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Overstern vs understern

Posted: Thu Jun 02, 2011 7:33 pm
by JDW72
Hi,

I've been offered a second hand overstern K1 which I think is a decent fit for me in terms of my progression and also size/shape.

I'm concered about the overstern rudder though. There must be a reason why very few modern boats, certainly racing boats, are made with overstern rudders these days. Are they inherently slower than understerns? Also, are they more difficult to steer/less responsive? I'm going to take it out and have a play to see whether I can figure it out but thought I would canvas opinion from the more experienced types that hang around here.

I intend to do some Watersides next so there are some advantaes in having an oversterm rudder for that but that's not necessarily justification to buy it.

Would appreciate your thoughts.
Thanks,
JDW72

Re: Overstern vs understern

Posted: Thu Jun 02, 2011 9:28 pm
by michielv
I'm no expert but as far as I know an overstern rudder is not according to the rules for sprint kayaks anymore. So if you would like to use the K1 in sprint events you need to have an understern rudder. However, for marathon I think overstern rudders are more practical. So are the slightly rockered noses of older K1 designs: weeds tend to have less grip on them.

But I suspect there is a lot more to it though :-)

Cheers,

MIchiel

Re: Overstern vs understern

Posted: Thu Jun 02, 2011 10:21 pm
by banburypaddler
I've always used an overstern for marathon and for sprint until last year when I bought a new, faster, boat, which happened to be understern.

I was quite happy with the overstern but there are some differences. There are steering problems with oversterns in choppy marathons as the rudder can sometimes be out of the water: this happens much less with understern. Oversterns can take a bit longer to respond but its not really a hassle - if you're used to it, you adjust. It's no different from paddling a K2 when you are used to a K1.

Disadvantage of the understern is, of course, that it's useless for descent races, or any marathon races involving shallow water or weirs.

I'd expected that my new understern boat would turn more quickly, but to my surprise, it;s way, way slower - though this is probably more to do with its stability than anything else.

Re: Overstern vs understern

Posted: Thu Jun 02, 2011 10:29 pm
by andya
Nothing wrong with overstern. Far better at taking knocks, and in most situations will equal understern.

After all ships have had rudders at the stern for quite a few years now ...

Re: Overstern vs understern

Posted: Fri Jun 03, 2011 8:09 am
by Mike_M
I can see no reason that a overstern is any slower than an understern.In fact some sprint boats have a rudder on the end of the boat

Image
Why did you place the rudder at the stern of your sprint boats?

Our drag calculations show that a rudder at the stern of the boat rides in the slipstream from the hull and therefore has less drag. Further, the rudder at the stern gives more resistance to cross winds. While the effect is minor, the decreased drag can play a part at the highest levels when races are sometimes won or lost by hundredths of a second. By contrast, our marathon version has the rudder further forward beneath the hull. This provides greater control when riding wakes, making turns or in choppy water conditions. The further up position also allows the boat to be carried with the stern dragging on portages (hull tipped to side) without hitting the rudder - as is commonly done in international marathon races
A quote from the Epic site

I find an overstern tends to be more responsive i.e is better for agresive turns. However an understern gives better contol i.e it is easyier to get the small adjustments required for wash hanging.

As Banburypaddler states in choppy water or surfing waves an overstern can be out of the water some of the time.

I think that the demise of the overstern has more to do with the look of the boats rather than practicality. Maybee if someone was to manufacture a flashy carbon overstern it would become popular again.

Regards

Mike

Re: Overstern vs understern

Posted: Fri Jun 03, 2011 3:03 pm
by JDW72
Thank you all for your replies.

I'm going to try the boat and if I feel comfortable-ish in it I will buy it. It's not expensive, looks to be in good nick, and should do me fine for the next 12 months unless I make some sort of remarkable breakthough. I'm not sure that hundredths of a second will make a massive difference in my next Hasler race to be honest :-)

I do need to master the art of wash-hanging and if I can do it in this then hopefully it'll be easier with an understern in the future, should I choose to go down that route.

Cheers,
JDW72