DEVELOPMENT 420 Boat Settings - Beginner's Guide
420 Boat Settings - Beginner's Guide
Courtesy of the British 420 Class Association, below is information on some basic boat settings written by Matt Burge:
- Guide to Barber Hauling
- Guide to Mast Rake
- Guide to Changing Mast Rake on the Water
- Guide to using Mast Chocks
- Guide to Spreaders
- Guide to Main Sheet Bridles
- Guide to Tuning
Guide to Barber Hauling
Barber hauling is the name given to tensioning the windward/slack jib sheet. This is not done in all boats (e.g. the Mirror) but in the 420 it helps to achieve a faster jib slot / leech shape. You apply barber hauler simply by pulling the windward jib sheet and cleating it. It is very important to know how much to pull it on though.
Barber hauling makes the jib fuller and therefore more powerful. It has the same effect on the jib as chocks do to the main, and therefore follows a similar pattern:
- In very light winds and when you are overpowered you want the jib flat, so none is needed, however it often pays to put on half an inch in strong wind because it makes the leech more stable.
- In wiring conditions before flat-wiring you again want power, so it is good to pull on about an inch and a half. If it is choppy as well up to two inches is good. Exceeding two inches however will close the slot and is not fast so be careful.
- Putting marks on your jib sheets in both the sheeting positions and the barber-hauler positions will help you to judge how much jib sheet and/or barber hauler you have on.
Guide to Mast Rake
- Pull on rig tension until it reads 30 on the tension meter. (Always take the reading at shoulder height up the shroud).
- Tie the tape measure to the end of the main halyard and pull to the top of the mast. Then lower it slightly until it measures 16’1½” at the top of the black band at the gooseneck.
- Pull the tape measure to the transom & take the measurement at the top edge of the transom. We are aiming for a reading of 19’11” here (with 30 on the rig tension). So if it is 19’11” leave it and put a pen mark on the mast lining up with where the rig tension block/hook is. Label this mark ‘L’ and record which hole the shrouds are in on the chain plates. This is your light wind setting.
- If it does not read 19’11” then take the rig tension off & move the shrouds down the chain plates if the reading is above 19’11”, and up the plates if it is below. (Each hole on the chain plates will make a difference of roughly 1½” to your measurement).
- Repeat steps 1-4 until you achieve 19’11” with 30 on the rig tension.
- Then, repeat steps 1-4 but to get a measurement of 19’9¾”. Once achieved mark the mast with ‘M’ and again record the hole number (which is usually a hole down from the light wind setting). This is your medium wind setting. Don’t worry if a rig tension of 31 is needed to achieve this measurement.
- Then, do the same again but to get 19’8½” using 31-32 on the rig tension. Mark this as ‘S’ on your mast and record the hole number, (which is usually a hole down from the medium setting). This is your strong wind setting.
- If you & your crew are very light you may like to set up 19’7” with 31-32 on the rig tension. Use this only in very windy conditions.
The strengths of wind at which you should change settings depends entirely on your crew weight:
Use the light wind setting upto the point where you become overpowered. i.e. your crew is flat wiring and you are having to play more than 6” of mainsail.
Then change to medium wind settings. If you are then having to play more than 6” of mainsail all the time on medium settings then change to strong wind settings.
Always choose the setting that best suits the strength of the lulls.
Guide to Changing Mast Rake on the Water
- Go ‘heave-to’. (Back the jib, let the main sail go completely & put the tiller down to leeward).
- Completely let the rig tension off & pull the kicker on hard. This will make the leeward shroud go slack.
- Change the leeward shroud to the new hole.
- Tack & go ‘heave-to’ on the other tack.
- Change the leeward/other shroud to the new hole.
- Release the kicker and pull the rig tension onto the new mark on the mast (that corresponds to the new hole numbers).
- Sail off!
This process will take a few minutes and so is not practical to do in a race. However it is useful to be able to do before a race and in between races should the wind get up or die.
It is a good idea to tie your shroud plate pins onto the plates so that you do not loose them whilst changing holes on the water. It is also safer to buy shroud plates that the shrouds cannot come out the top of should things go wrong!
Guide to using Mast Chocks
Chock are the small ‘mushroom-shaped’ plates that you can put in front of the mast. They affect the pre-bend and as a result affect the amount of power you have in the mainsail:
Less pre-bend = Straighter mast = Fuller mainsail = More power
More pre-bend = More curved mast = Flatter mainsail = Less power
Chocks alter the pre-bend by pushing back on the lower mast, therefore straightening it. So the more chocks that you put in the straighter the mast becomes and the more power you achieve.
Therefore; more chocks = more power
If you set up your light wind mast rake you will find a gap in front of the mast where the chocks go. If you fill this gap with chocks so that they are touching the mast but not pushing back on it this is your neutral number of chocks. Record/remember this number of chocks.
When you have neutral chocks in your sail is at its flattest, so neutral chocks are good when the wind is very light or if you are overpowered. As soon as you get on the wire there is enough wind for the sail to cope with being a bit fuller & more powerful put one more chock in (we call this +1). When you are well out on the wire (but not flat wiring/overpowered), and especially in choppy conditions put two extra chocks in (+2) for maximum power. However, as soon as you become overpowered (i.e. flat-wiring & playing the mainsail all the time) then go back down to neutral chocks because you do not need any extra power.
Also, do not exceed two extra chocks – putting in three extra chocks is likely to invert the mast!!!
It is not always practical to change chocks in a race so make sure they are right before you start. If the wind does change in a race such that you need to change the chocks then the best time to do it is on a run – there is less forwards pressure on the mast on a run & the crew is in the boat and able to reach the chocks.
NOTE: If you are very overpowered in very strong wind then you can remove one of the neutral chocks (-1). This will help to flatten/de-power your sail even more.
Guide to Spreaders
If you set up your light wind setting you will notice that your mast has a slight bend/curve going up it, this is called the pre-bend. The amount of pre-bend is controlled by the spreaders. You can measure pre-bend by following these steps:
- Set up your light wind setting & make sure there are no chocks in.
- Get the heavier of the two of you to pull and hold the main halyard tight against the gooseneck on the back edge of the mast.
- Meanwhile the lighter one of you needs to climb onto the boat (carefully) and stand next to the mast where the chocks normally go.
- From this position measure (using a ruler) the distance between the halyard and the back edge of the mast where the spreaders join. (This is the point where the pre-bend is greatest).
Different makes of sails require different pre-bends, these are:
Pinnel & Bax – 35mm
Olimpic – 33mm
Speed – 32mm
North – 32mm
If your pre-bend measurement does not equal your sail’s requirement then release the rig tension, adjust the spreaders so that they are angled further back if your measurement is too small or further forward if it is too large. Then re-measure the pre-bend using steps 1-4 and keep adjusting until its right!
Guide to Main Sheet Bridles
The bridle is the piece of rope that holds your mainsheet block and joins onto each end of the bar behind the centreboard. The lengths of the bridle are very important because they control the mainsail leech tension when block to block. The rules state that you are allowed two settings on your bridle length, so we set up one to be used with the light wind mast rake and one to be used with the medium & strong wind mast rakes. (The bridle length is changed with mast rake like this because the boom height alters with mast rake).
To set up the light wind bridle:
- Choose a day with a force 3-4 wind & set up your light wind mast rake.
- Check that the bridle ropes are equal in length by lining the block up along the centreboard. Adjust them so that they are.
- Hoist the main sail and set it up as if you were going sailing (eg outhaul on etc but no kicker on). Also, turn the boat 45 degrees to the wind so that it’s in the close hauled position. You will need to get your crew to hold the side of the boat so that a gust doesn’t blow it off the trailer!
- Pull the main in block to block and look at the leech. If none of the telltails are flying & it’s straight/tight then your bridle is too short. If the leech is very bowed/slack and all the telltails are flying then your bridle is too long. If your leech has a slight curve and the top telltail is flying 50% of the time then your bridle is perfect. (Make sure the kicker is off all the time).
- Adjust your bridle until this perfect leech is achieved, making sure you make equal adjustments to each side so it always lines up with the centreboard. Once achieved this is your light wind bridle setting.
To make the strong wind setting just tie two loops 7cm up from where the ends of the bridle join the clips on the bar. To use the strong setting you just need to clip the loops onto the bar:
NOTE: You will now need to set up your light wind setting again because tying the loops will have shortened the light wind settings quite a lot.
Guide to Tuning
The following is a general table on how you might set up your 420 for different conditions. This does depend upon your crew weight though and so should not be followed religiously. I would encourage you however to make a table of your own personal settings built up through trail and error.