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Thread: Self Righting Riggers

  1. #1
    Join Date
    Feb 2008
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    Default Self Righting Riggers

    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.
    Paul Upton-Taylor, Greased Weasel Racing.

  2. #2
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    Jun 2009
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    Default

    Zero buoyancy sponsons would mean a non existent sponson if built in traditional box fashion, as buoyancy is water displacement. (Flotation isn't a material such as foam. It is a consumption of space by a material less dense than water, that water can not fill.) The only option I can see would be to have a hollow AND open sponson.

    But because we are now at zero buoyancy, the rigger needs to be running or else it may tilt or rotate to the heavy side during idle. You could push through the water to force one side up, but then hole shot isn't something you can expect to keep.

  3. #3
    Join Date
    Jun 2010
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    Default

    Quote Originally Posted by NativePaul View Post
    Many of the latest Mini Hydros and Hydro 1s to come out are designed to allow self righting, the majority of them use a rear flood chamber to achieve it.

    I can't find a video if the Exe05 specifically, but here is an ETTI outcast which does it in the same way.

    Somthing NativePaul shared on a on a different thread.

    Aside, I cant seem to get a response from Rasch's about the new Exe05. I would love to get one.
    Cheetah, Super Rio, (Mod) Starship (Mod and sold),

  4. #4
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    Default

    I never said anything about traditional box sponsons. Sinking sponsons do have a small amount of displacement, but weigh more than the water they displace so they have no bouyancy and consequently sink. At rest they will lean a little, as a self righting mono does (effectively it is a mono at displacement speeds), but the hole shot is fine. What you lose from having to lift the nose up, you gain from the tub and drive line being flatter at rest, so you are able to apply more throttle without wheelieing out of the hole and risking a blowover.
    IMG_8155.jpg

    As an aside, Rasch is a one man band cottage industry, run by Randolph in his spare time, he builds to order and he travels to races, so even when he isnt working he isnt always in his shop. If you need a hull ASAP maybe his boats are not for you, but if youare willing to wait, they are well worth it.
    IMG_9574.jpg
    EXE05 at speed.
    Last edited by NativePaul; 06-25-2018 at 07:16 PM.
    Paul Upton-Taylor, Greased Weasel Racing.

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