Thread: Wood Selection in USA for a GIS

Vertical grain fir splits easily if not used properly?? What would be considered "proper usage" - staves for a square hollow mast? I had pretty much decided against buying the pure "vertical grain" stuff - as I couldn't justify the price in my mind USD$ 190.00 for ONE 2" * 6"?? I felt it is much more practical just going to my local lumber yard where the 2" * 6" lumber has some (if you pick through the piles) lumber with grain that actually runs through the board maybeat a 35 - 40 degree angle - the appearance on the flat surface is vertical grain - not real tight - but then a 2" * 6" * 16 = $48 instead of $190, and when done, it will look virtually the same. But now the question - for this box mast - is the 'horizontal' grain better to use - less prone to split? Or is the splitting something that is an inherent characteristic of fir??????? Maybe I should just use aluminum?? (just kidding!!!!).

Aluminum wouldn't be a bad choice.

Splitting is a problem with fastenings primarily or from impact loads or splitting when the grain wanders out hte piece. I don't think it will be a problem here (spars) as the edges are too well controlled and laminated building methods like this tend to reduce the risk of splitting.

I've never seen a split stick apart from ones that have had their coating broken down so the timber weathers or that they have been hit really hard.

The latter is possible but unlikely and normal impacts are unlikely to result in splitting.

MIK

Originally Posted by PAR

Aluminum wouldn't be a bad choice.

That's heresy!

But I agree.

Lighter, stronger, more uniformly flexible, you don't have to build it, yep can be a good thing all around. It does make an annoying sound when thumped by a halyard. My other half says it sounds similar to what she hears, when she swats the back of my head. Fortunately I don't dent as easily as aluminum spar stock.

I've been using a combo stick for free standing spars lately. An aluminum lower (6061 T-6 alloy) with a birdsmouth upper section. This offers a light mast, economically with excellent flexibility and low maintenance.

It's only heresy if you get caught.

Paul,

That's interesting. What's the advantage of the hybrid spar? How do you accomplish the join?

The advantage is cost effectiveness verses performance. An all aluminum spar in a free standing rig should be tapered, for flexural qualities and weight aloft. This is either a costly welded affair or clunky with step down transitions in tube diameters. The two piece spar offers a predictable bend rate, nice taper and is a good mix of economy and performance.

The last one I did had a 12' 8" lower section, which had a 30" bury at the partners. The upper section was 7' birdsmouth with a 12" bury in the aluminum tube. I used these dimensions so I could used the 8' spruce stock I had and still have a 12" bury in the lower tube for an 19' 8" mast. This also placed the transition from aluminum to wood very near the half way point on the stick. The wooden portion used a 17% wall thickness stave and the whole nearly 20' mast was considerably lighter then a wooden mast of similar strength and flexibility. The upper section is epoxied to the lower and a sail track affixed. This was a fully rotating spar.


If I wanted more performance, I would have used a carbon upper section, rather then birdsmouth. I couldn't justify the cists of a carbon spar, so, wood it was.

This is what I mean by a good choice between performance and affordability. You have to make choices.

Originally Posted by PAR

Lighter, stronger, more uniformly flexible, you don't have to build it, yep can be a good thing all around. It does make an annoying sound when thumped by a halyard. My other half says it sounds similar to what she hears, when she swats the back of my head. Fortunately I don't dent as easily as aluminum spar stock.

I've been using a combo stick for free standing spars lately. An aluminum lower (6061 T-6 alloy) with a birdsmouth upper section. This offers a light mast, economically with excellent flexibility and low maintenance.

It's only heresy if you get caught.

Almost the same amount of work or more by the time an inexperienced person adds a sleeve so the stick don't break at the partner (unless thicker wall than the 1.6mm wall available here in a range of diameters, probably need a pop riveter for that too, Problem of finding the right diameter for the load - in OZ we have a really small and diminishing choice of extrusions with 6000 series very uncommon or costly to transport.

But MAM did find a tapered flagpole, not too heavy, about the right wall thickness to match the timber spars so that it didn't need extra reinforcing at the partner.

At that point it becomes an Aesthetics choice rather than a technical one.

If the owner can find a nice suitable spar with taper - then I'm supportive if they want to do it. If someone thinks that is awful and they will do a birdsmouth - I support that too.

If someone can compromise so thoroughly that the part on the left is Alloy and the part on the right is birdsmouth ... I will pray for your soul but still nod that it is OK.

(I can say that to PAR because he knows that I think he is god. I mean GOOD, PAR, I meant GOOD - two Os.)

MIK

Vertical grain fir splits easily if not used properly?? What would be considered "proper usage" - staves for a square hollow mast? I had pretty much decided against buying the pure "vertical grain" stuff - as I couldn't justify the price in my mind USD$ 190.00 for ONE 2" * 6"?? I felt it is much more practical just going to my local lumber yard where the 2" * 6" lumber has some (if you pick through the piles) lumber with grain that actually runs through the board maybeat a 35 - 40 degree angle - the appearance on the flat surface is vertical grain - not real tight - but then a 2" * 6" * 16 = $48 instead of $190, and when done, it will look virtually the same.

Rick -

I'm curious. Why are you shopping 2x6 lumber for the mast staves? Unless I am reading the plans incorrectly, not thinking straight (always a distinct possibility), or misunderstanding what you are doing, the staves for the hollow box mast can be cut from 1x4 lumber.

2x6s could be resawn and planed to the correct thickness (12mm) to get two staves from each timber. But there would be more waste with a 2x6 than a 1x4 (or2x4 milled to size).

2x4s should cut the costs a little bit.

That's a real sin Mik, I guess we take for granted how good we have it here in the uncivilized colonies. I haven't worked anything out for the GIS in an aluminum spar, but a 2.5" 6061 T-6 alloy with a .125" (1.5 mm) wall will be easily stiff enough without a sleeve at the partner. You could insert a wooden plug or maybe even foam if you were that concerned. I guess it depends on how thin your partners are. It would probably be easier to just spread the contact area out at the partner (make it thicker).

The next common size down would be .83" which is pretty thin and I'd be hard pressed to put more then 70 sq. ft. on this size tube, with that wall. As you know Mik, it's all about diameter so a .83" at 2.75" diameter could be an answer, but now I'm well out onto the proverbable limb and I can hear cracking and moaning noises.

To directly answer the point I was attempting to make. I'll bet I could make a hybrid aluminum/birdsmouth spar of similar dimensions, flexibility and strength for near 1/2 the weight of an all wooden spar. This is the primary reason aluminum spars took over so quickly.

My Goat's spar started as a 17 foot long tapered aluminum flagpole, 3 inch butt with the taper starting up about 6 feet, to 1 7/8 inch at the top. Wall thickness at the butt is .125 but, since it is spun to get the taper, the wall thickness is slightly more at the top. The balance point before I added end caps and fittings was just an inch or two up from the middle. I cut the excess length (18 inches or so) from the bottom; taking the excess from the skinny end probably would have been wiser.

BTW--the whole thing weighed a few ounces less than 20 pounds when finished.

Howdy

I will bet you can't get down to half for the same bending stiffness and approx diameter for anything that has a long enough taper in the birdsmouth to look cute!

Gut feeling is you would save about 25% - which is still worthwhile for those who wanted to go that way.

MIK
(Problem with gut feelings is that they can be oh so wrong)

MIK

Bob - re 2 * 6's vs 2 * 4's. The issue I was looking at was the quality timber available. Seafarer marine recommended "vertical grain" fir - and they do sell some spectacular looking vertical grain 2* 6 fir - looks like it was engineered it is so perfect - but outrageously expensive. They said they can't get anything approximating vertical grain in either a 1 * 4 or a 2 * 4. With that comment I went to my local lumber yard, where they do stock quite a bit of clear fir (1/2" * 4; 1" * 4; 2" * 4; 2" * 6). The 1/2" * 4" was a "little skinny" - not quite a full 1/2" (looked to be 1/16th shy). The 1" * 4's and 2" * 4's almost exclusively had a horizontal grain - parrallel to the face. However in the 2" * 6"'s, there was SOME lumber - when you pick through - that had a grain that was not 100% vertical - but maybe at a 40 degree angle when you looked at the cut end. From the face you simply see vertical grains - but they are not vertical through the piece. My thought was, for just a couple of $$ more for my mast - instead of buying Four * 1" * 4's or Two 2" * 4's, I would buy the 2" * 6" lumber, mill to size and resaw my 1/2 inch boards...thereby getting the neat looking vertical grain for my mast. An extra $.50 per board foot = $16 premium for "vertical grain" - my way. Plus I have scraps I can cut for ??? braces to use when clamping rudder stock (possibly "reclaim" some fir centreboard & rudder stock).

Rick -
Thanks for the info... makes more sense.

I thought I had a good source for decent 16' 2x4s - a wood recycler had a stack of them in November when I bought materials for my sawhorses. One of the 2x4s I bought was vertical grain DF - of course I didn't discover that until after cutting it into parts for the sawhorse. Should have gone back right away but I didn't. Last week that stack was gone! So, I am still looking for my mast material.