Making gaskets - now for something different

[Neeves]

My bridle plate for a catamaran bridle is a simple plate within which are retained 2 threaded low friction rings.

Like this:



and this:



The idea is to allow the bridle to be extended when the weather worsens. The bridle plate works well, or I think so.

The LFRs have the snubbers doubling back on themselves, apparently bad for any cordage. I want to extend the neck, the threaded part, but retain the rings tightly in the plate and I thought to have thick gaskets between the two halves of the LFRs, - in the first picture the LFRs are kept tight with washers - I want to replace the washers with something with a bit more meat and with some elasticity.

The question is how can I make gaskets of the size for my LFRs (which are custom made) but of variable thickness to test out my idea(s).

I can make gaskets from Sikaflex of any thickness by making a sandwich between 2 plates (Sika being the filling) and vary the thickness with spacers and then cut to a rough circular shape.

What can I use as a peel coat to allow me to cleanly remove the top and bottom plate of my sandwich within which I squeeze the Sika?

Grease proof paper, cling film......?


The ideal would be to redesign the whole device and make the LFRs integral to the plate, all one piece - but that is more expensive (or I have not found a cheap way of doing it).

The concept is you can make your own at home. You simply need a bit of 316 stainless an angle grinder and something to bore out the holes. You can buy the LFRs off the shelf, Allen Bros in Essex (so drill the holes to match your supplier). The grey one is made from an HT steel so then needs galvanising, the black one is actually duplex stainless (no need for galvanising). The LFRs are 316.

Jonathan

 

[NormanS]

Why try to reinvent the wheel? Instead of using LFRs, you could just as easily use (pulley) blocks. They would be much kinder on your lines.

 

[Boathook]

Clingfilm should work but @NormanS idea of blocks would be cheapish. Blocks don't have to be fancy ones either.

 

[Neeves]

Why try to reinvent the wheel? Instead of using LFRs, you could just as easily use (pulley) blocks. They would be much kinder on your lines.

Get minds think alike



And for crude blocks a sheave and shackle just be best

They work well but the bridle plate is neater and improves scope (and most people worship 'good' scope (I'm less impressed).

Jonathan

 

[Neeves]

These are a bridle plate with blocks in use, I did try it



These are the LFRs in use.



Normally one calculates scope from the bow roller, which on our cat is just aft of the trampoline, at deck level. The actual scope is the angle define by the bridle plate, just below the boot top in the picture - a big difference in scope from the tramp.

The reason is straight forward the low friction rings are 'low' friction not no friction and the bridle does not slip, or move, easily - with a block (usually designed to be low friction) the angle is much less attractive.

In a tight anchorage you thus get better scope with less rode deployed using LFRs.

Jonathan

The cat draws a metre, so its about 1m to the bridle plate from the seabed. Its about 1m from the boot top to the bow roller. In this, rather extreme case, the scope would be calculated as 5:1 its actually closer to 10:1. The difference is obviously less with water under the keels.

 

[vyv_cox]

A slightly different approach. PTFE sheet is available in a wide variety of thicknesses. The thinner stuff is easily stamped to make washers and the thicker ones can be cut with a hole saw.

 

[Neeves]

A slightly different approach. PTFE sheet is available in a wide variety of thicknesses. The thinner stuff is easily stamped to make washers and the thicker ones can be cut with a hole saw.

Good lateral thinking!

Jonathan

 

[Neeves]

You can enjoy the same effect, of the LFR improving scope, on a monohull IF you have a pad eye on the stem at the water line (say for a bob stay for a bowsprit). You would then be employing a simple one line snubber.


Instead of the triangular bridle plate you simply have narrow plate and one ring, this one is from Viking anchor, made from SSAB HT steel (and I have not tried it).

Jonathan

 

[Boathook]

The bridle plate plate could still be in the same position by making the lines a few inches shorter. Cheap pulleys would also have friction but also kind to the ropes.

 

[NormanS]

The bridle plate plate could still be in the same position by making the lines a few inches shorter. Cheap pulleys would also have friction but also kind to the ropes.

Yes, no rope of any kind or construction, likes being tightly doubled back on itself.

 

[Neeves]

Yes, no rope of any kind or construction, likes being tightly doubled back on itself.

Which is acknowledged and is one reason to increases the length of the LFRs by introducing spacers or gaskets. Vyv's idea of using PTFE of different thickness, or much thicker than a gasket, has merit.

Jonathan