de-bodging an Osprey centreboard case - advice req'd

[TheGuvnah]

My notions of the boys having their own Osprey each have taken a big leap forward on discovery of what is practically a sister boat to "Flypast" up for sale in Wales...









looking good but... it has an issue in the form of prior damage to the c/board case where the mainsheet swivel had yanked its fixings out. this was 'repaired' with what looks horribly like a bit of softwood so of course it happened again.



eeek... the current owner has fashioned a saddle affair which he proposed to drop on top of the bodge and then refix the swivel to that.... thusly...





Hmmm...??? I've asked him to hold fire on that for the moment.

Obviously the c/board case will need a pukka repair with a new full length mahogany capping made up to replace the blown out piece. But how to extract that capping without causing any damage that is the question? Can this be done in situ? Without a construction drawing I'll be going in blind which is never the best approach. Anyone have any advice on how to do this.

The problem for me is that I already have "Flypast" and Ent 878 in the workshop and I want this boat on the water NOT in the shop for a month, the boys will also brook no further delay. Additionally the thought also occurred to me that I would rather not have that mainsheet and traveller hogging all that space in what will (initially at least) be a cruise-about boat, it obviously imparts load into the centre case by dint of the fact that it pulled its fixings out so how about removing that all together by re-configuring it for aft sheeting. Apparently this was a feature of its original design. With two young boys leaping around the cockpit the removal of that guillotining traveller would be no great loss either. Been googling for any images or advice on aft sheeting an Osprey but have drawn a total blank which I didn't expect.

First thoughts are that there will be little more to it than drilling and fixing which is going to be a whole lot quicker than the repair to the c/board case and can be done in the dinghy park in an afternoon with drill and driver.

Anyone have any thoughts on this proposition?

Thanks in advance for any advice

Guv

[PeterV]

The case may not need a complete new capping, I've got several pieces added onto my transom and my hog, all are very strong because they're epoxied in, so provided the rest of the case is ok I'd just do a local repair.
A rear bridle is very easy to do, and provided you've got a decent kicker you can dispense with the traveller.

[SoggyBadger]

I think you should be able to patch it up quite well using decent Mahogany to form something like he's fabricated. Glue the whole thing in with epoxy mixed with gap filler. Whatever you do, over-engineer it. I know from 20+ years of racing Ospreys that you need to err on the side of over-engineering. If funds allow, I'd recommend ditching the old jammer and putting in a good Harken one with a ratchet block.

[ent228]

Can you sheet an osprey off the boom? Gets round the whole centreboard case problem with the addition of an aft bridle. I thought I'd hate it on the laser 2 but it's a real improvement, so much more room in the middle of the boat.......

[JimC]

If the screws are pulling out then it seems as if the piece of wood glued in is quite adequately attached to the boat, so no real need for a complete full length replacement. What you need is a way of bolting the fitting in place. I'd fabricate a carbon saddle, bolt the fitting to the saddle and screw in from the side so the fittings are in shear. If happier bending aluminium bend aluminium. Or just use off the boom sheeting.

[TheGuvnah]

Apologies for the delayed response, been chewing over the options...

A rear bridle is very easy to do, and provided you've got a decent kicker you can dispense with the traveller.

Yup, that's the way I'm thinking of doing this, the graphic below seems as good an arrangement as any of the seemingly endless variations on the theme that I've found.

https://s6.postimg.org/p3xzceuip/aftmainsheet.png

...and realised in the wood on a smaller scale... cute,

https://s6.postimg.org/mlcabq8sh/32f_-_ ... igging.jpg

Can you sheet an osprey off the boom?

Looks like it, now the issue becomes one of hardware specifically where and how to anchor the bridle. I was initially a bit worried about taking the bridle ends to the gunwale timber but thinking it through says that if the gunwale timbers are beefy enough to take the rowing loads produced at the point the rowlocks penetrate them they should be able to handle the bridle anchors.

https://s6.postimg.org/loagglmo1/Flypas ... timber.jpg

But what anchors? Speed and much cheepniss are the prerequisites here so I'm thinking maybe a pair of these in stainless...

https://s6.postimg.org/6i4epnwn5/galvan ... -plate.jpg

or perhaps a single drilling lined with a Delrin bushing to take one of these each side, an M10 bolt size would seem to be sufficiently over-engineering it.

https://s6.postimg.org/6jecj2ygx/eye-bolt.jpg

Even galvo ones would do as a 'get y' going' expedient till I can source a pair in bronze or stainless.
Here's the u/side of Flypast's boom and its boom fittings track; oh aye, looks like it used belong to Ozzy325

Or.... would I need to go with upstand pulleys and camming cleats so that some adjustment of bridle length can be achieved from the cockpit?

I'd fabricate a carbon saddle...

Blimey! After you!

and screw in from the side so the fittings are in shear.

Definitely.

If happier bending aluminium bend aluminium. Or just use off the boom sheeting.

Hmmm thinks..., I do have a goodly quantity of bronze plate at 2mm thickness doing bugger all useful. But that's another week of design and fabrication. that said if I go with the 4 bolt fixing eye plate I'd still need to knock up some backing plates for the underside of the gunwale to stop the nuts being winched into the timber.

[JimC]

I'd fabricate a carbon saddle...

Blimey! After you!

No, its dead easy, honest, at least if you don't want a pretentious clear coat mirror finish with every fibre in place.
You start with a piece of wood which is the right thickness and same or greater depth, radius the corners nicely and wrap it in parcel tape. This is your mould. You get three more bits of wood , one the width across top, and the other the size of the sides, and wrap them in parcel tape too. Parcel tape is all you need as mould release for carbon components.
Put your first pair of disposable gloves on.
Ideally you damp a bit of peel ply in resin and put this on the mould first, but its not quite essential. Make the peel ply well oversize.
Now you get bits of carbon cloth and cut them to the size of your saddle. I'd probably have 4 bits of woven cloth and about a dozen unidirectional for this.
You wet out each piece of cloth in turn and place them on the mould, all at the same time, and before the resin cures. Slow hardener advisable.
Put a new pair of disposable gloves on
Put another piece of peel ply over the top and press it all down so its all thoroughly consolidated and everything wetted out. Have the last piece of peel ply overlapping the bottom and taped in place. You could skip this but best not.
Put a new pair of disposable gloves on
Place your 3 extra pieces of wood over finished layup. Get G cramps, and clamp firmly in place using plenty of pressure. Large quantities of resin should squeeze out of the sides. Just wipe it off with kitchen towel or something. Leave to cure. If its winter put it in a plastic bag and on a radiator for 24 hours to cure, because heat at this stage helps loads. In the summer - out in the sunshine.
Remove clamps.
Pull off the peel ply.
Paint. If you insist you can use filler to fill all the cloth marks first.

Yeah, it sounds complicated, but how much of it is skilled? Pretty much none, because you are painting it, not going for pretty pretty clearcoat.

[Ed]

I can only agree with Jim really.....

You could use aluminum. or indeed bronze....both would look great and work fine....

but despite what you might think....making it in carbon is by far the easiest and fastest way to do it.

Really the only problem with making stuff from carbon is knowing what to buy...and where from...and getting it at a reasonable price, if you are only buying little bits. ebay can help, or you have to find a helpful supplier. I have always gone to Wizz at Matrix Mouldings http://www.matrix-composites.co.uk/ in Bristol, but there are places all over the UK. You just need to find them.

The only thing I would add is that I think Jim took it as given, but the resin you want to use is Epoxy not Polyester. Polyester might work, but would not provide the strength of epoxy. The other thing I would say is that one tool you might be thankfull for is a grinder with cutting and sanding discs. These will be useful to clean up afterwards.

Working in epoxy/carbon is not hard at all, but does presume a certain amount of upfront investment in 'stuff' and a couple of experiments before you get the confidence that it works as easy as we make it sound.

The problem I sometimes have is rushing on too fast and not making really reliable moulds and tooling. It is so easy, I can be tempted to just throw it all together and hope for the best and sometimes it works....and sometimes.....well it could be better. Last week I was making 'cleat bridge' and originally planned to use vacuum to pull the foam/glass down onto the complex shaped mould, but my bench was untidy and I couldn't be bothered to pull out my old fridge compressor that pulls my vacuum, so figured I could do it with clamps and wood. I almost could but one bit I couldn't get a good pressure on. so now I have a cleat bridge with a wobbly top. Still it was a good test piece. Next one will be true and end up either with a pretty carbon top or possibly a nice manogamy veneer.

Give it a go, it really is very easy once you have played a bit.

Best wishes

eib

[TheGuvnah]

Thanks fellahs, I'll take your word for the ease with which it's possible to fabricate in cee-fib and a pictorial sticky would be the clincher not to mention a fascinating eye-opener for me and everyone. Aesthetically though I'm not sure it's what I'm after for this boat. If it was a modern composite boat then sure, I'd be all over it, for O-892 I think bronze would be the way I'd want to go.

In my mind I'm still preferring the aft sheeted main: the main tackle running on the bridle, the fall taken along the boom through a couple of track eyes under the boom to a block directly above where the original swivel jammer was fixed to the c/board case. From there take it straight to hand OR (better) down to the repaired swivel/cam cleat which seems a more 'handy', controllable and seaworthy set up.

The thought did occur to perhaps bring the fall of the tackle down at the stern thus removing the last bit of rope swinging across the cockpit but that would mean a bit of clever swap-handing at every tack with me ending up in some sort of @rse up masonic handshake with the tiller, there'll be mutinous ridicule from 'me hearty crew' , pointing, laughing etc, well at least until the old motor memory centres get it sorted and stored! There's also the possible obstruction of the tiller's arc? Can't figure a rig to solve that one immediately so it's back to the mainsheet terminating at the swivel cleat on the c/brd case again. Sooooooo that swivel mounting then.....

...I'm thinking a simple 'U' shaped bracket/saddle bent from one of these bronze plates, 4 or 5 countersunk drillings each side to screw it into sides of the c/case leaving an inch or so stand off from the case top, a 10mm (off the top of my head) hole in the top of the saddle/bracket to accept the swivel base.

QUESTION - when I'm driving those screws in, how long do they need to be? What I mean essentially is how much clearance is there in the case when the board is fully up and will I be screwing through the case ply and straight into the chuffing centre board if I use any screw longer than about 1/2"? Anybody got a sketch or drawing of the c/board case construction.

The lads and I will be going across country tomorrow in fact to pay up and trail her away Gotta be wary of an untried trailer so I've whipped both brand new 4"p.c.d. wheels off my trailer and stashed them in the car just in case but then thought "hmmm... lunched bearing, mid-Wales, late a'noon, on a Sunday? in the rain!!" so I hoiked a hub off, bagged it and stashed that as well. Got a bucket load of ratchet straps, fathoms of light cordage and sundry webbing and I'll chuck a 75mtr coil of 12mm braid in the back and a beefy home made snatch block, a tote full of 'go-to' tools, a multimeter for that godawful chinese tow bar plug and skt combo that has been a constant plague of corrosive woes if unused for more than a week, a couple of 'saws-all utility and hack saws, the battery driller's on charge as I type, a bunch of leads for the ciggy lighter USB charger, my bolts 'n bits box with all the electrical widgetry... and finally... aaargh no Sunday dinner! ...don't want to be stopping so I'd better put together some nosebag for the trip. Thank god that blast of hot weather has dissipated, didn't fancy being rotisseried behind that screen for 5hrs.

[Rupert]

Aft mainsheet are very out of fashion, but actually they are easier to tack with, open up the boat for cruising and solve all the centreboard case issues in one fell swoop, if that is really an expression.

Downsides are that you face backwards when tacking (in reality, for about 2 seconds) and the aft pull from the sheet can tend to get helms sitting too far aft. However, with nothing in the middle, sitting forwards is a doddle. Put a bridle on the transom, set so you go block to block when sheeted in, and centrelining the boom is easy.

Can you tell I grew up sailing Fireflies?!

[TheGuvnah]

...and solve all the centreboard case issues in one fell swoop,

Ah.... would that it were so...

Packed the lads off into town with their mate to a "MotorFest" or something and just got back from grabbing a few hours 'quality time' mucking out and examining the boat up close. It would appear that I didn't spot the strategically placed beads of epoxy that girdle the base of the c/board case. Bugger! They must have been put there for a reason and probably not a good one! True enough once all the accumulated dried silt and goops of varnish had been scraped back I found lot of damp timber around the for'd end of the case and a bit (hopefully just a 'bit') of penetration into the keel timber. Nothing for it but to get that centre board case off so I can see how far this has gone. Double bugger!

So, options?
Option 1) Remove and rebuild a whole new case from scratch (or from timber if scratch is unavailable): given its already visible issues this would be my preferred option. Downside is the time involved and the fact that I want this on the water in time for the school's Summer holidays. Although having said that, it does look to be of pretty straightforward construction with no fancy schmancy rebates. Also I don't have any drawings to go off but once it's off it becomes its own template I suppose so building a copy is a case of "monkey see; monkey do".

But here's a thing; would there be any benefit/downsides in increasing the thickness of the side panels from what looks like 1/4 ply to 8mm ply? Reason being that on closer inspection all of the screws that secure the various fittings to the case have penetrated through and out the other side because they're too long but anything shorter just wouldn't have any holding power. 8mm ply would resolve that.

Option 2) Remove the c/board case from Flypast which is in excellent condition and install it into 892.
This sounds easy when you say it fast but would it even fit? One design or not I somehow doubt that these things are dimensionaly identical or interchangeable without a lot of fettling and fannying about with shims and the like. Also I'd be adding to the job sheet for Flypast and "if it ain't broke don't fix it!" as they say.

Hmmm I think I've just talked myself out of that which leaves the option of stripping out and restoring the existing one or refabricating from new in 8mm. Would 8mm side panels take it out of class? Come to think of it there's enough mahogany in that old headboard to build a case out of solid timber. The two for'd knees are not in the best condition and could also be remade in the solid. With a solid mahogany case I'd feel a whole lot easier about reinstating the centre mainsheet rig.

The thought occurs that it would also be a good opportunity to machine up and install some Delrin bushes at every bearing point in the c/board pivoting arrangement as I have done with the rudder on the Enterprise. This has removed every remnant of slop and play in her rudder foil/stock, there's no longer that bare wood flexing and pivoting on bare metal mullarky which so offends my mechanical sensibilities so all wear on the timber blade is removed completely and they're a readily replaceable tight push fit when they do eventually wear. Doing a similar bushing job on the c/board will similarly remove all wear points from the wood and will surely add a few degrees more to its ability to point.

The lads are back in school on Monday so time will once again be freed up to get properly stuck into this.

Your thoughts gentlemen?

[SoggyBadger]

My advice is take the case out, clean it all up and glue it with epoxy. That'll hold for ever without the need for screws. Rot in the hog or keel may be an issue but there are plenty here with experience of sorting stuff like that. I think the urgent thing is to get the case out and get everything dry first.

[JimC]

Would 8mm side panels take it out of class?

No need. If you're taking the case out and stripping to bare wood then just glue (epoxy) on generous sized 4mm patches where you want the fittings to go. The glue area will be so great they'll never move and it will be just as solid as if the whole case were 8mm ply.

[TheGuvnah]

My advice is take the case out, clean it all up and glue it with epoxy. That'll hold for ever without the need for screws.

Hear what you're saying Badger but have to say I'm not that keen on introducing epoxy at the hog/case joint or anywhere else it might compromise the ability for either me (or the lads in the future) to take it apart and repair stuff that breaks or wears beyond use. I'll happily assemble the new case (for that is the plan) as a modular unit using epoxy but its actual interface with the hog timber I'd like to be able to release for inspection & maintenance without resorting to destructive methods.

Would 8mm side panels take it out of class?

No need. If you're taking the case out and stripping to bare wood then just glue (epoxy) on generous sized 4mm patches where you want the fittings to go. The glue area will be so great they'll never move and it will be just as solid as if the whole case were 8mm ply.

Yep, that'd work. Just been scanning the 2009 class rules and on p19 it gives a minimum thickness for the case side panels at 7.35mm but no maximum dimension. Job on then, solid mahogany case it is. The only fly in the unguent is that no matter how I slice it I won't get two sides out of the one board but there're always a couple for sale at any one time around the Midlands. Actually I've just discovered that these big old 70's Stag headboards (and most of the "Minstrel" range furniture) aren't mahog but makore (African cherry). Looking it up in the timber databases suggests that it is very durable and quite suitable for marine use as far as boatbuilding lumber goes.

I think the urgent thing is to get the case out and get everything dry first.

Damn straight. It would have been possible to put her (him?) in the water immediately and get a Summer's use but now I know it's there my conscience just won't allow it. I don't know what it is exactly; maybe the knowledge that I'm just stalling the inevitable, the knowledge that my slack attitude would be causing further gratuitous (nay sacrilegious) damage, the penetrating fact that I'll have my two most precious belongings sat in there with me, I'm no perfectionist (well maybe a bit) but the sight of all that depressingly stained timber would irk badly and further compound the nagging thought that the whole shebang could really give way big time... all of these and more. Chisels? Saws-all? Dynamite? whatever; it's coming out this week no matter what.

The thought occurs that it would also be a good opportunity to machine up and install some Delrin bushes at every bearing point in the c/board pivoting arrangement as I have done with the rudder on the Enterprise. This has removed every remnant of slop and play in her rudder foil/stock,

Further reading indicates this is NOT what I should do. accepted knowledge is that the foil actively needs that side play in order that it can bear against the keel slot rather than transfer the sailing loads straight up into the pivot and its bearing surface. In which case the pivot pin or bolt would always be trying to split the case timber horizontally with every blade flexing wave and gust. That can be resolved by boring the bush to the exact pivot diameter and then running a taper reamer in there to give a few degrees of lateral play but still removing any up and down play in the system.
At the moment there's what looks to be 3/8" brass bolt doing service but the engineer in me says that it wouldn't hurt to install something a bit meatier, say a 3/4" ally-bronze pin + captive 'R' clip. Cold wet fingers - fannying about with fine thread nuts, nah, got to be a better way.

Time for some pics...



A few nibbles out of the edges but also a repaired split. Still looks serviceable although I haven't tried flexing it in anger to see if the fracture is open or not.

Here's the front of the case... note fan heater (I set it on low power and have the bows semi tented with polythene to retain the heat rather than the temperature)





I'm liking the alternative 'muscle box' winches, one's for the Cunningham, gawd knows what the other one was led to, probably the vang arrangement? What I'm not liking is the finger piercing rat's nest of irrevocably twisted and fractured wire that issues from them. Replace with synthetics of some sort I think.



The two bump stops have taken a few too many heavy drops and this has split the wood along the screw line. I've found a worrying number of bare steel screws peppering the case all showing varying degrees of corrosion and its attendant staining. what if the screws into the hog are... Ulp! uh oh Cross that bridge when it comes.



...and something I wouldn't mind retaining...



This cleat board seems as good a way as any of marshaling the spaghetti, colour coded stop ends and so forth, I like it.

[TheGuvnah]

OK time to bite some bullets, pack the tote with all the sharp cutty stuff and set to getting this centre board case oot.

Uncovered the plugged thwart retaining screws with a few strokes of the rasp...



Lovely tool that rasp, practically sharp enough to shave with and you've really gotta watch your fingers with this bad lad, if you misplace a stroke it'll bite! It leaves a super smooth 'cabinet scraper' finish though and it'll even pull off the same trick on end grain. I can't think of another tool that can do that which isn't high speed and electrically powered? (As with saws I preserve their edge by never putting them down on a stone or concrete surface though, I keep 'em individually wrapped in anti-rust wax paper and a rag so they can't come into direct tooth chipping contact with other hardened steel tools)
Dug out the plugs: screw heads immediately stripped. Here we go... the torture never stops.

And so to the centre thwart fixings into the case...



Only the one long screw was doing anything productive towards keeping the case laterally fixed, the other two 1" and 1/4 no8's were just spinning in their holes.

As for the traveler, it's landed on some roughly carved sandwich of original timber and added packings...





Nah! sorry but I can't live with that it doth offend mine eye, s'gotta go!



Took half an hour to winch out those machine screws. Mind you one of those bits of packing will be perfect to reinstate the front taper of the Ent's keel where it turns up to meet the bow. He's done most of the shaping for me already.



...wait a minute... is that what I think it is?



Builder's foam and self tappers??? Oh that is definitely it, I'm having that out straight away. The trouble is it's lost a fight with a power driver bit so first up I cropped it back it to leave just a sliver of wood around the screw shank.



A sharp chisel and a quick tap with the persuader...

Gertcha!





Much better and the cockpit suddenly looks 6" wider and longer. So now there's nothing holding the case from above I thought I'd try a few of the hog screws before having to pack up and get back for the school run. They all seemed well covered with varnish which might lead the eternal optimist to think that they'd still be in a sufficiently sound condition to be withdrawn. Yeah right, tried two of them, both split their head slots immediately. Looks like they are/were brass originally now sadly more copper than anything. I'm not even going to bother trying to extract the rest.
What I'll have to do is get medieval on 'em and put an arbor with a fine toothed slitting saw blade in the battery driller and cut horizontally into the bottom rails and straight through the shanks as close to the hog as is safe. With some judicious wiggling, wedging and working of the joint I should be able to get it free and keep as much of the case shape intact as I can to take measurements off. Then I need to make up another hollow cutting bit to core round what's left of the shanks left in the hog, plug 'em and offset the holes in the new case and inch or so such that I'll be fixing into fresh timber.

Also had a quick exploratory session underneath to uncover the through hull fixings into the case knees. The one I managed to expose has pulled a long way into the ply and I have a horrible feeling that I'll need to scarf in a patch at each fixing. More embuggerance but then if it was easy everybody would have one.