Help required with Mast rake and nose diving

[pegasus]

I am new to the British Moth and acquired BM 708 “Bertie” in the middle of the summer and spent August getting her ready for the winter series. The boat came with centre (Loosely described) main. I have since then altered it so I don’t have to right to the back to tack or gybe. What I have noticed since I started to sail Bertie that there is weather Helm. Normally moving the mast step forward or leaning the mast forward solves this. Today in blustery 15mph+ winds going down wind the boat wanted to nose dive. Can anyone help with regards to mast rake etc to stop both these problems.

The rigging on the mast is very loose and I am looking at shortening the forestay so that I can tension it up more. At the moment it reaches right the way down to the foredeck.

[scruff871]

Yep an often asked question....how do you stop a BM nose-diving ?
Incidentally we know "Bertie" a little in as much as we went to see her when she first came on the Market.One of the most striking features about her was the wood used to deck her...very nice grain patterns and her all black rig.I mention the rig as it is probably by SSS,and is a very light and flexible mast, so needs to be set up correctly to minimise the problems you are describing.There are some "standard" settings buried on this Forum somewhere but they tend to be applicable to stiffer Superspar M1 or M7,or "Lambda" Selden Masts.
Would suggest that you get the forestay shortened first to be able to put some tension in the rig...but please ensure that "Bertie,s" Spine/King Post is strong enough to take some tension.
Before mentioning about what rake you need,what tension you need it may pay to take a good look at the C/Board and Rudder in respect of what angle they take up.Where and if possible set up the Rudder Blades front edge to hang vertically or even a little forward.I am presuming that the Rudder Blade itself is narrow-ish and not one of the older larger shaped Blades.As for the C/Board it is perhaps OK that the front edge can be vertical but in a Moth this is not a must have.The Centre of Effort of Sail to Foil on a BM is all wrong really with a "standard" shaped C/Board fully down ,which can result in Boat not handling well[weather helm possibly]if both are not balanced.
Would further suggest that you start with setting that lovely black mast up with quite a bit of tensionand try to limit the amount of mast bend by adjusting the spreaders forward when the boat is rigged and on its side.Aiming initially for just a tad of Aft rake.
A good staring dimension for mast position is 24-25" to the front of the Mast from the Forestay.
Will this stop the nose-diving ?
No !!! ...but it will help.
All single-handers suffer to a lesser or greater degree in stronger winds...BM,s are no different but maybe a little more dramatic than most due to the amount of water displaced usually over the foredeck !
An OK,Finn or Solo downwind all have similar characteristics and the remedy is common to all.
For a safer ride SIT BACK,keep the boom off of the shrouds or avoid the boom being let out too square and avoid the top of the sail curving/twisting forward of the mast i.e +90 degrees unless you are a 4th Dimension sailor !
Hope the above helps a bit...
Roger Witts
FRAMPTON MOTHS

P.S
Remind us where "Bertie" is now residing ...?
If you are reasonably local to Frampton-on-Severn why not bring her up and we may be able to help with some of the above.
with the above points.
Still think "Bertie" is a fabulous name for a Moth....

[pegasus]

Thanks for your help.

It looks as if I am going to do quite a lot of work this weekend before I take Bertie out. There is only a short thin rudder and at the moment due to lack of water (Normally there would be at least another 6’ of water) I have to sail with a maximum of ¾ Centreboard.

I doubt I will be able to much tension on the rig, as there seems to be very little strength in that part of the boat. While I was working on her I photographed my progress, which included the inside of the tanks. There’s not a lot holding up the mast! see this photo (full set)

Bertie is now residing at Maidenhead Sailing Club, and as I tend to sail the Winter Series I need to get the rig as near to right as I can, as I don’t want to spend the winter swimming! Having a BM on this water has raised a lot of interest, particularly as it is very good in light airs and is very manoeuvrable compared to the Solos and Albacore that make up the largest fleets here.

[Pie-eyed]

Hi Pegasus
What a great set of photo's and a great job you have done!
Would be great if we could have these as a permanent feature on the site to guide other restorers...
Looks like 'Bertie' ended up in the right hands, we had not felt skilled enough to do all the work need.
We have 'Bertie's' sister 'Tabitha Twitchit' Meritlock 700 she has a shorter foredeck than 'Bertie' but if you would like some pictures of her set-up send a personal message with your e-mail address.
We can even supply you with an original Meritlock Makers sticker as given to us by Jeff Ambrose (lovely chap) one of the Meritlock kit producers.
Regards
Laura

[BMBA Admin]

Just to echo Laura's comments, Pegasus; fantastic set of photos covering your restoration of Bertie. It would be great if we could have them in a gallery on the BMBA website.

Not surprised Bertie wanted to nosedive if you were sailing last Sunday. Fun though it was, I capsized twice myself [though in my defense I was tired and hung-over!]

Aside from Roger's tuning tips, I find the trick is to anticipate the dive and get your weight as far back as you can before the nost goes under. Keep the sail off the shrouds, keep plenty of kicker on, and keep a handfull of centreboard down to stop the death rolls kicking in.

And hold the tiller, rather than the tiller exention, keeping its movement to the minimum necessary to steer your course.

[pegasus]

I still have lots of improvements to make and will be adding to the gallery as time goes by. To me having a photographic record is important as improvements can be made, and they can help others. This was the first time I used Epoxy, although I have used old fashioned glass fibre on many occasions, and consequently learnt a lot of lessons in the process.