Pilot house roof camber.

Over the years I have built boats in Airex (Frans Mass system) and done cabin tops in balsa (owners requirement) and with Nadiacore.

PRICE! is the concern on a workboat , as there may be a reason for changes .

The cost of a cut beams from 2x lumber , covered with ply and a GRP "paint " job is about 1 /10 or less than Airex .

No question the Airex or Nadia core would be far less work, (flat layup one side , flip shim for camber and lay up outside) then plop it onboard.

Minor skills , quicker and less work , but the $$$$ required are not justified.

Any other ideas for interesting use of the PH overhead?

FF

 

Of course you're correct about the personal proficiencies, from previous posts I understood fast Fred to be proficient with composites. As I consider the design of products that I'm fabricating I think the strength of plywood is relatively easy to duplicate but we need to get pretty creative to match the stiffness on a pound to pound basis.
I can't provide a tangible foundation to support my weight gain theory, it's just been my experience with the type of craft that I've been involved in. I don't messed around in the epoxy world much.

I would suggest a cross-linked foam as opposed to linear for a hardtop which would not only be cheaper but also stiffer but you're correct that it would come at a premium cost, I would suggest the completed product would be in the neighborhood of 5 to 7 times the cost of the plywood structure.

 

For the ply, better to put down a thick layer butted on the beams (1/2") and epoxy a thinner layer (1/4") on that. This enables the two layers to really get pulled together. Did this several times when re-decking Monterey fish boats back in the 80s. Also the second layer doesn't have to butt on the beams, but can be stapled to the lower layer with monel staples. Then the dynel and epoxy coating over all.
If poly or vinylester is used with glass cloth, remember the resin shrinks quite a bit, pulling hard out at the edges of the coating and eventually causing failure, which is why epoxy is generally used.

 

The Nida seems to be a valid solution in your case. Remember that the stiffness goes with the cubic number of the material.

That may end in a very slim setup. But not in the cheapest. Ply is hardly to beat, even when ep coated.

Go find it out your way. You are a member for so long, you should have figured.

And please, learn quoting!

I mean, learn to use the bloody, shitty "QUOTE" button! Your contribution is not worth much with, but even less without!

My regards
Richard

 

Go get some doug fir in 3/4 thickness that is already planed. Sand it with 60 or 80 grit. Rip it into strips 2 inches wide, and don't change your setting on the saw. Pine that is already dressed, is a quarter the cost and ends up with a stiffer beam... just have to epoxy coat the piss out of it. Spruce works too, but why spend the time planing when you can get pine for .76 cents a linear foot in 1x8's? For 80 bucks you'd have enough lumber to do the job, and save the time of running everything through the planer. You'll be paying 15-17 bucks per 2x8 or 2x10. Count 6 ounces of resin to do an 8 foot beam, given you squeedgee your waste back into the pot.

Take two straight 2x8's and cut the camber you want on both of them. Use kiln dried stuff if you are using treated... the number 2 will warp and twist up when you cut it and come back in a few days. The curve isn't harsh enough to warrant a bandsaw, just grab a skill saw. I like freud diablo blades... table saw too. Lay a piece of 3/8ths or half inch plywood to the top and screw it down. Make it a foot wide or thereabouts. Make your jig 2 or 3 feet wider than the beams you want, as the ends tend to have a wider glue joint.

Mark the center on the jig, and lay mylar packing tape on the surface to make it so the epoxy doesn't stick. Lay your first strip down on the jig, screwing up from the bottom side to hold it in place even with the outside edge of your jig.

Mix up some epoxy and a little bit of cabosil, to about snot consistency. Paint it on with a 2 inch chip brush. Lay the next layer, screwing down with 1 inch stainless square drive screws. Alternate from one side to the other side ever foot or so, so that when you go to screw the plywood roofing down you can pop a line on the centerline of the beam and not hit screws.

Build up your 4 laminations, making a 3 inch tall beam. Squeedgee off the excess glue from both sides and put it back in the pot.

Now take 3 or 4 blocks of wood and cover them in mylar packing tape. Lay them along side the beam you just made, and set a straight strip down on the jig. Screw from the bottom. Glue up 4 pieces, squeedgee off the side... Pull out the blocks, and make your next beam.

You can make 4 beams on a 12 inch wide jig at a time that look nice, and require no clamps or you can put 5 on and lay plastic sheeting between each one jamming them all together and try to clamp the whole mess down.

Once you have your beams sand off the sides, and put them to work. I would just use hurricane straps, to the top of the wall plate if it is built like a wood boat. Otherwise, cut in notches or set them where the old beams were and keep on trucking. If you are starting fresh, 14 or 16 inch centers are plenty close for a span less than 8 feet wide... 12 is more like it for 10 or 12 feet.

From there screw a 2x8 to the underside, and pull them all to the same line. Plane off any high spots after laying a batten across them. (rip a piece 3/4x 2 inches out of a good clean strip and make sure it has no curves or warps...)

Now take your plywood and lay it over the top. You can either kill out the plywood on the beams, or take some scrap to double up as but blocks. Depends on the size of the roof... Make all your joints T's and not plus signs.

For speed I would use half inch. If you are wanting something totally bomb proof, 3/8ths with a bunch of epoxy and fender washers and square drive screws to pull it down tight will make something you can dance on.

I like to put two layers of 1708 down, and make something that will last forever and be smooth and easy to fair. It is heavy though. If it doesn't have to be smooth as a babys butt, cut some 4 or 6 inch wide tape and lay it on the seams. 1208 would be fine too, but I don't use enough of it to justify keeping a roll around.

I glass from side to side and cut the first piece in half so it is 2 feet wide, and then butt the joints on the first layer. The second layer starts with one piece full width. If it needs to be real fair, wait until it goes green and take a plane, scraper, or sander and buzz down the seam so everything is flat. If you need it done real fast, just leave a 1/2 inch gap between the bottom seam, and put a little cabosil or microballoons between the seam so you don't burn through the top layer over the joint.

Once the top layer is glassed, roll on some microballoons with a 1/8th inch roller. I like the red tree ones that are white and look like the prickly side of velcro. The yellow west systems ones work alright...

Come back the next day, sand it off with a pad sander... pull your putty of choice. I like Awlgrips awlfair... Pull it side to side following the crown and fill any lows or swoops that make themselves known. With that done, buzz it off when it kicks and spray it with primer, top coat, and call it a day.

Cheers,

Zach
http://83footernoel.blogspot.com/

 

Yup, looks like boatbuilding. I like frames, ply and local timber..fast and effective.

 

When the origional pilot house and rudimentry interior was installed , very happily the Maineiacs use the newer combination screws.

These have a #2 square drive as well as a Phillips style head.

They drove the screws in till the Phillips head pattern failed (as designed to do) .

Removing all the items was very easy as the #2 square part was still intact.

A thought for other builders, everything may need dis-assembly in the future.

Make it easy.

FF