Forestay bridle angle

[matt connolly]

Hey all,I've just stepped my mast for the first time on my rebuilt tangaroa mk Iv. I'm doing a version of wakatiateas crab claw,so have put a 10degree rake on my 7meter mast. My question is what kind of angles are too severe for my forestay bridle,as mine is very horizontal I'm wondering if there would be too much sideways pull bringing the stem posts together. Any thoughts?

[matt connolly]

I was t sure is all. Thanks BB.

[dave tomlinson]

This is the same situation as used with climbing/descending gear.  One loaded line going to 2 anchor lines/ points, each anchor point/line has the same load.  You could google it but from memory at a steeper bridle angle anchor line loads are half the main line, but at flatter angles like yours each anchor point can have a load greater than the main line load.  eg 100 kg main line and 120 kg or more on each anchor point.  So if you are keeping that angle make everthing extra strong.

[matt connolly]

Ok thanks Dave

[boatsmith]

Dave is right about the bridle loads.you have a trade off necessary here.the bridle load increases as the bridle legs get shorter. the jib gets smaller as the bridle legs get longer.

[matt connolly]

So my bridle legs are made from good quality 10mm spectra,4.5 tonne break,terminated in the centre by one loop and two bow lines to a shackle and two loops around the seem posts. Strong enough you think?

[Jeremy Walker]

If the jib tack point is far enough forward, you might consider dropping the connecting beam onto the decks, in line with a projected forestay. Then it would help to drop the bridle leg attachment points further down the stems. This would improve the bridle angle that you are concerned with, as well as lengthen the lower spans, at the same time as allowing for a reverse dolphin striker to  lift the bridle even further if needs be.

I would add a narrow ladder-like beam structure or a plank, lying forward of the mast, in order to take the jib tack even further forwards; it is handy to support the safety net as well as being good for footing when going forwards.

[matt connolly]

The bridle legs are at the lowest points on the stems. I will have a plank of some sorts and netting in the front there when I get some more time and money!

[boatsmith]

i think your angle will be alright

[Jeremy Walker]

Sounds as though you would like to move the jib tack further forewords when the extra walkway plank is added.

The following way to make fixing points for the connecting beam and the bridle legs may help.

I would fix  false stems to the existing stems, from deck level down to near the waterline.

About halfway down (these false stems), a bolt fastening the say 3x3" hardwood piece could serve to reinforce the bridle ends (one on each stem).

Transverse holes through the false stems can take the connecting beam lashings, in that the false stems will be like long deadeyes, with the fastening bolts going through the wood between the holes. 

[matt connolly]

Interesting idea Jeremy,but I can't quite picture it...

[matt connolly]

Thanks boatsmith,

[matt connolly]

Does anyone have any thoughts on mast rake? Mine is at 15 degrees aft.