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Dr Bob

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    316
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About Dr Bob

Profile Information

  • Gender
    Male

Previous Fields

  • Occupation
    Passed it
  • Boat Name
    Kharis
  • Boat Location
    Napton
  1. Plastic boats

    That was the big voids problem I was referring to giving large blisters, large enough so they are soft areas but still a blister. Thanks for clarifying.
  2. Plastic boats

    This is not correct. Osmosis causes blisters. The water flows into a void via osmotic pressure and keeps flowing in until a blister is formed. The water then doesnt move out to other parts of the laminate as the osmosis process drives 'low electolyte water' into high electrolyte areas - so it stays there. Most osmosis is due to small voids in the laminate so it ends up as a 'pox' on the gel coat surface. THis then is a cosmetic problem and will never sink the boat particularly if the laminate is thick. Occasionally you will see a boat with poor layup and big voids that will cause a few very large blisters on the gel coat. I would avoid this type of problem as there 'may' be some structural issues. I am not sure a boat that is not showing blisters yet is suffering. The cause for concern is when the gel coat is damaged due to impacts ie star crazing or cracks where water then has direct access to the laminate. Water then 'wicks' up the glass fibres and destroys the resin to glass interface which therefore weakens the laminate. This is where the problem of high water content can cause structural problems and it is not osmosis. If I was buying a grp boat, I would not be too bothered about osmotic blistering if it was over a large area of the boat. It is easy to repair and if it is a decent thickness, it will only be cosmetic. If however there were 2 or 3 sections with large blisters ie 3''+ across or clear problems of gel coat cracking/exposed laminate/damaged laminate then I would be very interested in water contents. You seem to be building up osmosis to be the main problem to look for on grp hulls. It isnt. Poor gel coats, poor layup, poor cure, unrepaired damage etc are far worse problems leading to reduction in tensile and flex strength of the laminate and a reduced lifetime. In general though, grp lasts for years and a good hull is going to be fine 50 years later as most boats built in the 70s/80s/90s had hulls so over designed. Shame grp boats look so tatty when they get old.
  3. Sim card Data deals

    Thanks MP
  4. Sim card Data deals

    That does sound like a good deal. Can you use the whole 60Gb tethered ie as a mobile hot spot. I need to put it in my 4g router so all the phones/tablets/macs on the boat can get the internet. I will call them tomorrow. Richard, thanks also for your input.
  5. Sim card Data deals

    We currently are using a 20gig sim from BT (EE) network and performance is great around the Warwick ring area. I need another 40 or 50 gig so we can stream stuff. Anyone seen any good deals out there recently? "3" are offering large data deals but only 30 gig can be tethered but probably the cheapest I am seeing at £25. I would get more BT sims but they have reduced the data since I got mine. Anyone using "3"? What is the reception like in the Napton, Braunston, Rugby, Warwick area and are the speeds good enough?
  6. Jabsco Par Max 2.9 woes

    No problem.
  7. Jabsco Par Max 2.9 woes

    Yep, sounds almost the same. You've convinced me. I'll get a new one as a spare. Like you the pump is a vital component. Now that is a good idea. I'll take it apart and have a look - and get a new one as the spare.
  8. Jabsco Par Max 2.9 woes

    Anyone with an input?
  9. Distribution panel question

    Yes, sounds plausible. Maybe I will look at getting some 20A ones for the water pump.
  10. Jabsco Par Max 2.9 woes

    My Jabsco Par Max 2.9 has decided it is not playing ball any more and telling the fuse in the instrument panel to not cooperate any more. I had bought a spare a few months ago so swapped the pump out and all is fine and the we can now wash. Question is, what should I do with the 'dead' one? We bought our boat in May - with this pump working but taking quite a long time to pressurise up the system (which includes a 12 litre accumulator). As it gets to pressure it would 'hunt' 10 -15 secs. Also when up to pressure the system seemed to loose a little pressure with time as when you turned a sink tap on, the pump would start almost immediately (with the new pump we get 2-3ltrs out before the pump cuts in). Once at pressure though the pump never came on unless a tap was opened so no leak in the system. When it died yesterday, the circuit breaker triped whilst it was doing its 'hunting' routine. Another snipit of background is that when we bought the boat, the overflow on the water tank was placed so part of the pipe dipped below the level of the tank so when overfilling, water remained in the overflow pipe causing a vacuum on the tank itself when pumping water out. Not sure if this had been going on for years (although the pump looked newish). Pumping against a vacuum cannot be good. My guess is that it is just the valves starting to leak so it is not pumping efficiently and a slight leak back through the pump. Is it worth replacing the valves - I assume there is a kit for this(?) - or just buy another new pump as a spare? My experience with these pumps is that we went through one in 3 years on our yacht and there could be other things that will break so wasting money paying for a refurb kit. Any thoughts.
  11. Distribution panel question

    Thanks Eeyore. Good to hear it is not only my buttons that dont pop. Any ideas why they would not work with motor circuits? I think I will buy a couple of new ones.
  12. Plastic boats

    Still not quite right! Osmosis occurs when there is a void in the laminate. This could be a microscopic air bubble or a big void caused by poor layup technique. The most common cause of big voids is where the glass mat (or glass rovings) were not rolled out well enough so the polyester did not wet the glass out completely thus leaving a dry area. Once the hull is in the water, the water then forces its way through the gel coat via osmotic pressure (which is very great) into that area of void and keeps coming swelling the void considerably. The gel coat will influence the speed of the flow of water but not that much. This may sound bad but it isnt really. In the days when people hand laid up using chopped strand mat (or woven roving), it was usually a very thick laminate that will last 50 years plus. In recent years where GRP boats are made with much thinner laminates, they tend to use resin injection or vacuum infusion or someother fancy technique which avoides the incidence of voids. Osmosis is not really a structural issue. Structural problems tend to occur when the hull has has impact damage which cracks the gel coat and therefore opens a path for water to see the glass fibres, with water then 'wicking' along the fibres destroying the glass to resin interface and hence weakens the laminate. This is not osmosis. Poor workmanship when laying the gel coat can make this more likely to happen. There was a 'rash' of high incidence of osmosis in the 70's which may have been partly due to some dubious gel coats on the market (despite my comment above that the gel coats influence is low) - but that is another story. I spent quite a few years in the late 70's developing gel coats for one of the 3 big UK manufactures.
  13. Distribution panel question

    Thanks for that link. I will have a look. I was meaning to go to their website but you beat me to it. I will post a new thread on the water pump problem tomorrow!
  14. Plastic boats

    ....but you didnt ask that. You asked if anyone lived on a plastic boat .....hence my first response. Plastic boats are great for rivers, estuaries and salty water (sailing and living). I would not park my plastic pride and joy on a canal with all these heavy steel boats around.
  15. Distribution panel question

    Thanks for that. I think I understand. Let me try and get this right. The breaker 'pops' when the current gets too high and hence the black button comes out and the switch indicator lights up as it is in parralell, and the power to the device goes off. That is what I originally thought, however the black button never seems to pop out. This has happened on 2 different breakers. I bought a new one but must have put it on one of the other circuits. If the black button does not pop out, how can you reset it? Do these breakers have a habit of not popping out or failing with age? Is there anyway of testing the breakers to see if they work? Sounds like I may need to buy a few new ones.
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