To strip or not to strip?

[Graham Knight]

I'm gradually gearing up to commence work on a Selway Fisher Edwardian 21 (http://www.selway-fisher.com/Steam2030.htm) later this year, intending to strip plank the hull in Douglas-fir as suggested by the designer.
But I've just been reading the article by Paul Gartside in WB #189, where he suggests that strip planking is not neccessarily a good way to build larger hulls, although he doesn't actually specify what he considers to be a "larger" hull, I assume from the context of the article that he means anything bigger than a dinghy hull?
If I strip plank it I would glass it inside and out which PG says is fine for a small dry sailed boat, but my boat will be kept at a mooring for 7-8 months of the year and will spend its winters on a trailer in my driveway, and this is where he suggests that problems may arise.
His recommendation for boats of this type is to strip plank the hull then add two or more cold moulded layers to create a stable laminate. This would suit me fine as I want a carvel look, which I was planning to achieve by adding a layer of 2-3mm planking over the strip planking.
Using PG's method I could strip plank with say 6mm strip, then add a 3-4mm diagonal layer, and then a final 3-4mm layer laid fore and aft to give the carvel look I'm after. Still finishing the whole thing with glass/epoxy inside and out.
I'll have a word with the designer Paul Fisher and see what he has to say about this, but I'd like to get a few second opinions, preferably from guys who've used either method, and maybe some who've actually had problems with either method?

[Farmer Diddley]

Hi Graham,

I'm facing a similar situation. I plan on building a MacNaughton Shilling (http://www.macnaughtongroup.com/shilling.htm) , a 22' LOA sailboat. The designer specifies sheathed strip construction (i.e. strip planked, sheathed inside and out with fiberglass cloth and epoxy). But I too have read Paul's concerns about this construction method. Tom MacNaughton (the designer of Shilling) swears by the sheathed strip construction technique. So, as often is the case, there is conflicting advice... what to do? what do do?

Also, similar to you, I'm considering cold-molding 2 layers of veneers on the outside of the strips. Although I have to admit, at this point I will probably shy away from doing this for several reasons (added weight, additional cost, increased construction time, deviating from the designer's recommendations, etc).

Anyway, I'm still researching, contemplating and deciding. A few resources I'm using to help with the decision are:

- Gougeon Brothers book (5th edition), has some updated information on sheathed strip construction, as well as wealth of information on other wood-epoxy construction techniques. I highly recommend this book.

- Dan and Tom MacNaughton's "The Sheathed Strip Alternative" ( www.macnaughtongroup.com (http://www.macnaughtongroup.com/) ). Definitely biased in favor of the method, but very informative.

- I'm also taking the Cold-Molded Construction (http://www.thewoodenboatschool.com/06Courses/BoatbuildWoodwork06/IntroColdMold06.html) course at the WoodenBoat School this summer.

- Finally, I'm going to build MacNaughton's 7' 6" tender/lifeboat Miranda (http://www.macnaughtongroup.com/miranda_sailing_life_dinghy.htm) , before I start Shilling. This small boat also uses the sheathed strip method. Granted, it is a MUCH smaller boat, and will not prove to me whether or not this is the correct technique for a larger hull, but at least I'll become familiar with the construction technique on a much smaller craft before tackling my big project.

I'm not sure if you'll find this information useful, but at least you know that you're not the only one out there with similar questions/concerns.

Keep ust posted on your progress.

Steve

[ 02-25-2006, 08:06 PM: Message edited by: Farmer Diddley ]

[Graham Knight]

Thanx for that Steve. I've built a few boats now but not a strip planked one (unless you count models!), the logic of Paul Gartside's argument is apparent even to me though and it does seem that a cold-moulded, or semi-cold moulded hull should be better than a stripper. You're effectively constructing a plywood skin, and as we know plywood is more stable than solid timber.
I'm glad I'm not the only one who wants to know the answer to this, hopefully we'll get some replies from someone with actual experience.

[Farmer Diddley]

I agree that Paul makes a very convincing argument. I read it on his website about 6 months ago. And I've waffled back and forth several times. But the MacNaughtons also make some good points too. I've got to complete a few other projects around the shop, but hope to start building Miranda in June of this year.

[George Roberts]

I don't know how good of material engineer either designer is but ...

It takes an unreasonable effort to validate either person's position.

It is easier to determine how much glass/epoxy is necessary to prevent water intrusion and then determine how much core material is necessary to give the hull the properties one wishes.

[sv Lorelei]

First of all "larger boats" are usually at some breakpoint where a design methodology reaches it's point of diminsishing returns over another method of construction. Cold molded strip planking has been very successful up through the the 50 foot range, and if you wanted to take it beyond that could probably be successful (my raw guess)on a larger scale incorperating frames of some sort, so I wouldn't be too daunted by using it to build a 21 footer.

Regarding sheathing. Here's my plan and opinion.

1. Wood needs to breath
2. All plastics are semi permeable

Because of 1, sheathing inside and out is probably not going to give you the longevity of the hull the way you think it would. Production companies have been using cored construction for decades and it's always been a potential problem, even when it was initially "done right". So you have to look at why you'd want to sheath in the first place. A cold molded hull, properly constructed is plenty strong, but wood doesn't do all that well on abrasion and it's much easier to fix a ding in a plastic hull than it is to repair a compromised wooden hull. But ultimately you have two (or more if you count gelcoat) materials that have vastly different hardness, thermal expansion, and strength matrices.

More problems: Amature builders see the process of skinning a hull as a dodge around having to be meticulous and craftsmanlike in the wood part of the construction and the skin's going to fix that up. Thanks for playing the game, we have some lovely parting gifts for you! Skinning or sheathing if properly done, actually demands as high or higher standard of detail orientation.

Our plans are this on a 36 footer. 3 ply Horiz, and two diagonal plys of plywood strip with an exterior sheathing of 8 oz biaxial (doubled on the keel for abrasion resistance) in epoxy. Strips with be treated with thinned epoxy prior to installation but after fitting to ensure a moderate amount of sealing, but still allowing the interior to breathe. Utmost care to be taken to fillet and seal the cabin to deck and bulwark to deck interfaces (because it only make sense). Remember the whole concept of a Hull to deck joint came into being after the methodology of fiberglass construction made it a necessity. NOTHING topsides should leak. Bilges should be dry. Added insurance in my design is carrying the ballast inside.

I think with any construction technique once you've gotten past the Will it work, and How well will it work questions, you need to evaluate the For how long question. All boats are in a constant state of decay from the time they hit the water or the water hits them. We can only slow that down so much.

[Todd Bradshaw]

I'd like to see the data that shows that wood needs to breathe in this type of construction. That statement is contrary to just about everything ever written or taught by the people who actually developed and pioneered the methods and materials you are using to build your boats. When cored constructions fail, it's generally due to bad workmanship, bad materials or bad engineering, not lack of breathability. Should the folks who developed techniques like cold molding and sheathed strip construction and the products used for them - and who have decades of success using those very methods and materials, ever change their tune and start telling us to let our boats breathe, I might listen, but at this point, I'm not buying that theory.

[JimConlin]

Two comments-
In selecting a construction method for a boat whose designer is living, i'd be strongly influenced by their preference.

Glass in epoxy can be more than an encapsulant. It can have structural value, no different from another lamination of veneer.

[Graham Knight]

In selecting a construction method for a boat whose designer is living, i'd be strongly influenced by their preference.
Absolutely Jim, and I put the question to the designer via the SFD forum and got this reply...

Dear All,
Just one or two notes re what will probably generate a lot of comments.
Whether to single strip or strip plus veneer depends on use and how the hull is
laid up with glass etc.
I have had steam launches built with a single strip which was then covered
with 2 layers of glass or glass plus kevlar and these hulls look excellent
today despite long periods in the water etc.
It also depends on the under lying strip - some woods will move despite
being epoxy coated and this may degrade the look of the hull over time.
There is no doubt that veneering over a strip armature gives an extemely
tough hull but will take longer to build, require further skills in
shaping/cutting the veneers and, if damaged, will be more problematical to repair - of
course, the risk of bad damage may be lessened by having a cold moulded hull
with all it's cross grain strength.
Cold moulding by itself can also produce lighter hull weights - in McGruers
in the 70's we were using a total of just 9mm for the hull thickness (three
layers of 3mm (1/8")) on 3/4 ton rated IOR racing yachts - 35' long and
weighing 4.5 tons although the hulls did have longitudinal stiffeners.
Just one more thing to watch out for if going for a strip armature plus
veneers - going for a thinner strip will mean going for closer spaced moulds
otherwise you end up with the "hungry dog" look as the thinner strip tries to
take the shortest route between 2 moulds. Surprisingly this appearance goes
right through to the veneers even if you try to use copious amounts of filler to
get rid of the dips - a beautiful double ender exhibited at Earls Court
several years ago was badly marred by topsides which looked like the hull plating
of a warship - all indents.
Just one or two thoughts.
Regards,
Paul
SFDesign
So it seems he thinks it's OK with a few provisions.

[sv Lorelei]

Originally posted by Todd Bradshaw:
I'd like to see the data that shows that wood needs to breathe in this type of construction. That statement is contrary to just about everything ever written or taught by the people who actually developed and pioneered the methods and materials you are using to build your boats. When cored constructions fail, it's generally due to bad workmanship, bad materials or bad engineering, not lack of breathability. Should the folks who developed techniques like cold molding and sheathed strip construction and the products used for them - and who have decades of success using those very methods and materials, ever change their tune and start telling us to let our boats breathe, I might listen, but at this point, I'm not buying that theory.Balsa core quite often fails because it rots after the integrity of the hull lamination has been compromised somehow. It rots because it takes on water faster than it can lose it. This can be due to an improperly installed through hull, it can be due to a bad repair or a material failure. It can be regional or widespread. It doesn't necessarily imply bad engineering or bad initial construction. Over the long haul, virtually every hull will find itself subject to potential compromise. Sail for a few decades and you'll arrive at the same conclusion.

The theory behind encapsulation is excellent assuming you want to build a boat that is never going to see extremes in temperature or stresses approaching the limits of what a sea/wind/coast/partially submerged container can put on a hull. When well executed, as a strategy it's still pretty sound, When designed as a structural element it often achieves a sort of Belt and Suspenders degree of redundancy. All my suggestion was is to allow each material to interface with an environment that best suits it's characteristics and plays to the materials strengths. i.e. wood wicks liquids and given half a chance will allow them to evaporate and thus maintain better dimensional stability than if shedding moisture were not allowed. Good choice for where the hull interfaces with air. Resins, though not entirely impermeable, can be considered virtually so, and when reinforced with fiberglass, kevlar, carbon fiber or others, will provide a superior moisture barrier where the hull interfaces with water. Otherwise you end up with a fiberglass hull with a wooden core and we're back at the top of the discussion again, because while some woods rot slower than others, they all eventually rot.

[curmudgeon]

Suggest a study of strip planking techniques used by Covey Island Boatworks who have built many vessels over 50 feet.
www.coveyisland.com (http://www.coveyisland.com) then click on What is Wood/Epoxy then click Wood Epoxy Boats Covey Island Style for the text of an article in Woodenboat Magazine issue 120 by Eric Sorenson.

According to this article, Covey use 1 ¼ square strips cut from local spruce, galvanized box nails and stainless steel screws to hold the strips to frames, glass cloth, epoxy encapsulation.
Covey’s proven method tends to dispute Mr. Gartside’s opinions and of course their use of galvanized and stainless fastenings is a bit unorthodox.

I like others am perplexed. regarding the diametrically opposed opinions.

I strip plank with ¾’ thick western red cedar plank for boats in the 18’-20’ range, square cut, thickened epoxy in the seams, epoxy encapsulation all as documented by Gougeon Bros. I also use barbed ring nails, 2 ¼ plank width in length in predrilled holes at about 6” centers to provide tensile strength to the weak cedar in much the same way that steel re enforcing provides tensile strength to concrete.

.

[Graham Knight]

In a further email from Paul Fisher he makes a couple of recommendations. Firstly that the initial strip planking shouldn't be too thin, he suggests 10mm, otherwise intermediate moulds need to be added to avoid a "starved horse" effect as the thin strips try to take the shortest route from mould to mould. He then recommends a couple of layers of 3mm or so veneer, at least one laid diagonally.
Apart from the thicker strip planking this is exactly what I was thinking of.
The sheathing business seems to have opened a whole new can of worms though, to glass inside and out, or just the outside leaving the inside to breath?

[George Roberts]

The "starved horse" effect is often caused by applying tension on the strips. This causes the strips to be flatter between forms.

The cure is to apply less tension or compression.

[Todd Bradshaw]

I'm sorry, but claiming that sealing one side of a hull with epoxy, fiberglass, glued-on veneer, etc. and leaving the other side open so that it can breathe strikes me as absolute horsesh!t. Do you truly think water that get's into a cored construction (even a one-sided one) is going to just find it's way out and not cause serious damage, because if you do you're dreaming!

As for your balsa example, balsa rots because despite some characteristics that make it desirable as a core material (lightness, stiffness, resistance to compression) it also has some which make it quite undesirable. If you have a leakage problem, it soaks up water like a sponge, mostly because the stuff used for coring is thin slabs of end-grain and will take any opportunity to soak all the way through. If you use balsa coring you have to be sure you completely seal, protect and maintain it or it will rot. It's that simple. Leaving one side "breathable" isn't going to change that, it will rot, delaminate or both. Production boatbuilders have generally made things even worse by trying to seal or cover it with fiberglass and polyester resin, which is a pretty lousy sealer and often a very poor bond to wood.

Gougeon Brothers has been building boats sealed inside and out with epoxy just about as long as anybody has, let alone developing materials and techniques now used world-wide. Most of those boats are still out there 30 years later and doing just fine. None of them were built to breathe, in fact they were specifically built to be as airtight as the materials would allow. When they begin to suggest breathable epoxy constructions, I'll think about it, but for now, I'm still not buying your theory. Perhaps you're the one who needs to go out and sail a few decades to find out what works and what doesn't, because it looks like the sealed construction method already has a three-decade head start on your experimental breathable boat.

[RonW]

Graham, it would appear that the question is not to strip or not, but which one of the many modern methods to use.The original strip planked hulls had plain old carvel framing, and then the carvel planking was merely subsituted with strips that where nailed together by galvanized trim nails.
Thus eliminating the need to stuff a rag in the joints to stop leakage.
Some of the modern methods are almost eliminating the frames, which create the situation of additional reinforcement.I have seen and got, boat plans in the low 20 ft. range with modern strip planking where there is no frames, just a transom and stem with a couple of spaced out bulkheads and then stripped and reinforced, either through veneers or cloth or a combination of both.I will submitt that the life span of these hulls is still not determined. Maybe they will last a 100 years, but we have a good 70 years to go.
Every disscussion on strip planking will be divided as to those who favor a certain method, and obviously those that feel that epoxy and cloth will seal out water and protect your hull.
The problem with wood is that it rots, but fiberglass and epoxy deteariates as well. Eventually your boat will return to dust as from which it came, with or without the epoxy and cloth.
You may be limited to your choices already by the designer, I am sure that Selway is quite competent. But even he, in his e-mail to you states that one of the old methods they did on tugs, still look good years later. So he is keeping his eye on these various methods to see how they are holding up as time goes by.
I will add the suggestion to muddy up the waters, as to what is wrong with traditional strip planking with out the addition of epoxy and cloth or veneers. I say it will be easier, more pleasant, and a whole lot cheaper as well as being worth more now and 30 days after you are 6 ft. under and your widow puts it up for sale.
Traditionally well built wooden boats hold their value and do nothing but increase in value.Compare the price of a traditionally built wood and canvas canoe to a modern stripper with epoxy and cloth in and out, no comparison.
Of course your plans would have to have the frame spacing, but I am sure Selway could solve this problem.

Here is a launch to look at. A original 1899 elco for sale $77,000. not a bad price for a 116 year old boat, that doesn't even have any epoxy.
http://www.electriclaunch.com/used_boats.htm

[RonW]

Here is a very interesting and informative article on boat building methods, by none other then John Atkin.

http://www.boat-links.com/Atkinco/Articles/Methods.html

In the 9th paragragh he disscusses strip planking, and in the 14th paragraph states his opinion as to the addition of fiberglass cloth to a hull.
He also disscusses m.d.o. the highway sign material, that some do not believe to be quality enough for a boat hull.It appears to be a better choice then douglas or occummee marine ply.

[RodB]

This is all very interesting, you would think there would be some concrete answers after all the time epoxy has been around.

Tom Macnaughton has said emphatically that "sheath stripping:" a hull and then adding layers of veneer is a waste of time...and is building the hull two or three times over. According to Tom, they based their scantling rules on very detailed engineering studies... If you read his Scantling Rules on "Sheathed Strip Construction), this method results in pretty much the lightest hull with the most strength of any other method. Also it must be pointed out that sheathing both the exterior and interior is mandatory because the fiberglass plays a vital structural part in the hull strength.

I read the arguments between Macnaughton and Gartside a while ago, and you must admit its quite perplexing for newcomers to boat building to get a fix on just what to do and thus...in reality, many builders err on the conservative side and cold mold three layers of veneer in addition to strlp-planks...and this makes for a really strong hull if one doesn't mind the weight.

This is an interesting controversy...and Tom Macnaughton is adamant that his scantling rules are correct. He also says in any case of failure with strip-planking if you look close enough you will find one or more reasons for the failure such as poor materials, poor workmanship, etc. you just have to look at what happened objectively and scientifically.

If my take on the articles I read is right, Mr Gartside doesn't like encapsulation because you can't tell whats going on underneath...but whatever is going to happen, I would think an epoxy barrier can only retard the amount of moisture and oxygen getting into the core of the hull. It kinda seems like you either accept the value of epoxy and encapsulation...or not...and proceed accordingly.

Are there catastrophic failures with epoxy built boats that we don't hear about? Are such failures attributed to reasons other than improper technique or poor quality materials? Has anyone read the appendix of Pardey's book "Classic Boat Construction: the Hull"???

Just wondering...

RB

[ 02-26-2006, 04:17 AM: Message edited by: RodB ]

[Graham Knight]

I will add the suggestion to muddy up the waters, as to what is wrong with traditional strip planking with out the addition of epoxy and cloth or veneers. All structural questions aside, seeing as there is apparently no definitive answer on which everyone can agree, IMO strip planked hulls look awful!
OK maybe canoes and other small boats look OK (and some really do look very nice), but on a launch like the one I'm planning to build the effect of all those narrow strips just looks horrible. For that reason alone, whatever building method I go with the final layer will be veneer planks laid fore and aft to replicate carvel construction.

[JimConlin]

In the last couple of years, there was a WB article about the Brooklin Boat Yard, Bob Stephens and his designs. In it, there was a table of the scantlings of the wood composite boats they've done in recent years. All started with strip planking and some did not have cross-banding veneers. IIRC, Lena (46') had only 'thwartships unidirectional carbon in addition to the strip planking. Somehow, I don't think that objections to the appearance of strip planked boats were borne out in her. The topsides were perfectly fair.

Can anyone dig out and post that table of scantlings? It would add light to the heat of this conversation.

[sv Lorelei]

Originally posted by Todd Bradshaw:
I'm sorry, but claiming that sealing one side of a hull with epoxy, fiberglass, glued-on veneer, etc. and leaving the other side open so that it can breathe strikes me as absolute horsesh!t. Well Tom, that's certainly your right to think. If you read back over what I'm saying (because you're obviously reading stuff that isn't there into it). I'm just advocating leaving the inner fiberglass skin off. Re-read my original post.

Do I think leaving a path for potential evaporation will keep my boat's wood from rotting? No. THERE IS NOTHING YOU CAN DO TO WOOD THAT WILL KEEP IT FROM EVENTUALLY ROTTING. Time wins. Every time. I DO think coating the wood in epoxy (but not laminating it inside with glass) will make a longer lasting laminate than a core construction, and I have my reasons to think so after 40 something years of building, sailing and repairing wooden, glass and composite boats. And let me tell you, you'd be hard pressed *not* to find something starting to fail in any boat of any construction after thirty years. It's a question of magnitude, not a question of whether or not.

People need to understand something about the way *most* production builders approach boat building. First off they build boats in a manner that will allow them to make money. Second they build boats that will outlive their warrantys. After that it doesn't matter a whole heck of a lot to them. The brokers can laugh and say something about how they had build problems *back then* or how that was an older design that had been improved on or phased out since then.

There are a minority of builders really trying to make boats that will outlive their buyers.

Secondly, you're preaching to the choir! My next major undertaking is going to be an epoxy cold molded 36 footer (after I finish up the skiff that I'm currently working on). Having done strip epoxy boats, conventional strip planking, plywood with epoxy and glass skins, I can say with some confidence that the construction method (regardless of which one you choose) is not going to be a substitute for good craftsmanship. The best result is one where the materials are put in the environment that takes advantage of that (and adjacent) materials characteristic for performance and survival.

I agree with everything you said about balsa core, but note that I presented it as a core material not as a structural material as you seem to want to imply. Cold molding and coring are two different things, and IMO if you're skinning a cold molded hull inside and out with glass, you're building a glass hull with a wooden core, without using a contiguous mold process to get an impermeable inner shell. How are you going to get 100 percent impermeability inside? You probably aren't. There's a big difference between sealing a piece of wood and encapsulating it. That's all that I'm saying.

[ 02-26-2006, 08:46 AM: Message edited by: sv Lorelei ]

[sv Lorelei]

[ 02-26-2006, 08:46 AM: Message edited by: sv Lorelei ]

[Tom Lathrop]

I thought the wood in my boats was dead when I built them. The thought that it needs to "breathe" in order to "live" longer never occured to me. Have I been guilty of killing my wood a second time by coating and sheathing it with glass and epoxy :confused: Is this what is meant by deadwood?

Now I find that I may be creating a second crime by painting the outside of my wooden boats :( Worse yet, they may not even be "wooden" boats any longer since I covered the wood with something else.

One thing remains true. Entropy rules :D

[ 02-26-2006, 09:58 AM: Message edited by: Tom Lathrop ]

[Graham Knight]

Just like to add yet another permutation to the strip planking debate, take a look at THIS (http://www.gartsideboats.com/22steam.php) 22' steam launch built by Paul Gartside, it's double planked with both layers running fore and aft with the seams staggered.
I don't like the look of the end result, the run of the planking looks all wrong, and if it were mine I'd paint it or veneer it to resemble carvel planking.
But it's an almost identical boat to the Edwardian, so I wonder if this might be yet another way to build my hull?

[JimConlin]

If a boat is to be finished bright, and great care is not taken in matching the grain and color of the planking stock and in lining off in a graceful way, the result can look just awful.
If the boat's to be painted and is properly constructed, the construction method will not be discernable.

[Todd Bradshaw]

Actually, it's Todd, with two "d"s at the end, but I'm not surprised that you missed that. Once you have brushed up on your reading comprehension, I'd suggest that you read the Gougeon Brothers book on wood/epoxy boatbuilding. There is a lot of information in there which would likely prevent you from making more mistakes in the future.

[George Roberts]

RodB ---

MacNaughton, Gartside, Geer ... Their scantlings are provably wrong.

1) The scaling exponent (usually chosen as 1/3) is determined by the assumed loading. Depending on the assumed loading the exponent varies from 1/6 to 1/2.

2) The range covered by their scantlings spans several types of failure. Whenever the failure type changes, the scantlings need to change. They don't appear to.

I have not placed my name and scantlings in this group. Why? Because I have scantlings for different assumed loading and the range of my scantlings is limited.

I make no claim my scantlings are correct. (I am sure they are not suitable for some uses.)

[RodB]

From the comments above, it seems folks either believe in the concept of encapsulation, or NOT! Those who do not will never be able to have a sensible conversation with those who do because both parties are comming from a totally different set of accepted ideas.

I have certainly found lots of feedback implying that a hull with only one surface sheathed is an "unbalanced structure" and doomed to fail compared to a completely encapsulated hull like in sheathed strip construction.

I had a detailed conversation with Mr Macnaughton on the "print through" of lines in strip-planking (sheathed strip) and I got the following from it. If you are building sheathed strip and take a long time like most amatuer builders, the epoxy completely cures and settles (stabilizes) and once you sand her for final fairing and painting, you end up with a fair surface....BUT if you build her fairly quickly (like professional builders for instance) and say one side is exposed to the sun over time, the finished surface will show "print through" as the heat allows for the epoxy between the strips to "creep" a minute amount. This "print through" is visible because the human eye can see just a few thousandths... but he assured me the first season you pull her out for bottom work, with sanding the topsides and repainting, the hull will most likely remain fair from then on ..... Obviously extreme heat or exposure to the sun could make a difference.

Mr Roberts,

I realize that intended use is a dominant factor in prescribed scantlings for a boat, I think the Macnaughton rules are based on boat length and suggest heavier choices if intended use will be heavy.....does it not?

I'm going to order the latest edition of the Gougeon book (I have the older version) as I would trust that source over any other as to the value of encapsulation and the merits and advantages/disadvantages of strip planked sheathed strip) construction.

RB

[ 02-26-2006, 02:08 PM: Message edited by: RodB ]

[sv Lorelei]

Originally posted by Todd Bradshaw:
Actually, it's Todd, with two "d"s at the end, but I'm not surprised that you missed that. Once you have brushed up on your reading comprehension, I'd suggest that you read the Gougeon Brothers book on wood/epoxy boatbuilding. There is a lot of information in there which would likely prevent you from making more mistakes in the future.Sorry Todd, I made a mistake. (I'm sure you never have). Tell me how to build my boat. I'm all ears. I want to know how to do it right, and as you obviously know it all, what better place to start! Please don't spare the denigration or obtuse hyperbole either. I want to know how to build a boat that's as thin skinned as you are!

[ 02-26-2006, 03:17 PM: Message edited by: sv Lorelei ]

[Graham Knight]

I thought I'd started an interesting thread here and was hoping to learn something, if you guys just want to have an argument can you please start your own thread and take it there?

[RonW]

I think it should be noted that as with all the disscussions on strip planking, that many variations always get lumped together.
Obviously scantling rules must be varied as to the method, the layup as to thickness and boat size.Mixing layups and scantlings can result in some poor results.Which needs to go back to the individual boat and designer for that particular boat.
But a healthy disscussion as to the various methods can result in opinions as to durability, cost, labor intense and so forth.

I believe it is just plain wrong not to seperate the methods and boats into those that stay in the water, and trailer boats. With trailer boats being seperated again, there is a big difference between a 25 ft. boat that may spend the summer in the water and a 300 lb. dingy that never sees more then 10 hours once a week in the water.
Which leads into the disscussion of water intrusion and deteariation of the core or laminates.

Just a couple of pages back is elcoholic's post on the early 1900's 50 ft. boat that he restored.
Remember that when he took the boat out of the water, for a 2 year restoration and drying out, that it weighed 77,000 lbs, but 2 years later it weighed 45,000 lbs giving up 32,000 lbs or 16 tons of water saturation weight.Who would have ever guessed. If it was a 50 year old boat that sat in the water and was laminated, cored, veneered or whatever including stitch and tape, would it be able to be restored or the core rotten and laminates delaminating to the point there is no saving. Of course this argument is irelavant to a dingy or canoe.

I find it ironic to believe that the gougen brothers is the final word on the subject, and their book is the absolute gospel.Blind faith.
They also have done one hell of a job in promoting their methods and selling their west system epoxy.I thought I read somewhere in their book, that they hope for or expect a 30 to 50 year life span on googed boats.So who wants to pay big bucks for a 25 year old stitch and taped or laminated epoxy hull.This may not be a consideration on a dingy, but should come into play on a large boat.

On the subject of starved dog look or just plain being unfaired. Mcnaughton had a good disscussion on this subject on his previos message board before it got erased by hackers.Basically it had to do with grain orientation. With modern variations always using planks that are wider then they are thick(to supposedly save time and labor) you end up with flat grain on the sides. Instead as he said the original strip plank method used square planking, which enables you to turn the strip so as to have all edge grain to the outside and inside resulting in stiffer and fair planking. The flat grain would then be stacked on top of itself up the side of the boat and also reulted in less movement of the planking due to swelling and shrinking. Also square planking has the ability to bend in a compound curve. I have even noticed this effect on Selways boats, where with wider then thick planks are used, eventually you have to trim them off and restart the planking.Leaving a area that is reliant on the epoxy to hold it in place. And veneers needed to fair things out so as not to have a starved dog look.
This leads back to John Atkin's comment I posted above, yes it is done but why, water intrusion will occure at some time and place and delamination or rot will follow.
All this in effort to use wider then thick planks to strip with. I see it as a whole lot of extra work and exspense just to be able to supposedly save time, and maybe over time a less stable hull, due to water intrusion.
What is wrong with the traditional method of strips being sized and framing being spaced according to the boat. As John Atkin says in his statements concerning strip planking that it has proved itself as strong as any method, and frames can be placed considerable further apart with this method.

Personally I don't find all this epoxy and fiberglass particullarly pleasant to work with, and it drives the cost up very considerably.In the end it may prove to be no where near as durable or as valuable of a boat down the road.

Cold molded hulls are a totally different subject.My opinion is why respace the frames far enough apart and use such thin strips, that to gain fairness and strength you need to lamiante additional layers over the strips.It might be easier to just double plank it.

John Atkin makes the staement that strip planking may well be one of the next popular building methods. I am sure that relates to the availability and cost of quality lumber for other methods. So let the disscussion continue.

[Stiletto]

This 42'boat from a successful designer (Laurie Davidson) is strip planked in WRC and has several Pacific voyages to her credit. Large boats can be strip planked successfully.
here (http://charterguide.co.nz/hts/1542.jpg)
Edited to add: In this case it was correctly viewed as a cored construction.

[ 02-26-2006, 04:34 PM: Message edited by: Stiletto ]

[RonW]

Well it would appear as if this thread has successfully been derailed.

For those that might be interested and have not seen it before, here is a interesting and informative article on the subject.
http://www.sredmond.com/strip_plank.htm

It is a shame that the wooden boat forum has turned into the EPOXY AND WOOD FORUM, with no tolerance for the debate as to the merits of or problems with the various construction techniques.
Now where was that link to the metal boat society?

[chucksw]

Strip planked or cold molded sheathed construction is a superb way to go. Size doesn't matter. 14' kayaks to 80+', proven time and again by many builders. Materials and workmanship and a great designer are the key ingredients all the time. The people cutting the corners and without the skills are the ones that get into trouble with this and end up with poor results.

[Paul G.]

Todd,

While on the subject, what are your thoughts on sealing or even sheathing a planked boat after the fact (60 years after!)

I have heard a lot of conflicting information about this subject, wood needs to breathe, epoxy isnt watertight etc. downright confusing. I am considering the epoxy route, only if it would keep the boat alive for another 60 years.

[Puka]

I make no claim my scantlings are correct. (I am sure they are not suitable for some uses.) George, do you have a publication on Scantlings for sheathed, strip planked boat construction? I would like to purchase a copy that covers ranges of intended purpose in detail.
(Even, limited)

The range covered by their scantlings spans several types of failure. Meaning, historical, documented failures?

I can't see the difference between strip planked with 0/+/- 45 epoxy glass over;
And,strip planked with +/- 45 veneer over and then glassed. As long as the extra core thickness of the veneer, and extra glass is allowed to replace the veneer is taken into consideration.
Except, time/cost to build.

[ 03-01-2006, 12:57 PM: Message edited by: Puka ]

[Todd Bradshaw]

Paul, I think I am among those who were asked to vacate this thread for fear of derailment from the original topic, so I'm out of here, but I'm a strong believer in fixing a boat with more of what was supposed to be there in the first place. What you're thinking of doing tends to be a quick fix which will most likely kill the boat within 10-15 years by trapping moisture in places where it can never get out.

[Puka]

Todd,
I don't see that your comments "derailed" the thread. The topic was "strip or not" and the author wanted to glass both sides, as I recall, so keep contributing. I value your experience.
Ignore the emotive venting and lets hear from posters experienced in this type of build.

Paul,
It seems to me there are definite prerequisites to total encapsulation. (glass both sides, if that is what you intended)
*That the encapsulation be maintained.
* That the substrate be of sufficiently low MC for maximum bond,not contaminated with salts(CCA.NaCl,)silica,or oil (natural or introduced).
*That specific glassing procedures are adhered to.
* That accepted scantling rules are applied and the original engineering,if not stable, is re-engineered to be stable.
*That doesn't preclude the method for salvaging an old vessel if these are met and you like doing it hard. smile.gif
* From what I understand exterior sheathing/breathable interior, favours cold moulded
as opposed strip construction.

These are by no means absolute as there are too many variables.

RonW...if you think this is a hijack, so be it. I just want to participate in the exchange of ideas/experiences on the strip plank method and all products associated with its successful execution. ;) Essentially, the main product is timber.

[ 03-01-2006, 04:14 PM: Message edited by: Puka ]

[Graham Knight]

FWIW I didn't ask anyone to vacate the thread, just to stop the personal slanging match which wasn't contributing anything to the discussion.

Im seriously considering the double fore and aft planking method now, it seems to offer a more stable construction than single thickness strip planking, but retaining the simplicity of this method.
With the seeming lack of any definitive information on any of these methods it's very difficult to make a decision, add to that the glass inside/outside debate and I think I'm more confused now than when I started!

[Puka]

more stable construction than single thickness strip planking, Pukka (Strip planked- painted ,no glass) has spent 35 yrs
continuous emersion (apart collision repairs)had almost no "mapping" and was stable except for localized glue lines let go from over zealous back stay tension.
IMHO,
Eight months in /4months drying out is the key. I would have thought--coldmolded, glassed bs.
Start a vote! ;)

[ 03-04-2006, 11:43 PM: Message edited by: Puka ]

[Stiletto]

Puka, putting her back as she was seems like a good idea, given that it was a successful method of construction. What has been done with others in the fleet?

[Puka]

Stilleto
Sorry wrong end of the stick.
"putting her back as she was seems like a good idea, given that it was a successful method of construction."
Pretty reasonable advice! Too late for me. Already replanked to above waterline with new
kauri ready for glass.
Good advice for Paul tho'.
Haven't been able to track the other strippers.
The 3-skin (dynelled) are still as good as new,
and the glass/balsa seem to be holding up well too.Twenty four racing at the moment! From 1965 to '83.
Pukka (http://www.imagestation.com/album/index.html?id=2120245606)

[ 03-02-2006, 01:31 AM: Message edited by: Puka ]

[Stiletto]

Sorry, put it down to encroaching old age. :rolleyes:

[George Roberts]

Puko asked:

"Meaning, historical, documented failures?"

Yes.

To make it easy on me I will phrase this in terms of beams, but there are too many engineering issues to cover here.

Short beams loaded in bending fail by shear, longer beams fail by deflection, and even longer beams fail by tension.

If one is used to engineering (with or without scantlings) short beams it is very easy to move up in length and end up with deflection failures. A bit of change in engineering/scantlings and the failures go away until lengths increase and tension failures occur. And the process of failure and change continues as projects grow.

The process is well documented for bridges, airplanes, and buildings. Looking for documentation in boats is just not my interest.

(Scaling down with scantlings is almost always safe. The results tend to be too heavy to be economically prudent.)

[Brian Palmer]

The Pulsifer Hampton is strip built with no glass or epoxy inside or out and they seem to last fine. They have been around for a long time and I expect many of them spend all season in the water.

I have a strip built boat (a Steve Redmond Elver) that was sealed with epoxy inside and out, but no glass and it is about 20 years old. It is dry sailed. You can see a few seams, but not many. I put a low-gloss finish on the topsides.

-- Brian

[Puka]

Thanks for the physics of boat material scalability, George.
I should start a new thread as it is somewhat of a diversion from the original topic.

Sorry, put it down to encroaching old age Now which day was it that I thought that?
Everyday! :D

[ 03-02-2006, 05:36 PM: Message edited by: Puka ]

[HarryH]

Brian, I am of your thinking. I owned a REAL BOAT once, a 17' Nova Scotia built lobster skiff of sweet lines. Put together with strip pine and oak, it knew neither fiberglass, nor glue, was a decade or so in service when I bought her, and was sold again many moons later, without a speck of rot within/without her.

I sometimes feel we can get ourselves constipated with rocket science (now THAT's mixing metaphors) as to ensure inaction. No matter the route taken, one can be sure to be criticized by some expert, real or imagined.

_H

[RonW]

Harry and Brian, excellent posts which gets back to the original strip planking method.And is the modern and latest technology in rocket scientist actually improving upon the original method? Or just creating additional cost and labor that eventually might fail due to either delamination or moisture intrapment.

Personally I believe that all of the various modern forms of and basterdization of the original method,are actually creating totally different construction techniques and are therfore dissreguarding some of the sound principles of the original method, such as grain orientation and strip sizes as well as frame spacing, nailing schedule and so forth.

We all know and respect John Gardner and his books such as the famous dory book. Well in his last book, -classic small craft you can build-(published 1993) a play in words off of his other 2 books, he has a very good article on strip planking. And further highly recommends it, as well as apologizing for not understanding the merits of this building technique earlier on in life, but simply dissreguarding it as a method used by those that either where unable or willing to properly plank a boat in either the lapstrake or carvel method.

Appearantly the man changed his mind, and upon examining some quality built traditionally strip planked boats, says the bilge where dry and clean enough to actually eat off of. And that the boats where in excellent condition even after sitting on the water for 10 and 20 years, and as for being fair, the hulls where as fair as the best of any wooden boats that he has seen.
He also makes quote from other advocates of the method, such as Weston Farmer and Fred W. Bates, well respected marine architects.

Bottom line might be the mixing of the technologies as well as mixing the boat types.
Strip planking a canoe and fiberglassing in and out, may be fine, particularlly since this construction technique has no ribs and or places to trap moisture or dirt that will suck moisture from the air. When you are done canoeing for the day, you simply can roll the canoe over and rinse it out with a garden hose and then hang it up side down in your garage. Excellent. Now figure out how to do this with your 25 ft.wooden boat and it will last a lot longer.

[George Roberts]

"but simply dissreguarding it as a method used by those that either where unable or willing to ..."

I think that phrase can speak of any "new" boat building method including lapstrake and carvel when they were "new."

[ 03-05-2006, 12:19 PM: Message edited by: George Roberts ]

[RonW]

Goerge: You are absolutely 101% CORRECT.

All things are at one time or another in history viewed as NEW.

Traditional strip planking dates to 1890.

And maybe it is just me, but - I fail to see what the meaning of new has anything to do with the high cost of low cut sneakers.

[Osborne Russel]

The WB article by Paul Gartside says there are two problems, wood movement and rot. Sheathing helps with movement, the article says. Says nothing about rot. What does sheathing do for rot?

[Puka]

:D The million dollar question!
IMO, poorly executed sheathing promotes rot,well maintained and applied from new, sheathing, eliminates it from the equation.

However successful the first methods of strip planking (with edge nailing) and paint in the seams were,I still have a logic problems with the
ensuing method of glued-edge nailed strippers, hydraulicing the planks relate to each other from uneven moisture absorbtion.(Continual immersion)
Well maintained sheathing ,IMO, controls this.
"Well executed & maintained" is the operative word.
Is it achievable for the average vessel?

For performance dry sailing, is it not the ultimate solution. Lightest, cheapest hull.
PG on strip planking (http://www.gartsideboats.com/faq2.php#strip)

[ 03-06-2006, 03:05 AM: Message edited by: Puka ]