Thread: GIS for the former small-dinghy sailor

Maybe ... but also it reduces the tensile strength (which will also affect impact, shear and compressive strengths.

The same resin is just spread a bit further apart by the solvent.

MIK

Just thought I'd mention something I noticed with regard to glueing Paulonia and Hoop pine.
When I was building the Eureka, I used Paulownia for the whole boat, and had to do some scarf joints of the gunwhales. Now, as per Miks instructions, I precoated the end grain of the join to alow it to soak up, well, with the Paulownia I didnt have to even apply a second coat. Once was more than enough.

Now when I bult the PDR, I had 2 scafts per side in the mast timber to get it to length. Here I used Hoop pine. Very nice clear stuff. When doing these scarf joints, I had to coat the end grain 3-4 times before it would be "saturated" then glue it up. And even then, after glueing up, in some spots I could see evidence of the glue being pulled in even more, never happend with the Paulownia....

I may do some strenth comparisons between the two timbers and even with WRC thrown in...

Tests by the University of Southern Queensland of Western Red Cedar and Paulownia showed that Paulownia had better compression and shear qualities. When this is coupled with the comparative density at 11% moisture of 275Kg/m3 for Paulownia and 450Kg/m3 for Western Red Cedar it makes Paulownia lighter but stronger.

I do notice it is very soft, and does dent easily, especially the gunwhale on the canoe.

I may have to try a lug mast out of it just for interest sake....

I noticed a similar thing with the end-grain on the piece that I coated with WEST 105/205 - I was expecting the end to appear "dry" when cured, but in fact it is quite glossy. The rest of the piece didn't soak up as much as I was expecting either. Before treatment the wood looked a bit like balsa but glossier.

Below is about the 20th attempt to take a decent photo of the end-grain (I need a tripod - and possibly a new pair of glasses!)...

Although it is a dodgy pic, you can see sufficient specular glints of the resin to show that the stuff is sitting there at the end of the wood. The resin sagged quite a bit, so there was less at the top than the bottom (visible in this photo as the yellowish band at the bottom of the side), but even so, there is still quite a lot of surface resin at the top.

The wood is as I received it: no sanding, sawing or other treatment (than the resin of course ;).

I might do a longitudinal section of the end tomorrow, to see exactly how far the resin penetrated.

Cheers,
Alex.

Howdy,

Purbond (a moisture cure polyurethane for exterior conditions) will be fine as the foils are glassed anyhow and the glass takes most of the structural loads.. The only criticism I have is that it tends to be a bit messy as it foams and expands as it cures.

An alternative is one of the Crosslinked PVA glues that are suitable for exterior conditions - often called "yellow glues". DO NOT confuse them with the old PVA cabinetmaking glues that are not even slightly waterproof - often called "white glues"

Selleys (in Australia) calls theirs PVA+ but there are many more on the market.

I don't like these glues in general for boatbilding (the polyurethanes and modified PVAs) - the manufacturers do not say that they are waterproof. They have the same defect as all the pre-epoxy glues ... that is that they are not gap filling and require relatively high clamping pressures. This means that fits have to be accurate and clamping has to be much better than a few drywall/plasterboard screws.

But areas where fits can be accurate and the highest levels of strength are not required ... they can be OK.

Foil blanks are ideal .. at least in my boats as the layer of fibreglass will hold everything together nicely and the epoxy will prevent water getting into the structure.

Best wishes
Michael

Hi MIK,

I'll try the Purbond on the wrc and - possibly - paulownia in the Goat and Duck foils. Am considering doing this after seeing Nick's Duck foils and desiring rather shamelessly to copy him. Well, they look cool :).

The pale timber looks at a distance like hoop, paulownia or radiata...you still around for comment, Nick?

The foils areat least onme part of the Goat (apart from the rigging) that I can do immediately - or rather, after I've got "Wood Duck" well and truly under way.

Hi Alex

here is a link to some pictures of Trim's foils being shaped and glued up last week. Think Chris uses Balcotan to glue the staves.

http://www.flickr.com/photos/10180659@N02/



Brian

Having been prompted by Brian:

I used Titebond Polyyurethane Liquid Glue, I am not as fond of it as Balcotan but it's what I had in stock. It foams a bit more than Balcotan and that causes a bit of nervousness - don't know why because I have tried breaking joints made with it and it is always the wood that goes first.
The main reason I opted for it, breaking my rule of trying to follow MIK's procedures on the RAID, was that temperatures have been low up here in North Britain. -1.5 deg C in the shed overnight and struggling to get to 10 deg during the day so poxy is taking forever to cure. I did the scarf joints on the spar timbers the other day, the poxy was still dentable with finger nail after 24 hours, then it warmed up a tad and it was hard 12 hours later - so 36 hr cure times. Challenging. It has been 10 deg outside all day today so it's looking up for the kit building job this week before winter returns next week.
One significant advantage of poly in my book is how much kinder the resultant laminate is to my edge tools. Poxy laminations always seem to take the keen edge away quite quickly. Relieved by MIK's comments re sheathing taking care of watertightness - feel I have a nod of approval - almost

Pleased to say that Trim's build story is back up following the recent hiccup.

Chris

Thanks for the input and nice pic, Brian & Chris. As I'm the world's worst edge sharpener (my oboe reeds are testament to that!), anything that keeps the edge longer gets promoted to the top of the list! Well, within reason of course. No point in having the bits float - or spring - apart after 5 minutes' use ;). Purbond (the Oz equivalent of your foaming PUs) is pretty tough: I've used it before in plug-making for my aircraft and it has been fine, although it's fair to say that that was a non-structural/load-bearing application! It's also been around quite a while here in Oz, so if it had been no good, it wouldn't have lasted long.

But the foils will be glassed in any case, so no probs there.

Off now to look at how Trim's going :).

HI Alex.

Not usre if you got me confused with some one else regarding foils, but I had a terrible time with mine... I used structural pine from the hardware store, it was full of knots and was just plain crap. I am kicking myself, because it cost me $80! I could have built 2 sets of foils out of Paulownia for that much!

My advise to you, use Paulonia with a thin hardwood trailing edge, and use the foaming poly-u glue. It will be easy to plane, nice to sand and with the glas covering, plenty strong. I can attest to how quickly the pox blunts a plane(mast). but the poly-u was fine, and strong, just make sure you clamp it tight when gluing it all up, wipe off the excess as it foams out, and please WEAR GLOVES, I didn't and got it on my hands, it is terrible to try and wash off. Use turps....

I will definitly be making a new set of foils once my sailing skills improve.

Hmmm...I wonder who it was?...<scratches head>. Saw the photos only the other day.

I've got a piece of 19 x 19 Vic Ash which might do the trick for the backs - depending on the width of the foils 19 mm before the end (< 19 mm, I think, er, hope... ;). Or maybe a trip down to the local timber yard for a piece of 19 x 30-ish would be better. I have other bits of hardwood that would do, but too heavy (e.g., jarrah!).

Hi Alex,

The Ash will be fine. I would estimate typical severe damage in these types of foils from a really heavy impact would be max about 3/4" (19mm) and all on the trailing edge. This is without a hardwood back, so 19mm looks like a good choice.

By the way ... it took about 5 years of sailing Beth around the lower Murray River with its limestone outcrops and shallows to do that sort of damage one time. There were many more and less minor "emergency stops" before that one.

Simply planed off the damaged bit a glued a new bit on and planed it to match and glassed.
20 mins the first day
1 hour the second day
30 mins the third day

Not bad for once in 5 years.

Also Ash has a nice straight grain so it won't plane too differently from the other timber you are using. Using Jarrah with its curly grain the plane would tend to slide over the top rather than taking a bite .... though it would be very happy digging in to the adjacent soft timber.

There will still be a bit of that effect with the harder ash ... but it should be less. Keep an eye on it

Best wishes
MIK

Hi MIK,

Thanks for the comments on the Ash. You will be pleased to read that I never really intended to use the jarrah (got to find some use for it, though!).

I used a bit of the ash a few weeks back when making up a sawdust "trap" for the Triton (when trimming thin slivers off stuff) <gasp>, very nice to work with. It was the only bit of timber that I had to had to hand at that point that was 90 degrees on at least one corner, so it got pressed into service ;).

Prettt good innings on the hard-edge, 5 years :).

Cheers,
Alex.

It's over year since I've posted on this thread, and one might infer that it's because I've started work on the Goat (to be called Setsuna, after one of the Sailor Moon characters) after having finished my 'Duck. Neither is the case, although there are stirrings afoot on both fronts. I got a warning message from the forum about reactivating this thread ("This Thread is more than 367 days old. It is very likely that it does not need any further discussion and thus bumping it serves no purpose") which I've chosen to ignore, rather than start up a whole new thread or bury the Goat query in a 'Duck thread.

This is a query to MIK (and anyone else :) regarding plywood weights. I recently weighed on of the sheets from my slighly-water-stained-but-now-dry stash of 6 mm Pacific maple ply acquired specifically for the Goat. That sheet weighed approx. 13 kg give or take, which seemed to be rather heavy, especially when compared with woodeneye's slightly larger 6 mm gaboon sheets weighing in at 9 kg (per some discussion on my 'Duck thread).

The query is: in your opinion (ignoring the question of cost and think purely of handling terms both on water and on land), should I junk** the PM and go for gaboon given this weight (as measured on the bathroom scales ;), or stay with what I've got? I've got over the fixation of having to use something that I've acquired for a particular purpose no matter what, ahem...

** i.e., use it for something else.

Cheers,
Alex.

I would go for the gaboon every time - if starting from scratch.

the reduction in weight for handling both on the water and on the beach is valuable.

MIK