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Author Topic: funnel angle  (Read 842 times)

Willit

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funnel angle
« on: December 08, 2017, 11:02:48 AM »

hi all,


does anyone have a known method of cutting a funnel accurately at an angle?  I'm building a steam tug and the funnel has to lean back a tad.


cheers


Matt
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Tug-Kenny

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Re: funnel angle
« Reply #1 on: December 08, 2017, 11:16:42 AM »


I would tend to 'sand it' on a flat bed sander.  That way you can hold it at the angle you choose.  Savage, I know, but better than a hand saw.   ok2

ken
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Colin Bishop

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Re: funnel angle
« Reply #2 on: December 08, 2017, 01:46:39 PM »

 And if there is still a slight gap (isn't there always?) then a thin strip of paper or styrene around the bottom will mask any irregularity and look good too.

Colin
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Netleyned

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Re: funnel angle
« Reply #3 on: December 08, 2017, 02:13:06 PM »

By Steam tug do you mean a Steam Driven
Tug as opposed to an electric driven model?
How accurate do you want?
Cut the base to the angle that looks right when
The hull is level at its waterline.
If the tug is towing or speeding to a Salvage, the
angle of rake will look different.
Just my hapoth 8)
Ned
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Willit

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Re: funnel angle
« Reply #4 on: December 08, 2017, 05:17:24 PM »







By Steam tug do you mean a Steam Driven
Tug as opposed to an electric driven model?
How accurate do you want?
Cut the base to the angle that looks right when
The hull is level at its waterline.
If the tug is towing or speeding to a Salvage, the
angle of rake will look different.
Just my hapoth 8)
Ned
no its an electric powered model but I just wanted to explain what kind of funnel it would be.

many thanks for the suggestions! I think I've enough to go on
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Pioneer

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Re: funnel angle
« Reply #5 on: December 08, 2017, 06:15:13 PM »

Hi Matt


My solution was to build the angle into the funnel. I've drawn a quick pic of what I mean. I made several ply profiles of the funnel shape, in my case not circular, and cut alignment holes in each for a brass tube to pass through. Ply formers with the correct angle glued each layer together and held the angle in place. The whole structure was then wrapped in thin steamed marine ply with the top correctly aligned and level. Once dry the base was simply sanded flush with the bottom former and there was the completed funnel at the correct angle. The unpainted example wasn't quite up to scratch. second attempt was the one!


Hope this helps


Regards


Andrew
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dreadnought72

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Re: funnel angle
« Reply #6 on: December 08, 2017, 10:20:21 PM »

You could chuck some maths at it.  O0


If a circular cylinder is radius 'r', cutting the cylinder at an angle other than perpendicular will result in an elliptical section.


The ellipse will have two axes: one is radius is 'r', while the longer one is 'r/cos(theta)', where theta is the rake of the cut.


Andy
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Big Ada

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Re: funnel angle
« Reply #7 on: December 09, 2017, 06:11:59 PM »

Accurate and a "Tad" don't seem to go together  {-)
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ballastanksian

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Re: funnel angle
« Reply #8 on: December 09, 2017, 07:36:03 PM »

The funnels I have made that required a rake I cut from tube on the bandsaw using an angle gauge to get all three at the same rake. It worked well. I destroyed on in the lathe whe machining the top but luckily had not re set the gauge, so I could easly cut another. Learnig from this, I would make all future funnels vertical and then cut/abraid the angle.

Some funnels have parralel tops and bases so do the same to the tops.
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