Hull Planking Question

[tomsimon]

Hopeful all are having a marvelous Holiday Season. Why is it appropriate to bead ACC  gap glue,  between beads of carpenter’s glue on plank strips when planking a hull?  It would seem easier to only use ACC, so that the plank strips adheres faster to each other with no need for pins or a wait time for the carpenter’s glue to dry.  What am I NOT understanding about the “ACC, carpenter’s glue” (repeat) method of planking, or is it just a preference?  Looking for insights, so that I build with less error. Thanks. 

Edited December 23, 2020 by tomsimon
Correcting punctuation

[ccoyle]

Wood glue is not absolutely necessary, but some modelers don't trust the durability of CA glue bonds. CA doesn't resist shear stress well, making its bonds somewhat brittle. This isn't a problem if you avoid sudden shocks to your model. But, on the other hand, I once saw a CA-bonded model fall off a table and literally shatter into all of its component parts once it hit the floor. Know the risks and advantages in advance, and then choose whichever glue suits your fancy.

[GuntherMT]

I use nothing but PVA (wood glue) for the vast majority of my construction and for all of my planking, no reason IMO to use the super-glue type glues if you properly shape your planks before fitting.  If you get super-glue type glues on a wood surface that you don't plan to paint, it can be impossible to remove the stain left which can soak deep into some types of wood.

 

 

 

[Dr PR]

I never use cyanoacrylate (CA) glue. Period!

 

Some folks use a drop of CA at a few spots when planking for a quick fastening, and use wood glue for most of the bonds. I just use the wood glue and tightly clamp the planks in place. It may be a bit slower that using CA, but it does produce a better bond.

 

One of the things to keep in mind is that wood expands and contracts with changes in humidity and temperature. This can generate some pretty strong local stresses, the sort of thing CA doesn't work well with. Some of the earliest planked ship models that I made decades ago eventually developed cracks between the planks, with some plank edges showing, even though I used wood glue between the planks!

 

The absolutely best way to prevent cracks from developing years after the build is to paint the interior of the finished hull with epoxy paint or something like fiberglass polyester resin. Some people even apply thin fiberglass to the hull interior, but I think that is unnecessary. I have used an epoxy paint that flying airplane modelers use to seal balsa engine mounts so they don't soak up fuel.  It should be thin and watery (a paint) so it will soak into the planks and bulkheads. After it hardens the hull will be rock solid and will never crack. I have 30+ year old hulls that are like new. You don't have to worry about the hull shattering if you drop it!

 

You don't need to try to get glue between the plank edges while planking - just glue the planks to the bulkheads. This way you don't get glue on the exterior surface where it can spoil the surface of unpainted wood. After the planking is finished apply the epoxy to the hull interior. The epoxy paint will seep between the planks and soak into the wood making a very strong bond between neighboring planks and between planks and bulkheads. After it hardens you can finish sanding/scraping/painting the hull and it will retain the final shape forever.

[Richard44]

The wood glue plus a few drops of CA (I use gel) method can be very useful if the plank to be glued is in such a place where normal clamping is difficult, if not impossible. You can then hold the plank in place with your fingers (with care!!) until the CA grips, and then let the wood glue do most of the bonding.

[allanyed]

What Richard describes is true, but I do the same thing without the CA.  Less stink, less eye irritation, less hassle in general.  Takes an extra half a minute waiting for the glue to start curing before letting go, then setting it aside and go to something else for a few minutes.   Ship modeling from me is not about saving a few minutes here and there.  If time is not on your side, CA might be the answer, but keep in mind the risks outlined above.  

Allan

[tomsimon]

Thank you: @allanyed, @Richard44, @Dr PR, @GuntherMT and @ccoyleall for the useful insights.  I especially like this method and will more than likely implement it on my soon to be, first build.

 

Quote

You don't need to try to get glue between the plank edges while planking - just glue the planks to the bulkheads. This way you don't get glue on the exterior surface where it can spoil the surface of unpainted wood. After the planking is finished apply the epoxy to the hull interior. The epoxy paint will seep between the planks and soak into the wood making a very strong bond between neighboring planks and between planks and bulkheads. After it hardens you can finish sanding/scraping/painting the hull and it will retain the final shape forever.

 

I, also, understand that CA neither handles stress well, nor does it age, best, on  a model one would like to keep for generations, so it would be unwise to solely use CA, for planking purposes.  

[Bob Cleek]

One should carefully consider the downside risks of gluing planking seams, whether by application of adhesive to the seams, or by coating the inside of a hull with epoxy resin adhesive which soaks into the seams from inside. As noted correctly, wood moves with changes in the ambient humidity levels of the environment it's in. This movement is primarily across the grain and its amount varies depending upon the wood species and, within the same species, even the location where the wood is grown. This is called tangential movement. Most woods will shrink tangentially six to ten percent when dried and will swell back depending upon the moisture content absorbed. The amount of movement is relatively small, assuming properly dried wood being used to begin with, but can still be considerable if the distance you are dealing with is relatively large. 

 

So, if you are building a model using vertical grain stock, as one should, the tangential (cross grain) side of its planked hull can easily total six inches. That's six inches of grain to shrink tangentially and even at a rate of movement of one percent, you are getting close to a sixteenth of an inch, which would be a quite noticeable crack in a model's topsides. If the planks are not fastened to each other, each will shrink individually and if you have maybe 24 1/4" planks, that shrinkage will only amount to 1/24th of a sixteenth of an inch. (You can do the math to get an exact fraction... a good example of the advantages of metric measurements!) That amount of movement isn't going to be noticeable at all and most coatings will allow for such movement without cracking at the seams. However, if the seams are all glued together, they all move as one, and the "weakest link law" takes over. In that case, a sixteenth of an inch crack along the weakest glued seam... or a crack in the wood itself... is going to occur at the weakest point. Conversely, swelling will push the glued sheet of planking for that sixteenth of an inch against everything it butts up against, again potentially causing a structural failure at the weakest point, or tend to buckle the "planking sheet" outward, breaking the glue bonds... or the wood... at the frames. 

 

Now, with prime wood species which have low movement factors and with relatively stable humidity, you may not run into any problems at all, but theoretically, the potential is there and I've seen its results in more than one model I've restored. More often than not, parts, cap rails, for example, start popping off and nobody knows why.

 

Monocoque wood hull construction is tricky. For my money, I prefer to give the wood as much opportunity to move on its own as possible without concentrating swelling and shrinking stresses within the structure.

 

Others' mileage may vary, of course.

 

Edited December 24, 2020 by Bob Cleek

[Rik Thistle]

Bob,

 

That's six inches of grain to shrink tangentially and even at a rate of movement of one percent, you are getting close to a sixteenth of an inch, which would be a quite noticeable crack in a model's topsides.

 

Yes, that does make me stop and think. Useful info, thanks.

 

As a non-sailor but ex-engineer how do full sized wooden boats and ships cope with that movement....pumps?

 

Richard

 

[druxey]

Most folk think wood is uniform in consistency, but it is not. While a plank may stay fairly stable in length, its width can change quite a bit, as Bob has pointed out. Try to keep models at a consistent humidity level if you can. Temperature change has a less, but still appreciable, effect.

[GuntherMT]

6 hours ago, Rik Thistle said:

Bob,

 

That's six inches of grain to shrink tangentially and even at a rate of movement of one percent, you are getting close to a sixteenth of an inch, which would be a quite noticeable crack in a model's topsides.

 

Yes, that does make me stop and think. Useful info, thanks.

 

As a non-sailor but ex-engineer how do full sized wooden boats and ships cope with that movement....pumps?

 

Richard

 

 

Traditional wooden boat construction does not edge glue the planks (they don't glue the planks at all actually) and there is a built in gap at the surface of the planks that they pound caulking into to seal the planks.   Basically there is a flexible 'gasket' between each plank to stop water ingress so some swelling or shrinkage shouldn't be a problem because they handle it in the design/construction.

[Roger Pellett]

Richard,

 

Wood shrinkage and expansion is a major problem in wooden boats.  The best solution is to leave them in the water so that the moisture content in the wood remains constant, but this is not possible for various reasons.   When boats are taken out of the water and the wood dries out the seams open up.  When the boat is relaunched these seams will leak to the point where the boat can sink.  For this reason wooden boats are often hung in slings in the water by the boatyard crane until the seams tighten up.

 

Over the years, builders of boats that are constantly in and out of the water such as ships boats or recreational watercraft, or lifeboats where time does not permit swelling of the seams, have used innovative construction techniques to overcome this problem.  These include a waterproof membrane between two layers of diagonal planking (Royal Navy Ships Boats), and planking seams backed up with a batten (American mahogany speedboats).  Lapstrake planking (extensively used in wooden lifeboats) also minimizes this problem.

 

WoodenBoat Magazine always includes a page titled “Save a Classic”  where they try to find new owners to rescue old boats.  They will often warn prospective owners with words to the effect that,  “She has been out of the water for several years and is completely dried out.”

 

Roger

[Rik Thistle]

Gunther,

 

Basically there is a flexible 'gasket' between each plank to stop water ingress so some swelling or shrinkage shouldn't be a problem because they handle it in the design/construction.

 

Ah, OK, that makes sense. Thanks.

 

Richard

[Rik Thistle]

Roger,

 

“She has been out of the water for several years and is completely dried out.”

 

Yes, I remember them saving the Mary Rose (?) timbers but keeping them constantly sprayed with water, not to save any seals I imagine, but to stop shrinkage nonetheless.

 

I assist with maintenance work on my friend's near 60 yr old wooden framed aircraft and I never fail to be impressed by what an amazing engineering material wood is...as long as it is looked after carefully.

 

Richard

 

 

 

[tomsimon]

Amazing insights here.  Thanks.  So, would it be agreed that the best method is to, ACC  gap glue,  between beads of carpenter’s glue on plank strip edges, when planking?  The original question is a result of  reading Frank Mastini's, Ship Modeling Simplified, Page 36, Planking the Hull-The First Layer of Planking.    

[allanyed]

Try different methods with some scrap material and see what works best for you.  Perhaps this type of CA is a good way to go for you, but gap glue is just a thick slow cure CA.  As it is a slow cure, it is just as easy to go with PVA.    Gaps on a first layer of planking, if tiny are no issue.  If large, mix a little saw dust with the PVA, fill the gap, let cure for a few minutes and sand.   Easy, and none of the toxic fumes and stinging eyes.

Allan

[No Idea]

Hi tomsimon - Your question is one that I wondered when I first started building and for me it came back to one thing - time!

 

If your in no rush and are happy to take your time then carpenters glue or better aliphatic resin is my choice.  It gives me loads of time to place whatever I'm gluing where I want it and the clean up is so easy.  It is for me the laid back enjoyable way of building.

 

If however you need to build somewhat faster, then CA can be dropped between the carpenters glue to grab what your gluing much faster.  I find this method very unforgiving but thats just my way of building  - others find this way better.

 

Try both and you'll find what suits your building technique 

[mtaylor]

On 12/24/2020 at 11:04 AM, Rik Thistle said:

Roger,

 

“She has been out of the water for several years and is completely dried out.”

 

Yes, I remember them saving the Mary Rose (?) timbers but keeping them constantly sprayed with water, not to save any seals I imagine, but to stop shrinkage nonetheless.

 

I assist with maintenance work on my friend's near 60 yr old wooden framed aircraft and I never fail to be impressed by what an amazing engineering material wood is...as long as it is looked after carefully.

 

Richard

I don't think it was "plain" water.  Most likely a mixture of glycol and fresh water.  The glycol displaces the water and helps to preserve the wood.  The same thing was done with the Vasa amongst others.

[tomsimon]

Is it safe to say that gap filling, CA, medium glue is the same as pva or would pva be better suited because it can resist stress better?  

[Richard44]

I personally would never use CA as a gap filler. If I need to fill gaps I use PVA mixed with sawdust (as someone suggested above), or more simply, putty or your favourite filler. As you know, CA is very unforgiving and could form a hard "blob" if used to fill a gap, and this can be very difficult to sand flush without damaging the surrounding wood.

 

I do use CA, and I'm using it on a current build to glue hull planks to the stem - it's impossible to get a clamp here. The rest of the plank is glued using PVA.

[GuntherMT]

5 hours ago, tomsimon said:

Is it safe to say that gap filling, CA, medium glue is the same as pva or would pva be better suited because it can resist stress better?  

 

CA isn't even close to the same as PVA.  Yellow wood glue is PVA (as is normal white glue).  CA is 'super glue' type glue which comes in various speeds and thicknesses but shares common attributes with, including that it will stick to your fingers (or anything else) and if it gets on a visible wood surface it will be extremely difficult to remove as it will soak into the wood fibers and create a super-hard spot that will show up through almost all finishes as even paint sometimes.

As I said above, I try to avoid CA at all costs when working with wood.  If I need to bind wood to metal or some other material CA is one possibility, but an epoxy would be a better solution whenever possible.

[tomsimon]

So, to sum it up, any type of CA glue is best only used as an anchor point, but not for a complete application of, such as, planking a hull. This arose out of CA being sold as gap filling glue, which now understand is not a best use of the product. It’s PVA all the way. 

[Dr PR]

Bob,

 

Thanks for the information about wood shrinkage and expansion with humidity. I have long been aware of the problems with expansion/contraction of metal and plastic with temperature change, and the large differences of thermal coefficient of expansion for these materials. I hadn't given much thought to wood, except that it has a relatively low thermal coefficient of expansion and the problems this can cause in constructions with wood, plastic and metal.

 

I have three plank on bulkhead hulls that date back to the 60s through 80s. All are single plank hulls. These have been in the western Oregon environment where we have humidity swings several times a year between 20% and 100% (normally 35% to 70%). Winters are especially damp. It can start raining in late October and not stop until May. Then we may have no rain from May to October. I would think this would make a good test of the effects of humidity swings on model hulls.

 

The first two hulls (14" to 15" long, built in 1969) had planks glued (or nailed) to bulkheads with no glue between planks. As you noted, expansion/contraction was localized. Both of these hulls have pronounced cracks between some of the planks. The ordinary lacquer or enamel paint applied to the exterior was not sufficient to prevent gaps from appearing.

 

The third hull (18" long, built in 1985) has no cracks after 35 years. The inside was painted with the epoxy paint as described in my earlier post (several coats until the wood absorbed no more). See the link to my Mantua Albatros build in the footer of this post. I think the reason it has not cracked is pretty simple. Every piece soaked up the epoxy so the bonds penetrate into the wood. Each plank is bonded tightly to the bulkheads, so the planks cannot move. Each plank is bonded tightly to its neighbors, making it difficult for gaps to appear. I would say 35 years in this environment without cracks is a pretty good test of the process.

 

One thing that may have contributed to the stability of this hull is that it probably was built in the winter (not many good days for hiking) , with relatively high humidity. So the planks may have been expanded when they were glued together.

 

For what it is worth, all three hulls were from kits, and the wood was whatever was thrown into the box. Back in the 60s to 80s I doubt if anyone gave any thought to how the grain ran in the wood. The plank dimensions of the 1980s kit varied quite a bit, especially in thickness!

 

These were fairly small hulls. If I was building a 3-4 foot hull I would certainly give some thought to wood expansion and contraction.

Edited December 26, 2020 by Dr PR

[Bob Cleek]

On 12/24/2020 at 4:07 AM, Rik Thistle said:

As a non-sailor but ex-engineer how do full sized wooden boats and ships cope with that movement....pumps?

Yes, pumps. It is common for a carvel or lapstrake planked hull to dry out when a boat is out of the water and dries out. Depending upon how much the planking is opened, the boat can be launched and pumped for a few days or weeks until it "takes up," or it can be left "in the slings" if launched with a crane or travel lift or "on the stocks" if dry docked to prevent if from sinking if there is concern that the amount of leaking is more than the pumps can handle. Another practice is to put soft soap into the seams with a putty knife to stop or at least slow the leaking. As the planks expand when the boat is launched, they "spit" the soft soap from the seams and is eventually dissolves. In the age of sail, it was a regular practice to tow a ship's boats astern every so often, or in anticipation of making port, so that they would swell up and not leak unduly when it was time to use them. It may surprise the uninitiated, but a dry bilge is something of a rarity in wooden hulls and even in metal and fiberglass hulls, as water always seems to find a way somehow. Generally, most prop shaft bearings will leak a little bit as the shaft turns, if nothing else.

[Bob Cleek]

On 12/24/2020 at 1:27 PM, tomsimon said:

The original question is a result of  reading Frank Mastini's, Ship Modeling Simplified, Page 36, Planking the Hull-The First Layer of Planking.    

 

The good Mr. Mastini's book is a good enough primer for beginning builders of boat model kits, but it has its limitations, as do most of the kits on the market, with a few notable exceptions. Mastini's book is a good book for beginning kit builders, but a lot has changed in kits since it was written. At that time, double planked model hulls were quite popular. That is not as much the case with the better kits these days which benefit greatly from laser cutting technology. (And, for openers, planking a double-planked hull requires twice the work!)

[Bob Cleek]

5 hours ago, tomsimon said:

So, to sum it up, any type of CA glue is best only used as an anchor point, but not for a complete application of, such as, planking a hull. This arose out of CA being sold as gap filling glue, which now understand is not a best use of the product. It’s PVA all the way. 

 

Yes. I would not advise using CA adhesives at all, although there are a few applications for it when nothing else will do. One big advantage of PVA adhesives is that they can be softened and "unstuck" with isopropyl alcohol. 

[Bob Cleek]

3 hours ago, Dr PR said:

The third hull (18" long, built in 1985) has no cracks after 35 years. The inside was painted with the epoxy paint as described in my earlier post (several coats until the wood absorbed no more). See the link to my Mantua Albatros build in the footer of this post. I think the reason it has not cracked is pretty simple. Every piece soaked up the epoxy so the bonds penetrate into the wood. Each plank is bonded tightly to the bulkheads, so the planks cannot move. Each plank is bonded tightly to its neighbors, making it difficult for gaps to appear. I would say 35 years in this environment without cracks is a pretty good test of the process.

 

Application of penetrating epoxy sealer will retard the speed at which moisture is absorbed and will repel water soaking, but epoxy coatings are all moisture-permeable, contrary to common belief. There are many reasons why one hull might crack and another not, so I'd hesitate to certainly ascribe the lack of cracking to the epoxy. I'm not a fan of edge-gluing planking in any way because if there is going to be significant movement, and if the adhesive is any good at all, the wood will break before the glue line does.

 

According to scientific testing, one of the best moisture barriers available for application to wood is thin shellac (one or two pound cut.) It is very nearly moisture impermeable. It also soaks into soft wood species, hardening their surfaces and makes it possible to sand them very smooth without any "fuzzing." I make it a practice to coat all bare wood with thin clear shellac. It makes an excellent base for paint and also makes an excellent sealer for wood which is not painted.

 

It should be added that glue alone should not be relied upon if one expects a model to last well. Every pieced joined to another should be mechanically fastened, If one is interested in ensuring an archival-quality result, planks should be mechanically fastened with glued-in scale trunnels or wire pins. 

 

See: https://thenrg.org/resource/articles/specifications-for-construction

Edited December 26, 2020 by Bob Cleek

[Bob Cleek]

Just as a general observation, if one has problems with "gap filling" in their planking, that's God's way of telling you that you need to work on your planking skills. Now, I know we've all had a painted hull that we've slapped some filler on here or there, but the object of the game is to avoid the need to do that. 

 

Given present-day planking techniques, such as Chuck Passaro's "edge-setting" heat bending method, and a reasonable amount of care, there should be no reason why plank seams shouldn't be tight over their entire length. For that same reason, there should be no reason to "double plank" a hull. (Unless, of course, you're doing an "as built" model of a prototype double-planked hull.) Double planking was a kit manufacturers' gimmick to sell more models and not have to invest in expensive solid-hull carving machinery, IMHO. Today, I would urge any beginning modeler to first plank a kit model that has laser cut planks that are certain to fit before they tackle planking a model that requires its planks to be spiled and got out of whole stock. Tackling something like one of Syren Ship Models' longboat models as a first effort is much wiser than tackling a Seventeenth Century plank on bulkhead ship of the line!

 

 See: 

 

 

Edited December 26, 2020 by Bob Cleek

[glbarlow]

Just so someone says it, a few of you need to add “in your opinion” to some of your bold unbending statements.

So in my opinion: 1.CA is the best choice for planking a hull using Chuck’s method linked above, PVA is just so unnecessary. 2. I have models over 25 years old done with CA that are just fine and look great. 3. I don’t think any well built ship model survives dropping to the floor, it’s best not to do that. 3. Edge gluing is not only totally unnecessary it’s also detrimental to the look of the hull. 4. I doubt the humidity variance in most first world homes creates an issue. 5. I’ll put up my nine models as examples of using CA for hulls any time. 
 

I don’t understand why people don’t just acknowledge design and build preferences as just that, a preference.  There are many ways that are right and many that work just fine. There are very few that are wrong, using CA for hull planking is not one of those. Why denigrate a method different than your preference, why not instead offer your method as one of many options.  In my opinion...

[Bob Cleek]

6 hours ago, glbarlow said:

Just so someone says it, a few of you need to add “in your opinion” to some of your bold unbending statements.

So in my opinion: 1.CA is the best choice for planking a hull using Chuck’s method linked above, PVA is just so unnecessary. 2. I have models over 25 years old done with CA that are just fine and look great. 3. I don’t think any well built ship model survives dropping to the floor, it’s best not to do that. 3. Edge gluing is not only totally unnecessary it’s also detrimental to the look of the hull. 4. I doubt the humidity variance in most first world homes creates an issue. 5. I’ll put up my nine models as examples of using CA for hulls any time. 
 

I don’t understand why people don’t just acknowledge design and build preferences as just that, a preference.  There are many ways that are right and many that work just fine. There are very few that are wrong, using CA for hull planking is not one of those. Why denigrate a method different than your preference, why not instead offer your method as one of many options.  In my opinion...

 

Well, I think the main reason people don't add "in my opinion" disclaimers to their answers to direct questions is because they realize nobody's much interested in anybody else's opinion. Facts, yes. Opinions, no. Everybody already has opinions. They don't need any more. If somebody disagrees with someone else's statement of fact, they are free to offer evidence to the contrary, and should. That's the problem with the internet. Any fool can pontificate about anything they know nothing about and most do. (Can you say, "herd immunity?")

 

For example:

 

1. "CA is the best choice for planking a hull using Chuck’s method." That's an opinion. It needs facts to back it up. The majority of people who've used CA are adverse to its use for many sound reasons beginning with the difficulty of working with it, the fact that it soaks into wood and affects subsequent finishing results, it is not a recognized archival material, has a relatively short "working time" before it sets up, is much more difficult to un-bond than PVA, has a relatively short shelf life and a relatively high price, and so on. Your mileage may vary. At the end of the day, "best practices" dictate that all parts of a model to the extent possible should be mechanically fastened, not just glued, anyway. 

 

2.  "I have models over 25 years old done with CA that are just fine and look great." The fact that you have models done with CA that are over 25 years old is a fact. That they are just fine and look great is an opinion, or, at best, an unproven fact. It's too early to call. Let us know how they are holding up in another 75 years. The "industry standard" is a model that properly cared for should last 100 years without exhibiting any deterioration. At present, CA hasn't been around long enough to know if it lasts that well.

 

3.  "I don’t think any well built ship model survives dropping to the floor, it’s best not to do that." Now, that's a fact. Don't ask me how I know this.

 

3. (Again) "Edge gluing is not only totally unnecessary it’s also detrimental to the look of the hull." That's a fact, not an opinion. 

 

4.   "I doubt the humidity variance in most first world homes creates an issue."  Whether it does or doesn't depends upon many variables in every instance, but "first world homes" isn't one of them.   It's a fact that humidity is a factor to be considered in any fine woodworking. Frolich addresses a substantial problem he encountered with wood shrinkage in his fine book, The Art of Ship Modeling. One ignores it at their peril. It's sort of like Covid in that respect. 

 

5.  I’ll put up my nine models as examples of using CA for hulls any time." Not to worry. I don't think anybody doubts you built them with CA adhesive and they are still sticking together. See No. 2. above.

 

Many don't offer what they have to say as "just their opinion" because they have little interest in expressing their opinions. They are only interested in sharing what they know to be true. If somebody prefers to offer opinions, they should go to FaceBook.   Preferences are largely irrelevant. There's a right way and a wrong way to do most things, and then there are "preferences," which, more often than not are just excuses for doing it the wrong way.  My wife insists that loading a toilet paper roll so the paper end hangs down the back of the roll, between the roll and the wall, instead of off the front of the roll like you've probably seen in every hotel you've ever been in, is her "preference." She was not convinced when I showed her the original patent for the toilet paper roll which clearly shows the roll coming off the front and not the back. That's obviously the way it's supposed to work. So, she has her own "preference," and i have my own bathroom.