Practical Boat Owner - January 2016

Ask the experts

GAS FITTINGSPeter Spreadborough, of Southampton Calor Gas Centre,
has 20 years in the industry
PAINT AND ANTIFOULINGRichard Jerram is former UK technical manager of
International Paint

TRAILER- SAILINGColin Haines is a design engineer who has trailer-

sailed for 25 years

ELECTRONICSChris Ellery of Greenham-Regis Electronics is a

former Merchant Navy officer

TOILETS AND PLUMBINGGary Sutcliffe of Lee Sanitation knows

about holding tanks, toilets and plumbing

YACHT DESIGNAndrew Blyth is a naval architect with interest in stability

and buoyancy WOODRichard Hare is a wood technologist and long-time wooden-boat owner

50 of the most frequently asked boating questions are answered by our experts on the PBO website. Visit http://www.pbo.co.uk

BOATBUILDINGTony Davies has been building and repairing wooden,

GRP and steel boats for 40 years

YACHT DESIGN WOOD

Q(18ft) day boat that I sail in the Torridge Estuary in Devon.Endeavour My question concerns extra ballast for my 5.5m was in a poor

state when I bought her four years ago. I made a new mast, gaff and boom, had new sails made and am delighted with

the way she sails. She has an iron centreplate but I have no idea of its weight.I have noticed that going to

windward she heels significantly in winds of Force 4 and above and I have to reef earlier than many other

similar-sized boats out sailing.original owner: she was built in 1980 and he asked if I still had By pure chance I met her

the extra ballast in her – but when I bought her there was no sign of this.She does float well above her

waterline so I’m going to try adding ballast, but the question is where should it go? My view

is to keep it as close as possible to her midships and along either side of the centre plate case.However a friend suggested

it should be located on either side of the boat as far from the centreline as possible. To me this would negate any

beneficial righting moment as they would be working in opposition to each other. What is your view?

Andrew LittlejohnBy email

Where to put some ballast? Andrew Littlejohn’s day boat Endeavour

ANDREW BLYTH REPLIES: higher than you’d expect. You have a choice of how to add ballast, or you may combine both approaches.Extra ballast added internally is undoubtedly best placed on both The boat does look to be floating

sides of the centreboard case, as low as practicable. I’d arrange it so that it is clamped or secured to the casing and cannot move or fall out if the boat should ever be capsized.If the ballast were to be distributed as widely as possible, as your

friend suggests, it would be placed higher up and thus have less effect on the stability. Doing this would increase the roll inertia and lengthen the period of roll, but this is not necessary for a sailing boat.Another measure you could take is to replace the steel

centreboard. Being 35 years old, it’s probable the original board has corroded significantly, and is therefore less heavy than it was. If you replace it check carefully what maximum thickness is possible while retaining free movement of the plate. Quarter inch steel weighs

10.2lb per sq ft (6mm is 47.1kg per sq m). This measure has the benefit that when lowered the plate has maximum effect on the stability – although raising it will be harder work.

Say cheese!

Q‘cheese wheel’ for the masthead of the main mast of my Drascombe Dabber. Should it be I am planning to make a wooden cap – we call it a

made with the grain horizontal (ie across the mast axis) or vertical? Symmetry would suggest vertical but then it

might be more prone to intake of rain water in the grain and perhaps split.Which wood/s are best suited?

I believe the mast is spruce or Columbian pine.to the masthead bearing in mind And how tight a fit should it be

the possibility of it splitting?Is it best varnished or white-painted?Finally, what about the finish?

RICHARD HARE REPLIES: Sandro PicchioVedano al Lambro, Italy

Considering the size of this component and its extreme exposure to weathering – particularly in your glorious

Mediterranean sunshine – I would seriously consider making it using a lump of plywood.You’re right to be concerned

about splitting: I can see how a 20mm-thick solid wood cap could easily fracture. Plywood, with its cross-laminating veneers, will

make splitting virtually impossible.source a small piece of 20mm thickness exterior or WBP grade It should be easy enough to

plywood from a local boatyard.tightness of the fit. I suggest you make the hole about 4mm larger You are also right to highlight the

diameter than the top of the mast. Your ‘cheese wheel’ can then be bonded on with a PU adhesive like Sikaflex. Do this when the

spar has a low moisture content, ideally at the end of the summer season. This will reduce the likelihood of the spar shrinking

after the cap has been bonded onto it.component I suggest you Once you have shaped the

encapsulate/sheath it using epoxy adhesive-soaked mat. One layer, well bonded, ought to be fine. This will keep the weather out. I

think it would be best to paint it to protect the epoxy from UV. A good quality single pack yacht enamel paint ought to be fine although

two-pack would be better.

Here’s a typical masthead cap made from plywood

80mm

57mm 8mm20mm

Richard Hare

➜