David W wrote:

[...] The additional area of bond created by the fiberglass is also an addition to your safety factor.

All the best with the project, David.

Thank you for taking the time to respond. Thanks also to David T. for the details regarding Weaverbird.

I will think about fiberglass between layers, running up the hull, and large fillets at the top.

I am trying to convince myself, one way or the other, that my reworked six-layer mast step is 'good enough' or 'not good enough'.

There is more than 12" x 12" of potential bonding area and it is a much better fit than my first attempt. But I still think there is more than 4mm gap between the beveled edges and the hull in several places -- and some gaps between layers where I made mistakes.

I am considering adding two more beveled layers. Each layer would need to be made in two pieces if I want to avoid cutting up the hull liner. I want to avoid cutting up the hull liner.

Keep thinking or keep working? I never know which one to pick.

Thank you David W.

I worked through the math following your advice. I assumed a 22 sqm sail with the COE at 15.0 feet LAP and the top of the mast step at 2.5 feet below the partners.  The result was 1420.848 lbs for the force and 142 square inches minimum contact area. This is roughly equivalent to a 12" x 12" area. I expect I will have at least this much on just one side of the hull. I should end up with double the needed area. I think this may be enough for the '[...] safety factor and peace of mind'.

I have more significant problems with the way I was trying to fit the plywood layers as a mast step. I am reworking the pieces and hopefully making properly beveled plywood layers this time after some very gracious help from Arne.

Scott.

>>> area_m2 = 22.0

>>> area_ft2 = area_m2 * 10.764

>>> force_lbs = area_ft2 * 15.0 / 2.5

>>> force_lbs

1420.848

>>> min_in2 = force_lbs / 10

>>> min_in2

142.0848

>>> min_square_side_inches = pow(min_in2, (1.0/2.0))

>>> min_square_side_inches

11.9199328857171

I had a nice sheet of 1/2" marine plywood. Now I have a stack of five things. I thought I had a clear idea how to get the mast step done, so I just went for it. I stopped to take a look at the bigger picture after 5 layers. Something does not look right.

Back at the computer I see that my stack of plywood does not look like Arne's mast step. The thing I have is a lot wider and still not as thick. It is so wide that I can't fit the biggest pieces through bow access in my boat. It is also so wide that I do not have enough plywood left. With the original plan I still need to make 3 more layers to finish the mast sole and 4 more layers for mast step (the collar section to hold the mast).

I would like to determine how much surface area I need contacting the hull on the beveled edges of the mast step. I hope that I already have more than enough. If that is the case then I will cut off the aft end of each layer such that I have the required amount of surface area. Then with a little more positive thinking this will actually fit in the boat.

Does anyone have a rule of thumb for how much hull contact is needed in this type of mast step?

Scott.

Update:

After some searching I found the comment I remembered from Arne. It is on the caption of a photo here. He says, 'With a contact area of at least 1500cm2, that thing will stay put'.

I think I will do some measuring and see how close I am to that number.

I made a lot of dust. Much more than I expected. I hope this indicates some progress.

I might have considered attaching a vacuum hose to the angle grinder some how if I knew how much dust I would be cleaning up later.

I did not grind the entire mast step area down to translucent glass. I tried to take at least a small layer off everywhere. Any opinions after reviewing the photos would be welcome. I plan on wiping the area down again with towels and acetone just before I epoxy the yet-to-be-made plywood layers.

The weather is reminding me why I like the inside 'control point' from PJR so much. It is raining and raining. I hope someday I will have a boat that is able to sail in the rain while I am inside dry and comfortable.

Now I am waiting for dry weather so I can cut and shape plywood. Too messy to do in the garage.

Scott