Today was a really fun day. The task took all day but I was so enjoying what I was doing I didn’t stop for lunch and hardly stopped to keep my fluids up (It is still warm here) and started to get a headache around 4pm. What I was doing was setting out a dummy of my rear steps. I used 3mm mdf to make up step risers and screwed blocks onto the boat to attach the steps to.
The process started with what I know I need to have. That is I am restricted by the size of the space below the steps that will house the outboards and they need to be able to raise up inside the well so the steps need to go around that space. I measured off a 15hp Honda belonging to Dennis for Nine Lives, (which is the same dimensions as their 20hp) and then added a little as I am not sure yet what brand I will go for but at the worst I fit the 20hp Honda.
I decided I needed 750mm deep and 900mm wide but ironically I don’t need anywhere near that much width but this measure came about for aesthetics. I also needed to have a minimum 1300mm height inside the cavity for the engine to retract fully into the boat, then I wanted another 200mm to make a door that closes from inside instead of having a plate attached to the skeg of the outboard. I purposely raised the height of the transom in the rear bulkhead to accommodate this but even with the raised bulkhead I am struggling to get the height I need. I settled on 1380mm as I get less depth the higher I go because of the curve of the rear of the boat back along the hulls.
I marked out a curve for the top step keeping in mind that the centreline of the hull (where the outboard is likely but does not have to be mounted) needs to still be full depth and continue for at least another 200mm (the outboard is 350mm wide so 200mm either side of centreline gives plenty of clearance) until it could start to curve. I experimented with a couple of curve profiles by bending my batten differently until settling on the shape I thought would work best, also having mind that the first curve affects all of the other curves. You can see on the second step in the first pic below (the second step was my start point) an alternative curve I decided against to show how you can start and finish at the same point but use a different radius to get to it by altering the rate of bend earlier or later on the curve.
Once I had the curve of the first step I then had to make each subsequent step to match the curve of the step above and to be the correct depth and the rise set. I originally had 300mm step rise and depth but quickly realized that 300mm risers were too high. I wanted to keep the 300mm depth as it spans even the largest foot so that anyone can walk up the steps without feeling they have to use just their toes and not traverse sideways which is also a subconscious reaction to shallow steps. Often there is no choice as the rise and overall depth limit one or the other or both. Once I had refigured the depth and risers I realise I was out about 200mm to achieve the effect I wanted with the bottom step but that I could build it out to get what I wanted. So I proceeded to lay my steps down cutting the curves for each one.
The next step I had to make after the first step I made had a further complication in that it had to be my traverse step from the hull transom around to the duckboard. I was originally going to use the height of the duckboard for this step meaning that I would need have a slightly higher step up than the rest at the original 300mm. I didn’t like this as I wanted to keep all the rises consistent for both practical and aesthetical reasons. Then I remembered that I need about 50mm under the step if I am to keep my outboard umbilical conduit hidden so I simply raised the step up 50mm to accommodate some space under that step when it reaches the duckboard. Easy. Then I needed to shape that step so that it transitioned around to the duckboard. I had already concluded that the best way to do this was to have a step on the bridgedeck (the original duckboard height) rather that extend the top of the duckboard directly into the steps. It just would not work that way.
Then it was a fairly easy to set the next 2 steps. The curves were of the right size and shape to match the width of the transom and the risers and tread depths worked. That just left the bottom step. I want a very big bottom step. I have seen what I want on the fusion 40 cat. (See pic below). I have spoken to the designer and the problem with this design feature (it seems everything is a compromise on a boat!) is that when underway the clean sides of the hull is broken by the step protruding from the sides of the hull creating drag as it cuts through waves. I have had this corroborated by another builder that chartered one and the step kicks up a lot of water when underway instead of a clean rooster tail so I am sure this must cause some drag.
So my solution to this problem so as to get the benefit of clean hull sides and water exit and still have the extended rear step is to build a hinged step side that when folded up forms part of the hull side and when folded down is the step extension. I can build it with a hinge arrangement that ensures it folds to a flat step (and no further) but can be secured when underway. It proves the old adage that there is a solution for every problem.
So a full day of messing with mdf just flew by and I have created my rear step profile. I can work on some of the aesthetics of the way the rear bulkhead is shaped from behind (at the moment it is just a flat surface) that may also add to the effect of leading you up the steps onto the duckboard but I don’t want to cut into space much, so I may settle on a flat looking section of bulkhead. I can also play around with the profile of the duckboard rise and give it curved ends to flow into the rear steps better rather than just the open step profile.
Next step on the step build will be to make up the steps and step fronts (the fronts are easy, just 250mm parallel planks to the length of the front curve) out of duflex (by transferring the shape from the mdf template to the duflex and just cleaning up the curves) and of course making 2 of everything so that the reverse of each step fits on the mirror image other side by just turning it over. Then once all of the parts are cut I can glue them all to each other and glass them. The outboard hatch lid will cut straight out of the finished steps to from the lid. I will also recess the step fronts back 20mm so that I can run a led rope light under each step.