Do you point up or bear away

Not a simple question. Depends on situation. Personally i go for speed makes the foils much better. High and slow, foils can't work, you drift sideways and makes you worse off. Was crappy westerly race last night.

DSS. On off breeze in Derwent.

+10 for those two!

Hi all

Thanks for your thoughts so far

Lets assume we have a steady 8 knots of breeze and pinching up to make the mark will give you 3 knots of boat speed and bearing away 10 degrees will give you 4 knots and the mark is 1nm away what do you do

Playing in Google earth if you bear away 10 degrees you need to sail 0.97 nm before you will be roughly 90 degrees from the mark to put a tack in and you will need to sail 0.17 nm to get to the mark after you go about so is it worthwhile with the time it takes to go about and get the boat up to speed again

Doing the math's it says that the boat doing 3 knots will take 33 minutes to make the mark whereas the boat doing 4 knots will take 28 minutes but this does not include the additional time it takes to go about and get the thing up to speed again

What do you do

Regards Don

Select to expand quote

NowandZen said..

Donk107 said..
Hi all

Thanks for your thoughts so far

Lets assume we have a steady 8 knots of breeze and pinching up to make the mark will give you 3 knots of boat speed and bearing away 10 degrees will give you 4 knots and the mark is 1nm away what do you do

Playing in Google earth if you bear away 10 degrees you need to sail 0.97 nm before you will be roughly 90 degrees from the mark to put a tack in and you will need to sail 0.17 nm to get to the mark after you go about so is it worthwhile with the time it takes to go about and get the boat up to speed again

Doing the math's it says that the boat doing 3 knots will take 33 minutes to make the mark whereas the boat doing 4 knots will take 28 minutes but this does not include the additional time it takes to go about and get the thing up to speed again

What do you do

Regards Don

Not sure about your maths Don.
If the mark is 1nm away and you are doing 3 knots (lets assume no drift or effect from current) then you will cover the 1nm in 20 minutes.
So first option to pinch: 1nm (the distance to the mark) divided by 3knots boats speed = 20 minutes not 33 minutes.
Or If you bear away 10deg and don't tack until you are 90deg to the mark, I make it you sail a total of 1.14nm @ 4knots= 21.05 minutes
This doesn't take into account time to tack and loss of boat speed.

Anyhow, that's how I make it.
To answer your question on the info given: Pinch up!

Hi now and zen

I was just laying in bed thinking about my maths and I realised the mistake where it should have been .33 and .28 of a hour not minutes and got up to fix it before anybody read it but you were too quick for me

Regards Don

Select to expand quote

NowandZen said..

Donk107 said..
Hi all

Thanks for your thoughts so far

Lets assume we have a steady 8 knots of breeze and pinching up to make the mark will give you 3 knots of boat speed and bearing away 10 degrees will give you 4 knots and the mark is 1nm away what do you do

Playing in Google earth if you bear away 10 degrees you need to sail 0.97 nm before you will be roughly 90 degrees from the mark to put a tack in and you will need to sail 0.17 nm to get to the mark after you go about so is it worthwhile with the time it takes to go about and get the boat up to speed again

Doing the math's it says that the boat doing 3 knots will take 33 minutes to make the mark whereas the boat doing 4 knots will take 28 minutes but this does not include the additional time it takes to go about and get the thing up to speed again

What do you do

Regards Don

Not sure about your maths Don - my apologies if I'm missing something.
If the mark is 1nm away and you are doing 3 knots (lets assume no drift or effect from current) then you will cover the 1nm in 20 minutes.
So first option to pinch: 1nm (the distance to the mark) divided by 3knots boats speed = 20 minutes not 33 minutes.
Or If you bear away 10deg and don't tack until you are 90deg to the mark, I make it you sail a total of 1.14nm @ 4knots= 21.05 minutes
This doesn't take into account time to tack and loss of boat speed.

Anyhow, that's how I make it.
To answer your question on the info given: Pinch up!

Hi Now and Zen, re your maths for the 1.14nm @ 4 knots, I get 17.1 mins for that distance.
1nm @ 4kn = 15mins
.1nm @ 4kn = 1.5mins
.04nm @4kn = .6min
15min + 1m30s + 36s = 17m:06s
Plus you should never be pinching up to a mark that you are 1n.m. from, especially in light airs, (3kn boat speed). In the 20 mins it will take you to get there the breeze could swing, or increase from the direction it is coming from, i.e. get as far to windward and into increasing pressure as fast as you can.
You are racing a boat, speed is king, 4 kn is 33% faster than 3kn, so your sails and foils are subject to 33% more pressure, i.e. your foils will be more functional and the apparent wind will go forward and could easily close your 10 deg down to 5-6 deg, depending on the boat. Just go fast and pay attention to your tacking angles / bearing to mark.

Sail best vmg but don you forgot the tide
changes everything again as tide changes vmg equation for a particular boat

Select to expand quote

NowandZen said..

morningsun said..

NowandZen said..

Donk107 said..
Hi all

Thanks for your thoughts so far

Lets assume we have a steady 8 knots of breeze and pinching up to make the mark will give you 3 knots of boat speed and bearing away 10 degrees will give you 4 knots and the mark is 1nm away what do you do

Playing in Google earth if you bear away 10 degrees you need to sail 0.97 nm before you will be roughly 90 degrees from the mark to put a tack in and you will need to sail 0.17 nm to get to the mark after you go about so is it worthwhile with the time it takes to go about and get the boat up to speed again

Doing the math's it says that the boat doing 3 knots will take 33 minutes to make the mark whereas the boat doing 4 knots will take 28 minutes but this does not include the additional time it takes to go about and get the thing up to speed again

What do you do

Regards Don

Not sure about your maths Don - my apologies if I'm missing something.
If the mark is 1nm away and you are doing 3 knots (lets assume no drift or effect from current) then you will cover the 1nm in 20 minutes.
So first option to pinch: 1nm (the distance to the mark) divided by 3knots boats speed = 20 minutes not 33 minutes.
Or If you bear away 10deg and don't tack until you are 90deg to the mark, I make it you sail a total of 1.14nm @ 4knots= 21.05 minutes
This doesn't take into account time to tack and loss of boat speed.

Anyhow, that's how I make it.
To answer your question on the info given: Pinch up!

Hi Now and Zen, re your maths for the 1.14nm @ 4 knots, I get 17.1 mins for that distance.
1nm @ 4kn = 15mins
.1nm @ 4kn = 1.5mins
.04nm @4kn = .6min
15min + 1m30s + 36s = 17m:06s
Plus you should never be pinching up to a mark that you are 1n.m. from, especially in light airs, (3kn boat speed). In the 20 mins it will take you to get there the breeze could swing, or increase from the direction it is coming from, i.e. get as far to windward and into increasing pressure as fast as you can.
You are racing a boat, speed is king, 4 kn is 33% faster than 3kn, so your sails and foils are subject to 33% more pressure, i.e. your foils will be more functional and the apparent wind will go forward and could easily close your 10 deg down to 5-6 deg, depending on the boat. Just go fast and pay attention to your tacking angles / bearing to mark.

Yes, you are right morningsun!
Wasn't sure on your method, but yes I agree.
Another way of calculating it is using the formula:
Distance
Speed X Time

So 1.14nm / 4 knots = 0.285
0.285 x 60 = 17.1 minutes or 17m:06s.

Sorry Don, back to the books for me!

No worries

That's what happens when you try to do maths after midnight

I think i will use this in future www.csgnetwork.com/csgtsd.html

Regards Don

Select to expand quote

morningsun said..

NowandZen said..

Donk107 said..
Hi all

Thanks for your thoughts so far

Lets assume we have a steady 8 knots of breeze and pinching up to make the mark will give you 3 knots of boat speed and bearing away 10 degrees will give you 4 knots and the mark is 1nm away what do you do

Playing in Google earth if you bear away 10 degrees you need to sail 0.97 nm before you will be roughly 90 degrees from the mark to put a tack in and you will need to sail 0.17 nm to get to the mark after you go about so is it worthwhile with the time it takes to go about and get the boat up to speed again

Doing the math's it says that the boat doing 3 knots will take 33 minutes to make the mark whereas the boat doing 4 knots will take 28 minutes but this does not include the additional time it takes to go about and get the thing up to speed again

What do you do

Regards Don

Not sure about your maths Don - my apologies if I'm missing something.
If the mark is 1nm away and you are doing 3 knots (lets assume no drift or effect from current) then you will cover the 1nm in 20 minutes.
So first option to pinch: 1nm (the distance to the mark) divided by 3knots boats speed = 20 minutes not 33 minutes.
Or If you bear away 10deg and don't tack until you are 90deg to the mark, I make it you sail a total of 1.14nm @ 4knots= 21.05 minutes
This doesn't take into account time to tack and loss of boat speed.

Anyhow, that's how I make it.
To answer your question on the info given: Pinch up!

Hi Now and Zen, re your maths for the 1.14nm @ 4 knots, I get 17.1 mins for that distance.
1nm @ 4kn = 15mins
.1nm @ 4kn = 1.5mins
.04nm @4kn = .6min
15min + 1m30s + 36s = 17m:06s
Plus you should never be pinching up to a mark that you are 1n.m. from, especially in light airs, (3kn boat speed). In the 20 mins it will take you to get there the breeze could swing, or increase from the direction it is coming from, i.e. get as far to windward and into increasing pressure as fast as you can.
You are racing a boat, speed is king, 4 kn is 33% faster than 3kn, so your sails and foils are subject to 33% more pressure, i.e. your foils will be more functional and the apparent wind will go forward and could easily close your 10 deg down to 5-6 deg, depending on the boat. Just go fast and pay attention to your tacking angles / bearing to mark.

Good answer, but actually the wind force increases by the square of the apparent wind speed, and the induced drag of the keel and rudder reduce by the square of the boat speed. So the increase in efficiency with speed is even greater than 33%. Of course, hull resistance also increases and around "hull speed" it increases dramatically.

HI Don,
When I'm on the course, I have a simple set of numbers I keep in my head to calculate whether I should bear off or not.

In other words, I ask myself is "will pinching more, or bearing away more, increase my VMG?"

I used your example, which was a wind speed of 8 knots, a boat speed of 3 knots ,and I used a normal close hauled course of 45 deg. This is expressed in blue, and becomes the reference. This gives you a VMG of 2.12 knots.


I added in a 5 and 10 degree variation of the TWA, pinching up to 35 TWA, and bearing down to 55 TWA.
The % change from reference shows you how much more boat speed, or less, you need to maintain the same VMG for each TWA change.

As you can see, if you bear away 5 degrees you need a minimum of a 10% increase in boat speed to maintain the same VMG.

So, when I'm on the course I can do a quick check without getting all techo, and that is :
- I'm at 45TWA. Check my boat speed.
- Bear away 5 degrees. Check my boat speed again.
- If my new boat speed is greater than 10% increase, it's a faster angle. Stay on this angle.
- If my new boat speed is less than 10% increase, its slower. go back to your 45 TWA.
- If the result is exactly 10%, then pick either 45 or 50 deg TWA. It doesn't matter which as your VMG is the same.

It's also a sobering reminder if you're lazy and inattentive and you end up sailing down to 55 or 60TWA, you need a BIG lift in boat speed to keep the same VMG (which in the real world you won't ever get!).

The cool part is the % change in boat speed does not change regardless of the wind strength.
See the following table where I used a higher wind speed (16 knots) and a higher boat speed (6 knots) to calculate the same thing.


The percentage increase in boat speed that you are looking for never changes regardless of the wind strength. A bear away from 45 to 50 deg TWA will always require a 10% increase in boat speed just to maintain the same VMG.

I've memorised the % numbers from 35 to 55 degrees, so when I'm helming I only need to calculate this % change to my current boat speed to ensure I'm not going slower.

35 TWA means a reduction in boat speed of no more than 14%.
40 TWA means a reduction in boat speed of no more than 8%.
45 TWA is my reference.
50 TWA means an increase in boat speed of no less than 10%. (This is the one I use most often as I'm normally playing in this range)
55 TWA means an increase in boat speed of no less than 23%

I've always found getting fixated and pinching to lay a mark means I get flogged. If I sail the boat to optimal VMG, even if that means throwing in a tack, I always get there quicker.
Important note: None of the above allows for tide and sea state as a factor. Or if you really suck at tacking!
Hope this helps mate,
SB

Hi Shaggy

Thanks for the explanation and information

unfortunately on my boat it is seat of the pants sailing with the only instruments being the cable driven speed log, compass, windex, wools on the stays and the telltails on the sails

Where we race we have fixed permanent marks so we know where we are heading even if the mark is too far away to see

We are surrounded by hills and the odd man made obstruction such as the shed on the Port Huon wharf so the wind direction can alter around the course and because we are in a river there is the flow of the river as well as the tide to consider

The next time we are out on the boat I will try your bear away in 5 degrees increments and see what increase in speed we see as I tend to try to sail to the mark or above it to allow for any knocks that might happen as we get closer to it

Tacking on mine with the large Genoa can be a bit slow by the time you get it across and in again and we normally don't let it go until it backwinds to help bring the bow around

During twilights our big advantage over the other Sailmaster and HG02's H28 is downwind with the large Genoa goosewinged with the pole so we will stick the big sail on when we probably should have the number 2 on because 90 percent of the time the wind will drop down as the afternoon wears on

I will do a bit of testing during the off season to see what variation we get in boat speed at different angles

Regards Don