DN NA Class

Guests & Members Post & Read => Building, Maintaining and Repairing => Topic started by: Bob Gray on February 14, 2021, 08:41:10 AM

Title: Breakaway Tiller
Post by: Bob Gray on February 14, 2021, 08:41:10 AM
I need some input. Like many of you I sail a DN with Sarns Hardware and a tiller setup with a wooden tiller that slides over a 2 ft long square aluminum tube that attaches to the steering post with a 3/8 bolt. Ive always been concerned about being severely injured by the tube in a head on collision or a really abrupt stop like stuffing the steering runner. There are several release systems out there now (thanks Eric) but Im cheap an hope Ive come up with an inexpensive solution. I attach my plank to my boat with 2, sometimes four
3/8 nylon studs with 2 nylon nuts. Works great and have only had a breakaway when I stuffed a runner. My thought is why not replace the 3/8 bolt used on the steering post with a nylon bolt. I done a Google search on nylon bolts and Im pretty sure theyd work. Id appreciate it if someone with an engineering background could look at the numbers and give me an assessment. 6/6 nylon bolts are the common bolts available. Here are the specs Ive found. Tensile strength 10,000 psi.. Shear  strength 9600 psi.. Double breakaway shear force 1173 lbs.. Glass reinforced nylon bolts are about 30% stronger. Any input would be greatly appreciated. Not being the sharpest knife in the drawer, Im going to put a reinforced bolt in my boat today and check it out the next time we have ice.

Title: Re: Breakaway Tiller
Post by: wnethercote on February 18, 2021, 08:43:48 PM
Bob, this is not a direct answer to your question but ...

The European Secretaries supported a proposal from Peter Hamrak that the "Steering post head shall incorporate a safety feature to release the tiller upon impact of the skippers body".  Most such 'features' rely on a slot.  Your 'shear bolt' would do the same thing, although it might not obviously respond to the proposal as written.  It speaks the to Governing Committee's discomfort with the rule change.  Personally, I'm happier with the shear bolt concept than the slotted tiller head, notwithstanding the number of satisfied users of slotted Euro-style tiller heads.

The rule change proposal was intended for last Autumn's ballot, but uncertainties led to its deferral - not to mention that a change to the official plans would have been required.

It has been many years since I dropped a runner in a crack and I don't wish to repeat it, especially the separated sternum.  A break-away tiller of some description is an attractive idea.  One issue - for a Euro tiller head the pivot bolt also carries the ratchet block, although I suppose it doesn't have to do so.