Lightened Strip Plank Idea

I've been making a railing and deck for a friend's vacation home. It's about 150 linear ft. of railing and I decided to get fancy. Instead of the usual 2x2's on 4" centers nailed to the upper and lower rails, I though using pipe would be a prettier way to go. I made a test rail with 3/4" steel tube on 4" centers and it looks nice. I drilled a 1" deep 3/4" diameter holes on 4" centers in the top of the bottom rail and the bottom of the top rail.

Naturally, this is a lot of holes to drill (about 900), so I made a simple machine using 4 Harbor Freight laminate trimmers, chucked with 3/4" bits. By removing the bases I could mount them to a 2x6 on 4" centers, using a parallel-o-gram rig , drill 4 holes at once, then advance the rail down for the next set. This reduces my hole cutting to only 225 plunges into the rail. I'm doing 8' rails so I plunge into each 6 times.

The rails came out very precisely and I'll install them next spring, but I got to thinking about drilling edge wise through 1x4's the same way. Say 1/4" holes on 1/2" centers, down the length of a 1x4. This will remove about 30% to 40% of the weight of the 1x4, without an appreciable strength lose. Yeah, a tedious thing, which is just what a strip plank job doesn't need, but I got thinking about the hole boring machine. How about a dozen or so motors, all chucked with the appropriate bits and maybe an auto advance mechanism. Then with more thought, filling the holes with closed cell foam, before ripping the 1x4's into strips.

A lot of convolution, but I'm making a 1,000 pound raw hull shell in the near future, using 1x2 (mostly) strips, has me thinking a 600 - 700 pound hull shell would be a better thing. How about a stripper canoe that's 10 - 15 pounds lighter?

The hull I'm about to make will require a significant sheath on both sides anyway, so . . . an insane idea without some level of mechanization, but with a hole boring machine . . .

 

I had to read your post a few times PAR, but I get it. Either I'm dense or more likely I just don't have your level of experience to think of these things.

I'd love to see a photo of that deck when you're finished.

It seems to me that what you're contemplating is similar in concept to what is done on aircraft wing ribs and fuselage formers to lighten things up.

MIA

 

Par,

I am dense, even after reading several times.
Could you share a sketch of the finished strips?

Are you putting 1/4" holes in a 3/4' - 1" strip from the side?

If I am thinking right you are making a fairly high density "core" out of wood and foam plugs.

 

I am already lost on how to get 2x2' s on 4" centers...

 

Okay, I try again. 2x2's are actually 1.5"x1.5" and I miss typed and should have said they are on 5.5" centers, which leaves a 4" gap, between the 2x2's. When most make this type of railing, they'll use a hunk of 2x4 as a spacer, leaving a 3.5" gap (5" centers). Oops.

The idea is to drill through the edge of a 1x4 (down through the 1" face, all the way through the 4" board), removing a portion of the planking stock. A 1x4 would be ripped down to the size needed. Unlike those that painfully use the smallest height necessary to get the strips to "flow" around the worse portions of the hull, I usually change the strip height, using wider (taller) strips in relatively flat areas and less tall strips in places where there's a lot of twist of curve. Most strip planked builds, size the strip to insure that the worst areas in the hull, will let them lay down fairly neatly, but I've found these area on most hulls are a fairly small percentage of the surface area, so I change strip dimensions as necessary.

So, the 1x4, with it's foam filled holes would be ripped down to the dimensions needed. On the hull I'll build, 3/4"x1.5" strips will get it done, with some areas needing them ripped to 1"x3/4" and other areas the full 1x4 could be used. Most of the strips will likely be in the 1.5" - 2.5" range, with turn of the bilge and forefoot strips likely needing to be trimmed to 1" and in portions of the run, maybe I can get away with a full 1"x4".

The deck is scheduled to get installed in May of next year. The piers are in, but I'll need to build the decking frame, then lay the decking, eventually installing the steps and rails. I've made this type of railing before, but just not so damn big.

 

I would think a balsa core strip would be cheaper in the end.
It does make me think that 1/4" dowels cold be used for alignment and fastening together of the strips.

 

I think the dowels idea has merit, but it could also create hard points inside the core. I'll use a 5 pound foam, maybe I'll make some foam dowels.

The idea with this is to have a stiff, load bearing core, which balsa really isn't. This is still wooden strip plank, as opposed to composite core, which requires a lot more laminate work.

As far as cost, there's no way balsa would be cheaper, unless you count the labor to mill the 1x4's to dimension and drill the stock. JamesTown is selling 3/4" Pro Balsa at nearly $6 a sq. ft., while a reasonable quality 1x4 will be in the $1.50 - $2 range.

 

A stripper canoe that uses this method would have some pretty tiny holes in it, like 1/8" every quarter inch. A hull made up of three layers, the middle of which is 100% foam sheet, would work if you could bend it without buckling. Same with a 3/4" hull I would think, a core of 1/4" foam would work. Shear loads would threaten to cause separation between core and innner or outer layers unless the core was strong enough in tension. if you're gonna glass it, why not alternate foam with planking strips? The foam could conform nicely to wood edges due to its slight compressability. Glass provides tensile strength athwartships. Foam could be shaped easily to tapers with rough sand paper, allowing wood strips to be square edged.
Just noodling. Carry on.

 

Interesting. I had a similar idea whereby I made my own panels with Paulownia. A layer of timber strips is laid on a table, then at 90 degrees alternating strips of foam and timber are layed finished with strips again. Then the panels are ripped into strips. Far less labour than drilling holes and filling them. No voids and customisable with various timber and foam properties.

Another idea I had to save weight was to fabricate stringers like an inwale. In that the stringer was two strips separated by blocking along its length. The ends of each block being finished with half a hole type radius.
But then I think too much !

 

Per,
Neat idea to machine multiple holes each cycle. I'd like to see how you mounted the laminate trimmers, V-Slots???
However, have you checked if there are any specifications on spacing between the 3/4" pipes your using as Balusters? I am in a volunteer group who have built several Handicap Ramps over the last several years for handicap people, seniors and Vets here in MIchigan. There are several different local specs to which you are required to follow. Local Communities and organizations Like the VA are all different. Might also pertain to Deck, handrails and such.
pw

 

Yep, the local code is 4" on center for railings. Most just use a hunk of 2x4 to space off their railings, usually leaving an odd gap at one or both ends. I planned the railing supports around the even distribution of these spindles (balusters).

The laminate trimmers are mounted to a 2x6, with 2x2 spacers to keep them vertical and appropriately spaced. 2 automotive style hose clamps hold each trimmer to the spacers. The fairly heavy assembly rides in a HDPE mortice at each end, also built from dimensional lumber. Once a good balance point was found, the weight of the assembly easily plowed the bits through the stock.