Class 5 front suspension MkII

I was never happy with my old suspension system and finally made a go at some changes.

The old version pivoted at the base of the mast, this always felt like too much leverage on the shock absorber and the pivot point had flogged lose allowing an uncomfortable amount of sideways play. Further the shock absorber was purchased for $14 of e-bay and had no damping only a spring. The lack of damping lead to the whole front end chattering at speed or in sharp turns.

The plan was to move the pivot point further forward closer to the sort of geometry I see on a mountain bike rear end and to resize the front forks to fit a 20" bmx wheel for light weight and low cost replacement.

A quick sketch in Inventor to play with the geometry and get the measurements figured out.



This first version reuses the same shock absorber from the old system. I figured I would start with the old and see how it felt.
The pivot point is now 2 x 6001 bearings in a machined housing, nice and firm all the sideways slop is gone.



Note the steering rod connection now pivots horizontally this puts much less stress on the flexible tendon and should increase service life.


I took this version for a 70km test sail on the weekend and am very happy with the result.
Feels like a brand new yacht, there is still a it of chatter when turning at speed.

I have ordered a better quality air damped shock so when that arrives Ill swap the old one out and report back on how it feels.

I started with a barrow wheel then progressed to a home made 16x2.5" both had significant chatter it was definitely exacerbated by the lack of damping and the length of the front swing arm.

It might be less in minis because there is more weight over the front wheel.
But I'm shore better suspension geometry and proper damping should reduce chatter a fair bit.

PS: this is Sylk from my work account.

The air damped shock just arrived. Hope here is enough wind for a good test this weekend.

Hi Sylk. When the front wheel rises as it hits a bump it will swing the whole front end and steering pushrod rearward. If you are not exactly compensating for that pushrod movement with your feet on the steering shaft then it will turn the front wheel to the right. The opposite will occur if the wheel drops into a hollow ie, the wheel will turn left. That will happen no matter what size wheel or damper is used.

So the effect as you travel over uneven ground is going to cause the front wheel to swing left and right unless you are able to hold it straight by compensating with the feet pedals. Seems a very different geometry is needed with the suspension and steering arrangement.

Is this chattering then related to the layover steering on class 5 ?
Do designs like the pacific magic have the same tendencies ?
Class 3 Yachts generally have more upright steering pivot angles Do they have similar chattering issues ?
Chattering wheel hop can be a safety issue
Unresponsive turning has resulted in broken bones fairly recently here

Im not sure if layover is the cause of wheel chatter. I have no lay over steering and still have wheel chatter. always when tacking upwind, gybing downwind no problem.it has done this since i build my yacht. I always assumed i had the geometry off or tire to skinny and not enough tire surface to grip, or not enough weight on front tire.



my plan was to add suspention or try a wider tire to see if that helps, but never got around to it. Just learned to live with it. I never feel like i will loose control and not make the turn. just annoying chatter. Im glad this seems to be a common problem and not just my yacht