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Beefing up the insides for JSD


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I'm planning to fit titanium pad eyes to the quarters of my small sailboat, to take the bridle-arms of a JSD. I reckon the laden 'mid-weight' will not exceed 9000lb, so Don Jordan's calculation of 'Design Loads' for rode and bridle arms at 7200lb and 5040lb each should be readily achievable using modern materials.

I dislike the external 'bolted-on steel strap on the quarters' idea. No work seems to have been done to determine the optimum load paths into the grp hull layup, nor optimum bolt size/number/placement. It's actually quite a complex engineering issue, and JSD users have just gone with 'That looks OK - probably. I hope....'

I want to put the reinforcement on the inside, and bolt on a pair of Harken 95mm titanium padeyes, rated at 20,000lb or better, as shown below. ( I happen to have them lying around ). The BUMAX bolts I've acquired are good for far more - each.

The issue I'm exploring is how best to beef up the inside of the grp hull, which is about 8-9mm thick. It will be seen there is a moulded-in 'rubbing strake' feature. On the inside this results in a 'dished' shape, which I propose to fill flat with thickened West epoxy ( G-flex or Six10 ).... adding a larger sheet of woven glasscloth, epoxied on/rolled flat ( with peel ply ), then a bonded-on  'plank' of grp sheet about 12mm by 700mm long by about 250mm wide..... each side port and starboard. This could be doubled, if thought needed. Access is not easy, but practicable.

I'll also bond on a section of 12mm grp 'plank' transversely into the transom corners, or a couple of layers of woven glasscloth.

The padeyes will be bolted through all this, with a 3mm by 700mm by 95mm strap of s/s bonded onto the insides acting as a long 'washer'.

I can't do a 'test rig' on the likely strength of the reinforcement when/if loaded to near 'Design Load' but am reliant on experienced guesses. Of course I need to make the whole setup 'massively enough' so there's no realistic prospect of catastrophic failure anywhere. A couple of good engineers have looked at the ideas and approved 'in general terms'.

What does the team think?

:unsure:

 

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These padeyes are to be mounted on the hull (not the transom) correct?? Then your 4 (each side) bolts are holding the load in sheer. Have you looked at how the bridles will attach to the padeyes? What happens when the hull slews to one side & the bridle has to wrap around the transom corner?

Since mount bolts will be sheer loaded, you need to determine the laminate thickness to hold that sheer load, then how much laminate to add to pick up that load & spread it forwards along the hull. Adding 'planks' won't do much, as the only added strength is the bond joint strength under the 'plank'

I'd add considerable laminate from transom corner forwards in a 45 deg fan (centered off horizontal). Considerable thought must be made as to thread alignment - you need uni threads going forwards to carry the loads, and 90 deg threads at the bolts to create sheer strength

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The possible max loads for a JSD (as per JSD) are the weight of the boat. There is nothing stock mounted on any boat (ex maybe a metal build) that comes anywhere near those numbers. Add in the need for a fair lead for the highly loaded bridle and you can usually eliminate anything not mounted to deck edges. I would guess maybe 1% of these ever get used in anger? So not a large data base.

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Thanks for the above. I've had lots of spare time these past two years to research. I've studied everything anyone has written on JSDs - including all Don Jordan's original material - I've scoured the forums and website comments, and I've spoken with all those individuals I could access who'd actually used a JSD - including one young lady who had one break on her. I've also consulted the rope makers, lifting gear manufactures, and the bolt makers in their Tech Departments. From all that, I determined that MY JSD will be way over-engineered, for there must always be assumptions.

Here are a couple of pics which better show what's intended, for joining the bridle legs to the padeyes and to the rode. The soft shackles are built for me from 11mm D12 Dyneema, which is rated 'single line' at 11600lbs. Some will recognise the Improved Soft Shackle - it gives notionally 230% of the basic s'shackle. Mine are made for me by probably the best in the biz here in southern England. I'm content to assume I'll get 200%.... That's more than 4 times the 'Bridle Design Load'.

The second pic shows the bridle-rode connection, before the anti-chafe sleeve tubing was delivered. Some expressed concern that the s'shackle could open during cyclic unloading. I'll use reusable cable ties to prevent that, although the antichafe sleeve also contributes.

As for chafe on the transom corners, there are plenty of glue-on antichafe patches available.

'Longy' is right in suggesting I should seek guidance on the number of plies of S-glass wide tape I would need to laminate in, rather than 'planks' of 12mm grp sheet which I already have. I'll probably go pester the tech director at Wessex Resins ( UK ) again, unless someone from West Systems - who sponsor this - reads the post and pitches in.

As for 'less than 1% of people actually use these', I view this kit in the same way I view my lifejacket and liferaft. The waters I sail include the Celtic Sea and Biscay, and are the exact same waters in which the Fastnet 79 storm took place. That disaster was why Don Jordan developed this solution. My boat is vulnerable to such conditions. It's entirely appropriate for my intended sailing.

 

 

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I don't think you want to use any basic level cloth. You have conflicting forces to deal with: sheer load from the bolts will want the threads running vertically (normal to the load) and to carry the loads out across the hull will want fore/aft thread lines radiating out from bolts. I'd be considering an un-woven heavy biax cloth (one layer of thread horizontal, the other vertical) possibly sandwiched by 45 - 45 cloth.

And your bolts need to be smooth shanked for the thickness of the laminate.

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Your original description of construction would be suitable for a load pulling nearly square from the transom. Basically adding some thickened filler to get a flat/smooth surface then bonding on a serious backing plate.

As others have noted that is not what you need to engineer. 

Easiest way to imagine this problem is to install your hardware and bridle. Hook the sling onto a crane and pick up the boat. It would be dangling bow down, transom up.  Beyond shock loading, the typical load is the weight of the boat.  What's going to keep the bolts from sawing thru the hull? 

You need to grind whatever texture is there back to bare fibreglass with 80 grit then get good bonding directly to the old glass. What about the hull construction? Glass/foam? Solid glass? 

If its a cored boat then you should grind thru the interior skin, remove the core, then replace all of that with solid glass. Otherwise you are relying on the outer skin and core to not be crushed or torn by the bolts. The load path is line, pad eye, bolts, outer skin, core, interior skin. You are trying to reinforce the wrong area. The bolt/hull interface is the key. 

The simple answer is you need to make that entire corner of the boat solid glass. If you look at your picture it's what's framed by that ladder looking thing. Rounded on the front, has to wrap around the transom. Minimum 100mm solid glass in all directions including around the corner. 

Better yet, pay a composites engineer for their opinion.

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It's not a cored layup, Captain Ahab, but thanks. As I stated, it is 'grp'.....

Conventional practice, if there is such a thing, is to take a strap ( or two ) of stainless, drill a number of holes in them, and bolt them with some gunk to the quarters. There's no known relevant 'composites engineering' on record..... as I stated. Don Jordan's comment on this was scanty - and he was an aircraft engineer. I have a bit of background myself in exposure to that discipline, and I know there are always 'other paths'. My task is to find one that fits, and is 'do-able'.

One example of 'that looks about right' without data is shown below, on a steel boat. There's no good reason I can think of why a 'horizontal chainplate' cannot be fitted internally as well as externally.... or both.

What is evident is that the mechanics of bolted-on plates is surprisingly complex. I've hunted for published info far and near, and found none that is directly relevant. I've looked at research papers, 'stress path predictions' and short of a complex/expensive Finite Element Analysis investigation - which I know has to make multiple assumptions for some of the input data - I can't afford to spend £/$thousands on a one-off small boat solution.

I need a tame engineer or three to exercise lifetimes of judgement, agree a consensus, and I'll go with that.

chainplate.jpg

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The layup on the inside of the hull for where the external chain-plates on my boat was for 7 layers of 600gm biaxial matt. Smallest 150mmx200mm - going out to 500x500mm.  (inside of the existing hull)
Rigging is 6mm 1x19, lowers & caps to the same chain-plate. There should be a good safety factor built in.
Loads seem roughly comparable to what you have stated above. Especially as your hull is thicker to begin with. 

However a strap would be more suited to bearing this kind of load, preferable one with an offset bolt pattern so they aren't all in line. 

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6 hours ago, bilbobaggins said:

 

chainplate.jpg

So the obvious difference between this and your design is the number of fasteners & the fasteners spread the load a far distance towards the bow. They are also up right on the deck where the load is driven directly into the corner & around.

If you go to a decent structural engineer and describe the crane scenario. Change the object to a rectangular box. I'm imagining a 40' shipping container made from 6061-T6 aluminum same weight. Give him the wall thickness, load point locations, number of fasteners. They will be able to calculate the load on the corner. They should be able to give you a description of how much extra plate there would be welded to the interior corner. This would be with a fat safety factor. 

 

 

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My amateur thoughts are rather than drill through the new interior 'chainplate' reinforcement, poke through the new fabric-tow to displace the strands around the fasteners before the resin sets up.

Put a generous fillet at the hull side-transom intersection in that area.

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5040 lbs = 22384 N

4 x 12mm bolts 

E-glass shear strength = 120 MPa  (semi-unknown CSM/woven roving layup)

So area needed = 22384 N / 120 MPa = 186mm2 

186mm2 / (2 x 12mm) = (not all 4 bolts because they're all so bloody close together) = 7.8mm thick. But that's a failure load.

So relatively little thickness of solid e-glass is needed. If it were my boat I'd want a laminate with a total thickness of 12mm and taper the new material patch over big area, dropping plys every 12mm. Smallest patch is a bit bigger than the padeye (say 200mm square)

S glass is a bit stronger than E glass but if you have some on hand...use it

300gm/m2 glass is about 0.12mm thick when hand laid up. So to get each 1mm extra thickness you'd need 8 layers of 300gm

Signed - a NA/mech eng. who has done a fair bit of composites engineering.

 

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just my personal opinion / design ideas for fixing and rigging

i wouldn't use a small ring plate for the anchor point i would favour a long strap ( as per the other pic ) .. i would use coach bolts from the outside to another inside plate to avoid the mess of hex heads shown

as close to the waterline as possible backed up inside with 2 - 3 x 24oz woven then csm to fair ( 3-4 x the area of the strap )

the bridle or first few meters made from bungy / shock cord to avoid the sudden high loads that will be the cause of most failures ( laid up to suitable breaking strain plus safety factor )

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In the OP's pic up top, the bridle has a very narrow angle, so not much added compression across the transom. If one did want to allow for that, reinforcement would need to run across the transom a bit, not just filling in the corner. A fillet would ease the cloth around the corner, keeping more strength in the lams. Fillets are usually done with a light weight filler are do not add much strength by them selves

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I'm quite happy to introduce a 'structural fillet' around the inside corners. That's easily done by wrapping some of the layers of cloth round/into the corners.
Aircraft engineer Don Jordan recommends the optimum 'throat angle' of the bridle arms is about 20 degrees - or 10 degrees either side of the longitudinal, so that's the angle at the transom/hull. The system is INTENDED to pull the stern back into line, until the ambient/transient load is equalised into the two bridle legs.

I've studied in depth all DJ's design notes and comments that survive, all the reams of published user-experience over several decades, and spoken to several experienced users of JSDs. There are also the views of those who make and sell JSDs, some of which - like builders and plumbers - exhibit resistance to innovative and better materials.

There is no need for 'bungee' elastic, stretchy nylon, or similar to absorb energy. The function-mode of the JSD supplies that 'progressive resistance to acceleration' by design. And it works. The only way a sudden shock load could be created would be if a submarine was snagged. I'll live with the statistical probability....

Grateful thanks to all above for valuable input - and especially to 'longy', and 'Zonker' for putting some numbers onto the task, which gives me confidence to do it like that. I'll aim to accommodate a 'Design Load' of 9000lb/40kN.

This is one modification to/for my boat where 'failure is not an option'.

:D

 

Edited by bilbobaggins
further thank yous
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I've installed two JSD anchor systems, so I can appreciate what you're going thru. You don't want failure. But short of having the build sced for the stern laminates and the a qualified laminate engineer, how do you satisfy (and pacify) the boat owner? Neither of the install's I did ever got used, one at least got tested under moderate conditions. 

    The corner of the hull transom intersection and the curve of that joint add a lot of strength to the transom area. The transom panel is curved aft - so any compression bending of the transom would be the transom bowing further aft. The backstay chainplates are just around the corner from the JSD padeye, so I suspect that area AND the corner are already built up quite a bit. A careful inspection of the inside will help ascertain how much has been added by comparing to the joint about a foot down. The backstay chainplate bolts will be quite close to the edge of the corner fillet, so to add lams to the corner will require removing bolts to allow the layer to extend out onto the transom far enuff to add strength.

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All this is much appreciated, people.

I misspent much of my innocent youth with my tender pink little bottom strapped to an ejector seat. I didn't ever need to deploy the thing, despite coming darn'd close on occasion. "When all else fails, put your trust in God and Martin-Baker"

I view the JSD in much the same light.

 

 

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There is a big issue that hasn't been mentioned.

You've got five options. Don't do it, Do it wrong. Almost do it right, Do it right, Over do it in terms of installation.

The last two might save the day. The first three may sink the boat. Unless you get your attachment point right on the shear line like in that picture, you are risking water coming into the hull if your attachment point fails.  

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On 9/27/2021 at 4:16 PM, longy said:

.....The backstay chainplate bolts will be quite close to the edge of the corner fillet, so to add lams to the corner will require removing bolts to allow the layer to extend out onto the transom far enuff to add strength.

I'll explore that. It would be easier to do now, as the boat is 'high and dry'.

An insurance surveyor will want to poke about in there, anyway, and if I can show evidence of 'enhancement' s/he probably won't poke any further.

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That's a pleasing video by James/'atomvoyager' which illustrates several facets with clarity. His boat is of similar size/displacement to mine.
I found myself stopping/rewinding at several points, which I'll offer up for comment.

He chose to use 5/16 or ~8mm dyneema. I purchased 10mm, not least due to its easier 'manual handling'. The cost difference was, to me, insignificant.

I chose a continuous 'rode + leader' with no join. I can't see the point of introducing a superfluous join which adds nothing and may have potential for a splice failure.

I, too, made my bridle from the same diameter rope as the rode. Why not?

The Titan shackles used are rated at 1 1/2 tons. The rope rode - several times that.

I used tubular s/s shackles so the spliced dyneema loops are captive under load.

Every rope manufacturer I consulted - New England, Marlow, Southern, English Braids, and John Franta of Colligo Marine- advises that joining ropes - rode to bridle - using knots e.g. cinch hitches is a 'no-no'. That is throwing away up to 50% of line strength. Yes, it's neat and quick, but....

James shows the now-accepted means of providing a 'lock point' for attaching a recovery line via a rolling hitch. Simple, cheap, effective.

James shows one method of deployment.... end-weight first. Some experienced users advocate feeding out the leader and 'closest' cones first, with end-weight last.

James shows and uses excellent purchased 'beefed-up' cones. Earlier DIY lightweight examples frayed badly due to violent 'flutter' and needed replacement.

The neat chainplate arrangement used has but 3 through-hull bolts. Sufficient? If so, how...?

 

FWIW.

:huh:


 

 

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Yes, I noticed that. Have to check on sheer strength of bolts AND know how thick the laminate is around them. I have seen race boat deck hardware that was migrating along a deck by ripping thru the laminate - not a pretty sight. And are the bolts threaded where they go thru the lam or are they full dia shank?

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I think he said 3 x 3/8" bolts. (9.5mm)

Let's assume he bought 316 and they were full shank through the laminate.

Cross sectional area for 3 bolts = 3 x pi (9.5)^2 / 4 = 213 mm2

Tensile is about 579 MPa. Shear strength is about 60% = 347 MPa

Failure load = 347 MPa x 213 mm2 = 73911 N  =7534 kg = 16,575 lbs.

If we figure peak load ~ displacement of the boat he's got an ~2 safety factor with new bolts. (I assume the load is not necessarily split by the bridle because an off axis load could really load up one side and the other leg goes close to slack.)

Notice I said "new bolts". Crevice corrosion etc and your bolt after 5 years of wave splashes could be not as strong as new.

If it was my boat I would probably want at least 1 more bolt - who knows how they are load sharing? If they were clamping metal parts together that are relatively stiff compared to the bolts you would have good load sharing but in a thick glass laminate I'm not so sure that the first bolt doesn't take a slightly bigger load.

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On 9/25/2021 at 12:42 PM, bilbobaggins said:

I'm planning to fit titanium pad eyes......

just a thought - did you give any consideration to building essentially aft facing composite chainplates.  Composite chainplates are typical and normal today on race boats (it is also common to have composite emergency rudder gudgeons).  You are talking about enough composite work already beefing the area up, why not just do it 'the modern way'?  

We had aft facing chainplate integral in Hawk's toerail and tied it to the frames for the jsd - along with 4 lifting strong points further forward in case we ever needed to be craned out.

As an aside - I personally am not a huge fan of having to hang a bit over the side or stern of the boat in breaking wave conditions to screw two shackles on.

..............................................................................

I'm just holding my mouth shut about dyneema issues - some of it makes me want to cry but i'm not Sisyphus, I stopped trying to roll the boulder. 

 

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Yes - I thought the original spec nylon main line was to absorb shock loading? Anyhow, the brief vid of the stern taking breaking waves & the rudder flailing about do not look like a modern (fat butt) boat wants to use one.

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I'm grateful again to 'Zonker'. Substituting for my 4 BUMAX88 bolts, I note ~18608kg/40937lbf, which should be 'quite sufficient'. I hope....
"Minimum specification for BUMAX 88 is a tensile strength of min. 800 MPa and a yield strength of min. 640 MPa. However, in reality BUMAX 88 counter-sunk bolts seem to be (on average), closer to around 960 MPa (tensile) and 860 MPa (yield)."

Among the many 'rabbit holes' I've dived down, searching for education and illumination, is this one: 'Simplified Procedure for Designing Bolted Composite Joints - NASA Technical Memorandum 100281' ( https://ntrs.nasa.gov/api/citations/19880005638/downloads/19880005638.pdf

At my time of life, this 'bear of little brain'  shouldn't be found delving into such deep matters ( 'The Tao of Pooh' - A A Milne )

Nevertheless, the notion of fabricated composite chainplates had escaped me - and it shouldn't have, for I raced a RORC Series on 'Triohe', a hand-built carbon Farrier F9AXR, which had plenty of those. Thanks again to Evans S. for the fresh heads-up. I have further uses and places for that idea.

People will be wondering how on earth I came to be using Harken Specials on my little old MAB from last century, and that's a tale best suited to a starry night at anchor, a bottle of uisge baugh, and some crystal glasses. Suffice to say that Old John Foulkes, late of The Chandlery Barge, Hamble is implicated.

I plead that I have the things. Here below is part of the haul - quite what I'm going to do with the thing in the middle is a conundrum.

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This is a Harken hi load padeye. The fasteners are 10mm. The pitch distance between the 2 fasteners in line with the load is 33mm. This is not enough.

The general rule of thumb for bolted fittings in composite is 4x-5x fastener diameter spacing. 

When they get closer together (3.33x) then the bolts start tearing out instead of the laminate failing in bearing stress. Now most boats probably don't load up the padeye close to the breaking strength loads, but it's why bolts in chainplates are widely spaced.

image.png.efc27007d2707c16578ab47f5edb17be.png

Composite chainplates are great (and easy to calculate) if the load is all in one direction, like, uh a chainplate. You always know the load direction because the rigging loads are a constant direction.

I'm not sure how good they are with off-axis loading, like a JSD. The load can be vertical say +/- 20 degrees (?) or angle inboard or outboard depending on how the boat is slewing down a wave.  The unis in a composite chainplate are very strong along their long'l axis, but strength drops off very fast when not in line.

Here is what I am talking about (this is a well thought out chainplate). The load can go inboard/outboard (red) or up/down (green) quite a bit.

For a JSD I think a metal plate makes a lot of sense. Most people's composite skills are not good enough to make a really good uni carbon or glass chainplate. They are good enough to add a lot of glass on the inside of the hull and drill some holes in the hull.

image.png.a5e57ced85e3292ff50aa4e2de79ee2d.png

 

 

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8 hours ago, Zonker said:

This is a Harken hi load Special padeye. The fasteners are 10mm 12mm The pitch distance between the 2 fasteners in line with the load is 33mm 44mm.

This is not enough.

The general rule of thumb for bolted fittings in composite is 4x-5x fastener diameter spacing. 

When they get closer together (3.33x) then the bolts start tearing out.....

Here is what I am talking about (this is a well thought out chainplate). For a JSD I think a metal plate makes a lot of sense. Most people's composite skills are not good enough to make a really good uni carbon or glass chainplate. They are good enough to add a lot of glass on the inside of the hull......

 

Damn!

Back to the drawing board....:angry:

Inked40773532463_1b24f77072_c_LI.jpg

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10 hours ago, Zonker said:

Composite chainplates are great (and easy to calculate) if the load is all in one direction, like, uh a chainplate. You always know the load direction because the rigging loads are a constant direction.

I have seen a whole bunch of composite rudder gudgeons, which have a wider range of load angles.  And composite tack points for asym's - which had a decent arc of potential load angles.  This just seems like a question of proper design.  (I might comment in my own use of drogues I agree with the yaw angles, but would comment that the fully loaded pitch angles were pretty steady)

regarding diy skills . . .yea probably . . . when you are building to high load requirements often diy comes up short . . . but he did hire a pro to make the soft shackle so ....

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Re the padeye bolt spacing. Yes that's why I assumed only 2 bolts are working. It doesn't mean you can't use them - just that failure mode will be tear our rather than bearing stress. If you make the glass thick enough it's a moot point. You're only dealing with a 5000 lb design load! Leave the fwd most bolts slightly looser and the aft bolts will take most of the stress :)  
 

Evans you're right about people making rudder gudgeons and tack fittings like that. Probably they get away with it because (if done in carbon) the bloody things are so strong when made to "look right" then there is a huge SF.  And they are incorporating more off-axis fibers (biaxial stitched cloth).

I have seen rudder gudgeons with the angle of the carbon straps well spread out (about 90 degrees to each other) so they do line up with the +/- 45 degree rudder load cases. Haven't really looked at assymetric tacks but again, I think it's just so much material (and lower loads) that it's ok. Or again, they are using lots of off axis cloth.

By the way - here is why you try to load up carbon uni in the direction of load. At 10 degrees off axis, you only get 1/3 the strength of 0 degrees. At 30 degrees you're really in trouble.

image.png.de380b4ee1f20f83e1be444556d3c7dc.png

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Autonomous,

You are making a big point of Structural Fillets. If I were doing this layup I would mix a thick batch of high density and do a larger than normal fillet in the corners. Then run the reinforcing fabric on top of the fillet. Is that what you going on about?

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4 hours ago, Zonker said:

Evans you're right about people making rudder gudgeons and tack fittings like that. Probably they get away with it because (if done in carbon) the bloody things are so strong when made to "look right" then there is a huge SF.  And they are incorporating more off-axis fibers (biaxial stitched cloth).

I have seen rudder gudgeons with the angle of the carbon straps well spread out (about 90 degrees to each other) so they do line up with the +/- 45 degree rudder load cases.

most of the strong point carbon constructions I have seen splay the uni's - which I imagine is both to get bonded surface area and also to make sure that you have sufficient fiber alignment to the range of load angles.

The bonded areas requirements are surprisingly pretty low - even with a 4:1 safety factor - bilbo's would seem to need only 9 sq inches per brible arm (sorry for the imperial measurement).  

load    5040.0    lbs per bridle
bond strength    2200.0    psi
minimum bond area    2.3    sq inches
safety factor    4.0    
safety bond area    9.2    sq inches  (EDIT: since he would be bonding to polyester I presume, you could double this - still not huge)

The fiber splay angles vary quite a bit between the different applications I have seen but I have seen ones for wide load yaw angles using upto 60 degree splays.  Obviously you have to add fibers to compensate for the ones at any moment that are off load angle.  But carbon is so f&*king strong that is not hard to do and still have it 'look right'.  Bilbo has mentioned s-glass, and if he has some (or access to some) it might be (you would be a much better judge than I about that) a better material than carbon here, but everyone seems to use carbon.

strongpoint.JPG.417d5c15317d7fea69cc6657c8472d58.JPG

I'm surely not suggesting anything you dont already know, just laying out some thinking.

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To do those splayed laminated are tricky. I've seen the "folded over a tube/pin style at an angle" before but never like your picture. It's cool but at a very high skill level versus flat laminates. 

Uni S or even E glass is fine too. Uni E glass is very strong so by the time you get to the "that looks about right" thickness you could do it in E glass as well. 

Yes, bonding areas areas for lapping onto a surface are always smaller than you think reasonable. As long as you never have a Peel load! I.e.straight aft load or inboard toward the vessel centerline is fine but outward of the transom is a very bad thing (tm) 

If I was doing this I would make them on a bench (flat, temp controlled), cure, trim, then take to the boat and bond them with Spabond. S3 Gelmagic or any one of the rubber toughened epoxies. Working with wet laminate on a vertical edge surface can be done but has high degree of difficulty. About 7-8/10 from the judges. 

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36 minutes ago, Zonker said:

 I've seen the "folded over a tube/pin style at an angle" before but never like your picture. It's cool but at a very high skill level versus flat laminates. 

 

 The guys doing those specific pieces are actually in Bilbo's neck of the woods: 


FLiNK Limited
Rosemary
Jubilee Road
Totnes
TQ9 5BW
UK

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On 10/10/2021 at 2:04 PM, CaptainAhab said:

Autonomous,

You are making a big point of Structural Fillets. If I were doing this layup I would mix a thick batch of high density and do a larger than normal fillet in the corners. Then run the reinforcing fabric on top of the fillet. Is that what you going on about?

I'm not the guy to engineer laminates but that sounds close. My experience is mostly with wracking forces on corners of heavy equipment and also small stitch and glue boats. Without adequate gussets materials joined at angles can too quickly become hinges. That's my point. 

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My understanding: the filler doesn't add much strength, it is to allow the cloth fibers to bend around that inside corner without crimping or forming too tight a bend. Is there any guide for fillet size vs laminate thickness?

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On 10/11/2021 at 1:54 AM, estarzinger said:

 The guys doing those specific pieces are actually in Bilbo's neck of the woods: FLiNK Limited.....
 

I've followed up on Evans' helpful pointer to FLiNK Ltd, and had a lengthy 'consult' with Julian S. their top specialist. He certainly has the background and the 'hands on'.... or pro CV.... and understood exactly the objectives and the constraints. He endorsed much of what was raised here/above and I'll be incorporating - insh'allah - his suggestions for a hand layup that is likely to have enough 'redundancy' to accommodate this ould fule's clumsy handiwork.

That includes about 10 layers of multiaxis quadriaxial 1200gsm, thicker than the 9mm titanium plate of the pad eyes, laid up as a sort of 'fat tadpole'.... and the aft 'edges' of these layers carried around the insides of the hull/transom corner - with a fillet - as suggested above. He didn't seem overly concerned about the bolt spacing. There is support for running a reinforcing structure across the transom, underneath the stern hull/deck join, as encouraged here-above. And a couple of other thoughts, including a thinner s/s plate inside acting as a v. large washer, and a 200mm wide tape of uni-carbon run horizontally forward from the bolts area, in the centre of the layup.

I had considered some 'great big' s/steel chainplates - but would still need a similar 'beefing up' inside.

The issue of maintaining bonding pressure/support on essentially vertical surfaces i.e. against gravity is still open, but the idea of using multiple small powerful 'rare earth magnets' ( wrapped in release film ) inside and out to hold a 'wrapped' support mat vertically in place.... has some traction and will be trialled.

We agreed there are no guarantees and, as it's my decision and only my sorry pink ass that's at risk, there's no issue of 'Liability'. I'm at ease with that.

 

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No need to get fancy on vertical laminations. Wet out your fabric, then sprinkle a light dusting of colloidal silica into the resin to thicken it. Squeegee/roll it a bit more. No more than 3x1200 layers at a time until the resin gets tacky. Then add more layers. 

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On 10/23/2021 at 1:50 AM, Zonker said:

No need to get fancy on vertical laminations. Wet out your fabric, then sprinkle a light dusting of colloidal silica into the resin to thicken it. Squeegee/roll it a bit more. No more than 3x1200 layers at a time until the resin gets tacky. Then add more layers. 

I'll do 'zackly that, thanks, Zonker. You're a star! ( You don't do 'housecalls', do you? :rolleyes: )
I'll also grab a couple of those IR heat-lamps used in pig hatcheries/incubators to keep me warm while the glue goes off.

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In case I wasn't clear: wet out the fabric on a plastic covered horizontal table. Then sprinkle a bit of silica and roll/squeegee it into the fabric. This thickens the resin and prevents vertical drain out (and makes it more sticky. Roll it up into an easy to handle piece.

Now apply to the vertical surface a bit at a time, squeegeeing it into place. If you have a helper, have them in the cockpit wetting them and out and passing the rolls to you. Given that it is probably pretty cold right now, you can likely wet out the pieces yourself and then climb into the tight spot with a handful.

You can also write on glass with a Sharpie to make sure you have the layers tapered in sequence.

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Yes, thank you, 'Z'.  I already have a 2' square plastic-covered 'table' I made up which clamps into a 'Workmate' portable bench ( https://www.youtube.com/watch?v=MtdblY_ChV8 ), which I've used effectively for smaller jobs. I think I'll make up a larger table to fit across the cockpit, rimmed around as a 'bund'.

I'll also do a trial run....

As for the 'Sharpie', yes, I'd planned to use 'strike up marks' for positioning, as clear line of sight may be challenging at times. I'll probably use some polyester release film between iterations, too. I'm wondering if I can source some veterinarian elbow gloves I could coat with release agent, so I don't have to spend the night 'on the job'....

 

 

 

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