PL Premium Construction adhesive vs. Sikafelx 291

[Norman Bernstein]

I believe there are a few folks here who are sold on the merits of PL Premium construction adhesive...

I'm still planning my faux teak deck, have decided to bond it to the epoxy glassed subdeck using weights while the adhesive cures, but can't decided between these two adhesive compounds.

I've compared the technical data sheets for both... and to the best of my ability to discern, it looks like they're basically the SAME stuff, polyurethane, moisture cured, similar temperature ranges, viscosities, densities, elasticity, etc.... highly comparable specs on both.

The big difference: PL is available in Home Depot and Lowes' for under $4/tube, whereas Sikaflex 291 is strictly a chandlery item, at $10 or more per tube.

I don't like to pinch pennies on materials, but I also don't want to run out in the middle.... and don't want to have to buy WAY too much of the expensive stuff to insure I don't run out. If I use PL, more can be bought at a place just 10 minutes away... better than 40 minutes away, or via mail-order.

Comments?

[emichaels]

When in doubt, test it. Take the time to do some test pcs and wait for the results. Post them here so we can all see what you came up with. The old adage applies on boats more than anything else I can think of: "If you don't have time to do it right the first time, when will you find the time to do it all over........"
BOL
[img]smile.gif[/img] [img]smile.gif[/img]

Eric

[Norman Bernstein]

When in doubt, test it. Take the time to do some test pcs and wait for the results.

I thought the point of asking the question on WBF was to avoid 'reinventing the wheel'... while I COULD run my own test, wouldn't it be worthwhile to ask people with experience what THEY think?

[Bob Smalser]

PL has lower open time than PVA's and requires gobs of clamping pressure.

Those two negatives make it real iffy for even small decks.

I'd go with a proven solution.

[Gary E]

Norm,
I would make a test setup to simulate the curve that your deck will really be, and then I would double that curve for the test. Use the weights as you would when installing the real deck, and then see how well this over sprung material holds on. Do not clamp it when testing if you cant clamp it when installing the deck. Also, how many tubes are you thinking of?... 10 tubes would be an extra $60... not a lot, but every $ saved now means MORE BEER on Memorial Day [img]smile.gif[/img]

[Doug B]

Norm,
I have not used much sikaflex, but my impression is that it is very much like 5200. I use ton's of pl premium and 5200 and they are very different animals; same genus maybe, but different species. In the obcenely expensive McMansions we build the exotic hardwood floors are nailed and glued with PL. When these floors are water damaged the areas that got wet come up relatively clean, the boards that remained dry usually take the sub foor with them. This makes me leery about using PL on a boat. 5200 on the other hand if used where the sun can't get at it will stick water to ice.

[Norman Bernstein]

Thanks for the observations, DougB....

The reason I was considering the use of PL was the fact that a number of people, on my original thread about laying a faux teak deck, were recommending it. That is why I consulted the tech data sheets and compared it to SikaFlex 291, and why it seemed to me that they were probably very similar.

I might indeed try a few test pieces with the PL, especially with some water soaking to see how they behave... but I guess I'll probably go with the SikaFlex in the end. A number of OTHER people warned me away from 5200.. although I don't remember precisely why.

[kulas44]

My experience, after having used several different polyurethanes and a few different types of epoxy may be of interest. I used epoxy exclusively on the teak flooring (1/4 inch x 2 inches, glued and caulked) with mostly excellent results, in my 40 foot sportfishing boat. However, after getting soaked a few times (it's a boat ya know) it has delaminated in two or three small areas. It seems to be from the epoxies lack of compressability, the teak just raised in a seam. It will be easy to dry and re apply epoxy. On my 54 foot trawler I have used polyurethane for all the teak flooring. This is glued but not caulked. At first I wanted to use "the best" so 5200 was it. After much research, and in no small part, the help of this fine and diverse collection of boat bums,I decided to try some "cheap" goops. The teak in the forward stateroom was laid entirely with PL roofing repair polyurethane, black, on new 3/4 in. marine fir plywood decking. About 4 months later I walked into the boat to find 6 inches of water up front, over the glued teak. (broken thru hull, forward pump stuck, rear pumps saved it) My best guess is it had been that way a few days. I pumped it out and fixed the fitting. A year later the flooring doesn't seem to have been affected at all, no humps or delams anywhere. The PL concrete repair lays out easier and gives you a lot of time, it's great for tile in a shower stall or head area. The PL door and window is good for anywhere you would use 5200, even under water. The PL premium construction, IMO, is for serious gluing, timber, frames, ply, things that can't move afterwards. It gets pretty hard, it's nasty to work with, will get in your ears, and finds every crevice to ooz out of, I love it !!! but not for bright work. Another line of products that "don't get no respect" is White Lightening polyurethanes. Try there stuff, it's even cheaper and you will be very surprised. I really like the concrete repair stuff, it's thin and self levelling, runs into cracks and gaps and stays semi flexible, neat stuff if that's what you need for a particular application.

[Thad Van Gilder]

I'm using the PL to lay the teak sole in my 1969 streamline camper. It's doing ok, but i dunno about on the boat...

-Thad

That said, my friend randy used a whole lot of it on his stonehorse.

[ 12-08-2005, 02:33 PM: Message edited by: Thad Van Gilder ]

[emichaels]

Originally posted by Norman Bernstein:
</font><blockquote>quote:</font><hr /> When in doubt, test it. Take the time to do some test pcs and wait for the results.

I thought the point of asking the question on WBF was to avoid 'reinventing the wheel'... while I COULD run my own test, wouldn't it be worthwhile to ask people with experience what THEY think? </font>[/QUOTE]Sure all the info you can get is worth asking for. But that said, every situation is different and everyone performs differently. So take Bob S. advice go with has been proven and test it in YOUR situation with your skill set. Use what works for you.

[ 12-07-2005, 10:12 PM: Message edited by: emichaels ]

[N. Scheuer]

I'm not sure about the significance of the various Sikaflex numbers, but in general the product is very similar to 3M 5200.

Both are elastomeric (rubbery) uretahne adhesive sealants.

Most of the construction adhesives that I have seen dry out to be fairly rigid. Sikaflex and 5200 are never rigid.

Moby Nick

[pipefitter]

Am I to understand that these decks are just glued down with no nails or screws or even blind nailed? Sounds crazy to me to trust an adhesive alone for anything on a boat. What did they do before there was modern adhesives?Would it not be wise to use a little of old technology combined with new?

[kulas44]

Screws were the major cause of deck leaks that in turn rotted the underlying support. Teak bungs inevitably leak. Marine ply and fir lumber eventually gets rot. No screws and the entire surface covered by a waterproof membrane that is protected by the teak overlay doesn't have the screw penetration problems. Some things can be improved.

[Norman Bernstein]

Am I to understand that these decks are just glued down with no nails or screws or even blind nailed? Sounds crazy to me to trust an adhesive alone for anything on a boat. What did they do before there was modern adhesives?Would it not be wise to use a little of old technology combined with new?

Frankly, if it weren't for the fact that the teak strips I'm laying will be 1/4" thick, I'd screw and bung them; I like the look of bungs! [img]smile.gif[/img]

However, at that thickness, screwing and bunging would be a marignal proposition, at best; the screw head would be gripping no more than 1/8" of teak, and the bung would similarly be that thin... strikes me as a disaster in the making.

Obviously, MANY people have glued down a teak faux deck... and, from what I can see, people have been successful using epoxy, polyurethane, and what-have-you... and people have failed using all three, as well.

In short, I'm no more decided about just what to use than before... except that I think it's pretty clear I WON'T be using epoxy; the arguments for the faux teak being to thick, and the epoxy too brittle, are convincing.

So, it's SikaFlex, or PL. 5200 is probably out; too many comments about it being too rigid to move as the wood expands and contracts.

[ 12-08-2005, 11:30 AM: Message edited by: Norman Bernstein ]

[kulas44]

I cut the teak for my trawler from salvaged boards that were originally 3/4 thick and bunged. after cutting them to a little less than 1/4 inch on a band saw and planing they had lots of holes where the bungs were. No problem, even better, they made a good place to put my screws and fender washers when installing and gluing them down. Afterwards I pulled all the screws, drilled all the holes for 1/2 inch long teak bungs, cut from the same wood, and glued them in. It looks great, and I also like the look of bungs.

[pipefitter]

Why are you stuck on 1/4". 3/8ths would probably afford room for screws.I guess the water penetration to the screws is a good point but from reading some of the above posts,water seems to find it's way into the glue only systems as well.And if some adhesive between 2 layers is not solidly uniformly coated,wont this create voids that we so try to avoid by using solid core marine ply? Causing condensation to be trapped between the 2 layers? I can't imagine the amount of sika it would take to achieve this. I may have this wrong and someone here probably has a good explanation as to why this works.I just haven't had good luck with any out of tube adhesives working without fasteners along with it.
Too bad someone hasn't invented a power nailer with stainless L nails. The fastening system they use to put down T&G oak floors in houses where it puts the barbed nail into the tongue of the board at a back angle which still enables the wood to move.

[ 12-08-2005, 01:01 PM: Message edited by: pipefitter ]

[JormaS]

Norman, you probably want maximum glueing capacity and then "some" elasticity. Choosing 3M 5200 for glueing capacity would probably be about right. The only question is, is it flexible enough?

There are three things to consider: Twisting of the hull/deck, flexing under the weight of a person, and dimensional change of the ribs due to environmental conditions.

The first two are difficult to quantify, but the third can be read from tables. The moisture content of the teak ribs will vary between 10% and 18%, if the relative humidity of the air fluctuates between 50% and 90%. The dimensional change of the ribs will then be between 0.1% and 2%, depending on how the ribs are sawn (quarter or flat sawn). Usually deck ribs are somewhere in between, because quarter sawn ribs tend to develop checks and flat sawn ribs have greater dimensional change of width.

Let´s say that your ribs are 40 mm wide and the dimensional change will be 1%. The change in width will then be 0.4 mm.

Now, this is pure theory of course. One can never predict the behaviour of a piece of wood in very exact terms. But it gives a clue as to how to approach the problem. The next question is how the glue will perform in the described conditions.

When cured, the Sikaflex 291 is reported to have a hardness of Shore A 40. 3M 5200 is Shore A 60, which is considerably harder and less elastic. 3M 5300 is 50, and 3M 4300 is 40 I think. For comparison, the Sikaflex 290 DC seam compound is 35 to 40 as I remember. The most elastic seam compounds used in construction have a hardness of Shore A 15. 3M 5230 (if I remember the figures right) is Shore A 80 I think, which makes it an outright glue. I did not find any such data concerning the PL products on their web site.

If the compound is to "give" under the ribs, it must have some minimum thickness. I don´t know if that is prescribed by the manufacturers. Clearly, 2 mm of compound will be more forgiving than, say, 0.5 mm. Without the use of spacers, one would assume that the latter is the more probable thickness if heavy wheights are used to press the ribs down. That would call for a more elastic compound. This may be the reason why Sika have decided to make it Shore A 40 for this application. But I´m not sure.

Anyway, I wanted to describe how I would approach the task. You´ll have to forgive me for not proposing a direct solution, but hopefully this will be of some use to you. [img]smile.gif[/img]

(The data are taken from "Physical and Related Properties of 145 Timbers", by Jan F. Rijsdijk and Peter B. Laming, Kluwer Academic Publishers 1994.)

[Bruce Hooke]

I number of people have proposed running tests. That is certainly a good idea, but it should be kept in mind that it is hard to simulate the various factors that go into aging. So, a test that fails right away gives reliable information, but on something like this, at test that does not fail gives at best indefinite information...

[Bruce Hooke]

Pipefitter...in the old days a teak deck would have been an inch or more thick, screwed straight to deck beams and caulked between the planks. This approach certainly still works, but it is expensive and heavy, and prone to leaking. The good thing is that the leaks go straight through to the cabin rather than sitting between the deck and a sheet of plywood, but this may not seem like good news when it is your bunk that is getting wet.

Lots of boats are being built these days using only glue in areas much more critical than deck planking laid over plywood.

I think the real danger comes when you try to mix old and new techniques in ways that do not mix well. Of course unproven techniques are questionable no matter how old or new they are, but we are not talking about unproven techinques here.

[sdowney717]

The PL will expand, which is nice in that it fills up the voids spaces with sticky glue. But this expansion can force the boards up from where you want them to lay.

As for clamping pressure with PL you could use screws and washers in between the planks to hold them down.

Or just go slowly laying only a few boards at a time using some type of weights or clamps to hold them till the glue sets.

If you are gluing this down to a smooth epoxy like plastic or metal or painted type of surface, you can mist this surface with water and make it damp to give the glue the moisture it needs to cure and setup quickly.
Regardless, adding a little moisture will speed up the curing by a large amount.

I would lay down beads and butter the deck areas and place the boards into the glue on the deck. This should keep the deck watertight with a layer of PL on top. It will setup completely by the next day and actually within an hour or so will be extremely tacky.

I would practice on some scrap wood since you have never used this before.

[StevenBauer]

I've used a lot of PL Premium (not on boats) and I haven't noticed any expansion. I've seen it with the other kinds of polyurethanes, like Gorilla Glue, but not PL Premium.

Steven

[sdowney717]

You can also mix in sawdust into the PL.
This will give it plenty of moisture to cure in thick layers. It will also bulk it up and make it go a little farther.

[sdowney717]

I used PL to fill the bung holes in my planks, over 4000 holes. The glue swelled up and formed a little mound in each one.
It swells up and squeezes out of evey crack I have laid it flush like between 2 boards.
It can be easily sanded or cut with a blade.
I once glued some nice luan to a metal door and I had to carefully clamp it because as it cured, it pushed that plywood right off the door from where I wanted it to lay.
The tube says dont layer it thicker than 3.8 inch. This is because insufficient moisture is present within a thick layer for it cure all the way thru. Adding somw sawdust to the mix allows it to cure all the way thru because the wood dust has some moisture present in the sawdust just from the air.

[Bob Smalser]

Surface moisture beyond what the poly glue needs to cure weakens the joint dramatically. If your wood is air dried and around 12% you don't need any additional moisture at all unless the air is particularly dry before the glueup.

The few failures I've had with poly glues were using them with too much wiping water.

I don't think I'd use PL as or on plugs or bungs, either. Very likely damage to the planking when it comes time to remove the bung to get at the screw. It'll likely take a chunk of wood with it when the plug comes out.

[ 12-09-2005, 10:29 AM: Message edited by: Bob Smalser ]

[StevenBauer]

I don't think sd used bungs, Bob, just the PL.

sd, are you sure you are seeing the glue expand? Or is it just normal squeezeout?

Steven

[Bob Smalser]

Originally posted by StevenBauer:
I don't think sd used bungs, Bob, just the PL.

sd, are you sure you are seeing the glue expand? Or is it just normal squeezeout?

Steven

Either way. Way too strong a glue if those screws'll ever have to come out in a repair or refastening. Plain old paint ot varnish works fine.

[StevenBauer]

He'd have to scape off the bedliner first anyway.

Steven

[sdowney717]

yeah well all you got to do is drill out the PL, very easy to do this.
Diggin in with a chisel and poping out bungs that are 1/2 deep is none too easy. I start by diggin a little hole. Then I use a modified spade bit.
I took a 3/8 spade bit, ground off the end till it was flat. This clears any wood plug right down to the screw head.

[sdowney717]

I suppose you could burn off the bedliner material and use a scraper, it melts when it gets flame hot from a propane torch.

[Bob Smalser]

Originally posted by sdowney717:
yeah well all you got to do is drill out the PL, very easy to do this.
Diggin in with a chisel and poping out bungs that are 1/2 deep is none too easy.

If you've tested this, then it's cool with me.

But running a deck screw into a wooden plug breaks the weak, varnish edge joint more cleanly and evenly than a chisel, and is faster than drilling.

[Norman Bernstein]

Why are you stuck on 1/4". 3/8ths would probably afford room for screws.

There are a couple of reasons. First, I'm not really set up to rip strips myself, nor do I have much room to work. I don't have a bandsaw, only a table saw, and based on a spreadsheet I constructed which accounted for saw kerf, the cost of teak, etc, it will actually be cheaper for me to buy the strips... and a whole lot easier. Secondly, it's a small boat, and I want to minimize the weight.

The one disadvantage of the 'store bought' strips are that they are flatsawn, not quarter-sawn or vertical grain... however, this is not a deck that will be walked on very much at all, and I'm laying teak for the visual appeal, not for any practical reason ( a practical deck would be painted dynel/epoxy!)

If they trust epoxy for 1/2 inch teak at Rockport Marine, then I can`t see how 1/4 inch should pose any problems. However, the planks must be vertical grain.

Well, there you go...mine won't be vertical grain.

Surface moisture beyond what the poly glue needs to cure weakens the joint dramatically. If your wood is air dried and around 12% you don't need any additional moisture at all unless the air is particularly dry before the glueup.

I work in an unheated garage, and it's the middle of winter... the air is VERY dry in there... I was contemplating using a misting bottle to lay a very light mist of water after bonding.

[maa. melee]

Bob, regarding the above picture, is that PL masonry or construction adhesive? There seems to be some definite foaming and boy did that stuff grip huh. There are many PL products out there, which one is used in the picture? I apologize if you mentioned this before. Here is a webpage with home experiments with PL and boatbuilding. I must say I am very impressed with his work.

PL PREMIUM

[ 12-09-2005, 11:24 AM: Message edited by: maa. melee ]

[sdowney717]

looks like the construction adhesive version.
I read about the misting technique in the companies own PDF on how to use the glue if you are using it on surfaces that naturally will have no moisture content such as plastics or metal. But you dont want it to be wet just dampness is all that you need from what I have read. Either way, it will eventually cure.

[bainbridgeisland]

I think a few problems are being mixed up here.

First, teak has an adhesion problem with epoxy due to the very oil within the wood that protects it from the weather. It is very unlikely that epoxy glued teak fails due to brittleness of the epoxy when used to glue thin pieces. Most epoxies used for boatbuilding have 3.5% to 4.5% elongation at failure and at least 2000-psi shear strength, more than enough to glue thin pieces together. When surface prep is inadequate, you won't get any where near 2000-psi shear strength though.

There are surface treatments that can improve the epoxy bond to teak but I do not think that is the best route to take. The long-term integrity of the bond is dependent on degradation of the bond line too. The degradation occurs when water plasticizes the epoxy, though this can be somewhat controlled by choosing the right epoxy adhesive. With some materials (copper for instance), the bond strength decreases with time due to localized chemical reaction at the bond-line interface. I do not know for sure, but read someswhere that teak has a similar problem. This means that you may obtain a superior initial bond that gradually weakens over time.

Polyurethane adhesives are usually (but not always) more flexible than epoxy. This makes them more tolerant of 'peel' loads (the best glue joints are loaded in combined shear and compression). Thus polyurethane adhesive is more tolerant of poorly designed glue joints. Polyurethanes also have a lower surface energy, which means they will 'wet' a bonding surface that has relatively low surface energy. The rule here is that a good bond requires contact (wetting). Since contaminates like oil tend to lower the surface energy of a bond surface, polyurethanes are more likely to be successful gluing them than epoxies. This means that polyurethane adhesives are more likely to provide a good initial bond than epoxy. However, polyurethanes are usually degraded more by water take-up than epoxies. So what you initially gain in bond strength can be lost with plasticizing from water. Also, polyurethanes are not as strong as epoxies, about 1300 psi initial bond strength. It is also possible that long term exposure to the oil in the teak could further weaken the bond line as has been suggested with epoxy, though I have never heard of specific tests for this problem.

So where does that leave us? Well, teak is hard to glue. The precise problem may vary from initial bond to long-term joint integrity depending on the adhesive you choose. Both adhesives have produced glued decks that have lasted many years. I believe this is due to the surface prep and to the precise adhesive chosen. There are thousands of epoxy adhesives and many polyurethanes available. There are obviously some that will work (as proven by those decks still in sound condition). My opinion is that it would take a lot of test time, and cost a lot for lab time to be really sure I chose the right product and the right surface prep.

One further suggestion, you might consider using Alaska Yellow Cedar or Port Orford Cedar. Both glue very well. Both have good rot resistance. Both are hard enough for decking. Both look good when oiled. Others are using these materials for faux laid decks, for example Legacy Yachts in Washougal WA.

David Mancebo

[JormaS]

Bainbridge, that was a very informative post. You seem to indicate that it does not really matter (roughly speaking)if one glues the strips with epoxy or polyurethane. This probably also means that elongation is not an issue; e.g. that the small dimensional changes in the wood do not have to be taken into consideration.

In that case Norman should just choose between a good epoxy and 5200 which is known by most people here as a good polyurethane glue. But why would Sika recommend a Shore A 40 product? I´m assuming that a rather stiff polyurethane would make a better glue than a soft one.

Any thoughts on that?

[Norman Bernstein]

One further suggestion, you might consider using Alaska Yellow Cedar or Port Orford Cedar. Both glue very well. Both have good rot resistance. Both are hard enough for decking. Both look good when oiled. Others are using these materials for faux laid decks, for example Legacy Yachts in Washougal WA.

The decision to go with teak is one of personal taste, not practicality. Frankly, the easiest and most servicable deck would probably be Dynel set in epoxy, and painted.... but the point of spending three winter seasons building this boat is to please ME, not to be practical...so, teak it is.

So far, the choices remain:

1) Epoxy
2) PL Premium
3) PL Concrete Sealer
4) 3M 5200
5) Sikaflex 291 LOT

After distilling all of the comments made so far on this thread, the best candidate seems to be the Sikaflex.

[Tom Lathrop]

David, thanks for introducing some engineering reason into the discussion. Since you mention "surface free energy", I wonder if you have a table listing the SFE for different materials? I know that Teflon would be at or near the bottom and oil would be near the top, but what about other materials?

[bainbridgeisland]

Norm, I know you are interested in the look of laid teak decks. Have you ever seen laid cedar decks? You may be surprised at how much they can look like teak whan you are a few feet away from them. To see what they look like, go here:
http://www.legendaryyachts.com/legendaryyachts/

I will try to post a picture from this site with cedar decks. Here is what they look like:
[img]www.legendaryyachts.com/legendaryyachts/images/KELSIH1.JPG[/img]

You can use teak if you want, but the glues you are considering will work much better with cedar.

Tom Lathrop, yes I have the surface energy of some materials. Which ones are you interested in? I don't remember seeing teak or cedar, but I might have them somewhere.

Well I don't know why the picture link isn't working and don't have time to mess with it now.

[ 12-09-2005, 03:37 PM: Message edited by: bainbridgeisland ]

[Superflid]