The design of the top of the well


this is the latest iteration from our cad man

he has pasted in an outline of a long shaft Tohatsu into an accurate scale of the back end of a Centaur - looks pretty good to me. In fact, the way everything is falling into place anyone might have thought that old Jack Laurent Giles made the dimensions to fit just right.



this is great news because ebay and boats and outboards  have scores on offer of all conditions. It means that I can afford to buy an older one and use my good Tohatsu as a back up. I am hoping that we can try a 6hp, a 10hp and a fifteen.  I have a contact who has an Achilles 24 and he runs it with a 4hp long shaft - he says it goes beautifully

So - I think we have the shape for the bulkhead and clamp lip sorted.

I am now thinking about the best way of creating the part where the well meets the cockpit floor

Just to to remind you here is the well and cockpit more or less to scale - and yes it is wider than it is long - see previous posts for why.

Centaur well cross section from the stern


plan view

well construction


the clamp lip is the final barrier before water hits the cockpit. It is eight inches abover the waterline - the same as an Achilles 24. I am not bothered about water slopping around the cockpit behind the clamp as that is all part of the well.

sectioin through well


I am thinking of bolting the well sides firmly to the stout cockpit floor so that there is no lip.  Bolts will be passed through the hardwood (yes hardwood chaps) 4cm x 4cm joining sections vertically into the cockpit floor and horizontally into the 18mm side of the well. I will then get the man from Wessex resins to put epoxy and cloth right around the lip. I am not bothered about the way it looks - I want it to be well stuck together. Then I will make a removale U shaped collar which will just slot into place around the engine - made of ply and the 4cm x 4cm joiners. It will just drop into place when it is needed. I would expect that most of the time it would not be needed.

does this make sense.  I think that the achilles well is the best pattern so far. Similar size boat, similar depth of well.






This is about Centaur Project, Dylan Winter's Blog. Tags:

5 Responses to “The design of the top of the well”

  1. 30 November, 2013 at 11:23 amtony corcoran says:

    I may have missed an earlier drawing. Will you route the cockpit drains directly into the well?

  2. 30 November, 2013 at 12:49 pmdylan winter says:

    Apparently the cockpit drains run forward

    so I shall leave them where they are

    the transom plate will be like a 4 inch sill across the front of the well and right across the cockpit

    so I assume that not much water will pass over the transom


  3. 30 November, 2013 at 5:31 pmtony corcoran says:

    Thank you. I had thought there might be some benefit in taking the short route from the cockpit drains into th e well but I suspect you are right to leave them as they are.

  4. 8 December, 2013 at 1:39 pmSimon Carter says:

    Gday,Dylan I have a Tohatsu 9.9 two stroke two on my 6m Spacesailer on OZ two things to bare in mind is back pressure if the out board is to lower in the water with mine dropped down very low, not as low as you have in your drawing it it misfires a bit due to back pressure exhaust gas not clearing the chambers. The outher more worriny aspect is the engine being being very low to the water line in the drawing even if you close off the well around the outboard the water pressure of a following sea might flood the bottom cylinder. So you might think about being able to raise the outboard up a bit whilst underway.

  5. 8 December, 2013 at 2:03 pmdylan winter says:

    thanks Simon

    I have been looking at the back pressure issue

    it does look as though not all engines are born equal in this manner

    I have been looking at the Honda specs….such as they are

    I understand that 8 inches is now the standard depth for a well

    so mine will be around 9 inches

    I have been watching the water in the Katie L well – it does not move much and the Centaur well is much closer to the CoG of the yacht

    do you have any snaps of your boat and the outboard

    I am assuming the Tohatsu is on a bracket on the stern

    one of the reasons for going to a well is that I should not get the hobby horsing or digging in that you get with a bracket

    when you get this problem how deep is the engine?

    incidentally –

    I am assuming that with this much power your little ship really flies along

    Twin Hondas?


Leave a Reply