Fitting a strongpoint on deck for an inner forestay

[Kelpie]

As a long-term project I'd like to add a removable inner forestay to my boat (Albin Vega, 27ft). I know that there are various ways in which this can be done, e.g. by simply installing a deck eye with a good backing pad, or by taking the load down to the stem using a wire strop.

I don't want to use a simple deck eye and risk pulling the deck up... but the thought of installing a wire strop which cuts into the sleeping space and/or chain locker doesn't appeal much either.
So I am contemplating fitting a deck eye which is backed up by a sturdy beam mounted athwartships under the deck, to prevent upwards movement of the deck. What I have in mind is a piece of angle-section metal, spanning the width of the foredeck, and with its faces flush against the deck-head and the forward bulkhead, so it would not take up any space.
From a quick look at what's available I think I would have to go with aluminium as this can be bought in bigger sizes than stainless angle.

Has anybody else tried a solution like this? Will it work?

See attached hi-tech diagram.

 

[GrahamM376]

Sturdy beam is the way to go but, if bolting an eye through the deck, you may need to drill holes oversize then fill with epoxy and drill again correct size, to avoid compressing deck - if it's foam or balse cored. Beam could easily be made up in GRP sheathed timber.

Emergency stays sound good but, in practice, can be a PITA to rig at sea. The length when attached is longer than when parked so, it's normal to have a wire strop on deck and a "seasure" type lever on the end of the stay. Holding the stay (47ft of 8mm in our case) and the strop and trying to get the pin in is not easy single handed even in a light chop. If it's likely to be "lively" it needs rigging beforehand which means you may have to furl the genoa to tack/gybe. Also, don't forget extra track cars needed if you intend leaving sheets attached to roller furled genoa.

 

[Independence]

I had this fixed and epoxied to the hull on my She 31b

 

[Kelpie]

That looks a good sturdy bit of stainless work!
I much prefer the idea of a beam to having to make holes through the hull near the waterline, as would be needed if carrying the load down to the stem.

Some thought will have to go into how I intend to rig the forestay- can a carabiner or snap shackle be used instead of a pin?

 

[Bajansailor]

Rob, your proposal looks sound - remember though that even on that relatively short span there is probably still a bit of camber in the deck, but you could pack the gap with epoxy.
Are you planning on bedding the A/A angle bar down on epoxy or (eg) Sikaflex?
I would still include a couple of bolts through the bulkhead as well as the glue.
Albin Marine probably didnt skimp on materials when they were laminating in that forward bulkhead, so it should all be be massively strong.

We have a removable inner forestay, set up with a quick release lever to a deck eye about 3' aft of the stem - in practice we tend to leave it set up all the time, and if using the roller genoa on the outer stay we roll it up to tack it.
I realise though that this is not very practical for short tacking, but then we would probably be using the hank on stay sail on the inner stay anyway.

PS - The quick release lever is attached to the deck eye with a conventional S/S shackle and it doesnt take very long to set it up. The shackle pin is attached to a lanyard tied to the stay, as I am good at dropping things........

 

[Independence]

I guess it depends what you are going to do with the boat. If the job is done properly 'holes' near the water line (actually the bow) shouldn't be a problem as the bolts are epoxied over and faired into the hull. I was told by a boat builder and surveyor friend that this was the correct way of doing it but like all these things they are always open to opinion.

I also had a 5mm forestay shoe fixed the same way. It meant cutting the deck out but I'm working on the basis that if I was in a big sea the forestay deck fittings will now be a little further down my worry list.

I haven't yet finalised my forestay fitting but am reviewing the Sea Sure mechanism as it can be pre-tensioned and put in place quickly therefore minimising the amount of time on the foredeck. You'll see whats available from them on page 2 of the rigging section on their website.

Good luck

 

[john_morris_uk]

Rob, Your suggestion will work but you might like to consider a couple of alternatives. Firstly stainless might be stronger than aluminium and you might come up against corrosion problems with the Al'. Secondly, some boats have eyes fitted to above and below the deck. The lower one has a strop that would be 'in the way' if it was permamently rigged, but you only have to have it fitted when you are using the inner forestay. Just an idea in case your removeable forestay needs to be a little further aft than is possible with the Al' or S/S beam up against the bulkhead.

What the lower end of the strop attaches to depends on your boat and how the forpeak is constructed.

 

[Kelpie]

Thanks for the replies.
I had originally considered stainless angle section, but the biggest 316 grade I can find is only 40x40x5mm, or 50x50x3mm which might be a bit too thin. I can get 304 grade up to 75x75mm which is more the size I had in mind- but will this grade be OK?

If I switch to aluminium I can get much more massive sections and it will be much lighter and, importantly, much easier for me to fit DIY as I will be drilling plenty of holes in it. I'd have hoped that with use of a bit of duralac I could counter any corrosion worries. The Vega already uses aluminium backing plates under the stanchion bases, I had to replace a stanchion base recently and whilst there was a bit of white powdery corrosion I didn't think there was anything to worry about.

The deckhead is not a flat surface, there is a moulded toe-rail which forms a void on the underside. I would intend to pack this out with glass- open to suggestions as to whether the final bedding of the beam to the deckhead should be with sealant or resin.


On the tensioner, again, would it be right to consider that there are three options- blocks/lanyards, highfield lever, and bottlescrew- which can achieve progressively greater tension at the expense of adjustment potential (thus making it harder to fit the stay on a heaving foredeck).

 

[aluijten]

Your setup seems a bit too light to take up all the loads. I would consider using a square tube section, this will be much stronger. As an alternative you could use a piece of main-track from Lewmar. There is a version designed to take up high loads and only be supported at the end (in your case the points where the deck and the hull are joining. Just have a look the online Lewmar catalog.
For attaching the removable forestay, there are special (very expensive) tensioners to do exactly what you want. Look for Wichard Babystay adjusters.

Cheers,

Arno

 

[Kelpie]

Your setup seems a bit too light to take up all the loads.

I'm wildly guessing at what sort of section I need for this. Any scientific way to work this out?

 

[aluijten]

Obvious there must be. Regrettably I'm not a yacht designer. In my own boat they used a additional pulling rod that goes directly from the deck-point down to a strong-section below the forward bunk. This does mean you need to decouple this if you want to sleep there, or more specific, want to do something else then sleeping in the forward bunk
Luckily on our boat they did think about that, so you can remove this rod quite easily.
You could look at the dimensions that Lewmar uses for their mainsail track. My guess is that the loads on this track are a bit higher, but it's nice to have some reserve.

 

[30boat]

I would do it this way.A 5mm SS chain plate is bolted to the bulkhead but reaching further down than in your drawing.Bolted to it is a bracket made of 5mm stainless 90º bracket that has been triangulated with a welded on web in the middle.A fitting that has a SS loop welded on top is bolted to this bracket through the deck.The triangulation is needed to stop the deck and chainplate/bulkhead twisting under the upward loads imposed by the stay.Ideally the loads should be taken to the stem through a tie rod or a rigging screw (that's what I have) but providing your bulkhead is sturdy enough you should be OK.

 

[aluijten]

Seems sensible enough given the size of the yacht.
I think the triangulation is a very good idea.

 

[Kelpie]

Good diagram
Unfortunately I'm not sure it will work, because a) it would block access to the chain locker, which I need to rearrange the chain as it inevitably piles up in a big pyramid; b) I don't think the bulkhead is really strong enough to become the main/sole attachment point.

The way I was intending the beam to work was as an evolution from a simple backing pad, but spreading the load across the width of the deck to the hull/deck joint, and with the depth of the beam giving it much greater stiffness to resist being deflected upwards. The placement of the beam fore/aft against the bulkhead, was more to keep it out of the way than anything else.
There would be an argument for putting the beam further aft, for better placement of the stay, but this increases its span and therefore the tendency to bow upwards under load. Perhaps in that instance a channel section would be more appropriate than a simple angle?

Also, if I cannot rely too much on the bulkhead for support, the beam will be wanting to curve not only upwards but backwards as well. Fortunately the steel would have just as much depth in this direction and therefore, presumably, just as much ability to resist this bowing.

 

[30boat]

How about this then?Seen from aft you have a length of SS angle 5mm in tickness running across the bow and bolted to the bulkhead.Welded to the left and right tips there are two lengths of 5mm bar that run paralel to the hull sides and also bolt to the bulkhead.The fitting on top is bolted through the angle iron with the bolts located on either side of the triangulating web.You''ll still have access to the chain locker and as a bonus the bolts go through the strongest part of the bulkhead ie the fiberglassing to the hull.If you can't find suitably sized angle iron(in stainless) it can be easily fabricated from flat bar.

 

[Bajansailor]

Comparing aluminium and stainless steel - the modulus of S/S is approx 200 GPa, while the modulus of aluminium is approx 70 GPa.
Or in other words, for the same size angle bar, the S/S bar will be almost 3 times 'stronger' than the ally bar.

30boat makes a good point re how a triangulated web will enormously improve the strength of the bracket he has designed.
Depending on the type of deck eye you use, maybe you could have a web (or 2) welded into your section of angle bar, locally in way of where the deck eye will be bolted through?
That would stiffen it up enormously.

If you can get a section of aluminium angle bar in a marine grade alloy that would be good for resisting corrosion.
But if not, then it should still last a long time if you use Duralac in way of the bolts, bed it down well to the bulkhead and the underside of the deck, and perhaps then etch prime and paint it (the same colour as the bulkhead or overhead?).

Re scantlings, how thick is the bulkhead you will be bolting through (assuming that you can get to nuts inside the chain locker)? Can you see if the bulkhead is laminated to the hull on both sides (fore and aft) or just the aft side?

 

[john_morris_uk]

If you really want to stick to your original idea and not have a tie rod down to the hull, then why are you sticking to stock stainless section? If you make a mock up in cardboard of the section that to follow the curve in the deck etc then a s/s fabricator will weld up a curved section of angle s/s that will fit exactly. Shouldn't cost too much, and you can specify it to be mm's thick. I would ask them to punch the holes in the s/s as well - makes life a lot easier for you than finding cobalt drills and slow drilling the s/s! The fabricator will polish it up nice and shiny for you, or you could paint it to match the forpeak once its in position.

 

[William_H]

Support for inner forestay

I find it surprising you have dismissed the bulkhead as not strong enough.
Looking from a geometrical point of view the bulkhead has all the triangulation to take the load. It is in effect a beam across under the deck with huge depth and bonded to the hull at the sides and bottom.
A plate that takes the loads and goes down into the bulkhead should be fine.
An attachment further aft say 20cms with a stay wire down to a chain plate on the bulkhead about 40 cms should not interfere with space in the forecabin.
If you really have doubts about the strength of the bulkhead surely it would be easier to add more fibreglass layers to the bulkhead either side. Use carbon fibre if you want more strength.
good luck olewill

 

[Kelpie]

Thanks again for the replies and input.

The bulkhead is not really as strong as you might think. It is fairly thin plywood, maybe 6mm, certainly not more than 9mm. Yes it is bolted to the hull via flanges at the sides and to the deckhead as well. The opening in the bulkhead is pretty large- around half of its area.

When I asked on the Vega Yahoo group about fitting the deck eye, it was suggested that a fairly simple eye with under-deck backing plate extending over most of the area of the forward end of the deck would suffice. Indeed, several Vega owners are doing this without complaint.
The potential weakness of this solution is that the deck can be pulled upwards. I was hoping to improve upon this by adding a beam which would have much more rigidity, through a combination of its strength and also its depth.

What I am hoping to ascertain is what size of beam would be needed for this job- it might be that it needs to be much more massive than is practicable, for example.

 

[Wunja]

How much tension is needed on an inner forestay. I'm guessing that increasing Inner forestay tension would reduce main forestay tension.
It seems some of the suggestions would have more strength than the stem fitting!