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Information on history of Guppyanna


Trina

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8 hours ago, Trina said:

Hi yes the bow is flat. I might need to think about welding a pointy bit on it. Thanks? 

Actually I think I would celebrate the eccentricity and keep the front just like it is. I'd put a counter on the back though with an inboard engine. Nice to see something a bit different.

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23 hours ago, Alan de Enfield said:

It comes down to the design of the Hull - its called a 'displacement' hull.

This means that it just pushes a wave of water in front of it, if you use a bigger engine you get a little more speed, until the 'wave' in the fron gets to a certain size - you can then put a 1000hp engine in and it would not make an iota of difference. Once it reached design speed it cannot go faster.

A small OB with a small prop (8", or, 9") will not give you the control. steering, or reversing that an inboard engine with a 20" prop will.

 

I'll look and see if I can find the 'scientific' reasons.

 

If you were to watch a displacement vessel move through the water you would notice that they create both a bow wave and a stern wave as they push through the water . The faster the boat goes, the larger these two waves become until at some point they become a single wave. It is at this point that the boat has reached its "hull speed". That means that this is as fast as it can go. It can't go faster because it is caught in this wave. The longer the boat, the faster it can "theoretically" go because it takes longer for the bow and stern wave to become one wave. 

 

The max speed for a given hull I have read somewhere is: 1.3 X the square root of the waterline length in knots.

For a 40 footer that should be 8 knots.

 

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25 minutes ago, Mad Harold said:

The max speed for a given hull I have read somewhere is: 1.3 X the square root of the waterline length in knots.

For a 40 footer that should be 8 knots.

 

That's correct for a 'boat shaped boat' I'm not sure if this would work for a square / flat fronted  skip shaped object.

 

I think (it is just a thought) that the bow wave would just be building and building until it was impossible to push it any faster.

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On 16/11/2018 at 11:11, Trina said:

Hi yes the bow is flat. I might need to think about welding a pointy bit on it. Thanks? 

The skip-shaped compartment boats used for carriage of coal on the Aire and Calder were formed into a long train for the tow, and there was a short "pointy" section strapped to the leading one to act as a cut-water and avoid them becoming swamped. A false bow does not have to be anything fancy.

 

Tam

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5 minutes ago, Trina said:

I'm so glad you let me know. I've been trying to research it but without luck. CHEERS ?

Keep asking questions - there are loads of different people with loads of different skills and knowledge on here, all conversation is good - it can lead you to information you didn't know you need and people you didn't think to ask. So keep plodding away and I'm sure it will be fruitful. 

 

:)

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I think crafting and grafting on a pointy bit at the front will be a lot easier than constructing and adding a counter stern and engine bay. How advanced are your steelworking skills and facilities?

 

I was wondering if a 'Z' drive sort of transmission (as fitted to many GRP boats) would be an easier way of adding a grunty engine for the river. 

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6 minutes ago, Mike the Boilerman said:

I was wondering if a 'Z' drive sort of transmission (as fitted to many GRP boats) would be an easier way of adding a grunty engine for the river. 

Looking at the back-end it has a 'cut-out' and well for an OB, I not sure how any of it could be modded to accommodate an Inboard.

Maybe its a case of cut it all away and went  weld on a complete new stern.

There is absolutely no 'shape' to it, or space for an inboard as it stands.

 

IMG_20181111_083505_opt (1).jpg

Edited by Alan de Enfield
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4 minutes ago, Alan de Enfield said:

Looking at the back-end it has a 'cut-out' and well for an OB, I not sure how any of it could be modded to accommodate an Inboard.

Maybe its a case of cut it all away and went  weld on a complete new stern.

There is absolutely no 'shape' to it, or space for an inboard as it stands.

 

 

Well the OP earlier mentioned fabricating an extra ten foot stern section to form a counter and engine bay to weld directly onto the back, so the shape of what is there now is pretty much irrelevant. 

 

I was thinking fabricating a new  stern to take an outdrive would be quicker and easier than a whole 10ft counter stern, rudder etc.

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1 minute ago, Mike the Boilerman said:

I was thinking fabricating a new  stern to take an outdrive would be quicker and easier than a whole 10ft counter stern, rudder etc.

It would, but there doesn't look to be enough room for an engine and drive, probably pretty much the 10 foot the OP mentioned would be needed.

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21 minutes ago, Alan de Enfield said:

It would, but there doesn't look to be enough room for an engine and drive, probably pretty much the 10 foot the OP mentioned would be needed.

 

I thought the whole point of the outdrive format was to fit an engine and drive into about 4ft length of hull.

 

 

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13 minutes ago, Mike the Boilerman said:

 

I thought the whole point of the outdrive format was to fit an engine and drive into about 4ft length of hull.

 

 

The stern currently looks to be about 2 feet long with a 'veranda' on top of it.

 

It will need to accommodate an engine  (4 foot ?) + space at the front to get to belts etc, then at least 2 feet + for the gearbox/internal part of the drive leg.

Maybe 7 or 8 feet would be enough.

 

IMG_20181117_103620_opt.jpg

 

 

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3 hours ago, Alan de Enfield said:

The stern currently looks to be about 2 feet long with a 'veranda' on top of it.

 

It will need to accommodate an engine  (4 foot ?) + space at the front to get to belts etc, then at least 2 feet + for the gearbox/internal part of the drive leg.

Maybe 7 or 8 feet would be enough.

 

IMG_20181117_103620_opt.jpg

 

 

The simplest although not the cheapest solution would be to fit a diesel outboard.

Mercury and Yanmar make them and probably others too,but I don't know for sure.

I had a quick look on the web when I had my last boat,and found that they were about the same price as an inboard.

They don't appear to be made less than 20hp.

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8 minutes ago, Mad Harold said:

The simplest although not the cheapest solution would be to fit a diesel outboard.

Mercury and Yanmar make them and probably others too,but I don't know for sure.

I had a quick look on the web when I had my last boat,and found that they were about the same price as an inboard.

They don't appear to be made less than 20hp.

Yanmar D 27 Diesel Outboard - picture 1

https://www.findafishingboat.com/yanmar-d-27-diesel-outboard/ad-98479

 

At £4250 they are not cheap - A second hand Lister LPWS4 (inboard) can be had for £1000

Obviously the convenience of an OB fitting straight on the boat has some value.

Not sure what would be gained - the OB still has a very small prop which affects steering, reversing, accelerating, braking etc etc.

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