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islandteak
02-12-2010, 07:42 PM
When caulking teak decking/seating with epoxy resin it is customary to turn the epoxy black with graphite powder. If you read the label, graphite is not something you want to inhale too much of. I have experimented with common black chalkline chalk and the results look good. Does anyone have true life / over time experience using chalk as an epoxy additive ? The suppliers of the epoxy say it should work fine, however, chalk is hydrophillic (attracts water) but it is encapsulated in epoxy. In theory it should be a cheaper and safer blackening agent for epoxy.
Opinions ?

regards...Ken

Ian McColgin
02-12-2010, 08:09 PM
Hello. My name is Ian and I am an epoxyholic . . .

But I must say I am not sold on this application for both quality and cost reasons.

If the teak is a pure laid teak deck, it's simply nuts. Don't even think about it.

If your putting teak over plywood it's really cosmetic - a very expensive alternative to pumice in the paint - and you're using a thinner layer of teak. You'll be setting the teak onto something, epoxy or something wigglier, and normally screwing it down. This is trouble point number one as the room for bungs is limited and it's really hard to keep moisture from wicking down into the ply sooner or later. Almost no one gets the screws backed out after the deck is down and stabile, the holes epoxied and redrilled and tapped.

But no matter how you do it, there's movement. Blackened epoxy for the seam lines is absolutely destined to make long moisture admitting cracks. These don't necessarily lead into the plywood underdeck unless the coating there also fails, but they can let moisture in between the ply and the teak leading to traveling delamination that will reach the screws and then travel into the ply. You'll have a generally more durable and especially more repairable time with a black polygloopide, which is why the plywood with teak veneer uses that.

Anyway, G'luck

Bob Cleek
02-12-2010, 08:17 PM
Double ditto to what Ian said. I know, I know. The Googe Brothers talk about paying deck seams with graphite loaded epoxy, but it's pure bunk. BTW, I've sanded a bit of graphite thickened epoxy. It's about the blackest, messiest, job I've done in a long while. It would pay hell with your teak decks. By the time you were done, they'd be covered with the stuff and it doesn't just vacuum up, either!

Don't go there.

JimConlin
02-12-2010, 09:25 PM
I'm also an epoxyholic and I beg to differ.

If bonding teak to plywood, there will be tension between the teak wanting to move with the weather and the substrate resisting it. If the teak is thin, the adhesive can restrain the veneer. If it's thick, the forces are greater and the adhesive loses. The Gougeons recommend that the teak be no more than (IIRC) 1/4" thick and they report on long-term successes of such decks.

As to what to fill the seams with, some recommend graphite-loaded epoxy and some softer goos, with many recommending the Teak Decking Systems SIS 440. I've used both and they both work fine. If using the graphite-epoxy mix, a dust-sucking sander is a very good idea. There are lower cost sources of graphite, including McMaster-Carr.

For more on this topic,, see the West System (http://www.epoxyworks.com/20/Teak_deck.html) site.

paladin
02-12-2010, 09:51 PM
all the above....if laying thin teak down on plywood with epoxy, I'd pay the seams with a flexible compound. One edge of the teak would be rebated and used as a seam for the filler. I would pay it in carefully, then trim with a scraper, not sandpaper.

islandteak
02-13-2010, 11:50 AM
The question was whether anyone had experience over time using black chalk rather than graphite to mix with epoxy.
I am experimenting with a simple way for the average fellow to add teak battens to their cockpit bench seats. Making up a poster board template and then going back inside your shop to construct finished bench panels using fiberglass roving and epoxy is an easy and convenient way to proceed (especially in winter). Come spring you simply epoxy your new teak seat panels and weight them down with concrete blocks until set. The black 'caulking' is only cosmetic as the teak panel is sealed on the underside . Slight expansion of 3/8" x 1-7/8" teak battens set in epoxy saturated fiberglass roving will not be sufficient to break any teak to epoxy bond, in this situation.
...Ken

wizbang 13
02-13-2010, 09:17 PM
3/8 by1 7/8 battens. that is a wide flat piece. As regards dimensional stability," square," will be more stable than flat. (thats why real deck planking is never wide) zis make any sence?

paladin
02-13-2010, 11:24 PM
I used3/8ths teak strips, 1 7/8ths inches wide, epoxied down to a deck made of plywood and one layer of xynole fabric in epoxy over. Hell would freeze over before I punctured that deck with anything sharp and pointy. Used a strip of plastic about 3/16ths thick to separate the teak planks, laid down in epoxy, with weights to keep them in place while it was setting....then the blac poly was squeezed between the planks, cleaned with a lollipop stick, allowed to set and then cleaned up with a scraper, far less work involved and the boat is still in nice shape.

Boatsmith
02-14-2010, 10:10 AM
I too would recomend gluing 3/8 x 1 7/8teak planks down with starboard spacers and then filling the seams with a silicone based deck calk such as TDS 440 or Maritime Wood 's deck caulk. IMO one should never fasten a teak deck overlay with screws. You are just tempting the gods.
http://farm3.static.flickr.com/2677/4355774631_a612415886.jpg

http://farm3.static.flickr.com/2783/4355774387_452e2a1d42.jpg
David

PAlien
02-14-2010, 11:19 AM
Ken, sounds like a great idea. Also sounds like you are not gonna find anybody with experience to help with the chalk. I might try to allow for a little more motion between the seams by using West's G-flex, either straight up or in a ratio with 205. Either way, I like it. Let us know how it goes, I may try it with dink I'm building where weight is an issue. Sounds like a way to make lightweight teak thwarts.

Bruce Hooke
02-14-2010, 12:22 PM
boat smith-

how do you or do you hold the teak in place while your epoxy sets? or are you using epoxy as your glue. I've always epoxied and screwed my teak down, but if I could skip the plugging stage it would save some work......just dont know how to keep everthing from sliding around before the glue kicks off. Do you maybe use 5200 or Sika as your adhesive?

The one time I did such a deck, I held the teak in place while the epoxy set by running sheet metal screws down between the planks with washers under the heads. The screw size was chosen to create the right space between the planks. I can't remember if we did something like lightly waxing the screws or taken them out when the epoxy was slightly green to make it easier to get the screws out. In any case, putting the screws between the planks eliminates the whole issue with trying to plug screw holes in thin planks.

DuncanvdH
02-14-2010, 12:48 PM
I used black epoxy pigment instead of graphite powder. It turned out 'ok', but the seams where not as deep black as I expected after sanding. I also had a lot of very small air bubbles=holes, I had to fill afterwards.

I made sort of 'press down spacers' of wood covered in wax, with a small wood screw to hold them down in the seams. My project was a small section of the cockpit, and some floor boards. All straight strips, no bending required...

islandteak
02-14-2010, 11:37 PM
The black chalkline chalk epoxy mix comes out very black, close to black Sikaflex. I have made up a number of panels 14" x 36" all set in epoxy saturated fiberglass roving. Some with Sikaflex 291 as the cosmetic caulking and some with the blackened epoxy. They both look good and can be set into place with sandbag weights. However...those damned air bubbles are difficult to eliminate in both situations. Holding your breath and squinting one eye seems to help. With normal flush decking I would bead them proud and then sand the excess off hoping I would not open a hidden air bubble. In this case I have put a 1/4" round on the top edges and leveling the 'caulking' down an 1/8" to make it more difficult and maybe a more comfortable bench seat. Placing the masking tape on the teak battens prior to setting them onto the epoxy/fiberglass roving is best as the tape may not stick as well to the teak when epoxy slop has attached itself to the teak. Clean up of epoxy on the teak is always best when the epoxy is only half cured....same as with any poly goop.
I use a specially shaped chunk of plastic for the troweling, but there still has to be a better way to eliminate those damned air bubbles. They are almost impossible to repair and still look good. Cockpit seats get looked at far closer than any decks. Once you have your template, it takes 1.5 hours to make up one 14" x 36" ( 3/8" x 1-7/8" battens) panel, set in epoxy and caulked with either epoxy or Polygoop. ...still not sure if epoxy or polygoop is best in this situation.

regards...Ken

Jay Greer
02-15-2010, 12:03 PM
Teak decks that have seams made of blackened epoxy can look good for up to ten years. After that time, the constant expansion and shinking of the wood will take its toll and the epoxy will begin to crack and fall out. Since the epoxy is harder than the teak it will be nearly impossible to remove it in an efficient manner in order to allow a new seam filler to be let in. You will be labor and bucks ahead by sticking to an accepted flexible seam compound.
Jay

Boatsmith
02-15-2010, 06:11 PM
We hold the deck panels in place with small blocks super glued to the subdeck. If you apply glue to the block and spray the activator on the subdeck. The bond is almost instant but will separate later easily with little or no damage. For areas where the risk of any damage is unacceptable we put masking tape down first and super glue to the tape. We usually glue the blocks down at one edge of the panel and on the other side space the blocks to allow the use of wedges. Care must be used with the wedges as it is possible to compress the caulk seams and distort the panel. In the photos above these blocks and wedges are visible. Here is another photo of the panels prepared for gluing. David
http://farm3.static.flickr.com/2718/4360133041_568be698cf.jpg