Ok thanks Microbe. Top plan to set everything right.

That strap installed is on the right track but it is very poorly executed as you allude to. It should be under tension and taking the cap and diag shroud load down to something solid but it is doing neither sorry to say. Why it is bent like that can be guesstimated but let's go forward to the solution. The single bolt through the topsides at the lower end of it is no good and needs correcting.

Without doing a rig calc on your boat I would suggest that the input from your SS22 owner contact is probably correct - and it is against normal intuition I agree - but the issue is that maximum load in the standing rigging depends on the initial set-up tension and elongation from zero load in that stay, and the added deflection compared to the original loaded stretched length, from that state when under load during sailing - the worst load case being the knockdown to 90deg due to whatever reason. So for the ss22 rig the diagonals have about (say) 3/8 the true length of the caps - but under the worst case load case their relative extension would probably be more than the caps - so the extension divided by the original length which is strain and hence proportional to load, will be more. There is more to it than this but it is hopefully a reasonable answer.

To get to your solution - totally agree - see my real bad mudmap of the suggestion for;

Item 1 - the 3 bend chain plate flat bar which is bolted to the cabin side and the inside flatbar strap item 2. 3 bolts items 1a, 1b, 1c. Bends in stainless flat bar are not usual but if they are done carefully with a smooth radius they are a lot better than welds. Bolt size to be sorted.

Item 2 - the flatbar strap with 4 bolts 2a/b/c/d. Bolt size to be sorted.

Item 3 - the ply gusset as you mentioned. Epoxied into the original structure, probably 16mm, good fillets and glass each side.

Item 4 - the saddle for the diags, 4 and 4a,b,c being the saddle, bolts and underdeck ss plate all of suitable scantlings and suitably connected into the ply gusset. The connection into the ply gusset with the 3 bend chain plates and strap 90 deg to it needs sorting.

Of course please advise of any clarifications needed and pass this across your ss22 owner for his comment so this can be optimised as regards effort, time, cost, but still get the result you need.

Wow! Thanks r13. That's an amazingly detailed plan.

In your diagram do the cap shrouds attach to 1 - the flat bar on the cabin side? That would put them a bit inboard of where they currently are. Also, currently they are in line with the mast with the lowers astern of that position. Not sure if your plan brings the caps back or the lowers forward?

One point to bear in mind is that the Swan River has three bridges near Fremantle that require me to drop my mast in order to transit. Having the caps in line with the mast, and having a connection point in line with the mast pivot bolt helps keep some tension on the stays so the mast doesn't flop from side to side.

Thank you so much for all your suggestions and sharing your knowledge. I really appreciate it.

Thanks,

I was considering something like this - sort of a combination of what you're suggesting and what the other SS22 owner did.

I'll glass a ply semi bulkhead under the deck and run a stainless strap along either side. Chainplates will be saddles on either side of the deck on the same bolts. Then I'll run a turnbuckle from the saddle to the strap. I could also run a strap down the front of the ply and bolt it to the same point on the hull as the existing one for additional strength.

I'll put a stainless strap on either side of the ply and then could have two turnbuckles - one attached to the lowers and one to the caps.

r13 said..
No problem, good to be able to assist. Yes caps to 1. Ok good point best to have the 2 shrouds located where they are now.
See below have added sketch (not to scale) top left with possible arrangement - this is a cross section through the new bulkhead and deck on port side showing the caps ss flatbar forward, and diagonals ss flatbar aft. The latter has 2 careful bends so as to get the take off point located where it is now. The hatched item is a hard timber wedge - say spotted gum epoxied securely. At least 3 bolts through both straps. Need tapered washers under the upper 2 nuts on the aft bent diagonals strap. On Sunday I will measure the ply bulkhead thickness on the Col22, also the bolt diameters and ss strap thickness, width and length. SS22's are a bit heavier overall than C22 (but a bit lighter keel) and deeper draft than C22's - displacement 1200kg and 998kg respectively, keel 408kg and 499kg, draft 1.22m and 0.97m. SS22's will probably have a bit higher righting moment.

Columbia 22 measurements today as mentioned above that I would advise. See 2 photos below.

Ply bulkhead thickness 15mm.

Chainplate bolt diameters 5/16". 3 bolts per chainplate. A bit light imho. Would suggest 4 bolts at least, and 3/8" diameter. Also as per the photo the shear loading in the bolts is going through the threaded portion of the bolt which is a big no no for single shear joints - the shear loading must be going through the unthreaded bolt shank for a single shear arrangement like this - the other side of the bulkhead is the head of the bolts with washers as per prior photo - the bolts should have been inserted from this chainplate strap side.

Chainplate total length 300mm (240mm below deck level), width 32mm, thickness 4mm. Again imho a bit light. Would suggest 50mm wide 6mm thick. Suitable length for the 4 bolts.

So these are from the Col22 ~1975 build. For your SS22 as above I would beef these up a tad including 16-20mm certified marine ply for your semi-bulkhead infill gussets. A few grams extra weight here for assured strength is well worth it. Seems like you will use another arrangement than strap chainplates but the comments above stand for the record.

The 2nd photo below is of the cap shrouds and their chainplates. The deck cover plate self tapped in to the deck is not attached to the chainplate - it with suitable adhesive/sealant provides the weather / moisture barrier to the deck cut-out and the ply under the deck and is a well used system, usually works well and is easily refurbished if needed. This ply bulkhead is not epoxied to the underside of the sidedeck or the inner topsides - see prior photo and below it is screwed to grp members and presumably has suitable adhesive as well - but it is essentially a full cross section bulkhead (except for the cut-out to the fwd berth) not two partial bulkheads like you will fit.

Microbe said..
Thanks,

I was considering something like this - sort of a combination of what you're suggesting and what the other SS22 owner did.

I'll glass a ply semi bulkhead under the deck and run a stainless strap along either side. Chainplates will be saddles on either side of the deck on the same bolts. Then I'll run a turnbuckle from the saddle to the strap. I could also run a strap down the front of the ply and bolt it to the same point on the hull as the existing one for additional strength.

I'll put a stainless strap on either side of the ply and then could have two turnbuckles - one attached to the lowers and one to the caps.

Microbe said..
Thanks,

I was considering something like this - sort of a combination of what you're suggesting and what the other SS22 owner did.

I'll glass a ply semi bulkhead under the deck and run a stainless strap along either side. Chainplates will be saddles on either side of the deck on the same bolts. Then I'll run a turnbuckle from the saddle to the strap. I could also run a strap down the front of the ply and bolt it to the same point on the hull as the existing one for additional strength.

I'll put a stainless strap on either side of the ply and then could have two turnbuckles - one attached to the lowers and one to the caps.

Finding this thread very interesting, I am no expert on rigging but that very detailed drawing brings to my mind quite a complex amount of fittings and only one of them has to let go to lose the lot , is there any such thing as a tested saddle? They look to take the most load.

Thanks Microbe

Yes was concerned with your busy schematic including turnbuckles under the deck..........but didn't want to interfere........

Edcon over here in the east are brilliant suppliers of all steels including stainless and will cut to size. Last time I was there (Revesby Sydney) it was $10 min order.

Maybe Stirling over your way can cut the 6x50 316ss flatbar to the 2 off 300mm long pieces needed? In the 2m length they have 5x30 for $22 plus tax which would surely be fine. Or 6x50 $46+tax.

see here;

www.stirlingsshop.com/500/index.php?route=product/category&path=35_40_286

You would make up the chain plate straps very easily in your workshop. No machining needed. Cobalt 32tpi hacksaw blades and cobalt drill bits would assist, slow speed drilling. Say r5mm radius on all 4 corners of each chain plate strap. Neatly finish off each radius with filing.

Good one Zzzz I thought Ronstan saddles would have been load rated but they are not - this is very surprising and Ronstan must address this.

www.ronstan.com.au/marine5/range.asp?RnID=246

In the lifting tackle industry Rud links are load rated for every angle and application they are certified to be used for...............get them from Bullivants if you are doing any serious lifting and don't want to spoil your day.

www.rud.com.au/product-category/lifting-lashing-solutions/lifting-points/

Looks like you are fully onto the deck repair scheme needed.

Hello Microbe

Q1 - I don't expect you will get chain plate deck covers for any size chain plate flat bar strap off the shelf sorry. Have to make them up yourself - only 1-2mm thick stainless is needed. Cobalt drill out clearance holes ducks in a row and hand file them out to make the slot. Drill the 4 corner holes for the self tappers.

Q2 - wobble stoppers to cap shroud chain plates - flat bar and shackle making wobble wobble stopper. So we need to be clear here that during the mast raising / lowering process there potentially is wobble (and hence loads needing to be resisted in strength and fatigue) laterally as well as fore and aft.

a Having difficulty answering in the correct order so this might be a tad out of sequence - firstly obviously the saddles in your latest photos of the other SS22 are 90deg differently oriented to yours - so their bolts are fore and aft whereas yours are lateral. Your orientation is far better for the case of the saddles not being loaded exactly in their vertical plane as the load direction will surely shift inboard under the wobble loading of mast raising and lowering. So the caps might load the saddles in the vertical plane under normal use but for the case of the sideways wobble when the mast is being lowered they surely will not be loaded only vertically - there will be an inwards load orientation onto the saddles and for the latest photos that is by far the weakest strength direction of the saddles and a real concern - depending on the load and angle magnitudes obviously. For the diagonals there is an inwards load angle by design and again your direction orientation is far better.

b But for the mast raising / lowering case there would be loads in the fore and aft direction on the saddles during the whole process. So in this case the fore and aft oriented saddled would be preferred.

c The stainless tube with toggle end at deck and flattened out higher up to meet the cap shroud turnbuckle is very unusual, unexpected, and not recommended as you surmise, with the 1.6mm wall of the tube subject to very high bearing stresses from the pin connections at each end. Bearing stresses - compression loads on the hole due to the through bolt or pin - have the highest allowable steady state load magnitude of all stresses but the arrangement is not recommended imho. The fatigue performance of bolt hole bearing stresses is well reduced from steady state load stresses. Note however that this tube arrangement and the turnbuckle and toggle end higher up in effect has rotational freedoms in both planes due to the pins being in 90deg different orientations - but the deck saddle loading for inwards loads is still not advised.

d The 6x50 chain plates with turnbuckles (and their toggles) for caps and diagonals should be far more resilient in strength and fatigue than your original welded arrangement, and any saddle arrangement. Note that for fatigue a repeated cycle load case of less than 1000 is not considered - obviously if a strength load case of less than 1000 cycles occurs, of a magnitude so as to cause yielding in any component, then there is a problem.

e So your flat bar in the caps and the above tube in the caps - why cannot a normal cap shroud with turnbuckle and toggle be fitted to a flat bar chain plate? Have the turnbuckle toggle end pin as low as possible to the deck so that the chain plate flat bar bending moment at the deck junction is not amplified under the mast fore and aft loads when raising / lowering.

Ok got it, good one. Certainly agree you need that wobble stopper function to be maintained for the reasons you outline.

Yes good thoughts.

The first option with short 30x30 square bar length to the flat bar length seems too busy sorry to say, is unnecessarily introducing more components and all the edges on those square and flat bars will not do sails or ropes or hands/fingers/arms /legs any good.

The 2nd option with 25mm round bar for the whole length seems a lot more palatable. For the fork end to the chain plate drill a hole 1mm larger diameter than the chain plate thickness and hacksaw into the sides of it so that the stress concentration of the fork end is not excessive. Finish carefully with hand files - rat tail and flat files. For the flat ground end similarly fair the flats into the round bar with suitable radius - finish with suitable 1/2 round files. Your workshop would benefit with a drill press for the hole drilling - and also a suitable drill press vice. Or a mate could have these? Bunnings have both for <$200.

The RF816 looks good but its breaking load of 1000kg (point loaded pins) and 1200kg (uniformly distributed loading of pins) is below a typical 4mm 1x19 316 ss wire which you are maybe using as caps - at around 1340kg. All fittings in the standing rigging must be greater breaking loading than the wire.

Ok good.

If you have a drill press a good strong clamp can suffice to hold the part being drilled - albeit a round bar makes it more critical for securing integrity as it can inherently rock / roll. Need to centre punch the hole location really well and start with small drills and work up to the final diameter.

Zzzzzz said..
I understand the modern way of doing chain plates through the deck into the bulkhead is better for the sheeting angle, but I have never seen one that doesn't leak a real pain never ending And of course most get bolted to plywood bulkheads so eventually you end up with rot and structural integrity.
As a cruiser I have always liked the simplicity of straps down the side of the hull , and if I am right the extra strength of the rigging from the wider angle .

And the important benefit of having clear side decks to walk along

The purpose of the deck cover plates with 4 self tappers (see photo above) is, in conjunction with suitable sealant and properly done, to seal the deck chain plate slot from any and all water ingress. I have had many yachts with this arrangement which do not leak.

Without getting into semantics or being pedantic, a wider chain plate base won't increase the strength of the rigging, it will reduce the loads in the rigging.

Yes longer spreaders would be needed if widening the chain plate location.

Fantastic news I have some work for you

A big day today, and the first of many to come. Today I dropped the mast, removed the furling gear, took off all the standing rigging and secured the mast to the crutches that will have to hold it for a month whilst I do the deck repairs.

Here's a shot showing the wobble stopper in action.

The seagulls seem to appreciate the nice long roost I set up for them.


Lots of wire. Pockets full of clevis pins. Hope I remember how it all goes back together.

Whilst out in the moorings I took the opportunity to do a survey of the chainplates and wobble stoppers on nearby boats.

This is from a Spacesailer 27. Nice strong through deck chainplate. Wobble stopper is tube with welded lugs either end.

This is the chainplates on a magnum 8.5. Solid piece of steel, but welded to a deck connection plate. Nice long weld, but I wonder if the lowers pulling forward like that is good for it.

This is the wobble stopper from a 30ftr. Tube with a welded u at the bottom (had a welded tongue at the top). Not sure i like this one.