses the mark. Many cruisers stay for extended periods of time at an anchorage and would run out of water because they haven't moved. Not acceptable. -- Geoff > Most RO systems work by pressurizing water against a membrane that > only passes fresh water. Pressurizing and the pumping is done either [quoted text clipped - 16 lines] > in a lot of wind. > Havent done th ecalculations yet but it may be reasonable. You *might* get 1 or two PSI from the ram action. You need about 3000! Actually you only need 800 PSI which is still way past what a ram pump can produce. There is a tow behind RO watermaker called the Waterlog that uses a small mechanical pump powered by a propellor. Though JAX claims them to be mythical I met two cruisers in the BVI who used them all the way from Gibralter and were very happy with their performance.  SignatureGlenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com > You *might* get 1 or two PSI from the ram action. You need about 3000! >There is a tow behind RO watermaker called the Waterlog that uses >a small mechanical pump powered by a propellor. Though JAX claims them to >be mythical I met two cruisers in the BVI who used them all the way from >Gibralter and were very happy with their performance. ============================ 72 gpd: http://www.watermakers.ws/ >>There is a tow behind RO watermaker called the Waterlog that uses >>a small mechanical pump powered by a propellor. Though JAX claims them to [quoted text clipped - 6 lines] > >http://www.watermakers.ws/ 50 gpd = $2 grand.... Brian W > Actually you only need 800 PSI You can certainly do it with far less than that. A home RO unit runs off the water line pressure, which is usually less then 75 PSI. > which is still way past what a ram pump can produce. There are always ways to convert a flow of water and one pressure to a lesser flow at higher pressure. You might have better output running a solar still, however. > There is a tow behind RO watermaker called the Waterlog that uses > a small mechanical pump powered by a propellor. There are a lot of instances of a towed electrical generator. It certainly would not be conceptionally difficult to convert it into a water pump. I can picture a small prop on a steel cable that runs up to a gear box on the transom rail. Enough gear ratio can turn the spinning cable into sufficient torque to generate just about any PSI you wanted. I would think that you would be better off to just generate electricity and then run the standard electric pump. Perhaps not as efficient, but much more versatile. Rod > > Actually you only need 800 PSI > > You can certainly do it with far less than that. A home RO unit runs off the > water line pressure, which is usually less then 75 PSI. Osmotic pressure is directly related to the concentration of salts in the water. Tap water has a maximum concentration of 200 PPM salt so that the pressure is about 10 PSI. Seawater OTOH at 36,000PPM salt and 68F has an osmotic pressure of about 376 PSI. That is just enough pressure to STOP the osmosis of salt into the low concentrate side. To REVERSE the osmosis requires more pressure. Generally double or about 750 to 800 PSI. (When you build your own watermaker you learn a lot of normally useless stuff. :-) ) SignatureGlenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.