Caulk-type adhesive/bedding compound or epoxy?

[reeljob]

I am building a 20' Simmons skiff. The bottom planks, chines, floorboards, and garboard strakes will all be glassed over and epoxied. From the aterline up, would it be better to use somethink like Sikaflex 291 to fasten planks (3/8" ply fastened every 3" or so with 3/4" sil br ring nails) and fasten the frames to the side planks, gunnels, etc. instead of using epoxy? For what should I use epoxy on and what should I use Sikaflex? I was origionally planning on epoxying everything, but once I do that I couldn;t go back later and remove a plank, etc. Any suggestions as to how I should go about bedding things down?

Thanks

[Hal Forsen]

You will have a devil of a time trying to replace a plank if you fasten your boat with ring shank nails. The boat will be nearly impossible to repair.
You may want to rethink that.
Careful use of a heat gun will remove epoxy BTW.

HF

[westinghouse]

I agree with Hal, and so it's really a question of whether or not getting to know the job of building with the fastplanks interests you, enough so that you're willing to sacrifice convenient future repairability for the fun of switching up building processes a little now. I'd do it for kicks, if only for kicks.

[reeljob]

I was reading last night in the WB book about glued ply lapstrake boats. The author used epoxy putty to secure the planks. I'm really not sure what would be the best for this boat.

[pipefitter]

Any glue that is to survive things such as trailering,flexing,pounding and what not is gonna be a mother to get off come repair time.Are you leaving the boat in the water or is it going to be dry stored? If you are going to glass the bottom,which would most likely be the first part to need replacing,the epoxy isn't going to hurt the top planks. After you go thru building this hull,I doubt you will let anything such as rot get to epidemic proportions.I would rather use epoxy and screws than ringshanks as Hal said. If the plank is rotted it is no good anyways so it can be taken apart epoxy or not.There is many composite ways to fix a composite hull. Keep your boat dry and covered when not in use and you should be fine with using epoxy.Sometimes it's better to have the absolute of one type of construction than the best of many.

On 2nd thought,I dont really think it matters what kind of adhesive you use for the plank laps as long as it's waterproof being as you are using fasteners along with it.It seems that anything would be strong enough collectively.I think after that considered,it comes down to ease of application and one of the construction adhesives would suffice.I don't think a semi soft bedding compound would give you near the strength as a glue would though.Glue allows you to use less framing,lighter planking material etc.

I used epoxy because I didn't want the planks moving and screws loosening etc.

[Ellis Rowe]

I use thickened epoxy and copper rivets to fasten the plank laps on these boats, with ring shank nails at the frames. The rivets are easily removable, and you can easily drill the head off a bronze ring shank screw.
I strongly recommend that you don't use screws on the plank laps. The very pointy end of a screw going into 3/8 plywood just has no holding power.

[reeljob]

I'm thinking i'll go with thickened epoxy then. Once that epoxy gets anywhere, its not going to be easy to remove, so I might as well use it everywhere. THis boat will live a pretty sheltered life on a trailer. I'll go ahead and use the ring shank nails (already got them, coming in the mail. I also have a smal,l box of 3/4" screws- there really is not much there for the plywood to grip too. I will use the screws to attach to the frames, and also might use screws on the garboard plank where there is some meat behind the plank.

[pipefitter]

"I strongly recommend that you don't use screws on the plank laps. The very pointy end of a screw going into 3/8 plywood just has no holding power."

How much holding power do you need on an epoxy glued lap. You could remove all the screws and I doubt you could seperate the planks. They are strong enough to let you regulate the amount of epoxy squeeze out and every 4" or so?Once set in epoxy and all is cured,you have to give the screws a good firm twist with a driver to unscrew them evident with that little "pop" as it initially breaks free. Also,if the screw holes are drilled through,the pointy points aren't holding into plywood but in the epoxy that it pushed through the hole ahead of it. Aren't alot of glued lap boats built without screws or fasteners at all?

I am sure that rivets is the bombproof way to fasten planks but what about come repaint time and you have to prep around all those little buggers.It's not a wrong way to build a boat by far using rivets but to say screws have no holding power in that situation, seems kind of questionable when epoxy is added to the equation. You are right to suggest rivets as being the strongest,Ellis,but try mocking up a glued lap with epoxy and tiny # 6's and see if you can pull it apart or even beat it apart with a sledge hammer.

Reeljob, you would be better off using bigger screws when going into frames than 3/4" with more like 1¼"x12 with a good coarse wood thread or about like the size of a sheetrock screw and after your epoxy is cured they should be backed out and then set in epoxy in the holes.Remember also that on the Simmons,the frames are put in after and pounding little ringshanks in plank laps with no backing doesn't give something substantial to knock against.The screws are faster when setting the laps with wet adhesive on them and you can keep from pulling puckers or divots in the plank laps that you will have to fair out after.

Are you leaving all the nailheads exposed or countersinking them somehow?

[Chan]

I'd listen to Ellis, I think he knows what he's talking about !

[Ellis Rowe]

Ring shank nails are not intended as clench nails, they are brittle. If you wanted to use clench nails, copper would be the best choice. Yes you could fasten the plank laps with glue only, and in my opinion that's what you are doing with screws on the plank laps. Essentially, you are just using the screws as a clamp until the glue kicks. Rivets are better than screws in thin material because of the flat bottom, rather than the tapered coutersunk head of the screw. You can use a flat countersink, and sink them much shallower than a countersunk screw. Or, you can leave them proud, and just paint over them. Besides the advantages I've already mentioned, looking at the rivets when I'm trying to make some time in a three foot chop on Penobscot Bay gives me a warm fuzzy feeling.

[Ellis Rowe]

I just noticed pipefitters recommendation of a nr 12 screw fastening planks to frames. A nr 12 into the edge of 3/4" stock is much to big. A 1 1/2" nr 8 would be the proper fastening in that location.

[pipefitter]

Ok an 8. About the size of a drywall screw. In 7/8ths thick mahogany it could probably hold a 12.

If I had used rivets,people would have thought I had an aluminum boat being as using f-glass will make people think it is a glass boat. With a frame every other floor timber and those "8's" fastening the planks to the frames,surely that is enough fastenage to not need rivets and the little #6 SS machine screws to be enough to hold epoxy glued laps(between frames) if you dont want an exposed fastener hull.

The plans told what fastenings could be used and it seemed to hit spot on without issue throughout the project.The info stated that Simmons used clenched ring nails with glueless construction but that it wasn't neccessary with the glued version.If the plans had not had such satisfactory following,I might have questioned it but if sticking to the methods stated in the plans,I dont think any of the methods are wrong and will still end up with pretty much a bombproof hull.After that considered,rivets could possibly never be more than decoration if the epoxy never breaks free to actually use the fastener.

I am sure there is as many believers on either side of the issue but I don't recall anyone having failure with properly glued lap boats when epoxy was used.Just issue with getting them apart at a later date if need be and that kind of answers all the questions to fastening methods or the lack of.

[erster]

I feel that there is a lot not being addressed here.After being exposed to multiple building methods, with several bedding and adhesive compounds, and also dealing with both new and used Simmons and lapstrake construction, there is a lot of mismatching taking place here with the issue of epoxy and fasteners in building the Simmons. Clinch nails were used as was small ring shank nails, both for the laps by Mr. Simmons, early on and I have also seen the ringshanks as clinch nails in some of the 1950s boats. Keep in mind that he never used glue or any bedding between the woods, but also keep in mind, he specialized in fitted parts, even using solid woods, which has some issues with deminisional changes, depending on the elements of the weather.

So fasteners did a lot more than just hold the planks together till any glues took up. It held the boat together, sorta, and was the only thing that did this job. So fasterners played a important role, indeed, in the boats. He never messed with high gloss paints, and fancy two part paints. So whatever happened to be placed between the framing, was really not an issue, or is my opinion, to Mr. Simmons,.


WIth today's paints, this also requires good primers to substain the longivity of the expensive products and to fill and removed the wood grain issues and unfairness of the hulls, being built with numerous types of woods. Its also an issue that most builders and owners will be repainting and dealing with bumps and dimples with greater pains taken to remove any and all flaws each time this happens. We are dealing with numerous builders and building skills now, and completely different building methods. I have been told numerous times that there are more than one way to do a job. In this case this really applies here.

In doing composite hulls, incorporating epoxy with woods, epoxy has proven itself and the fasteners are doing less of a job than before, at high rates of open water and speeds, unlike the older Simmons with the iron lung engines. Removing parts that have no fasteners, as we know it, if glued properly, will splinter the woods, showing us that fasteners only hold the components together as one unit, in most all cases.

In the case of building these lap boats, its also the case of laps. But with the nature of thin plywoods and bending the long and narrow runs, the complete compression and uniform gap, or minimum gaps are also important, closing and seal the joint and get a good bond in the two parts. also making a hull "fair" for cosmetics. This is key if you are indeed using thickened epoxy. After the fact is too late.

As we all know, wood bends differently, so however you accomplish the matter, joing the seams together, between the framing, Alternative methods such as the invention or creation of lap clamps, which also has been written up in Wooden Boat magazine, as an article. will create this function. As far as I am concerned, with this mission accomplished, the only fastener that is needed is the fasteners in the frames, and wooden framing parts, such as the bottom and rails. And yes any removal of parts, create its own set of issues, and removal of parts can be a pain.

In lieu of using epoxy to build, many good flexible caulks that also have strong adhesive properties, that will make life a bit better for the dealing with repairs. Just make sure you use paintable types. And if fasteners make you feel better between the framing, two to three of your choice, certainly does a pretty good job, if the adhesive properties are there with these type caulks. One huge issue, especially in thin plywoods, too many holes and too large of a fastener, actually weakens the wooden parts, by creating a mini saw cut along the area of the woods.



Keep in mind, the two components need to be clean a free of soil to obtain this bond. In some cases, priming the sections of the bonding areas, gives an increase for this feature, since most adhesive caulks use a form of oil that is sucked up by the wood, deminishing some of the adhesive properties. We all must learn to depend on glues, if we are going to use them, spending the amounts that is being spent on epoxy for bigger hulls than the Simmons. my opinion of course. my thoughts....

[RonW]

Interesting, and I will make the suggestion to use nothing between the laps of the planking, as was originally done.

All caulkings, sealants, glues and so forth do have a life expectancy.
Which may vary from product to product, but it still has a life span that is much less then the actual boat.
Hard glues such as epoxy may have less then a flexible sealant, if the flexible sealant doesn't dry out to soon.

A couple of years back, I examined a 18 ft. runabout that was lapstraked 3/8 douglas fir marine in 5 ply.It had oak steamed bent frames and the ply was riveted to the frames, with copper clenched nails between the frames in the laps.There was no sealants, or glues used in the boat. One of the tags on the transom said 1956 state of ohio department of park service. The boat was half filled with water and was absolutely water tight still yet.

[erster]

The unfortunate part of your post is the differences in the fir plywood now versue then. I personally would never forgo using anything between Okume plywoods, which seems to be in full use now for several reasons. The lack of strength in the same thicknesses scares me, not withstanding the faces of the two contrasting two woods.

[RonW]

You are correct oyster, the boat I mentioned above was built from douglas fir marine... not our modern so called imported marine plywood....by the way, 3 years ago I built a 18 ft. boat from some very nice 3/8 douglas fir marine ply of 5 plies, I had to travel a little over 100 miles to pick it up, but good stuff is still available if you look hard enough, and it may very well depend on which mill it came from..

[pipefitter]

Good points that make sense.It would be nice to not use sealants on these boats and it is easier on these because there is no bevel on the laps.The plywood laps naturally has a near machine fit all on it's own except for the gains on the ends which would be not too tedious to finish good gains for a good fit which is much less comparitive to beveling whole strakes. The one thing the glued laps do accomplish is a much more rigid hull. It allows the use of lesser scantlings being that todays lumber dimensions are still yet smaller dimensionally and even getting into the lesser metric sizes.Especially when buying clear lumber. Hindsight has showed me that the screws wouldnt have been needed other than that I used frameless construction which made for about 4" more of deck space in this narrow hull and not having to sand and cut in around all the frames. I really only used the screws to tune the glue joints and I did use thickened epoxy.Just thick enough to where it stayed in place at the amount I applied it.

Launch is tomorrow.

[Ellis Rowe]

Mr. Simmons used no sealant between the plank laps primarily because it would have slowed production, and he thought it unnecessary. His boats had thwart risers, and three thwarts which strengthened it greatly. I hear a lot said about the well fitted planks not requiring sealant. Most of the lap is factory face of the plywood with the gains cut in the end with a radial arm saw rigged with a taper jig. Earlier boats had a slight tumblehome transom, which required some hand work on the aft gains. Mr. Simmons quickly dispensed with these when he found a quicker method. These were production boats, and Mr. Simmons was very good at devising ways to build them quickly. Witness the incredible number of boats that he built in a small shop with few workers. Somewhere between 900 and 1,000. He very quickly switched from juniper to plywood when it became available, and he realized it would be stronger, more stable, and yes quicker. Mr Simmons considered himself a cabinetmaker that backed into boatbuilding because of the economics involved.
A lot of old timers like Mr. Simmons didn't have the knowledge about materials that we now have. In a lot of boats he used brass bolts to fasten frames to floors. Would any of you guys do that now? He used the bronze nails as clinch nails because they were readily available and he thought they were OK. That doesn't make it so. It's brittle, and copper would be a much better choice.
If you're not in a production shop, and are building one boat for yourself, why not use the best materials and methods available. If you want to trust glue to hold the lap together fine, but don't think that some little ss tapping screw is holding it together, because it's not. No, you can't pull the joint apart, but that has nothing to do with the screws. If you want to test the ss screw against a copper rivet, make the test laps without glue and see which one holds. Like I said before, copper rivets make me feel secure in heavy going. I've seen glue failures.

[pipefitter]

Rivets are definitely stronger. I just think any force great enough to try either of the methods is going to result in damage beyond rivets or glue. The plank would just break somewhere else first. I still think any damage or failure of any glue would not be the entire hull. One would have to basically peel (and you would have to start at the top)the plank to get it to fail.It's the lapstrake sides we are talking about and it would get you home at any rate.The worrisome part would be the bottom pan of the boat which has no rivets. I wouldn't thru-bolt the bottom planks to the floors even though it would be a hundred times stronger. If the foundation of the boat is sound then thats going to be pretty much what lends integrity to the rest of the hull. I used to work out of framed skiffs and they moved alot but the frames were only bolted to the floors with galvanized carriage bolts and no glue. Seems to me they had gussets as well but hulls still flexed alot. Enough to have to go back and retighten the brass deck screws and the screws or bolts that held the thwarts in place. The planking wasn't where the problems were. It was at the chines,side plank/stern juncture,stem/bottom,decking or thwarts.Even in that condition,the boats were still hard to break apart,even if only held together with bolts and common nails.
Your way is one of the many right ways to build a boat. It wont ever fail. With all the framing in your boat and all the ringshank nails and glued laps,I dont think it would fail either. Sure rivets are the final say in never fail beyond a shadow of a doubt but I have yet to hear of or seen a dry sailed, glued lap boat fail at it's laps.If the boat was to live in the water,then maybe the rivets could be more beneficial.I dont think we let our boats sit full of water much anymore either which could also be problematic to a glue only boat.