Volante 390 floor

TmMorris · 04 June 2022, 09:22

I noticed yesterday evening when washing the boat off that the two boards under the air deck were no longer sitting correctly.

Mulling over the board issue this morning, the rear board never had this problem but the forward one did always jut slighting on one edge.

I think the reason that all four ends can now be seen protruding against the hull is due to the boards having curved. This would also explain why the air floor was domed up yesterday when in the water. Something it did on land when you first pressurised the sausage keel but went flat again once in the water.

The question is what to do about either preventing the boards from flexing or what material to replace them with.

Also, if I'm going to replace them, should they be a little longer so that they sit in the V where the hull meets the tubes or will this cause the air deck not to seat correctly at these points?

My current thought is to consider fitting appropriate rounded edge angle iron to the leading and rear edges of the boards. 10mmx25mm and the board routed so they fit flush?

The other thought is that maybe the ply used in the factory boards is junk. It's a thick enough piece of wood that this curve would be difficult to imprint given the support above from the air deck.

Fenlander · 04 June 2022, 09:54

Hasn't someone on here addressed this issue and made up a more substantial arrangement? I'm sure I remember some photos.

TmMorris · 04 June 2022, 10:28

Yes. Wasn't it Steve or Jeff?

Looking at the leading board this morning, it looks to be located to far aft on the air deck anyway.

I'm inclined to make a 3 foot long, 12mm phenol ply board with a few half round, brass braces across the top side, lay a sheet of rubber on top and then install the air deck? Keeping the factory boards for when I want to transport the boat packed away?

TmMorris · 05 June 2022, 17:00

Ok. Settled on a redesign, with thanks to Steve for clarifying some details.

The key is going to be to fabricate a more rigid board. Obvs!

I could maintain the same size so that it fits within the air deck straps but I'm not convinced that the straps are in the right place or that the 30cm board length is going to ever be totally strong enough without switching to some form of composite material.

I'm going to use 12mm phenolic ply and increase the length to 40cm while also trimming to the correct angles. Of the added 10cm, that extra will be on the forward edge so as to cover most of the sausage at its widest point.

I'm also going to fit a pair of 50cm stainless steel strips across the board on the underside. I'll rout these to be flush but their presence is going to mean it'll be close to impossible to bend.

Steve509926 · 05 June 2022, 18:16

Quote:

Originally Posted by TmMorris

Ok. Settled on a redesign, with thanks to Steve for clarifying some details.

The key is going to be to fabricate a more rigid board. Obvs!

I could maintain the same size so that it fits within the air deck straps but I'm not convinced that the straps are in the right place or that the 30cm board length is going to ever be totally strong enough without switching to some form of composite material.

I'm going to use 12mm phenolic ply and increase the length to 40cm while also trimming to the correct angles. Of the added 10cm, that extra will be on the forward edge so as to cover most of the sausage at its widest point.

I'm also going to fit a pair of 50cm stainless steel strips across the board on the underside. I'll rout these to be flush but their presence is going to mean it'll be close to impossible to bend.

Hi Tim, when I redesigned my keel board I moved the front board forward approx 5 cms. I initially thought I would bond /glue some new straps to the underside of the airdeck to keep the new keel board in place. After using Redneck for more than 20 hours with the new keel board I have found that the straps aren't needed. The redesigned board doesn't move so I haven't bothered.

Steve509926 · 05 June 2022, 18:33

I don't really understand the benefit you will gain using phenolic ply? As soon as you have broken the surface (stainless steel strips), machined the edges, cut the angles, everything will need to be made water tight again negating any benefit.

TmMorris · 05 June 2022, 20:31

It's the extra rigidity. The existing boards are 10mm ply, 12mm phenolic is 10mm ply with a mm of hard plastic either side.

I used 8mm phenolic board to remake the floorboards on the Redcrest and they're extremely stiff. The edges seal easily with yacht varnish.

It also helps that of all the leftovers in my woodpile, the 12mm phenolic is the best fit by far

Steve509926 · 05 June 2022, 20:53

Makes sense if you already have it, then it would be a waste not to use it.

If I was to remake the keelboard I did, I would probably use 9mm WBP exterior ply and fibreglass.

TmMorris · 06 June 2022, 06:41

Agreed. I have some 8mm board and did consider buying some resin and matting. The fumes are better than varnish also!

TmMorris · 10 June 2022, 07:03

First prototype underway.

The board is a much better fit than the original. The original had been cut to a profile based on a positioning at least 10cm further forward than the air deck straps were going to hold it. Hence why it protruded so prominently on one side of the hull from day one and as the bend set in became worse on both sides.

The replacement board is of stiffer material (I'm not going to cut into the old boards but from the weight, flex and where you can see the fibres I would hazard they were made from ply more akin to shutterboard than proper ply. In addition to being stiffer, it is 10cm longer which is a reasonable increase in material taking the load.

The routed slot in the underside is for a 3mm 316 stainless steel flat bar. This element is a little bit of an experiment and the plan is to check it after the next few uses. It's either going to take the load within its spring limits or bend.

First, sealing coat of diluted varnish has gone into the edges and is being left to dry. Next step is the shaping and knocking up of an 8mm support board. This may not be required but while all the tools are out and the varnish, it's logical to make it.

Fenlander · 10 June 2022, 11:47

It's an interesting refinement you're making and one you'd think the factory would have sorted with feedback from the UK dealer. It wouldn't cost any/much more to get it spot on at the factory.

Happens to the best of them though. On the last few years of Bombard Aerotec production for assembly convenience (I assume) they relocated the multiple straps which hold the floor down. The new position lost much of the mechanical advantage to the way the strap pulled so they no longer tightened the floor into place properly.

Several of us have devised a work around and moved the straps to the previous position. But really with a company of the Zodiac/Bombard longevity and tradition of making SIBS we shouldn't have needed that mod.

TmMorris · 10 June 2022, 12:24

Yup. My guess is that this is a big related to a product made overseas and a component that is generally out of sight and also covered in enough paint to mask the material quality.

It's cheap, lower density board that's then shaped for one position and fixed in another.

Secondary support board now fabricated.

I'm mulling over whether to simply bond this in, on top of the steel strip, from the outset as there's almost no way that set up could flex. If I were to do that the steel band would actually be redundant I suspect.

Steve509926 · 10 June 2022, 17:25

If you bond the 2 boards together, will it be 24mm thick? I assume the shorter board will go against the inflatable keel?

TmMorris · 10 June 2022, 18:43

Hi Steve,

The secondary board is 8mm but yes, the additional thickness needs to be considered.

I'm not sure it will be an issue. It's 20cm long with well chamfered edges so the sausage keel will to some extent, deform around it.

I'm currently pondering how to fix the two boards together. I could simply use sealant such as Sikaflex or a pair of countersunk Allen M8 screws flush on the top side and domed nuts on the underside, well away from the sausage.

I think I'll do a loose test fitting prior to deciding.

Steve509926 · 10 June 2022, 18:57

Think it depends on what you are expecting from bonding the two boards together.
If you want a bit of flex, it's in the name, use Sikaflex. However if you want it to be as stiff as possible I'd use a proprietary contact adhesive and numerous countersunk screws.

TmMorris · 11 June 2022, 13:28

I always forget how long yacht varnish takes to dry! Currently using some solar power.

TmMorris · 12 June 2022, 11:53

Sanded down and final coat applied. Will leave now for a couple of days before a light wet&dry on the edges where the board may touch the PVC.

Waiting on some fibre washers anyway for the fuel assembly on the 4hp outboard and will also use these for attaching the boards.

I suspect that just the main board will do the trick as it will be a better fit than the original and is notably stiffer. I also suspect that what really put the permanent curve in the original board was leaving the boat on the trailer with too much pressure in the sausage keel last summer. Something that won't be repeated.

TmMorris · 21 June 2022, 10:58

Added another coat the the edges and a bit of wet and dry yielded nice smooth edges. Decided there had been sufficient cure time to install the board. Nice fit and under full inflation showed no discernible flex. Will test on the water next time out where the plan is to not inflate the sausage to full pressure initially but rather to see how much pressure is required to prevent cavitation.

Steve509926 · 21 June 2022, 12:13

Hi Tim, what's the theory of not inflating the sausage keel to full pressure?

TmMorris · 21 June 2022, 12:44

Hi Steve, the theory stems from the fact that neither the boat nor the new board were designed and fabricated by NASA so the numbers on the valve will basically be a best guess which would be subtly different between each boat that falls off the factory line in the first instance and as I've changed the depth of the lead board I will have changed the ideal pressure point anyway I suspect so I figure it makes sense to start at a base level and tinker upwards when on the water to find the right pressure?

I only started getting cavitation once the original board developed a permanent curve and suspect that the sausage won't need quite as much pressure as before. Just a theory to test.