18.5" x 20' vs 17" x21" : Cruising speed diff?

4 years 1 month ago #29775 by PeteCress
If I can maintain 6 mph on a 18.5" x 20' Huki S1-R, what sort of speed increase should I expect on a 17" x 21" ski?

Flat water, assume no capsizes.

Not sprint speed, just max aerobic cruising speed.

I'm not looking for great detail - just ballpark: a few tenths of an mph? .5 mph, more?

Please Log in or Create an account to join the conversation.

4 years 1 month ago - 4 years 1 month ago #29777 by agooding2
Here's the chart that Greg Barton of Epic put out: www.surfskinews.com/blog-2016-decjan-201...son-with-greg-barton

So if the 20' x 18.5" ski is most similar to the Epic V10 sport, then the 21' x 17" ski would be similar to the EPIC V12, so you would save between 10 seconds and a minute over 10K depending on whether you are closer to an intermediate paddler or closer to Greg Barton.

Nelo 550L, Streuer Fejna, Nelo Viper 55

Braca XI 705 EL blade, 17K shaft
Braca XI 675 marathon blade, 19K shaft
Braca IV 670 soft blade, 19K shaft

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29778 by zachhandler
It is always surprising how little additional speed a faster hull actually provides. Also surprising is how little speed a lighter boat provides. According to this exhaustive tome, lightening the boat by 1 kg will save seven seconds in an hour of racing. So going from a fiberglass to a carbon boat will speed things up by about 35 seconds an hour.

www.lcrk.org.au/pmwiki/uploads/Main/WeightEffect.pdf

Current Skis: Kai Wa’a Vega, Nelo 550L g2, Epic V12 g2, Carbonology Feather, Think Jet, Knysna Sonic X

Former Skis: Epic V12 g2, Epic V12 g1, Epic v10 double, Fenn Elite S, Custom Kayaks Synergy

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29779 by PeteCress
Sounds to me like the diff would be in the neighborhood of .1 mph.

Which is bad news for Yours Truly because now he cannot ascribe the paddlers walking away from him to having faster boats .. -)

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29780 by LakeMan
The thinner the ski the less people will ask to borrow it because they can't fit. It's a win win for me.

"Success is not final, failure is not fatal: it is the courage to continue that counts." - Winston Churchill

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29782 by AR_convert

Here's the chart that Greg Barton of Epic put out: www.surfskinews.com/blog-2016-decjan-201...son-with-greg-barton


Just remember although helpful this is an "Estimate", not real world figures.

I've done real world testing over 1km at set HR and the results are really surprising for various boats in the same conditions.

I'd say as long as the weight, construction, rocker and hull shape is the same.a .2km/hr difference would be the minimum I'd expect to gain from moving down from 18.5 to 17in.

Always looking for the next boat :)

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29783 by Cryder
Last week at a local race meet-up I paddled an Epic V8 Ultra just for giggles.

The course is roughly 3.5 miles, and I paddled without much draft benefit to a 26:45 (7.8mph).

My typical time in my V12 Ultra is usually 24:45 in similar conditions (8.4mph) and I don't usually get a draft benefit from other racers.

My typical V14 time over that distance is 24:30.

When I switched from a V14 Ultra to a V14 GT, I paddled roughly :20 seconds faster per mile (GPS verified).

My K1 (Epic Legacy XXL) time is considerably faster still, and I've been hovering around 24:00 flat, and my PR is a 23:55.

I chewed on this a lot because neither number matches the theoretical's I run into out in the world wide interwebs. But I attribute it to the following 1) boat acceleration is affected every stroke I take 2) boat glide is dramatically better in a narrow waterline, long ski. A heavy, short and wide ski doesn't like to accelerate or glide. A narrow, long and lightweight ski likes to glide very much.

Paddling a V8 Ultra, I could get it up to mid-8's in the first 1k, but it was very, very expensive from an energy perspective and I had to back off.

I asked Greg B about it, and he thinks that the V14 and K1 rewards speeds above 8mph in dramatic fashion, but much less so in the sub 7mph range.

Hope that helps.

Cryder
The following user(s) said Thank You: SurfskiEstonia, [email protected]

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29784 by Dicko
Don't underestimate the difference 0.1 or 0.2 kmh makes during a paddle. We are talking 100 to 200 metres over an hour of paddling.

For 12 odd years I have paddled with the same group for an hour 4 or 5 times a week. I get annoyed when I'm 20 metres behind. 200 metres would be buy a new boat territory....and I have on more than 1 occasion.

Small numbers do add up over a longer paddle or race. Try and imagine how far 200 metres is after a relatively short paddle. The distance will probably increase as the distance increases.

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29787 by fredrik
My experience is that is is about 1.0-1,5 kph difference between Fenn XT to a ElitesS /V12 on reasonably flat water in the 11.5-13 kph range.

Please Log in or Create an account to join the conversation.

4 years 1 month ago #29788 by nell
At a level of aerobic power that produces an average of 6.0 mph, I don't think you'll see any difference in speed between the two skis that you mentioned. At that speed, and with skis that long, and assuming a similar rocker, most all your resistance is wetted surface area. With one ski shorter and wider and the other longer and narrower, their wetted surface area might be similar - or the shorter one might be lower in overall resistance. Once you get into the high 7's and 8's, wave resistance comes into play big time, and that's when strange things happen and narrower really helps.
The following user(s) said Thank You: [email protected]

Please Log in or Create an account to join the conversation.

4 years 3 weeks ago #30002 by red_pepper
When I've compared my cruising speed on flat water between different boats I typically find about .1 to .2 mph difference going up a level. You'll really notice the improved glide and lower resistance, even if the speed gain seems small.

Please Log in or Create an account to join the conversation.

Latest Forum Topics

Surfski at night (1 Posts)

3 hours 8 minutes ago

Think Six v Epic V9 (10 Posts)

10 hours 22 minutes ago

Epic V9 Ultra test paddle (9 Posts)

1 day 11 hours ago
Protected by R Antispam