Thread: GIS spars

I think we should use a some amount of water as a standard measure.

We also need to remember than we're comparing between different woods, that is the trick. Bruce, it will be really interesting to hear the feedback after sailing with the new spar. One trick would be to get together with another GIS owner and have two rigs with the two different spars and sail for awhile then trade to really have that side by side comparison. I may be able to do that here, eventually, with Dana's Goat.

Also, take video of the rig looking up at it while sailing so we can see it working in the gusts.

Clint

Originally Posted by Compass Project

I think we should use a some amount of water as a standard measure.

We also need to remember than we're comparing between different woods, that is the trick. Bruce, it will be really interesting to hear the feedback after sailing with the new spar. One trick would be to get together with another GIS owner and have two rigs with the two different spars and sail for awhile then trade to really have that side by side comparison. I may be able to do that here, eventually, with Dana's Goat.

Also, take video of the rig looking up at it while sailing so we can see it working in the gusts.

Clint

As Mick has mentioned in a previous post, it really doesn't matter about the weight used to take the measurement as the flex is elastic. For recording and tabling the results however it would be nice to have the same direct comparison.

So if it's decided to compare measurements with say, a 10kg weight as the standard, then a flex reading of 20mm using a 5kg weight would be recorded as 40mm. Species of timber is not really important I don't think as each spar will have different diameters along its length, but it would add some interest.
Weight of the spar is also of interest I think.

As for the performance of the spar I've just made, it will indeed be interesting because it's made of really cheap Monteray (Radiata) pine. I'm certainly no advocate of using Pinus Radiata for boats, but because this stuff appears to be from a slow growing tree, it could well prove to work quite well. The trick (and the luck!) of finding good clear Radiata is to look for untreated structural grade stuff. This is because to be graded structural the tree cannot be felled prior to 18 years, so giving it time to develop strength. The really crappy stuff is usually felled in under 10 years.

The fact that radiata rots very quickly is not an issue as it will be sealed. (Okoume and poplar also rot quickly, but they still make marine ply from it!)

Also, the milling date on the sample I found was on a sticker attached to the timber. As the 42x42 stock was milled over a year ago and was still dead straight, I figured it would likely stay straight. Anyway, no real dramas if it's not as yards can be made very quickly.

Howdy

Am just thinking through this ... 20kg is quite a bit of weight which might make it difficult for some people. 5kg seems to deflect the spars insuffiently.

HOw about we make 10kg the standard and use multipliers to match to that as the standard. It should also work for the BETH and PDR Spars.

MIK

My very limited experience suggests 10kg would be a good benchmark. Stuart at Dabbler Sails had me use either 20 or 25 pounds for the deflection tests. IIRC the deflection of both yard and boom (built to plan of DF) was around 1 3/4 inches.

Using my incredible powers of deductive reasoning, I am going to take a wild guess here... 1 liter of water weighs 1kg.

Did I do good?

Originally Posted by MiddleAgesMan

My very limited experience suggests 10kg would be a good benchmark. Stuart at Dabbler Sails had me use either 20 or 25 pounds for the deflection tests. IIRC the deflection of both yard and boom (built to plan of DF) was around 1 3/4 inches.

10kg is a good call. Easy to manage and get a decent measurement too.

Originally Posted by BobWes

Using my incredible powers of deductive reasoning, I am going to take a wild guess here... 1 liter of water weighs 1kg.

Did I do good?

Yup. See what you've been missing out on Bob?

Let me know if this works for you. Those with better skills than mine can make it look better and feel free to make changes.

Login username: GisSparData
Password: goat

Open the file on the left titled "Welcome"

Zoho Sheet - Untitled

Originally Posted by Watermaat

Really well done "scientific" work !
I think that 10kg central weight is pretty perfect as a standard, at least you see any differences quite well. I have played with a "standard" 5cm deflection and measuring the weight with a digital scale. ( the other way round )........but that's not very practical.

I am surpized that there is so much difference in flex and so little in weight ? Must be related to the basic structure of this wood ? ( we do not have both species in Europe )
It really fits with my experience that you need to see and feel the pieces to pick something right, and that there are huge differences even within one species of wood.

from the other thread

Yup. See what you've been missing out on Bob?

So, I guess an old dog can learn new tricks!

I'll redo the measurement of the box boom using the bucket method and enter the data on the spreadsheet.

Spent a little time cleaning up the boom... decided it is "Okay" but not great, so I plan to build another box boom and take a little more care with it. Now, if I can just find some 4mm ply...

Let me know if this works for you.

Bruce -

That data sheet worked just fine for me. Clicking on "Welcome" opened the sheet (no user name or password needed). I made a test entry (boom deflection measurement) and was able to save it. I'll go back to revise the entry after checking the deflection with a legitimate 10kg. Nice way to collect the data.

Originally Posted by BobWes

Bruce -

That data sheet worked just fine for me. Clicking on "Welcome" opened the sheet (no user name or password needed). I made a test entry (boom deflection measurement) and was able to save it. I'll go back to revise the entry after checking the deflection with a legitimate 10kg. Nice way to collect the data.

Thanks Bob, I was wondering about the username or password. I had to create these to become a user/member in the first instance, but then after that it seems optional. As it's not super critical and for the benefit of us all, I don't think a login is critical but we can always change this if if we get some silly hoons visiting.

You can save the spreadsheet onto your own computer as well so we'll always have backups if the unthinkable happens. I see it also supports Open Office formats. A plus for those of us who've ditched MS products.

Modified link, opens document directly: http://sheet.zoho.com/open.do?docid=703747000000005003

Howdy .. I just get a blank spreadsheet. I can save it or share it but I cant' see what other people have put in or where to put the password etc

MIK

Originally Posted by Boatmik

Howdy .. I just get a blank spreadsheet. I can save it or share it but I cant' see what other people have put in or where to put the password etc

MIK

Did you click the "Welcome" link on the LHS Mick?

It's a pity HTML is turned off as the spreadsheet could be embedded here on the forum and we could make it a sticky. That way it would update automatically if somebody added data.