How would you build these?

MiddayGun

Super Anarchist
1,179
442
Yorkshire
A part of my outboard chain-plate project was that I had to rip out a lot of the existing cabin interior on my MGC. 
While I've rebuilt the saloon backs & shelf a long while ago, I need to build some storage lockers under the deckhead.
I've been scratching my head about the best way to go about it, requirements are:

  • No / minimum of visible fasteners
  • Front panel needs to be removable for access, so no plugging holes if it can be avoided. 
  • Needs to be fairly strong

Here's the area in question. The shelf & main bulkhead has been painted since & holes filled etc, but you get the idea: 80284419_10157546860650519_271182650226507776_n.jpg

I'm looking to arrive at a shelf cabinet a bit like this:

Pic1.jpg

Edge trim I can take care of, as well as boxing in the stiffening web. That's all straight forward.  
In my case I may have to split the front panel in two as the web sticks out further.  

SA.jpg

The shelf part of the locker I can fillet & glass on the outboard edge as the glass will be covered by the hull ceiling & there's no need to remove it. 
I really like the seamless no fastener look of that top example and the bottom of the face overlaps the shelf a little bit so I don't need corner trim, just not sure the best approach to go about fixing it in place. 
The plan is to use 9mm plywood which seems a good balance between strong & too heavy. 
Current thoughts are:

  • Wooden cleats epoxied to the deckhead and screwed in from the backside into the front. - Deckhead not especially flat on the underside, not much room to get a screwdrive in or drill pilot holes
  • Cleats on the back face of the front panel & screwed into the shelf. - Would interfere with the runner for the sliding doors
  • Screw it in & plug the holes (I really don't want to have to do this)
  • Screw it in & just accept there will be visible screws.

Can anyone think of a better way to go about it? 

A sheet of teak faced plywood costs more than some boats I've seen advertised these days so I want to get it fully templated up before I cut any decent ply. 

 

Zonker

Super Anarchist
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Sika 292 is your friend. Glue in all the parts. Use hot melt glue to jig them while the Sika cures.

If you make the hinged / sliding door big enough then don't you have all the access you need?

 

MiddayGun

Super Anarchist
1,179
442
Yorkshire
Sika 292 is your friend. Glue in all the parts. Use hot melt glue to jig them while the Sika cures.

If you make the hinged / sliding door big enough then don't you have all the access you need?
Hmm, never thought of using something like a Sika adhesive, instead of epoxy.  
How well does it do on the end grain of plywood? Or would it be advisable to use some extra cleats for more surface area? 

Although I suppose I could dowel it as well. 

 
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Zonker

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In inch units, 3M 5200 is called that because it's tensile strength is around 5200 psi depending on material. Sika 292 is about the same strength.

Commercial boat builders use tons of it instead of screws because it is fast and strong. It will stick to end grain just fine.

 

SloopJonB

Super Anarchist
68,646
12,336
Great Wet North
If you want that big panel somewhat removable with no fasteners on the face then cleats bonded to the back side of the ends could be screwed into the bulkheads.

If you 5200 the thing into place then only a Sawzall or an axe is ever going to get it out.

 

MiddayGun

Super Anarchist
1,179
442
Yorkshire
Hmm sounds like a shout, cheers Zonker, bonus points because its way easier to use than epoxy. 

Jon, cleats screwed to bulkhead already planned, but they only support the ends, I was thinking of the flex in the top and bottom in the middle as its roughly just over 1m long. 

 

Zach

Member
160
19
Beaufort, NC
Buy a red end folding extension rule, and a mechanical pencil, and a stanley low angle block plane.  Makes life easier, as you can measure inside dimensions closer than with a tape, mark closer than a #2, and not chip out your plywood veneer face when doing fitting work. 

I use a mahogany cleat on the underside of the deck, drilled with a pocket hole scew jig to hold the face up.  Depending on the dimensions that can be a right angle drill job to get in from the back side, but it lets you dry fit things.  Tip is to double the number of screw holes you need, before the cleat goes up...  Then if you re-cut, use different hole, if your re-cut is less than a 1/4 so you don't find the same hole in the face and end up wonky.  Post-it notes work well for solvent addled brains to remember which screw hole you are using on test fits.

Other that works well, if you stay inside the profile of the trim is to use headless finish nails to glue the face to the cleat, then nail set them into oblivion if steel... or leave alone if stainless.  That works great if you are bang on with the template work, and don't have a helper.    As you can shoulder it up into place and pound til enough are half sunk that it is weight supporting.  You can test fit that way, but the nails have to be into pre-drilled holes in the face so they pull through easily.

For assembly ease, cut plywood L's out of 3/4 or doubled 3/4 with a 4 - 6 inch depth same height as the plumb face, with the bottom leg the same length.  Rabbit in for a pair of 1x2's on each face, so the jig sits flush on a table on the plywood.  Stay back from the ends far enough that you can work, but try to get 3 or 4 plywood 90's so it's stiff enough to be an assembly jig, and will keep things from going out of rack on your sliders when working it into the boat, as the assembly is then tough enough to carry down a dock or throw into a pickup truck bed.  Double sided carpet tape works great on one side of the L, if you add a cleat to the face.  Spritz of denatured alcohol or acetone and it lets go.    

The trimless look, puts the cleat on the inside with the face panel extending lower than the bottom panel.  On a lot of motor yachts, trimming the underside of those is done in black formica, as you can eyeball it all day long laying on the settee, and it's just a black void of nothingness instead of trying to get a perfect finish of veneered plywood with a finish coat, upside down, laying down on a settee.  With formica you can use MDO for the back panel and supports, and it takes fiberglass cloth fine.  I glassed up a scarf joint and threw it overboard for a few weeks and had no delamination.  It's paint grade and paint ready, so it makes the interior paint work on the cabinets a breeze.  Paint everything first...  Then install. 

I'd tab the shelf to the hull on the inside, as it's a hell of a squeak point if you fit it tight and don't.  If you go bulkhead to bulkhead, then you are asking for the shelf to be a box stringer, and if you don't glass it... when the boat turns banana shaped it squeaks.

Ideally get it within a 1/4 inch, and leave it slack to the hull evenly by that 1/4... then if you need to adjust for square or plumb you can.  If it fits tight somewhere, it'll open more than 90 but won't close less than 90, as it's already touching.  That lets you account for the level of your bevel, as the deck isn't level and runs off at a bevel... so unless you template in full width material, to get a trimless fit to the deck edge, the top has to be beveled.  When you bevel that off, the angle takes off 3/16, and if you weren't slack a 1/4 to the hull, it won't fit plumb any more.

Gist there, is if you want to install the bulkhead cleats once, you can tape a paint stir stick to them and do your test scribe, cut to scribe, and remove the stir sticks.  Otherwise drill your cleats with the screw holes off center.  I tend to do 2 inches from one end and 3 from the other, so you can end for end the cleat in the same location but a 1/4 inch higher and not hit your old screw hole.

Unless you've got solid veneered plywood that is dimensional everywhere else, I'd do the face in MDO or marine grade, and then use an 1/8th inch veneer. 

The tab only need a 2 inch or so tab, so you can do your paint work, and leave a blue tape line around the shelf edge... pull the tape, and tape plastic into the piece then tab where you need it. 

I like to tack weld it into place with hot glue, or bondo blobs kicked off shades of red... and lay a layer or two of 1708 as a tab, layer of finish cloth, and a brush coat of 410 filler to fill the weave.  Scuff it off with 120 grit, and paint it.  Formica the bottom side, and call it done and dusted.          

 

slug zitski

Super Anarchist
6,156
1,199
worldwide
A part of my outboard chain-plate project was that I had to rip out a lot of the existing cabin interior on my MGC. 
While I've rebuilt the saloon backs & shelf a long while ago, I need to build some storage lockers under the deckhead.
I've been scratching my head about the best way to go about it, requirements are:

  • No / minimum of visible fasteners
  • Front panel needs to be removable for access, so no plugging holes if it can be avoided. 
  • Needs to be fairly strong

Here's the area in question. The shelf & main bulkhead has been painted since & holes filled etc, but you get the idea: View attachment 445596

I'm looking to arrive at a shelf cabinet a bit like this:

View attachment 445592

Edge trim I can take care of, as well as boxing in the stiffening web. That's all straight forward.  
In my case I may have to split the front panel in two as the web sticks out further.  

View attachment 445593

The shelf part of the locker I can fillet & glass on the outboard edge as the glass will be covered by the hull ceiling & there's no need to remove it. 
I really like the seamless no fastener look of that top example and the bottom of the face overlaps the shelf a little bit so I don't need corner trim, just not sure the best approach to go about fixing it in place. 
The plan is to use 9mm plywood which seems a good balance between strong & too heavy. 
Current thoughts are:

  • Wooden cleats epoxied to the deckhead and screwed in from the backside into the front. - Deckhead not especially flat on the underside, not much room to get a screwdrive in or drill pilot holes
  • Cleats on the back face of the front panel & screwed into the shelf. - Would interfere with the runner for the sliding doors
  • Screw it in & plug the holes (I really don't want to have to do this)
  • Screw it in & just accept there will be visible screws.

Can anyone think of a better way to go about it? 

A sheet of teak faced plywood costs more than some boats I've seen advertised these days so I want to get it fully templated up before I cut any decent ply. 
It’s difficult to edge trim and mechanically fasten to 9mm

go thick , use Liteply or other 

https://www.roberts-plywood.com/balsa.html

applying  your own veneer give a better result 

use plenty of fasteners to knock down squeaks 

aluminum flat oval tubing makes good dividers and book shelf restraints

the pictured book shelf uses teak veneered flat oval tube  

D444BFF3-7F53-4BEA-8982-21E9AC72DA37.png

100CA9AA-1CAE-43CB-9193-DAA09BEF7FC1.png

 
Last edited by a moderator:

MiddayGun

Super Anarchist
1,179
442
Yorkshire
It’s difficult to edge trim and mechanically fasten to 9mm

go thick , use Liteply or other 

https://www.roberts-plywood.com/balsa.html

applying  your own veneer give a better result 

use plenty of fasteners to knock down squeaks 

aluminum flat oval tubing makes good dividers and book shelf restraints

the pictured book shelf uses teak veneered flat oval tube  

View attachment 445686
Cheers Zitski.
I use those oval tubes in a different locker to hang my life jackets & harness tethers, didn't think about veneering them, did you do that whole build or just the book restraints? 

Any tips on veneering, do I have to vacuum bag? Epoxy / some other glue? 

@ Zach, thanks for typing all that out. I think I need to re-read it a couple of times before I understand it all! Agreed with the squeaking & shelf glassed in. 
 

 
I would go with cleats glued on and bed the face with something soft, butyl or dolfinite.  Fasten with oval counter silicon bronze screws.  They disappear in brightwork and are not noticed just make sure to not set too deep and that the holes get finished with the rest of the surface. I set all our bulkhead edges to the interior ceiling with 5200, as Z said it works well and has held up fine.  I wanted a little give as we have a wood boat.  It's not something that is a clean job and doing out front like that would take alot of prep to get perfect if you went without cleats and set the panel to the hull/deck.

 

CaptainAhab

Anarchist
844
230
South Australia
In inch units, 3M 5200 is called that because it's tensile strength is around 5200 psi depending on material. Sika 292 is about the same strength.

Commercial boat builders use tons of it instead of screws because it is fast and strong. It will stick to end grain just fine.
291 isn't in the same league of 5200 in terms of shear strength. The 5200 cures more rigid/denser and is a better adhesive. 291 is more elastic and is easier to remove. Its more of a sealant type goop. Both are amazing products. Sika does make some adhesive products more similar to 3m 5200. We can get them in AU.

 

MiddayGun

Super Anarchist
1,179
442
Yorkshire
Every time people post pics of their lovely brightwork / cabinetry I just feel inadequate!
Got some good ideas to be getting on with. 

Actually I had a great day on the water today, & with summer here I'm very tempted to put this off (again) until Autumn. 

 

DDW

Super Anarchist
6,529
1,093
In inch units, 3M 5200 is called that because it's tensile strength is around 5200 psi depending on material. Sika 292 is about the same strength.
You got a reference on that? Because 3M says it is <700 psi in lab conditions. The shear strength depends on material but still <700 max. Still pretty strong if the area is large, but nothing like epoxy.  

 

Rasputin22

Rasputin22
13,894
3,454
You got a reference on that? Because 3M says it is <700 psi in lab conditions. The shear strength depends on material but still <700 max. Still pretty strong if the area is large, but nothing like epoxy.  
I was doing some major wood sheathing with C-Flex and after trying all sorts of combinations of polyester, epoxy, and vinylester to bond dry C-Flex to wood, my boss Bill Seemann walked in the shop one day with a caulking tube of something he said 3M had sent to him to evaluate. He said it was called 5200 and that was the bond strength in PSI that 3M had determined. That was supposed to be an early 'code name' until it went to market, but apparently the name stuck. We did peel tests but I don't recall what sort of numbers we generated. We troweled entire boat hulls with the cursed stuff and then embedded C-Flex planking in it before additional bronze staples and there was no way that combo was going to peel off. 

 

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