Hard Dodger Interior Roof Headliner

[peaceOUT]

Hi,

I am having an aluminum hard dodger and bimini made for our sailboat. I would like to line the interior underside of the dodger roof with cedar strips. I'm thinking of 1/4" thickness. Any suggestions for width of strips, profile and installation techniques? Also, any suggestions with regard to insulation?

Any help appreciated,

Thank you

 

[fallguy]

Cedar is very expensive. I built a canoe 20 years ago using deck boards. They had one rough side which was nice for glue holding. I recommend using deck boards or 3/4” material because it will take a radius better than 1.5”.

Honestly, though, this is a less is more thing. I’d put some really good epoxy primer or aluminum paint system on it and leave it bare.

If you want to insulate it, use pink or blue polystyrene under the headliner. It has very low absorption of moisture properties. Do not use beaded or expanded foam!

You can also make a decent looking headliner from 4mm okume and use some hardwood strips to support it the opposite direction of frame parts.

 

[peaceOUT]

Thanks for the input. We really want to cover the underside for cosmetic reasons as well as cover some wire runs. The size is not huge, so cost is not a real concern. Also, I like the strip plank (beadboard) look. Really, just looking for input on application techniques. We can screw or glue or both. 1/4" thickness won't allow for tongue and groove but will easily handle a radius. We could go thicker but I don't think that is really necessary.

 

[Rumars]

Since it has to cover wire runs it has to be demountable so you can access the wiring. I suppose said wiring isn't a single wire channel but something more complicated like several light fixtures. Since you don't want the entire thing coming down in one difficult to handle piece there's not really much option.
To the underside of the Al skin you affix transverse hardwood battens two for the bimini, three for the dodger. For this you weld some tabs to the Al to screw them in (Al screws) and cover the contact surfaces with a polymer sealant (Sika, 5200, etc.). Then you glue (5200) the closed cell insulation foam (XPS, PU, PE) to the Al. Now you either route wiring channels into the foam or simply fix the wiring to it with staples (make sure the battens stand proud of the foam). Foam thickness to accommodate your chosen lighting fixtures without them touching the Al.
The cedar slats get rounded edges (it will look like tongue and groove) and get screwed to the hardwood battens with dome head wood screws. To hide the foam color (the wood will eventually move) you can run some black tape on the foam under the joint.
If you have particular slats you expect to remove more often you insert nuts into the battens and use machine screws for those.

If you don't like the exposed screwheads it's more complicated, you have to glue the slats to a backer (3mm plywood) and bung the screwheads.

 

[peaceOUT]

Thanks Rumars. Yes, wiring will be for two lights in dodger and probably two lights in bimini plus wiring for solar on top of bimini. I don't mind exposed screwheads. I can countersink those.

 

[peaceOUT]

Any suggestion for width of slats? Thickness will be about 1/4".

 

[Rumars]

I don't mind exposed screwheads. I can countersink those.

That's exactly the problem, you shouldn't, not with 1/4" cedar. Countersinking thins the wood down and cedar is a soft hardwood. It would work with oak or teak but for cedar you need to use a screw with a wide, non countersunk screw that stands proud of the surface. There are several head designs that are made specifically for this, the "washer head" for example. There are also countersunk washers made for using "normal" wood screws to increase the bearing surface. You just have to accept the screws as decorative elements and live with them. Or you can cover the heads with another transverse slat if you can stand that better.

As for the width of the slats that's a personal preference. With good knotless material you can go pretty wide, and if in doubt you can always fiberglass the backside of the slats so they don't crack. The usual seems to be somewhere between two to four inches. The thing has to look good to you since you're the one living with it.

 

[peaceOUT]

Yes, maybe 1/4" is too thin. I could go a little thicker ... Or consider a different wood. I'm not necessarily married to cedar.

 

[fallguy]

For my 4mm ply headliner, I used oval head screws #8 with a finish washer all 316ss. They look quite good, but the wood joints creak a bit in seas over 2’ or boat wakes.

A dome head screw as Rumars suggests also works.

If you decided to go with wood, cedar is light, but if you don’t sheath it 1/4” is going to be prone to splitting. You really need to drive the size up a bit thicker and predrill it all to the screw od and let the washers do the holding work. You also may consider ripping the cedar from 1.5” flatsawn stock as the rips will be rift or vertically grained then.

Otherwise, painted okume ply would be my advice and you can make bright finished accents to match woodwork on the boat. The woodwork will be easy to retouch say in 3 years and the paint should be something that’ll last 10.

 

[Skip Johnson]

I built enough wood strip canoes out of cedar that I'm I'm fairly allergic to the stuff now. If you can source some some full 1" stock that would be good. It doesn't look like there's any real long pieces needed so ripping strips should be easy, there's a lot of really thin kerf carbide saw blades out there now. A little more than 1/4" up to 5/16" should work well. Resawing some 2x stock for blanks gives you a little more control over grain orientation and strip width, you really want vertical grain. Bevel the exposed edges and it should look great.

Just writing this makes my eyes start to swell up

 

[peaceOUT]

Excellent advice . Thanks for the tips.

 

[wet feet]

I agree that countersinking the screws into thin strips is likely to be a sub-optimal solution.What you might consider is gluing really thin strips to some 3mm plywood and attaching it to wooden blocks,just a tiny bit thicker than the foam,which are bonded with Sikaflex to the underside of the biminni.The wood ought to be sealed first and a one pack polyurethane varnish ought to do the job.I would suggest leaving perhaps two access hatches in the lining panel that are fixed with the decorative screw and washer that have been suggested and using 3M Dual Lock tape at strategic locations to hold the large panels in place.You don't need huge quantities of it and it doesn't have to be too precisely aligned.Too much will be very difficult to separate but it can be removed and replaced numerous times and doesn't degrade like the more common hook and loop tape.You absolutely have to use the dedicated primer on bare wood and a firm pull will bring the panel down.Begin with less than you think you need and add more strips if it needs them.

https://www.3m.com/3M/en_US/p/d/b40072056/

 

[gonzo]

I would glue the cedar to plywood to make a panel. The plywood can be 3/16 or so. Then you only need a few screws to secure it. They can be the usual oval heads with beauty washers.

 

[forwiw]

A number of years ago I put a headliner in a trimaran using cedar that was sold as closet lining that I purchased at one of the big box stores, it was thin and came in widths of about 3" as I recall, as mentioned already, no countersinking, used it to cover the wiring, and the bolts that held the hardware to the cabin top. Could be an option that that just needs cutting to length to fit your application.