Bullett - Comparison Test (Video)

9 years 3 months ago - 9 years 3 months ago #7173 by Kocho
Video below: comparison of suction of the Epic V10 Sport (2011 model) with and without a custom bullett.

Watch in HD (720p) on YouTube (just click on the YouTube name in the bottom right of the video below).



I first started the test with a bullet that was a little fatter than the one here. It was still smaller than the vent cover but it still did not work well at all - the suction with the bullet was worse than without it.

Then I reduced the dimensions of the bullet to what you see in the video and now there was some improvement: both in the suction force generated as well as in reduced turbulence behind the scupper vent cover.

I might play a bit more with different shapes yet to see if I get any better than this. As it is, adding this bullet increases the force of suction by about 25% (eyeballing it from the higher water level in the clear tube) and visibly reduces the turbulence (by looking at the thread patterns).

Not sure how this translates to in-water performance: have yet to try it. My first test some weeks ago was in the water with a bullet of size and shape that today I saw did not work at all and actually decreased the suction - on the water that same bullet did exactly the same: reduced the effectiveness of the drain. So I am hopeful that my new shape will work better in the water since it works better in the air ;) Will see about that soon enough...

There were some other interesting profiles that I think might be tested - for example, adding a sort of "wing" or a "spoiler" over the cover, like on the back of some SUVs or minivans/wagos to direct the flow down and smooth it to increase the local velocity and decrease turbulence.

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

9 years 3 months ago #7174 by Tom_D
I built a bullet for my SES that seems to work well. It seems to drain a little faster (nice satisfying sucking sounds) and definitely drains at a slower speed. While your design actually goes up into the drain venturi I rounded the front and had it end just barely entering the drain venturi. All the rest appears similar. Have you tried such a design and if so what were your results.

Great work.

Cheers,
Tom

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

9 years 3 months ago - 9 years 3 months ago #7175 by Kocho
Yes, I tried the bullett at several locations and this seemed to work just a hair better than when the bullett was about 1/4" away. Not a big difference and probably other factors would be at play more.

I did another test with a different shape bullet. That seems to work best a little away from the scupper cover.

The version of this video is here (the beginning is the same, added more to the end):

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

9 years 3 months ago #7176 by Tom_D
Thanks for the addition. That bullet looks more like mine with more squared off nose. I rounded the front piece a little more. The SES does have a flat exit so the attachment was simple too (no radius matching). The problem for SES boats is that the cockpit holds A LOT of water. I also added mini-cell foam to take up some of the room behind the foot plate (probably not an option for taller paddlers).

Thanks
Tom

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

9 years 3 months ago #7177 by wesley
i put bullets on all my Stellars. At first I had small bullets built by another ski manufacturer that worked pretty good, then I received the much bigger Stellar bullets. I velcroed on 1st bullet placing it about 2/8 inch from drain and that ended up being perfect increasing the draining time by approx 30-35% particularly on decelerating. This made a huge difference in the Stellars since they drain slow any way. Then i placed another bullet too close and it did not work as well so I now have all my bullets about 2/8 inch away. The best draining skis I ever had were my 3 Legends and my Uno. Virtually no water after one stroke!!

Wesley Echols
SurfskiRacing.com
#1 in Surfski Reviews.

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

9 years 3 months ago #7178 by Tom_D
I talked to Ed a few months ago about "factory made" bullets. Are they available now? I haven't seen them on the web site.

Cheers,
Tom

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

9 years 3 months ago #7179 by Kayaker Greg
They are available here in New Zealand, I fitted one this week. Get the updated rudder too if you don't have one already, makes a huge difference.

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

9 years 3 months ago #7182 by Slime
What sort of Legends did you have? I have a glass Legend and it certainly takes more than one stroke to get the speed to empty the cockpit. Or maybe it is my technique.

Cheers

Simon

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

Latest Forum Topics

Fenn Fennix Boats - any different? (26 Posts)

45 minutes ago
zachhandler's Avatar

Epic v10g3 upgrade? (13 Posts)

4 hours 16 minutes ago
eh.haole's Avatar

Remounting a Think Evo.... (3 Posts)

8 hours 38 minutes ago
Protected by R Antispam