Mast Rake - what is the best setting for 13st Helm? [Martin

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Martin Searle wrote:

Folks,

Now I'm new to the dizzy low of being just 13st having been 14-16st for most of my Sprint 15 sailing time. I'm sensing that I'm loosing speed to my rivals ( a certain Mr. Dutch to be precise) at Seasalter Sailing Club especially downwind in the medium wind speed (8-15mph wind) which has always been a bit of problem wind speed for me, I much prefer winds 15-30mph!

I still have my old setting of the 5th hole down on the shroud plates for setting my mast rake aft. I figure on moving it upto the 3rd hole and see whats what there before trying the 4th, but if someone has already gone through the loop and found a fast setting then do tell? Also the forestay tension is tight. The wave action at the club is short sharp chop usually.

I mostly sail sport but am thinking of going to Netley for the Nats so una rig settings might also be of interest if different.

To get all technical: I have been doing some data logging using a wrist mounted GPS unit (which I think are 'in class' since its just a timing device that does other things ) and found that my upwind and downwind speed in 13mph of wind max out at 10mph and beam reaching speed at 15.9mph using the Sport mode rig. I suppose my next step would be to loan the device to my rival (or 'attach' it to his boat nefariously) and get some data for him and compare.

Martin S.
Sprint 15 1331

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Bob replied:

Hi Martin,
It makes no difference how heavy you are. The optimum mast rake is in the position which ends up so that when you are going upwind and you sheet in really tight it just does not quite go block to block. On most boats with standard length shrouds this ends up as being the 3rd hole from the top. Do not have the rigging too tight - it needs to be such that the mast will rotate 90 degrees in each direction (but no more). If you grease the ball it rotates better. It also make no difference if you sail with or without the jib. The mast rake remains the same.
Happy sailing & hope to see you at the Nationals.
Cheers
Bob
PS Kevin is fast - he was good at Instow.

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Martin Searle replied:

Bob,

Hmm just been down to the club in my lunch break from work and set the shrouds to 3 down as suggested. The shrouds are now very loose, ie no tension at all with the boat level, with the forestay loose as well I even tightened it up with the rope and brought the eye down to same level as the shackle on the roller reefer, still loose. But prodding Kevin's boat sees some similarity although his rig is tighter overall.

The mast rotates real easy but I have feeling everything may be a little too loose. But I'll give it a try on Saturday and see if the mast falls down , then I'll know to try 4 down.

With my previous 5 down setting I could sheet the main till it was past block to block I could bring the two top spindles next too each other, I guess this was the result of the aft mast rake I had. So it will be interesting too see what the result is with regard to the main sheet.

Martin S.

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Bob replied:

Martin
From the way you talk you have forgotten one essential modification. We have all shortened our forestays by about 75mm and put "a bit of string" (about 900mm of 3mm spectra or dyeema) between the furling drum and the forestay. This enables you to adjust the mast rake and maintain rig tension. If you think about it changing the shroud adjusters without shortening the forestay does nothing other than give you a slack rig - which is not the object of the exercise.
Cheers
Bob

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Martin Searle replied:

Bob,

Looks like a 1 step forward and 2 back scenario!

Well I do have a piece of string there too but before it was about 2-3 inches away from the roller reefer but after adjusting the shrouds there isn't any gap left. So yes it does seem that the forestay maybe the original length, its the only bit of rigging I haven't replaced over time.

I'll move the shrouds down a hole or two and get the rig tighter before sailing at the weekend and then sort out the forestay later.

Are new forestays of the shorter length these days? might be easiest to replace it.

Martin S.

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Bob replied:

Martin,
This dialogue convinces me that you have the original length forestay and that your mast was raked too far back. As a short term measure you would be better off taking out the bit of string and putting the forestay directly onto the shackle on the furling drum (although it is much harder to put the mast up with this arrangement. In future new boats will come with a shorter forestay - I'm not sure if Windsports stock of forestays are now at the new dimension (which I think is 3330mm)- you could ask
Cheers
Bob

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steve willis replied:

Boy is the competition getting worried! - Maybe now we know why the shroud cover was up on Joan's boat the other day when we went to go out (anything to do with her winning margin in Summer Series 2 ??).

To add to Bob's comments. My 756 originally had the old non-furling jib and I converted it with a new forestay.

After you sailed it on Open Day and said you could not get the blocks closed up I did drop my shroud plate down a hole. However when I do try to get closer to 'block to block' the sail does hook - this was very apparent yesterday when we all sailed to Leysdown beach and I could play around with sheet tension out of the race regime. John Dutch said he really struggled to overhaul me when I was sailing with the sheet slackened a bit going over to Sheppey. On the way back we stayed within 100 metres of each other all the way - and on returning we found about a great pool of water in my starboard hull acting as ballast!

Unfortunately Joan and I both had our boats on the beach over the training weekend so they did not get put into the 'line-up' for checking mast rake. But I do remember that both yours and Kevin's old boat (640) were the only two significantly raked back when nearly all the others were the same.

I slackened Joan's rig a bit after the training weekend but left it at the same plate hole - maybe that helped towards her stunning performance last time out racing the 15 with her much patched original sail on 842.

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steve willis replied:

By the way - Joan beat JD and me both there and back yesterday!!!!!!!!

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Martin Searle replied:

Steve,

Well one has to do ones research you know . But there is nothing wrong in a bit of healthy competition since its a great way to get better at sailing. Also provides a great motivational factor.

I suppose I set it to the 5th down because thats where I could get decent rig tension with the standard length forestay.

I'm going to sail with my rig in the 4th down with the forestay as tight as I can get it tomorrow and see what happens as an experiment. It still produces a fairly slack rig that way without being completely tension less as with the 3rd, amazing what effect a couple of extra cm's has.

I'm acquiring a new shorter forestay (mine's probably past its sell by date anyway) and will be able to setup mine as Kevin's is and will be able to properly compare everything.

All for that extra 1mph speed all around the course, hard work or what!

Hopefully my starboard hull water ballast problem has been sorted too, now is that a co-incidence you have the same problem? hmmm..... .

Martin S.

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steve willis replied:

Your plans sound a good trial. JD is now getting panicky about you getting additional speed (spoke to him this a.m. about NOT going out today as it is 25-30 ENE and chomping).

I will have a look in my stock - I have several 15 forestays that came with our boats when we bought them. I will measure them up ( presumably you do want to keep the sprint kit on ).

Looking through my old Panthercraft D15 manual the original forestay specification was:

3440-3550mm, (mid=3495mm) for the unarig boats (Dart15 Fun)
3540-3650mm, (mid=3595mm) for the jib rig boats (Dart 15 Sport)


This was replaced by one of 3365-3385mm with the jib furler fitted (with the short strop at the top being 130-150mm). Sum = 3515mm middle value.

When you add the furler bits top and bottom this seems to be quite a bit longer than the original single forestay.

Bob's value of 3300 sounds much better to get back to the original length.

See you Saturday (if the seas drop a bit). Steve

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Bob replied:

Steve/Martin
I have not received an entry form for the Nationals from Kevin Dutch - can you give him a prod when you see him, please?
Cheers, Bob

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steve willis replied:

Bob,

Kevin is definitely planning to come with Martin (two up on Kevin's trailer) . Unfortunately Kevin's new boat was rammed by another 15 just before the start of a club race this Saturday afternoon and has been holed below the waterline.

Luckily our excellent local repair man was at home 5 minutes away and we all helped dismantle the boat and within 1.5 hours of the accident the hull was washed out with fresh water and with him for repair - due back by next weekend with any luck.

Regards

Steve Willis

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Bob replied:

Hi Steve - thanks for the info - regards - Bob

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Martin Searle replied:

I said in a previous post: "I'm going to sail with my rig in the 4th down with the forestay as tight as I can get it tomorrow and see what happens as an experiment."

APPARATUS: 1xSprint 15, una rig mode. 1xME!

METHOD: Sail boat in strong wind, with shrouds 4 down and as tight as possible forestay, which was umm not very tight, lots of deflection of bridle wires by use of fingertips.

RESULTS:

Well having sailed the winds on Saturday, NE Top End F6 mostly, with the rig setup as above I found that the mast would fall back toward me, bit unnerving, every time I climbed up a wave and then it would fall forward when going down the waves! so the shock loads for the forestay and bridle were probably quite considerable. Mast rotation was very smooth and the loose rig definately let it rotate past 90 degrees on a few occasions which was undesirable so I used the main sheet to help prevent it.

Upwind speed was bad but then again I was pinching a wee bit to fetch the mark in just one tack since tacking was tres difficult I wanted to keep it to a minimum.

Reaching speed could have been a bit better if I had decided to push the boat to the max but I wasn't confident in the rig to be honest and didn't want to damage anything, averaged about 13knots on the reaches.

Downwind the boat really shifted! and surfed the waves readily.

I didn't really push the boat hard during any point of the course but did achieve a GPS top speed of 18mph or just a shade over 15knots, this was during a downwind surf on 7ft waves! had both bows out in space just forward of the main beam whilst sitting at the very top of the wave, nice jacussi on the trampoline though!

CONCLUSION:

Not bad for a unarig Sprint 15 with a less than desirable rig setup in a very lumpy sea. But it was good fun, especially having the waves break over me and almost washing me over the side on a few occasions.

I did win the race but Kevin D. getting taken out before the start was unfortunate because I would have liked to compare. Although he did return to shore like a scalded cat to prevent sinking, I know a terrible pun....

Martin S.
Sprint 15 1331.

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john replied:

"The optimum mast rake is in the position which ends up so that when you are going upwind and you sheet in really tight it just does not quite go block to block."

The grafham club boat is nowhere near block to block when sheeted in! have you been sending me out with a dodgy mast rake? no wonder I keep coming last...