bow tank full to empty speed impact

[glen76]

Curious to know how much speed people loose when they fill their bow tanks up. Especially if you know how big your tank is.

ta gt

[andymac]

I wouldn't have thought to many people have calculated the difference,because the ballast tank is generally used in rougher conditions when top speed is not an issue.however I will say, when coming back from cowes last year,playing with Renegade,I was unaware my quite big tank was filling/loading weight up front,which then when I hit a bit of slop,stuck the nose in and put me into a semi hook.not funny at 70ish mph

[beyondhelp]

How many litres do they typically hold in the 19-25ft boat range? I understand they are used to keep the front down in rough conditions? Surely as you said, makes you more likely to plant the bow in the sea?

[andymac]

Originally Posted by beyondhelp

How many litres do they typically hold in the 19-25ft boat range? I understand they are used to keep the front down in rough conditions? Surely as you said, makes you more likely to plant the bow in the sea?

I'm not sure, I think the one in mine is to big (approx 90lts).if I was to put a new one in, I'd proberbly go for about 40-50lts.that for my p20

[beyondhelp]

Ok, so say 40-50kg. Having never been on boat with one, how does it help? I mean I'd have assumed that you would trim up/down as needed, or is it case over heavy chop, that a light front can get pushed up too easily regardless of trim?

[S2art]

You're basically right on all counts. The idea is to get weight into the front to keep it down, if the set up is right it would allow for level flight, and to stop kiting where the wind picks up the nose and holds it up. If your using a bow tank your top speed would be down anyway because of the conditions. The only real issue with a bow tank is in a following sea, when it is quite possible to drive of a wave and stuff into the next. This is when the art of using a bow comes into effect, some may trim out to hold the nose up, when others may empty it and refill when required.

[gar163y]

Bernico F1 bow tank is 280 litres.

[beyondhelp]

Interesting stuff, thanks.

[glen76]

Originally Posted by gar163y

Bernico F1 bow tank is 280 litres.

thats a big tank. I have just down sized mine, must have been 5-6m long along hull length.

I appreciate most people wont ordinarily use the tank unless its sloppy, but i sure as hell know ill be tryinh mine on pickup and fill to count the time, and note the speed. Unfortunately the boats not ready to answer my own question.

[Cookee]

Originally Posted by gar163y

Bernico F1 bow tank is 280 litres.

Bow tanks for ski racing are a different thing, they are used to flatten the water for the skier as well as for handling.

We always go faster with a bow tank, otherwise there isn't a point! We never have any water in ours going downwind and never have a gauge for one either - it''s by feel, every boat is different but the tank itself will slow the boat down in very flat conditions when you take account of the weight of the tank itself in the bow - but not by much at all.

[Renegade]

In contrast I fill mine and leave it for duration of the race.

[DAVE]

Cookee is spot on...its all done by feel as you go.....some even fill the tank with a hose at the pontoon, to make sure they can get on the plane, then let it out as they go till the boat feels right.
It all depends on how the boat is balanced. where and how big the fuel tanks are, where the crew sit in relation to the c of g etc...whole idea is to fly flat if you fly at all.....and identical looking boats can be very different.
Batboats are the worst in a following sea....been half drowned many a time trying to get the things to run sensible....
Probably doesnt help much but its mostly trial and error.....with empahasis on the error...

[RR 880]

Hi Glen,

It takes about 90-120 seconds to fill my take up on my Scorpion at about 45mph, it does take top speed off but only 3/4 knots but at the same time has allowed more trim to be used.

[Mike_G]

I have done some speed test on my SR23 last year
I had 130 litres bow tank.
Empty tank was 117 km/h
Full tank 109 km/h
That was riding on a lake on flat water

[Marinautic]

On flat water I'd expect to loose somewhere in the region of 10% of your max speed, not that you'd need to use it in flat water of course.

[scottyboy]

Originally Posted by DAVE

Batboats are the worst in a following sea....been half drowned many a time trying to get the things to run sensible....
Probably doesnt help much but its mostly trial and error.....with empahasis on the error...

You know when ya deep if you can hear the engine revvin to try and get to the surface and ya navigators voice slowly turns to a sort of gurgle! Hey Dave! Atleast we finished the race though! ilfracombe wasn't it?

[glen76]

Really good feedback. Much appreciated.

Especially from another scorpion of similar size as mine

[Piranha]

....150 Liter at my Piranha Carrera......

[DAVE]

Originally Posted by scottyboy

You know when ya deep if you can hear the engine revvin to try and get to the surface and ya navigators voice slowly turns to a sort of gurgle! Hey Dave! Atleast we finished the race though! ilfracombe wasn't it?

Yeah...every bloody lap on that one leg....I wonder who has that picture of the whole boat (and us) right under...just an orange blur below the surface....I'll never forget that....we could have done with gills.

[scottyboy]

I remember stirling sticking it in hard and retiring. We just kept plodding round to finish. Checked out Sunday though! Didn't see anyone for the whole race! 😎