Wood glue / epoxy

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Roscoe
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Joined: Mon Dec 12, 2005 3:59 pm
Location: Ireland

Wood glue / epoxy

Post by Roscoe »

Since epoxy resin, carpenters glue and gorrilla glue all make a joint that is stronger than the wood itself is there any benefit in useing one over the other? It will soon be time to fit the outer stems to the F17 and I haven't got the epoxy yet would it be ok to use gorrilla glue?
Roscoe
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Glen Smith
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Post by Glen Smith »

Either one would be fine for laminating stems. For installing the outer stems on the boat I prefer to use epoxy. I first brush on several coats of straight epoxy until the wood will no longer absorb any more then I wipe off the excess. This is done on both the outer stem and the end of the boat. Then I apply thickened epoxy to affix the outer stems.

You could use other glues for this job but: carpenters glue has no gap filling properties. Gorilla glue fills gaps but just with a foamy substance that has no structural integrity. Normally, when installing outer stems there are always a few little gaps that require filling and this is best handled with thickened epoxy.
Snowman
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Location: Gatineau, QC

Post by Snowman »

Roscoe,

I sort of pondered the same thing when I was at the stage you are currently at. My experience has been that it is almost more of a case of the job being done and and ease of application which dictates what I use. I found that yellow carpenters glue was great for laminating the inner stems. I was not worried about the water resistance, because it was an appliation that has little risk of having the external epoxy being breached and exposing it to water. I found that the convenience of using it straight out of the bottle was a huge advantage to having to mix epoxy and worry about it kicking off before you have finished juggling the strips - although it can be done. So why not just use Gorilla glue? I just recently bought a bottle and was reminded why I would not use it extensively when I went to pay for it. If you use it in large volumes, it will cost significantly more.

For my outer stems, I used a water resistant glue during the strip lamination, once again avoiding epoxy because of the convenience factor. When it came time to fit them to the hull (which I believe you are now doing), I used epoxy. You need a fairly large quantity of glue, as it will soak in to the end grain. There are also significant gaps that may need filling and thickened epoxy works well.

Another place I used a water resistant glue is on the scarf joints my "rub strips" along the shear of the kayak. Although they will be protected with epoxy and varnish, there is a pretty good chance that the protection may become breached, exposing the bond line. While there is no structural concern, it would be a cosmetic dissatisfier. While I wanted to use epoxy, I didn't (see next para).

Other applications where I would like to use epoxy and I won't are when I have small quantities to mix. It is harder to get the quantities right (unless you use syringes) and also I find that you end up throwing out more than you use...

Give us pictures of your progress! Best of luck.
Snowman back East
Rick
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Location: Bancroft, Ontario

Post by Rick »

Snowman,
Other applications where I would like to use epoxy and I won't are when I have small quantities to mix. It is harder to get the quantities right (unless you use syringes) and also I find that you end up throwing out more than you use...
A less messy way of mixing small quantities of epoxy, instead of using syringes or those small measuring cups (which might not be all that accurate either) is to weigh out the amounts on a gram balance. It works with East epoxy at 5:1 and I might use about 15g epoxy and 3g hardener.

I threw out the pumps when they started letting in air bubbles (didn't bother cleaning them out for reuse) and the weigh scale method's worked fine ever since.
Roscoe
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Location: Ireland

Post by Roscoe »

Not quite ready for the outer stems. Just thinking ahead. Still have half a hole to fill in
I will probably wait on the epoxy as I have no doubt there will be plenty of gaps to fill.
Image
Image
Snowman
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Location: Gatineau, QC

Post by Snowman »

Rick,

I have tried all of the different methods for measuring quantities (except for the pumps that you can purchase from the vendors). I guess what I really meant to say in my previous post is that small qantities are "less forgiving". When you deal with large quantities, a small error is insignificant. Small qantities mean that small errors could actually be a high percentage. So, unless you have a good way to get all of the resin or hardener from your measuring contraption to your mixing bowl, you can be off. Once again, the syringes are really the only good way (that I have explored) to ensure that all of the resin/hardener that you measure (either by weight or by volume) actually makes it way into your mix.

Roscoe,

It is looking good. You are making good progress. What is the wood "discolouration" at repeated intervales near the turn of the bilge?

Nice big shop you got there too!


Snowman
Snowman back East
Roscoe
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Location: Ireland

Post by Roscoe »

Snowman

The blotchy patches are marks from my hands where I was pulling on the strips to get around the bilge. The white marks are from washed off glue which shows up well with the flash. Hope it all sands out.
The nice big shop is an unused shed provided by my employers. Big Big thanks.
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Jim Dodd
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Post by Jim Dodd »

Hi Roscoe
I've always felt using the bead and cove method, that massive amounts of glue for stripping was unnecessary.
All you need is enough glue to hold the strips in place until you are finished sanding the outside hull.
When you apply the seal coat of epoxy this will soak into the voids of the B and C, creating a very strong joint.
Scraping and sanding excess glue has not appealed to me.
What kind of wood are using for the hull? I like the light coloring!
Jim
Keep your paddle wet and your seat dry!
Roscoe
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Joined: Mon Dec 12, 2005 3:59 pm
Location: Ireland

Post by Roscoe »

Hi Jim
I hope you are right about the seal coat of epoxy soaking into the joints and making the joints strong. When I was trimming the keel line from above using a chair to stand on I felt that the hull was very fragile and that if I made a slip I would fall through it. I've never seen a finished cedarstrip before so I am assuming that the glass is going to make it very strong. I'm a little nervous of it at the moment.
The wood for the hull is WRC. It looks an even colour in the photo but it ranges from a pale yellow to a chocolate brown. ( in the same strip ) The suppliers here won't let you sort through the timber. You take what you get. The way they look at it is, It all has to be paid for so if people start picking through it they will be left with the scrap.
STAPLES....has anyone got any tips on pulling staples or what to do with the bits that stay in the wood? Around the molds are ok but there are a few in the stems. Ash holds them real well. Maybe I should start a new thread.
Cheers Jim .Thanks to all for looking in and for your input.
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Glen Smith
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Post by Glen Smith »

A seal coat will soak into the joints and strengthen them, in fact if there are any gaps in the planking you should try to put a strip of tape inside the hull to prevent the epoxy from soaking through and creating more work when it comes time to clean up the interior. On kayaks, I strip the deck and sand it then cut out the recess hole, strip the recess area then cut out the cockpit hole, strip the coaming riser and sand it then make a fillet around it. All of this is done before sealing or glassing the deck so the joints are strong enough and I build with 3/16" strips. The one in the photo has been seal coated and is ready for glassing.

For pulling staples I use a bent screwdriver with some electrical tape around the shaft just at the bend to protect the soft wood as I pry the staples out. If any staple legs break off I use a pair of pliers to pull them out. I have never had any break off under the surface though. Pry slowly and if you see one leg isn't coming out as well as the other, concentrate on pulling up just that leg until the two are even.

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Roscoe
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Joined: Mon Dec 12, 2005 3:59 pm
Location: Ireland

Post by Roscoe »

Thanks for that Glen. I will have to be a bit more careful when pulling the staples. Thats a beautiful kayak. I have admired it many times on your site. Looks really good in the water too.
Roscoe
Dan Both
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Location: Wellandport, Ont

Post by Dan Both »

In reply to Rick's comment;
Weighing is a very accurate way to mix small amounts of epoxy,
I am not sure about the epoxies used in building canoes but in the aerospace industry the epoxies have different ratios depending on whether you are mixing by volume (like a pump or measuring cup) or by weight (like a scale), the mix ends up the same but due to the differences in specific gravity the ratios are different.

Dan
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Jim Dodd
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Location: Iowa

Post by Jim Dodd »

Hi Roscoe
Found a staple puller made by Stanley-Bostitch, it is a real quality tool! A friend put me on to it. Cost about $10. Check with an Office supply store, or catalog. I wish I had a picture! It's chrome, spring loaded, and the blade that slides under the staple is thin, but strong! I hope you can find one!

I modified my staplers, so that they don't drive the staples deep into the cedar strip, this makes it easier to pull as well as saves sanding time, big time!
Good Luck!
Jim
Keep your paddle wet and your seat dry!
Rick
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Joined: Thu May 27, 2004 9:23 am
Location: Bancroft, Ontario

Post by Rick »

Dan,

Good point on the volume vs weight mixing ratios. I had read earlier that mixing West epoxy could be done at the same ratio either way, so went ahead and tried mixing East at 5:1 by weight, and it seemed to cure to the same properties as by volume.

However, reading through the East technical datasheet, it seems that the correct mixing ratio is actually 100:18 (rather than 100:20 as the 5:1 ratio was). Maybe the previous mix fell within an allowable margin of error, since the final product didn't appear different. I'll use the recommended ratio from here on in, and thanks for pointing that out.
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