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Thread: A plastic boat.

  1. #11
    Join Date
    Jan 2013
    Location
    Guernsey
    Posts
    386

    Default Re: A plastic boat.

    Looks a nice chunky boat BB. Will she be able to make it over to Guernsey when finished?

  2. #12
    Join Date
    Jan 2009
    Location
    Stratford on Avon
    Posts
    11,208

    Default Re: A plastic boat.

    Quote Originally Posted by burgundyben View Post
    I used Deacons as a launch pad, home port is Yarmouth.

    Right opposite me in Yarmouth is a Sealine called Rafiki.
    Cheeky Booger. There's only one proper Rafiki, and she is visiting Yarmouth next week

  3. #13
    Join Date
    Mar 2002
    Posts
    17,630

    Default Re: A plastic boat.

    Quote Originally Posted by AndieMac View Post
    Well I'm up for a mini rebuild/refurb thread, I like this style of boat.
    Positively +1.
    Regardless, all the very best BB!

  4. #14
    Join Date
    Mar 2009
    Location
    Home=Surrey / Boat=Hamble
    Posts
    6,226

    Default Re: A plastic boat.

    Quote Originally Posted by Fishtigua View Post
    Looks a nice chunky boat BB. Will she be able to make it over to Guernsey when finished?
    Absolutely, with Tulana tagging along..

  5. #15
    Join Date
    Jan 2009
    Location
    Lochaber
    Posts
    7,261

    Default Re: A plastic boat.

    Ford engine with an oil leak, how unusual! "They all do that sir". When I started using Millers oil my Ford's seemed to need a lot less topping up.
    Will the engine rev to 2500rpm in neutral?

  6. #16
    Join Date
    Nov 2002
    Location
    Colwell Bay
    Posts
    5,666

    Default Re: A plastic boat.

    I made a cover. (Sewing machine a 1949 Singer 201k)

    One very annoying crease! I've never done it before, this was a trial run using very cheap fabric, a quick fix for a couple of issues, namely a pigeon infestation including a bloody nest the cheeky bloody airborne rodent and since I removed the aft cabin, when it rains I have to go empty the bilge.





  7. #17
    Join Date
    Jun 2011
    Location
    Volos-Athens
    Posts
    4,850

    Default Re: A plastic boat.

    my mom had a similar singer, must find it!
    cover looks good, I guess you hope a strong wind form the bows will enter on the two triangles on the side decks and just lift the aft section and exit without making any damage, right?
    Can't you turn the cover around so that you don't see the crease when you walk up to the boat on the pontoon?

    V.

  8. #18
    Join Date
    Nov 2002
    Location
    Colwell Bay
    Posts
    5,666

    Default Re: A plastic boat.

    Why is my boat so slow? Thinking out loud and trying to assimilate my thoughts....are you sitting comforatbly?

    The brochure says with a 120hp Ford, 12knots continuous and 14 knots max. I can see Fairey massaging the truth a little, but both the brochure*and the manual quote the same figures. I reckon I get 8 knots max through the water at 17/1800rpm. Don't seem to be able to deliver more revs than that. Prop demanding more than engine can give. Not sure tacho is correct.

    I reckon hull*speed, waterline length is 28ft, so sqrt28ft * 1.34 =**7.1 knots. Seems to concur with my 2 gallons/hr burn.

    See this pic, that is a single 120hp Ford and its defo looks to me like its doing more than the 8 knots I get.



    Manual says 70 gallon tank, 12 knots continuous, 160 mile range, which suggests endurance of 13.3 hours, which equates to 5.35 gallons/hr at 12 knots (assuming the numbers in the manual do not consider a %age safety, but run to dry).

    My tank is actually 63 gallons.

    You get about 20hp for each gallon per hour you burn, I seem to be burning about*1 or 2 gallons per hour, perhaps that would be a different number if I ignored the time idling in the river where there's barely any burn, but even so, I'm not burning anything close to 5.35 gallons/hr.

    I can't get past 1800rpm - but I've taken at least half a ton off the boat, I'd have expected to be under propped...not over.

    Haven't checked morse cable is operating the pump fully......! Must check that.

    1. The engine might be knackered - it leaks oil, although the leak might be fixable, so I'm not clear if its burning any, but it does start instantly which suggests its not worn out.

    2. There is 2 silencers in series in the exhaust, which could be choking the engine? I'm not sure how sensitive to back pressure a NA diesel is.

    3. The rudder. My boat is I believe unique with the* Kitchen rudder gear, I'm certain that all the figures above are based on a boat with a standard blade rudder. I have noticed that underway the wheel that opens and shuts the rudder loads up, it becomes impossible to turn, which I think suggests a lot of drag. If I ditch it, then I will need a bow thruster £1k, plus maybe a stern thruster at another £1k. Or maybe not.

    If the 120hp Ford didn't leak oil and did give 12 knots, or 14knots* max, I would keep it.

    Other options.

    I have everything to marinise a Cummins 6bt, which could easily give 220hp, or more with a charge cooler. But at 2600rpm I would be at the limit of the reduction box.

    A chum has a spare Cummins 4bt 250hp which I could buy. They are rated at 3000rpm, so make the power at higher revs/less torque, which may help the reduction box.

    I find my self wondering, if I had the Kitchen Rudder dangling in the water on a stick, how hard would it be to hold onto it while the boat moving at 7 knots? Or more? ie, how much drag is it?

    The reason this is important, I live in Yarmouth, on springs, on the ebb, there can be 4 knots of tide, so with only 7.5 or 8 knots available, progress home could be walking pace! Need a bit more speed.

  9. #19
    Join Date
    Jun 2005
    Posts
    316

    Default Re: A plastic boat.

    One thing that would be relatively easy to rule out and quite important to your calculations is the RPM figure. Can you check it somehow?

    Then maybe do something temporarily with the rudder?

  10. #20
    Join Date
    Jun 2003
    Posts
    483

    Default Re: A plastic boat.

    Well, having had the pleasure of being aboard 'The Dawg' last weekend at the Yarmouth speed trials [we weren't entered, we were the finish timing mark! but it took an age to get back from the far end of the course against the spring flood] I can confirm that she is dog slow.

    In my own admittedly biased opinion a 4 cylinder diesel is the work of the devil so a 6BT it has to be, with tons of engine box sound proofing and a big bore well silenced exhaust.

    I agree that it must be several tons of drag from the enormous kitchen rudder, have you a picture of the actual appendage you can post? for those not familiar with the principle [as I wasn't] this is the thing and it's like towing a blinking parachute.

    Kitchen-rudder-us-patent-489509.gif

    Best thing for that thing is to take a gas axe to it and drop in a nice new blade job with a pair of thrusters.

    Then your 220 hp Cummins should get you into the mid teens and the ability to punch the tide through Hurst narrows without a care in the world.

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