Glue for strip canoe

[bobmc]

I'm going to have a go at a strip canoe, and I'm slowly getting getting my facts and bits and pieces together. I'm not sure how I will go as I'm not really a wordworker, a reasonably handy home renovator maybe, but this is stepping up a notch or two to my mind. Anyway, I'm going to start with a Gil Gilpatrick 16 ft White Laker to develop my skills and if that goes Ok I might try a Redbird as I have a copy of Canoecraft as well. Got a major boost when I was able to source enough WRC for the job at the recycling centre at the local tip for a whooping $42. Anyway, one thing that I am unsure of is which glue to use for the strips. Most of the books are Nth American and not sure the products they quote are available here. Can anyone help? Also I did some carpentry once with PVA glue and found where it had run showed up under the varnish despite sanding back. Inevitably with strip canoe building you get glue squeezing out of your joints and running down the strips. As all the books say, this needs to be wiped off immediately, but I'm worried about shaving/sanding back enough depth to stop the glue marks showing through the final job.? Grateful any insights. Thanks.

[Boatmik]

Howdy, most use epoxy. WEST and Bote Cote are the most common ones here.

With strip planking there is no problem with glue staining the wood ... it is just that the glue is so hard to sand later!!!!

There are also some good pics here with some adaptations .... the timber is paulownia so is softer than cedar. We just use the nails and the plastic tube pieces threaded on to hold cedar down.

Don't need the ply pads shown in the pics

The full detailed set with comments is here
http://www.flickr.com/photos/boatmik/sets/72157603490801279/

http://farm3.static.flickr.com/2054/1492155615_6b20fd6ccc.jpg

[KJL38]

If you are using bead and cove strips yellow carpenters glue (aliphatic resin) such as titebond is generally recommended.

An alternative method is to use square cut strips stapled to the frames without glueing then coating it all with epoxy and working it into the seams. http://www.thomassondesign.com/building/building_manual/hull_and_deck.aspx

[b.o.a.t.]

Successive proprietors of a boat builder & my supplier of choice have suggested expanding polyurethane is more than adequate for the edge glueing, as the whole thing will be encased in, and reinforced by, epoxy/glass anyway. It is also much easier to sand & plane. As is PVA, but as PVA doesn't have PU's gap filling properties, it is restricted to bead-and-cove strips.
Care to comment MIK PAR? Ross? Andrew?

I note that JW has an article on glue strengths on duckworks too.
http://www.duckworksmagazine.com/08/columns/welsford/index5.htm
Interesting what he found regarding surface prep. As someone who has -always- sanded my glue surfaces, I am relauctant to change, but....

cheers
AJ

[bloggs1968]

Hi Bobmc,

I use WEST and 411 filler for strip planking with cedar. Test pieces always break in the timber and it is easy to sand/plane off when fairing. Only issue is the colour of the mixture is white so if you are going to clear finish, you may want to use a different colour filler.

I'm not a fan of Purbond. I used it on one strip plank boat using square edge strips. It was great to use from the sheer up to the turn of the bilge but beyond that, it was a nightmare to keep enough glue on the strip whilst fastening it into place as the edge of the strip was near vertical and the glue would just run off. Once finished, there were a number of gaps in the glue from it running out of the joint so I had to go back and clean out the joint and fill with epoxy. ( you should have seen the mess under the boat!) The "gap filling" properties of the glue are pretty crappy if you ask me. Yes it foams up like a rabid dog on wet timber but the subsequent "foamy" glue line has little strength.

I have also seen a couple of failures with it under pretty normal circumstances so I am wary of using it. From memory I think the instructions warned against using it in joints under high stress?? It has it's uses but not for me. Makes your hands black too which is not nice.

A few people rave about Titebond III and yes it is a good glue but not thick enough to stay in a vertical joint and requires good fits.

Personally, I'd go with epoxy and you won't go wrong. It will glue well, will gap fill and is easy to use.

regards,

AD

[Ramps]

Bob
welcome aboard and well done for starting a new thread.

... well there you have it 4 replies ... 4 opinions ... that's the beauty of the forums ... often it's opinions that you want after reading all the facts

... and here's another opinion.

I see the glue holding the strips little more permanent than the nails/staples holding the strips to the forms. Once it has poxy all over it (and filling the gaps) I question the actual contribution to the overall strength of the initial adhesive? (prepare to get shot down Ramps!)

I just used cross linked PVA when I built my redbird. ... "aquadhere exerior". .. and I didn't use bead and cove AJ

Why?


well as was mentioned by AJ ... it's all encased in epoxy and glass
It doesn't matter about the gap filling properties as if you're as good as me you don't have any gaps:no::U ... joking ... but really the epoxy fills any gaps anyway.
doesn't have any colour (good with paulownia like I used ... PU comes out brownish ... could be better for WRC)
doesn't stink (like PU and poxy)
no mixing (like poxy)
non toxic ... (unlike pu and poxy)
easy to sand/plane (less sharpening) (unlike poxy) ... yes you sand/plane enough away that you wouldn't see any staining... not that I noticed any
I used the waterproof stuff cos it was just as easy to use and not significantly more expensive than the interior stuff
readily available
cheap

Would I use it again for a fibre-glass encased canoe/kayak? most definitely

And like I said don't worry about dribbles if you're using pva it sands off a dream ... and you will take a fair bit off (scuse the pun :doh: ... wasn't intended ...really). I have never noticed a stain as such (as in discolouration) from pva but I have noticed a difference in the way it takes up/ repels stain/varnish.

And don't worry too much about the woodworking skills, patience and persistence will get you through ... ok and a bit of logic and troubleshooting ability

Don't need to write an epic like me but we'd be rapt to see you get on

Cheers

[b.o.a.t.]

Bob
I just used cross linked PVA when I built my redbird. ... "aquadhere exerior". .. and I didn't use bead and cove AJ
Cheers

Won't be me as shoots you down Ramps.
I'm making a rudder blade using Aquadhere Exerior for gluing the strips.
As I can't plane a straight line to save me life, there are plenty of gaps.
Planed it to shape without blunting the plane on unfriendly epoxy. :2tsup:
None of my pretty "ordinary" glue lines showed any sign of movement whilst
planing, :2tsup: and the trailing edge join is pretty thin. :C Once shaped, I
raked out the worst of the gaps & filled & faired with thickened epoxy. Now
have to sand the epoxy fair & glass the board.

Haven't used PU except to spot-glue stitch & glue panels so I could remove
the wire ties prior to filling & taping the joint with epoxy. Was merely
repeating what I've read & has been said to my face. But having used PVA,
subject to on-water preformance, I may well use it again. JW's findings that
PVA can offer a stronger join than epoxy is also somewhat reassuring. Just
have to keep the water out of it. Would think twice about it if the boat was
going to spend time off-shore though. :no:

cheers
AJ

[Boatmik]

Howdy all ...

Good discussion!

As far as having a hard time sanding or planing epoxy ... it depends what powder you put in it to glue.

With the strip balsa and the strip paulownia I have done I generally use a q-cel (white, low density filler) to thicken up the 'pox. If I feel particularly inspired I add some wood flour of (fine sandings) of the same timber that is being used for the strips. The gluelines can just about disappear.

I used the lightweight filler because I was worried about getting bad ridges if the gluelines were tooo structural. That combo is pretty easy to sand you can just about do it all manually.

With cedar I usually use the standard Bote Cote gluing filler in the epoxy and the belt sander is my baby for the first go-over. Don't do much planing at all.

have heard comments that the PU glues leave a funny bubbly glue line when clear finishing. But you can respect the opinion of thems who have done it more than me who have just heard!!!

One of the complaints I have heard (and seen) is square edged strips can let light through to the inside of hte hull when the sun is directly on the outside. Didn't much like the look ... but have seen other square edged strip boats that did not have the problem.

Best
MIK

[bobmc]

Wow, thanks a lot everyone that certainly gives me plenty of options.

I'm going to bead and cove the strips (amazing how easy and relatively cheap -compared to local suppliers anyway - it was to get the bit via the internet from Lee Valley Tools - an exchange rate in the mid 90s at the time was also a help).

I think I might have a go at the fishing line technique also.

I'm sure I'll have plenty of other questions along the way so its good to know there are very helpful people on the forum.

Thanks again.

Bob

[Boatmik]

Howdy,

I did read John Welsford's article at Duckworks at the comparison of glues. This may not be the place to write a critique of it. Note I am not disagreeing with Johns assessment .. because he agrees with my own (hehe) and in strong terms too. But at the same time ... there is the risk of misinterpreting if you look at the figures provided in the article only and ignore the comments of the very experienced Mr Welsford.

The point is ... that I am sure for the testing that all glues followed the manufacturer's specification.

Epoxy is the only one that is gap filling.

The others all have the manufacturers stating something like "joints must be close fits and medium clamping pressure must be used".

As pointed out the 'gap filling' foam from polyurethane glues has little strength.

And that is where the article is limited. Because it is very difficult to build boats to that standard.

So when the article gives epoxy 100 and something else 115 ... it is almost completely irrelevant to most boatbuilding as you cannot get the fits and pressures.

You can with masts, you can with centreboard and rudder blanks and you can with flat pieces that can be fabricated out of the boats like centrecases. But when you go to assemble the centrecase in the boat ... the system falls down ... you cannot get the closeness of fit without excessive time (and the required skills) and you cannot get the required clamping pressure with a few plasterboard/drywall screws driven up from the bottom.

John would have been very careful to ensure that the test pieces followed the manufacturer's recommendations.

Back in the '70s and through the '80s I and all my friends were racing mostly plywood boats. We knew the boats had real limits in durability ... mostly because of leaks and cracks in the joins.

The boats degraded because of that and we had to reglass the chines every few years (polyester resin).

The common glues during that period were the ones that John looks at in his tests ... they also required significant clamping pressure and close fits in their specification.

When epoxy came on the scene for gluing and glass taping we realised just how bad the older glues were in comparison. Suddenly it was possible for boats to operate with the high racing stresses and mistreatment and still keep going year after year with (almost) no structural issues whatsoever.

A revelation.

Since then I can see over hundreds of boats just how successful epoxy has been and just how many of the boats built with the non gap filling glues have fallen apart. Fixing old boats where seams have become unstuck or hulls have delaminated from stringers is run of the mill work for most boatbuilders.

John is very careful to state


"
The most common glue in use for boatbuilding today. Gap filling in ways that builders in the past find hard to comprehend, needing only very low clamping pressures, and with the use of appropriate hardeners fairly tolerant of temperature and humidity. Most suppliers can supply resin, with measuring devices and additives that make epoxy a boatbuilding “system” that can provide high and low density fillers, coatings to preserve and densify the surface, and of course glues in various viscosities and configurations.


“Epoxy “ is the most versatile of all adhesives for wooden or plywood boatbuilding, like many glues its somewhat toxic and should be used with appropriate protective clothing and good ventilation. It varies a lot from one manufacturer to another, hardener formulations vary, as do the many additives available, I suggest using product from a “name” company with a reputation to preserve, and who are prepared to provide advice and assistance when you need it."


The only disagreement I have is with the word "toxic'. You can see why here

http://www.duckworksmagazine.com/08/columns/storer/index7.htm



And Johns text

http://www.duckworksmagazine.com/08/columns/welsford/index5.htm


Best wishes
Michael

[Boatmik]

Oh .. by the way ... that last post was a little off the track. I wrote it to suggest that strength measurements by themselves are no indicator or what will work. Something that Welsford is also clear about.

It is not necessarily closely related to the strip planking question here (though you do want it to be quite strong enough for some serious effort sanding and fairing before the glass goes on!

You would probably need a low clamping pressure gap filling properties where glue is just being screed into the vees (I really don't like the lack of control in that method - but that is a prejudice maybe)

But do think about the appearance of the gluelines too. They can be quite wide sometimes and a white filler with a red timber or a red filler with a white timber can look rather ordinary as seams vary in width considerably.

Best wishes
Michael

[bloggs1968]

Mik,

I think that there is a common misconception that epoxies are really safe non-toxic adhesives. There is a lot of conflicting information out there - both anectdotal and factual. Whilst I can understand your differentiation between toxicity and allergy sensitisation, most chemical data sheets do list epoxy as moderately toxic.

When you have a look at technical info in Australia on epoxy and I'll use WEST as an example, the manufacturers recommendation for personal protection is in their Material Safety data Sheets (MSDS). (Bote Cote is similar and according to their MSDS, their epoxy is Classified as hazardous according to the criteria of Worksafe Australia)

Below is an extract from the WEST 205 hardener MSDS;

Respiratory Protection : Wear a NIOSH/MSHA approved respirator with an organic vapour cartridge whenever exposure to vapour in concentrations above applicable limits is likely (approval #TC-23C).
Skin Protection : Use protective clothing impervious to this material. Selection of specific
items such as faceshield, gloves (rubber or latex), boots apron or fullbody
suit will depend on operation. Although a full body suit is
recommended. Remove contaminated clothing immediately, wash skin
area with soap and water, and launder clothing before reuse.
Contaminated leather items, such as shoes, belts and watchbands, should
be removed and destroyed.


I wonder how many people have actually read the MSDS on the resin they are using or even have the MSDS?

Even the "bible" of wood epoxy construction (Gougeon Brothers book) has 4 pages on epoxy health and saftey issues and refers users to the MSDS.

Gloves are another issue that most people aren't up to speed on when handling epoxies. The $10 per box of coloured gloves from Woolies doesn't do anything to protect against epoxy exposure.

Epoxy sensitisation through handling exposure is a major OH&S issue for employers. Have a look at this article for some food for thought

http://www.ansellchemsafe.com/Assets/contentFiles/Epoxy%20Resin%20For%20Website.pdf

Toxic? I guess subject to interpretation. Sorry about the rant but I have seen a number of people in the industry have to give the game away due to adverse effects of epoxy. I don't want to put anyone off using epoxy as it is a great boat building adhesive but it must be handled correctly.

Sorry about the thread drift bobmc but probably a bit applicable if you are going down the epoxy road.

regards,

AD

[Boatmik]

Howdy AD,
Yes ... there is a misconception that a lot of materials are safe.

Where what is really needed is a clear understanding of where the risks are and what the warnings are. I am quite specific on that ... the warnings of toxicity are likely to be lethargy, headaches, muddle headedness ... and they are strongly emphasised in the article.

What I responded to in the article that is on duckworks (http://www.duckworksmagazine.com/08/columns/storer/index7.htm) was the general assertion that compared to other boatbuilding materials that epoxy was toxic, while because of no others being mentioned it seemed that they were not. And that is the way the discussion was going on the forum.

There are SO MANY hazards and to choose epoxy to stand out seems strange.

Is Epoxy safer or less safe than Acetone, Turps, lacquer thinners, Fine ground copper, Polyester Resin, WR Cedar Dust, colloidal silica, ground up glass dust/sandings, petrol fumes, heavy metals, pulverised cotton ...?

My argument was about "how to proportion the risk and then what can we do?"

For epoxy the biggest risk is sensitisation. However if it is one of the cheaper or building trade grade epoxies with solvent added then the solvent is a far, far bigger risk than any of the epoxy components - I've seen people with pupils the size of their irises working in confined spaces on the edge of passing out (one was about to light a cigarette) - solvents are a clear and immediate danger. In Chemistry labs we were restricted from decanting more than 6ml of acetone at a time, but in the bad old days there used to be a BUCKET of acetone beside the sink for workers to plunge their hands into. Or think of the fine layer of glass dust in just about every boatbuildng business - still common practice.

Be careful about everything! And the article was specific about some bad practices with epoxy that also happen to be common practices.

The only realistic way to deal with the risk is in terms of work practices that will protect us from all risks simultaneously. Clean Air, clean skin are two most important factors and will protect you from the hazards you know about ... and the ones you don't!!!

Michael

[Lewy the Fly]

Hi all,
I used Titebond III on my Paulownia strip planked Run about. easier to use than epoxy less messy etc. Yes you can argue that its not as strong as epoxy however the whole lot is encased in glass reinforced epoxy and thats where the strength is. As for the comments on health and saftey, I avoid using polyurethane glues as they have isocyanate, I wont let my staff use it. With the amount of dust created when fairing a hull, I would not like to be around breathing that stuff, mask or no mask.

Regards

Lewy