Hi in Naviga racing most of our mono hulls have been self righting for about the last 20 years, but something fairly new to us is self-righting riggers, I first saw one of these about 5 years ago, and only a couple of years ago they started to become commercially available, and only this year have I seen them becoming the majority in racing here in the UK, and still more in the smaller classes than the larger ones. I got asked about this in a Mini Hydro thread but thought it may be interesting to more of you.
The vast majority of self righting riggers I see are of the tail sinking variety.
For a tail sinking self righting rigger you need fairly form fitting tub behind the CoG, with a flood chamber at the rear big enough to sink the tail vertically, and very well designed sponsons.
For it to right itself you need to keep the weight as low in the tub as possible, and have sponsons with most of their buoyancy above the CoG, the further back on the sponsons the bouyancy is, the better the launch angle is once it has past vertical, but also the harder it is to sink the tail to vertical in the first place, so there is a fine balancing act.
Alternatively you can have a tub with a low CoG again, but a much less form fitting rounded top and no buoyancy at all in the sponsons, to self right by rolling sideways like mono.
I have also seen a fairly normal looking full size 4s rigger, with a car headlight washer pump in one sponson, at rest, that sponson sinks a little due to the extra weight in it and switching the pump on gives it enough thrust to lift the other sponson out of the water and roll it over. It is far from ideal as it adds a fair bit of weight, but as far as I know the only way to convert an existing rigger to self righting. Probably couldn't do it with cheap and available scrapyard parts for a rigger much under 30" though.
