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Author Topic: Springer Tugs  (Read 835311 times)

Arrow5

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Re: Springer Tugs
« Reply #575 on: September 24, 2007, 11:28:49 PM »

Ken, you cant ! It is very random :o PS for another source of smoke pellets try plumber`s supply shops for drain smoke testers. Made by PH Products Ltd. unit C7 Baird Court, Park Farm Industrial Estate. Wellingborough Northants. NN8 6QJ . Pricey but for special events worth it.
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djrobbo

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Re: Springer Tugs
« Reply #576 on: September 24, 2007, 11:44:07 PM »

Hi guys. Well that u tube film made me chuckle.Is that turning circle on a single 4 inch rudder? If it is ,it is quite manouverable.         Nearly finished the basic hull, still cant decide on a top yet. Will a two blade 40mm prop work or is it best to use a three blade ?       regards  bob.
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Arrow5

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Re: Springer Tugs
« Reply #577 on: September 25, 2007, 09:02:34 AM »

Yes that is the standard rudder with the Gurney strip on trailing edge. Never tried a two-blade prop. I guess they are for high revs on high-speed boats. I use a 3 blade  40 mm cut down to 38-ish. A 35mm 3 blade is pretty much best, less load.  I see Youtube has clumped together some other Springer clips we shot, check the menu under the main picture at end of clip.
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boatmadman

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Re: Springer Tugs
« Reply #578 on: September 25, 2007, 09:04:41 AM »

whats a gurney strip?
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Martin [Admin]

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Re: Springer Tugs
« Reply #579 on: September 25, 2007, 09:17:07 AM »

Aren't they something to do with hospital trolleys?!!?  ::)

But I did find this.... http://www.aoe.vt.edu/~mason/Mason_f/AIAA2007-4175.pdf
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kayem

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Re: Springer Tugs
« Reply #580 on: September 25, 2007, 09:33:57 AM »

Your link on Gurney strips was fascinating Martin, but I had no idea that the concept had spread to aeronautics in general. A Gurney strip is nothing more than a lift modifier on the trailing edge of an aerofoil section, which could I suppose be a boat rudder. The name comes from one Daniel Sexton Gurney, one of the best racing drivers that the USA has ever produced, still a regular visitor to the Goodwood Festival, and an absolutely charming gentleman. His original idea was to add a narrow strip of aluminium, or aluminum as he would have caused it, to the full width rear bodywork of sports racing cars, as far as I can remember, he first did this to cars he was racing in the 1960s, but after a while most such cars were equipped with fairly substantial downforce inducing shapes moulded into the bodies, and a Gurney was an additional metal strip bolted to the rear of the moulded part, usually with slotted holes to that it could be moved up and down to alter the effect. The term is still used in racing today, and I never imagined that my early employment history would ever be useful in this way on Mayhem.
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kayem

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Re: Springer Tugs
« Reply #581 on: September 25, 2007, 09:43:08 AM »

I've just found this pic that I took at Goodwood this year, a good example of a fairly elaborate Gurney flap. The car is a 1970 approx Lola T70, and I was responsible for some of the styling of the bodywork on the original car. 1970. All of a sudden, I feel terribly old.....
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djrobbo

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Re: Springer Tugs
« Reply #582 on: September 25, 2007, 02:07:07 PM »

Hello martin. I used to live in gurney road, does that count ?. Please excuse me if i seem ffiiik (DER) ! BUTTHIS ERE GURNEY TAB IS FITTED UNDER THE WING TO IMPROVE LIFT.if you put one on each side of the rudder do they not cancel each other out ? regards....confused.......bob.
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Tug-Kenny

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Re: Springer Tugs
« Reply #583 on: September 25, 2007, 07:48:55 PM »



I was wondering if it was on one side only, then the boat would veer against straight running.  ;)


Cheers...Ken
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djrobbo

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Re: Springer Tugs
« Reply #584 on: September 25, 2007, 09:02:12 PM »

Hi ken. i reckon that if it was on one side only it would make it turn unevenly .i.e,it would bias towards the side with the tab, i could be wrong of course but thats what i fink............regards bob.
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Arrow5

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Re: Springer Tugs
« Reply #585 on: September 25, 2007, 09:04:47 PM »

They are fitted like a T on the rear of the rudder. The other term is " fishtail" or "Salmon tail".
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chingdevil

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Re: Springer Tugs
« Reply #586 on: September 25, 2007, 10:07:57 PM »

They are fitted to make the springer turn in a smaller circle, handy if you are going to play football. The drag is minimal, I have a piece of 4mm square brass on the back of one of my rudders, fitted so from below it looks like a diamond. If I can get my camera to talk to my PC I will post a photo.

Brian
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djrobbo

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Re: Springer Tugs
« Reply #587 on: September 25, 2007, 10:19:30 PM »

Hi brian   Theres a photo of one of those on the american site exactly as you describe it.  Wondered what it was. My hull now built with 1/2 inch ply sides 2 x 1 pine bow and stern...3/16 ply bottom (in one piece)...interesting to bend....internal bulkheads from 3/16 ply, its already as heavy as a skip...now theres an idea for a top, could call it sprippy.................regards......bob.
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chingdevil

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Re: Springer Tugs
« Reply #588 on: September 25, 2007, 10:25:14 PM »

You got me bob I was just posting this as you posted yours.

Brian
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chingdevil

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Re: Springer Tugs
« Reply #589 on: September 25, 2007, 10:32:46 PM »

Hi Bob
Both of mine are built the same, 8mm ply sides, 10mm ply ends and the deck is 8mm. The bottom is 1.6mm ply on one of them and 2mm light ply on another, I reinforce the front area with another piece of ply inside all epoxied into place. I do not have any internal bulkheads.
With all the internals in them my springers have a fighting weight of about 4.2kg dripping wet so do not be surprised at the weight of yours.

Brian
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djrobbo

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Re: Springer Tugs
« Reply #590 on: September 25, 2007, 10:54:13 PM »

Hi brian ..If i can find out how to put piccies on here i'll take some of my build for you.  The only internal bulkhead as such is across the bow three inches back from the front, this spaceis filled with foam just in case....I'll definately try one of those gurney thingy's now i know what they are....cheers......regards...bob.
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Arrow5

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Re: Springer Tugs
« Reply #591 on: September 25, 2007, 11:25:25 PM »

I`ve just added a very short clip of a Springer spinning at fairly slow speed on Youtube. It spins just as quick when going fast. Great for footy. http://www.youtube.com/watch?v=aiaVcy-kQIO   or search for posts by MacSpringer for others.
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Arrow5

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Re: Springer Tugs
« Reply #592 on: September 26, 2007, 03:50:27 PM »

I`ve just added a very short clip of a Springer spinning at fairly slow speed on Youtube. It spins just as quick when going fast. Great for footy. http://www.youtube.com/watch?v=aiaVcy-kQI0  or search for posts by MacSpringer for others.
  Dont think I got that right , the last digit is zero not an O, or just search for post by MacSpringer and a couple should come up.
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Tug-Kenny

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Re: Springer Tugs
« Reply #593 on: September 26, 2007, 09:52:59 PM »



Brilliant, Arrow.  I'm definitely going to try this.   8)

Here is the corrected address for those interested in seeing it.

http://www.youtube.com/watch?v=aiaVcy-kQI0


Cheers...Ken


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Arrow5

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Re: Springer Tugs
« Reply #594 on: September 26, 2007, 10:29:37 PM »

Thanks Kenny, it is even more impressive at speed :o  Some smashing and bashing footy practise on www.putfile.com/Arrow5   
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boatmadman

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Re: Springer Tugs
« Reply #595 on: September 27, 2007, 07:39:24 AM »

Been thinking about this gurney thing and it hurt! ;D

I wonder how effective it really is on this type of rudder, as its origional intent was to work with an aerofoil section. I think that when fitted to a flat section rudder its effectiveness may not be as expected, mainly because when the rudder turned, the vortices set up on the low pressure side are far greater with a flat section than with an aerofoil section and thus possibly overriding any gain from a gurney.

Also,and I stand to be corrected here, I think a gurny should be at 90deg to the fluid flow to be effective, hence a box section effect may be reduced.

It would be interesting to see some proper tests carried out to judge the effectiveness.

I seem to recall, from college days - waaaayyyy back - that on an aerofoil section, if you finish the trailing edge with a flat surface set at 90deg to the width of the foil that drag inducing vortices are reduced. This flat surcface was about 1% of the width of the aerofoil.

Food for thought?

Ian
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anmo

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Re: Springer Tugs
« Reply #596 on: September 27, 2007, 09:14:43 AM »

If you need to improve the effectiveness of a rudder, especially at low speeds, there's a simpler way than adding complicated square sections to the trailing edge. I've never felt the need to try this myself, but several of my friends have, and they all assure me that it works. All you do is make a cut in a length of round brass tube, and spring this over the trailing edge of the rudder blade. It should be glued on of course, but will hold well enough for a few experimental sailings to see if it works or not. Many full size boats have something like this, though it seems to work best on short fat hulls like modern inshore trawlers, rather than the long thin ones that I usually build. Dimensions don't seem to be at all critical, you can't scale water so almost anything will do, but it needs to be centered so that you get the same shape on both sides.
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toesupwa

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Re: Springer Tugs
« Reply #597 on: September 27, 2007, 05:15:29 PM »

I wonder how effective it really is on this type of rudder, as its origional intent was to work with an aerofoil section. I think that when fitted to a flat section rudder its effectiveness may not be as expected, mainly because when the rudder turned, the vortices set up on the low pressure side are far greater with a flat section than with an aerofoil section and thus possibly overriding any gain from a gurney.

Sort of 'incorrect' Boatmadman...

Even a flat plate (imagine looking down on the rudder from above) will produce a certain amount of 'lift' when angled in to the flow.. in our case, water. That means low pressure on the 'upper' side, higher pressure on the 'lower' side, just like an aircraft wing..

The addition of a 'flap' or square section (at 45 degrees) to the rear of the rudder directs the water flow at a greater angle than the rudder can achieve on the 'underside' of the rudder, but has very little effect on the water flow on the 'upper' side

http://www.rolls-royce.com/marine/downloads/mano/hinze_fact.pdf
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Arrow5

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Re: Springer Tugs
« Reply #598 on: September 27, 2007, 07:57:04 PM »

Whew ! All this sophistication on a hull shaped like brick. Next thing you know will be folk fitting Kort nozzles and bow thrusters, rivets and lighting systems,smoking funnels etc etc......madness ::)
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djrobbo

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Re: Springer Tugs
« Reply #599 on: September 27, 2007, 09:39:12 PM »

And there i was thinking of making my springer a recovery vehicle complete with crane and hook and of course some flashing orange l.e.d's......that would make it a very nice tug . a very very nice tug.   Oh well!
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