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

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TheGuvnah
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by TheGuvnah » Thu Jun 08, 2017 11:11 pm

Well the arbor and slitting blade cut OK but the end clamp on the arbor meant I couldn't get it closer than about half an inch from the hog plus it's far too uncontrollable to be safe and I like my toes.

Plan B - Rummaged through the tote and retrieved a Starrett 16mm hole saw without a pilot drill in it. Bingo; I know these will work because in extremis I've even used them sans pilot drill to cut holes in steel trunking. The trick is to get the drill at top speed, get a really firm, braced grip and caress it at a slight angle into the timber such that it almost 'sands' out a horseshoe shaped guiding kerf for itself. If you try to plunge it in or chicken out and try it at slow speed it will just kick violently and chatter but once you're a couple of milimetres in it'll stay there. No matter how careful you are or slowly you try to feed it at the start it'll probably grab and kick back sooner or later so I wouldn't be doing this on any timber I wasn't prepared to scrap.

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Sorry about the cruddy phone pics btw.

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See what I mean about that arbour saw, it gave the case a little 'love bite'! :shock: But that's the head and half the shank removed from the system and you can get an eyeball on the remaining bit. Now I switched to coring it vertically to a few mm shy of the hog timber.

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Can't really call that a screw any more never mind a "fastener". I could have spent another two days having a go at digging out the heads and extracting each individual one but it would have been completely pointless. all were in the same state and "not for turning". (Oop, liddlebiddapolitix there :shock: )

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Once I'd got the required depth I did another cut below the first to gut out as much of the remainder and as close to the joint line as I dared.
The last one on the port side was the only one that's come out damp so far but I'm pretty sure there's another one lurking under the knee.

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That Starrett is like a knife through butter and rigidly made of quality steel; I would definitely NOT try this with one of those multi-blade multi-size 'universal' pound shop hole cutters. A few hours work and I've got 3/4 of the way round the case, that's pretty good going I reckon.

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and the "Remains of the Day"....

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In theory the only thing holding the case on now is the 2mm long stumps of the screw shanks, a bit of epoxy doing its best to grip sodden timber at the front and whatever was used as the jointing medium when it was built, be that sealant or adhesive?
The objective is to get this fellah out as one complete undamaged unit, firstly so I can use it as the dimensioned 3D template for the new one and mainly because that's how it's gonna have to be re-installed. It looks as though it will as there's enough flex in the main thwart to allow for some twisting and shoving. If it really won't wiggle in then I'll throw a pair of ratchet straps around it with a temp brace inside to hold shape and chop out the rear thwart. I've already put a pair around the launch trolley's frame and tightened them up to meet the hull and support the weight of me inside. I've cut some rough 4mm ply floors to spread the load as I'm standing/kneeling on the hull panels.

Any thoughts on the best way to separate the glue or sealant line or do I just start at the aft end by working a few scraper blades in there. The case doesn't matter and I'm thinking that the blade will take the timber of least resistance. If I chamfer or bevel the underside of its edge that will also encourage it to preferentially cut upwards away from the hog and into the softwood rails. Desperation tool is a wire saw with me on one end and a bungee on the other end to do the return stroke. Could work? Ah wait a minute, there're those new oscillating blade side cutter affairs out now aren't there. They've always looked a bit too 'model builder' rather than serious DIY/site tool though. Anyone ever used one in anger on anything bigger or tougher than picture frame stock?

Now is also the time to consider what material to use for the new screws. It's a toss up between Sil-Bronze or stainless steel. I'm looking at the tub of stainless fasteners I've removed so far and not one shows any sign of corrosion at all. OK they've only been in there a few years and not strictly speaking in an anaerobic environment but nevertheless they look good to go again. The actual real world longevity of the sil-bronze option I'm not sure about although they would look better, ...maybe... A mix of bright stainless fittings and polished or patinated bronze never really looks right through my eyes.

So my real question is; will stainless fasteners be suitable for the case hog joint?
Last edited by TheGuvnah on Fri Jun 09, 2017 5:34 pm, edited 1 time in total.
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SoggyBadger
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by SoggyBadger » Fri Jun 09, 2017 11:14 am

I've never had to take a centreboard case out but I think I'd try using a chisel. I'd start at the aft end of the case where there's load of access room. I bet once you've go a decent length detached it'll basically "unzip".
Best wishes


SB

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

Post by TheGuvnah » Fri Jun 09, 2017 6:48 pm

Got another few hours in this a'noon, first job get those winches out of the front of the case. you'll recall me mentioning it drawing blood every time I went near it, here's what they've done to the inside of the case.

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Aha! full size pics at last. 8) I'm having no more of that which is why I need to replace the lot with synthetics.

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The wire threads into the hollow spindle and secured with a figure '8' knot at the end and drawn back inside the spindle.
SoggyBadger wrote:I've never had to take a centreboard case out...
Me neither...
SoggyBadger wrote:...but I think I'd try using a chisel. I'd start at the aft end of the case where there's load of access room. I bet once you've go a decent length detached it'll basically "unzip".
Great minds think alike, that's exactly what I did. :D

First thing to come out had to be those knees, the only screw I managed to extract from the underside was a 3/4" stainless self tapper which was holding the outboard end of the l/h knee, the other three just span in their holes. The knees are marine ply and cold to the touch from the floor to about a third up the height of the knee. No point trying to save them as replaceable so I thought I'd repeat the method I used to open up the Ent's rudder stock i.e. splitting the plies off one by one with a chisel. If a modicum of care is taken I should be able to retain the outline of one half for a template.

The 60yr old ply was impressively difficult to part until I hit the damp at which point it practically fell apart. ( So glad I didn't opt to chuck her straight in the oggin! :shock: glug glug glug :oops: )

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Cor me knees are knackered! :roll:

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That took all of half an hour to get them out so now to turn the weaponry on the (Douglas fir I think) case rails. i applied a few cursory strokes of the panel saw more out of hope than optimism but it was impossible to get a comfortable stroke and safe angle of attack to make any decent progress with it as I suspected. Sod it, there's nothing I need to save so in with the chisel, it's the most effectively 'destructive' but the least 'damaging' tool for the job and I would echo the Badger's advice if anyone's doing anything similar. Bloody time consuming though.

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Two hours work yielded about a yard of cleared seam.

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Tomorrow I think I'll chuck a 20mm Starrett in the driller and core out the whole length of each rail to take out the bulk of it and save the old muscles for the clean up back to bare wood. The bit I've cleared now looks to be fully separated from the hog. :) :) :)
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ent228
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by ent228 » Sat Jun 10, 2017 7:50 pm

April 2017 issue of RYA Wavelength recommends a spindle diameter of 8 times the diameter of the rope. Otherwise the breaking strength of the rope is considerably reduced. So get rid of the wire rope but you might have to make the winch spindles bigger.

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

Post by SoggyBadger » Sat Jun 10, 2017 8:44 pm

ent228 wrote:April 2017 issue of RYA Wavelength recommends a spindle diameter of 8 times the diameter of the rope. Otherwise the breaking strength of the rope is considerably reduced. So get rid of the wire rope but you might have to make the winch spindles bigger.
The best thing to do with the winches is bin them. A cascade kicker is trivial to make and 100 times better. The other winch might be for the jib halyard. I'm not sure what the current fashion is on Ospreys for tensioning the jib halyard but the photos I've seen suggest they're still using a muscle box on the mast like we did in the 80s.
Best wishes


SB

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TheGuvnah
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by TheGuvnah » Mon Jun 12, 2017 4:28 pm

SoggyBadger wrote:I'm not sure what the current fashion is on Ospreys for tensioning the jib halyard but the photos I've seen suggest they're still using a muscle box on the mast like we did in the 80s.
Is the positioning of these theoretical muscle boxes critical? What I mean is I'm loathe to drill holes in a mast without very good reason; how much travel would be needed (I've found a pair but would 100mm be sufficient?) and could they be sited on the c/board case instead of the mast?
I need to have a full picture and a plan of where and how ALL the strings are going to be run fair before I start fixing anything in place to avoid potential downstream conflicts and the ugly work-arounds that will result when I realise I've forgotten something (spinnaker controls spring to mind as I've no plans to be flying that thing initially)
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by Michael4 » Mon Jun 12, 2017 4:48 pm

As an aside I have twice used a multi tool to remove a centreboard casing. Simple but scary. After trying to undo one screw I gave up. Brass screws crumbling to nowt.

On both occasions I used a fine blade and went through all the screws, glue etc. The trick is in getting the angle of blade just right so you don't start slicing off slivers of hog or case. Take the board out first!!!

Obviously when replacing it I re-positioned the screws and this time used silicon bronze (which broke the bank) and bedded down into a mastic. Stainless screws would be fine.

This on boats where the case is held by long screws coming up through keel and hog. The result is invisible.
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by SoggyBadger » Mon Jun 12, 2017 10:53 pm

TheGuvnah wrote:
SoggyBadger wrote:I'm not sure what the current fashion is on Ospreys for tensioning the jib halyard but the photos I've seen suggest they're still using a muscle box on the mast like we did in the 80s.
Is the positioning of these theoretical muscle boxes critical? What I mean is I'm loathe to drill holes in a mast without very good reason; how much travel would be needed (I've found a pair but would 100mm be sufficient?) and could they be sited on the c/board case instead of the mast?
I need to have a full picture and a plan of where and how ALL the strings are going to be run fair before I start fixing anything in place to avoid potential downstream conflicts and the ugly work-arounds that will result when I realise I've forgotten something (spinnaker controls spring to mind as I've no plans to be flying that thing initially)
I don't think the position is critical but they're generally on the mast just under the gooseneck. I think a 100mm box might be a bit short. I suspect two triple blocks arranged to give a 6:1 purchase would be just as good. That's actually what's inside the muscle box. I strongly advise you to join the class association. They'll be able to give you lots of good advice.
Best wishes


SB

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

Post by TheGuvnah » Mon Jun 12, 2017 11:15 pm

Michael4 wrote:As an aside I have twice used a multi tool to remove a centreboard casing. Simple but scary. After trying to undo one screw I gave up. Brass screws crumbling to nowt.
Yeah I tried one... :x ... then I tried another one... :evil: :twisted: bugger that for a game o' Russians, time to go smorgasbord on these things.
Michael4 wrote:On both occasions I used a fine blade and went through all the screws, glue etc. The trick is in getting the angle of blade just right so you don't start slicing off slivers of hog or case.


Aha.. supplementary question: How effective are they? With 10 being 'hot knife through butter' and 0 being blunt antler pick on concrete where on the scale would you rate them?
Michael4 wrote:Take the board out first!!!
Ho yusss! :lol: thank God the workshop has a traveling gantry crane, had to sling the stern and hoik the back up a whole two feet before I could wiggle it out.
Michael4 wrote:Obviously when replacing it I re-positioned the screws and this time used silicon bronze (which broke the bank) and bedded down into a mastic. Stainless screws would be fine.
Well I'm toying with the pros and cons of using these fellahs, hex head A4 stainless sleeper screws.

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First up, I could actually and happily live with that line of glinting stainless soldiers doing security duty around the perimeter of the case. There is a countersink and an additional flange (looks to be 10mm diam) which offers slightly increased load spreading. The 8mm hex heads should be a lot more resilient than a 0.5mm deep brass slot to the torque required to drive them in and shouldn't be visually intrusive but it wouldn't be too onerous to turn up some wood 'buttons' to cap them off. Just as importantly it should be a whole lot easier and less intimidating to withdraw a few for inspection every now and then so there's an element of planned / preventive maintenance involved here.
Michael4 wrote:This on boats where the case is held by long screws coming up through keel and hog. The result is invisible.
That's the next unknown, how long are they? Won't know that to the nearest quarter inch until I've got the case out and can core out the remains of a few.

Cheers Mike
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by Michael4 » Tue Jun 13, 2017 5:20 pm

Regarding the multi tool, at full speed it is too quick to be accurate. Hence the value of one that you can slow down in order to see how much of a mess you've made before proceeding.
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by TheGuvnah » Tue Jun 13, 2017 9:36 pm

SoggyBadger wrote:I don't think the position is critical but they're generally on the mast just under the gooseneck. I think a 100mm box might be a bit short. I suspect two triple blocks arranged to give a 6:1 purchase would be just as good. That's actually what's inside the muscle box. I strongly advise you to join the class association. They'll be able to give you lots of good advice.
Panic over - finally found a spec list for the Holt Allen box and its got 150mm of travel.
Michael4 wrote:Regarding the multi tool, at full speed it is too quick to be accurate. Hence the value of one that you can slow down in order to see how much of a mess you've made before proceeding.
Oh right - sounds a lot more bitey than I imagined. Not half as bitey as a 20mm Starrett though I'll bet. Got a few hours in today and managed to get the lhs of the case free & clear.

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Quite a few soggy cores came out of the leading 12" of timber.

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

Post by TheGuvnah » Fri Jun 16, 2017 4:04 pm

SoggyBadger wrote:
I don't think the position is critical but they're generally on the mast just under the gooseneck. I think a 100mm box might be a bit short.
There is/was a pair of Holt Allen H233 boxes on Fleabay at the moment which initially caught my interest...

http://www.ebay.co.uk/itm/252982958382? ... EBIDX%3AIT

...but closer examination of the packaging revealed that they are only 75mm travel not even the 100mm so a coupla 3 sheave blocks it is then. K.I.S.S. as they say.
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by SoggyBadger » Fri Jun 16, 2017 10:47 pm

TheGuvnah wrote:
SoggyBadger wrote:
I don't think the position is critical but they're generally on the mast just under the gooseneck. I think a 100mm box might be a bit short.
There is/was a pair of Holt Allen H233 boxes on Fleabay at the moment which initially caught my interest...

http://www.ebay.co.uk/itm/252982958382? ... EBIDX%3AIT

...but closer examination of the packaging revealed that they are only 75mm travel not even the 100mm so a coupla 3 sheave blocks it is then. K.I.S.S. as they say.
Yes from memory the old Allen ones had a lot less travel than the much beefier Harken ones. But I'm not sure if Harken still make theirs. I can't find them on P&Bs catalogue.
Best wishes


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

Post by TheGuvnah » Sat Jun 17, 2017 6:18 pm

SoggyBadger wrote:
Yes from memory the old Allen ones had a lot less travel than the much beefier Harken ones. But I'm not sure if Harken still make theirs. I can't find them on P&Bs catalogue.
I did quite like the funky wheeled winches but I think triple blocks win the day for the purposes of a quick re-commissioning.

Got all the seams cleared but she wasn't having it with that thwart in the way so it had to come out.

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Still no joy so it's out with the rear traveler thwart, not fannying about with this now if it's going to delay anything it's coming out.

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... and out she comes. Hallelujah! :D :lol: 8) Image

So what's it like where it matters?

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Well the scraper could take out about a 1/4" of depth and after that it seems fairly solid which is encouraging.

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First up is to get some definitive measurements off it so I had no alternative but to loft it out on the living room floor where the floor tiling makes a handy ad hoc datum line.

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No worries, it all washes off and it's me that has to wash it. :cry:

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The plan is to whizz down the m40 tomorrow and pick up another headboard and then we're ready to go.
Last edited by TheGuvnah on Wed Aug 02, 2017 2:19 am, edited 1 time in total.
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Re: de-bodging an Osprey centreboard case - advice req'd

Post by TheGuvnah » Tue Jun 20, 2017 11:07 pm

Well you live and learn and today I learned that old Stag headboards are not in fact solid timber but heavily framed around the perimeter with a thick band of timber and the rest is particle board. :oops:
My belief was based on my setting the plane to a "manly" depth and taking ten heavy passes along the top of the one I already have to see if it was just a veneer shfffft, shfffft shfffft. Must have taken off a 1/4" of crisp, curly shavings, lavverly stuff, that'll do fer me! Didn't think that it might be framed (top and bottom) in solid. my bad! Credit where it's due though it's perhaps the best slab of high density chipboard I've ever seen, properly consolidated all the way through, no hard outer skin with an interior the consistency of Weetabix, it grips annular ring nails like they grew there. No good to me though other than (very heavy) shelving. Aha, :?: just what I need to fit out the lathe's stand with cupboard and drawers now I think about it and it was only a tenner. It's an ill wind an' all that. :D

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Plan C - I still want/intend to beef up the construction of the c/brd case by upping the thickness of the sides to 12mm the better to take reliable fixings. To this end I'm in process of sourcing some decent looking Blue Gum (Eucalyptus) marine ply fairly locally and have found an offcut 'project remnant' of 18mm even more locally from which I can fabricate new knees and also the top faces of the case. 18mm top rails should again be more able to receive and more importantly, retain whatever gets screwed into it.

So this Eucalyptus ply? Anyone ever used it? Apparently Blue Gum is widely used in Australia and New Zealand as a boat lumber even for pilings, jetties, Samson posts and wharves so it's obviously durable.
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