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Author Topic: How do I get out of this one ?  (Read 1038 times)

Baldrick

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How do I get out of this one ?
« on: February 14, 2018, 09:13:17 pm »




 Just starting on the tug Cervia.  According to the plans I should be fitting a 60mm propellor . However checking the fibreglass hull shell I find that the moulded prop tunnel is set 5mm lower than the level shown on the plans.  The consequence is that a 60mm prop will not fit, it will not clear the foot of the rudder support frame.  Not wishing to start with a compromise should I .


 1) wince and fit a 50mm prop.


 2) grimace , file off the propshaft entablature  and build up a new one in the correct position with Isopon. ( will loose the plating detail. )


 3)  ?.




  Thoughts please
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tizdaz

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Re: How do I get out of this one ?
« Reply #1 on: February 14, 2018, 09:31:45 pm »

personally, i would just go for smaller prop, will hardly be noticable & you will still have all the fine plating detail intact etc.

RST

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Re: How do I get out of this one ?
« Reply #2 on: February 14, 2018, 09:54:28 pm »

Think you've said it yourself...

"Not wishing to start with a compromise should I"

3) throw the hull away and build it perfect, litho plates and perfect rivet lines etc according to the builders plan and shell drawings (only joking)

...just make it right then with re-positioning and filler etc. Thats's what scale modelling is about and it sounds like it's a good enough base to work from, retification sounds minimal.  Anything else is a compromise to prototype and not acceptable!

Or, however, as tizdaz says -something realistic, nobody will really know, probably makes little difference unless you want ultra scale.  Better things to worry about I think.
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derekwarner

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Re: How do I get out of this one ?
« Reply #3 on: February 14, 2018, 10:08:32 pm »

Baldrick.....Cervia was a steam tug, so her propeller would have been designed for steam with an applicable pitch

Do you have the 50 mm diameter propeller?....is it a steam or motor design?

Would altering [increasing the NME] pitch by 20% <*<  be of consideration for you?

Derek
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Derek Warner

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Baldrick

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Re: How do I get out of this one ?
« Reply #4 on: February 15, 2018, 12:56:18 pm »

Hi Guys.


    I am intending to go electric and was thinking of the same motor as the [size=78%]TUG CERVIA HULL BUILD  by Bluebird[/size] in the masterclass section , similarly geared down 1:2.   Having sketched it out it does not look right with a 50 mm prop off centre of the rudder window.  I think I am going to have to bite the bullet and attack the stern post with the Dremel to get the shaft into the correct location.  The wall section is quite thick in this area and I will pack the inside area solid with Isopon and drill the shaft through it.




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Baldrick

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Re: How do I get out of this one ?
« Reply #5 on: February 16, 2018, 05:18:03 pm »




 It's a known fact  (facts)  As you get older the eyes go dim , the brain slips into neutral and cognisance  becomes minimal.


  The more I looked at my prop , shaft and rudder entablature problem the more I became certain that their was something wrong with the geometry that I was missing . I spent hours checking different dimensions trying to figure it out and finally in an eureka moment it came to me.  The line of the keel plate which should be straight from bow to stern isn't. The last 150mm at the stern kicks up about 3.5mm. This means that rudder frame space gets squeezed and thus no space for the 60mm prop.
 Thankfully this means I do not have to resort to cutting and carving the hull . I will plant a piece of plank on the keel and taper it to square up the keel. Thats what I love about making model boats , another day another problem




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