bathing platform design considerations/ideas wanted

[vas]

hello all,

since MiToS will stay on the hard for another 6m I'm planning to do a few more things that I would originally postpone for next year.

So, bathing platform is #1 in the list.

MiToS originally had no bathing platform as per the 70s boats, and featured a v.well engineered and designed alloy ladder that was fixed on a couple of mounts on the aft deck.
At a later point PO built a joke of a platform around 90cm wide (as in deep/long how you wish) for the full beam (around 3.6m down there) made off 20something mm ply featuring a series of random and non-aligned 50mm holes
Pretty awful
Frame mounts were a real joke with 18mm ss thin wall tubing (3 out of 4 mounts were cracked and platform was mainly supported from two top mounts and boarding ladder.

Ripped them all out, looks like I wont be keeping anything of that lot.

Plan is to have a 1.4m-1.5m long platform again for the full beam of MiToS.
Would like to support it from underneath on the two 1m long beams where the trim tabs are mounted.
V. strong and decent spot for the mounts.

Plan with frames looks like this sketch:

Was thinking that in section the 3 supports could look like that with the lower slanted ending aligned with the support points and the top part of each section "cutting" into the platform material.

Actually this setup would work if I had beams of solid teak (or mirande, or cedar or whatever) at 20x25mm running bow to stern. Then each beam would be supported laterally from the 10-14mm bits of ss coming up. The right hand side one on the sketch (rear end of the platform) V shaped would be capping the whole construction keeping the beams spacing right. Doh, reading it, it's not at all clear, need more sketches

However, since having a bathing platform made of solid teak or whatever strong enough timber is going to cost me a fortune, I have to think of alternatives!

Series of Qs:

Assuming I dont want solid deck with caulking, what is the acceptable gap between pieces of timber to step on barefoot. I'd say for 25mm material I could get away with 10mm gap. Agree or should I stick to 5-6mm? Remember talking smallish kids playing about there, dont want to have broken toes and legs there!

Alternative ideas on constructing a 3.6X1.5m platform? I don't want a GRP construction for many reasons.
Happy to have a strong ss frame supported as per the plan and filled up with ply+9mm teak+caulking.
Happier to have a more dense ss frame and 20x15mm solid teak or cedar without caulking around...

Ideas?


cheers

V.

 

[jfm]

Vas
I gotta dmit that I can't follow your post. I don't understand either of the two drawings, and I dont get what you mean by "the 3 supports " and "10-14mm bits of ss coming up". Perhaps edit a bit for readers who have zero in their heads about the job spec?! I do understnad "UWL" of course

I would think 10mm gaps are fine ref ergonomics, but you can set up a test using scrap wood. Gaps are hard work maintenance wise becuase you cannot scrub the edges down the gap, so you end up with brown tops and silver edges when you clean the teak

I think you should abandon the custom SS profiles in 2nd sketch, if that's what they are. Huge expense, and surely pointless. Use stock profiles only imho

Howsabout a s/s frame, made from 90 deg angle for the edges and tube for the supports, with a top deck cut from solid sheet of white "plastic wood" with a non slip finish, caulked around the edge (where end grain kisses the s/s angle)? Later, or now, you could put 6mm thick real teak or flexi teak in the form of a caulked sheet, just glued on, but that alone will be a £1000 upgrade item

If you do decide to use 20mm thick slats (very expensive if teak...) then why not rout a 6mmx6mm rebate along one top corner of each one (easy job as you know), and install them touching, then caulk and sand. this will make it look like a real deck, which it will be. It will increase material usage by factor of 1.4 of course (compared with 25mm slats and 10mm gaps). BUT, if you use 6mm thickness as I suggest above it reduces your materal usage to 42% (6mm iso 20mm thick, and x1.4) though adds the cost of the plastic plywood

Will think some more...

 

[rbcoomer]

Hi Vas,

I kinda follow the thinking, but had to re-read at least 3 times!

I gather you are looking at 4 lateral beams with the first attached to the transom, three struts/supports reaching to the second and four reaching out to the third? The forth beam is unsupported vertically as in an overhang, serving as a tie for the fore/aft slats?

If so, rather than creating 7 fixing 'points' (read pressure points) where I imagine there could be a tendency for the platform to warp, how about triangular supports running fore/aft that supports all three outer lateral beams - a bit like a shelf bracket? This would surely better distribute the weight?

e.g. a larger version of:

In terms of the platform, I'd make the gaps a bit smaller in view of the children's toes - unless going down the routed option and they're not deep enough for injury! I'm looking to do similar on a much smaller scale and plan to rout rather than slatted - just drain holes one end in the routed channels...

Regards,

Rob

 

[rafiki_]

Vas, you will be more aware than most on here that struts at an angle work best in tension. I guess you have also checked out similar aged boats for their retro installation? What does Alf's boat have? I have seen boats with an SS frame, filled in with varnished planks. Looks great when varnished, and needs a bit of maintenance, but nothing for a man of your abilities.