Biscuit Joint Dory bottom?

[neilm]

I was re-reading John Gardner's Dory Book and noticed he said Dory bottoms were sometimes made with a single wide board when big Pine trees were plentiful. I was wondering if a person could biscuit join boards for the bottom if they used vertical grain wood? I would love to build a traditional boat someday but it seems to me that floor as he describes would be a leaker unless the boat stayed in the water all the time. Yes, I know about glued lapstrake but I think building a traditional Swampscott type dory would be a hoot.

Neil

[Jon Etheredge]

Biscuits are a bad idea.

Solid wood planks with caulking or plywood are probably the best ways to go. If you use plywood for the bottom you could still use traditional materials and methods for everything else.

[dmede]

Some of the boats in Gardners "the Dory Book" are planked with several longitudinal planks for the bottom that are simply edge glued together. The rest of the boat is built in a normal manner, no glue or ply.

I have a small solid wood lapstreak canoe at home with copper clench nailed planks and a glued up bottom made from 3 planks of POC. Works just fine.

[Thorne]

If you want to build a trad boat using trad materials and processes - do it. Don't change stuff or it won't be a trad boat.

That said, as mentioned above, ply can be used if you want to mimic the "huge wide planks" of yesteryear, which is why Gardner mentions it.

In a pinch the edge-glued planks can have thin cotton caulking applied in any gaps.

[Bruce Hooke]

When it comes to boards joined edge to edge, biscuits do nothing to strengthen the joint. All they do is help keep the joint aligned when you are clamping it together. Assuming you do a good job of making the glue joint, it will be as strong as the wood itself, which is all you really need. If you don't do a good job, I don't think biscuits will do much to hold together a failing joint.

To really work properly, biscuits also depend on the glue getting the biscuits wet and causing them to swell. This only works with water-based glues, which rules out the usual waterproof glues used in boats.

If you feel the need to have some sort of alignment aid to help you keep the edges of the boards lined up as you glue them together, I'd go with splines over biscuits.

It does seem to me that edge-glued planks would be a pretty good substitute for a single wide plank, but I don't feel like I know enough about traditional dories to comment on whether this is a good idea or not.

[erster]

Many of the older solid planked skiffs with wide planks did use bronze pins or dowels.

[dmede]

My point above was that in reality some of these older designs like those of Atkin and Gardner often include construction notes on building a glued up bottom with otherwise traditional construction methods. I don't think this in any way negates it's "traditional-ness". I think a lot of builders assume the line between a traditionally built boat and one that is a compromise is the inclusion of glue in it’s construction. When in reality it’s a bit of a continuum. As certain glues began to prove themselves reliable for marine construction they were adopted by many of the old guard designers we think of as “traditional” boat builders. A Gardner dory built with a glued up solid wood bottom is a traditionally built boat in my opinion.

[Thorne]

Dave, I agree in theory -- it is all a continum.

But when you start adding processes and materials that were not used in trad boat construction, like biscuits, you can quickly end up with problems or materials failure.

I've owned two dories with multiple plank bottoms, both leaked a bit but took up well. I found that a little cotton caulking worked in most cases.

If it leaks too much you can consider using a more modern **sealant** (NOT adhesive/glue) like Seamseal or Vulken116.

[dmede]

No, not talking about biscuts just edge gluing solid wood to sub for wide planks. I do think there is a point at which you will cross over to something that can only be considered modern or hybrid construction. I just don't think that edge glued planks are enough to warrant a non-trational label for any particular design.

Seems like a minor detail but I keep reading new builders who say they want to build traditionally, ie without glues or goops, but are having a hard time finding planking materials in widths speced by the plans. They often assume that any glueing or any use of modern adhesives or sealants makes it a non-trad boat and I guess therefore less valuable or fun to build. Which is a shame becasue I think being able to build trad with layed up planks or bed with 3m goopta is just fine in an otherwise old school boat. And I know anybody with CPES on their old dory bottom would agree ;):D

[neilm]

This is an interesting debate. My primary motivation for wanting to build a traditional boat someday is being able to work with solid wood and copper nails. It's the fun factor. I never pondered what makes a boat traditional or not but perhaps I should. Is a 100% traditional boat worth more?

I think even John Gardners struggled with this concept. He respected tradition but didn't let it get in the way of building a better boat. He often mentions modern substitutes.

Neil

[Thorne]

Wot, someone with CPES on their bottom should agree with what?

;0 )

I have a solid fir over oak dory, fastened with copper nails, and I love it.

http://www.luckhardt.com/THORNE011web2.jpg

If you want to build to a known/popular plan with trad materials, go for it -- it will be worth more than a home-designed or heavily-modified trad boat plan, particularly one built with mixed Trad/New materials and/or fasteners.

I modified my boat for sail, and tried to stick with the 1880's era plans from Mystic Seaport, and was largely successful. Used all bronze fasteners and traditional-style hardware and rope, and it certainly adds to whatever value the boat has.

[Oscarvan]

Value....hmmm. I see this as restoring old cars....take a 10X car, spend another 15X on it, and it will be worth 17X...in other words, don't do it for the money.

As far as being a purist (or a rivet counter as the Land Rover restorers say)....it is a laudible goal, but as someone pointed out, ya don't find 3 foot wide boards much these days, so re-creating such a board using modern methods would be ok.....

As long as everything you see in the end looks "proper" as the Rolls folks say.....

In the end it's a matter of personal preference, or points if you get into 100 point cars.....but that's a whole other story.....

[Todd Bradshaw]

Both the bottom and sides of my 22' 1960 Lippincott Starboat were made from cedar planks glued together with a tongue and groove sort of joint - and I really doubt that 1960 was the first year they ever did that. I don't know how old a method needs to be to be labeled "traditional" but making wide boards (either flat like the sides or cup-shaped like the bottom. as a Star has both) by glueing together a bunch of narrow boards has been around for a long time.

[Oscarvan]

And after thinking about it for a while, a biscuit in epoxy should imho make gluing up a large plank easier, and in the end you wouldn't know it's there.....

[Ken Hutchins]

I would use a finger joint, stronger, cheaper, traditonal, they used it back in the horse and buggy days.:)

[pipefitter]

One wouldn't not be building a traditional boat by gluing boards together,they would be building the wood. In many parts,it becomes plywood anyway when you start stacking parts together whether glued,bolted or not. These days,most people you will encounter,will be impressed enough with the fact that you built the thing at all. You would have to be part of a wooden boat club or forum such as this to even find a few that really care or would bother to get in debate over it as if it made a difference. I would totally rely on the situation and intended environment for what manner of construction I used and have a better boat all the way around.

If selling is the concern,a more modernly constructed boat will be maintainable by a much larger group of people with a broad range of abilities in which to do so. With an epoxy /ply boat a simple reference to the importance of keeping it covered will go a long way to keeping maintenance minimal without having to find the right person that is willing to keep it's planks swelled after they find they don't have time to use it as much as they had hoped.

I work on boats every day with quite a few boaty people and they don't have a clue and I should have come across more people in the know by now,even if for conversation sake.In any event,mixing the 2,even if it is only trimmed traditionally, will still give most people a good dose of handwork and it will show that it is indeed handmade.

[3pepper]

i love the trad / modern discussions
if you go purist in either direction you end up with a kevlar/epoxy boat with wood as a veneer or core material or none at all , the other end is a dug out canoe made from a log felled only with flint tools and moved around by horse , ox , or lots of friends , wearing only grass skirts and sandals

i think of trad as solid wood , no glass cloth , maybe no plywood , but mainly it means hand built . its your boat and no one elses . let buget , time , tools , skill level be your guide

i have a 16 ft jon boat of local yellow pine . i had to edge glue 1x 6s with epoxy to get the 14" planks for the sides , no biscuits or splines . i t&g 1 x 4s for the bottom and shoot a bead of pl window& door in the groove for the bottom . i used boat soup for the finish . she is only a month or so old but does not leak , and after some very hard use , no failures of any kind .
is she a trad boat ? i think so , so does my wife and friends . there may be a museum curator or other purist who may say differently and thats ok because i have a boat

[boatbear]

I feel able to add a bit here.
I love biscuits. I have used them to glue slabs of redgum together for table tops. Those little bits of cross-grain add so much strength when glued in with thickened epoxy, especially when done in pairs. I would also seal both sides and all the edges with a couple of coats of epoxy, maybe glass too. Actually I’m much more likely to use an appropriate thickness of good marine ply if it can conform to the shape.

Some people are driven to recreate an historic tradition and that is highly commendable. Others undertake heroic conservation projects – I am continually awed by the results. History is preserved for future generations and it is also good that there are people who are prepared to pay builders for fine wooden boats, ‘cause it keeps the profession alive. My preference is to take a traditional design and use whatever technologies are available to create a practical and beautiful object that fulfils its brief without fuss and has every chance of being around in 100 years. Wood is such an easy, satisfying and forgiving material to use to create a boat. With modern adhesives and fixings and sealants longevity is pretty well assured (er, with a bit of regular maintenance of course).

Neilm, the Dory Book is a cracker. Which dory/ies are you contemplating?

Charlie (I love biscuits. Thanks for reading.)

[Bruce Hooke]

I've yet to see anyone provide a good reason for introducing a highly rot prone wood (beech, which is what I think most biscuits are made of ) into the structure of a wooden boat, especially when those biscuits will make no meaningful contribution in strength to the joint and will just sit there waiting to be a place for rot to get a foothold. As I see it, the boundary line between traditional and non-traditional has nothing to do with edge-gluing boards and everything to do with introducing biscuits into the mix.

[pipefitter]

I've yet to see anyone provide a good reason for introducing a highly rot prone wood (beech, which is what I think most biscuits are made of ) into the structure of a wooden boat, especially when those biscuits will make no meaningful contribution in strength to the joint and will just sit there waiting to be a place for rot to get a foothold. As I see it, the boundary line between traditional and non-traditional has nothing to do with edge-gluing boards and everything to do with introducing biscuits into the mix.

I agree with that Bruce. I would make my own biscuits if I was to use them in a boat or I would use splines if I had to.The grain positioned across the joints has to add some strength as well as glue surface.I did use homemade biscuits in my boat in the trim pieces and such that were made from the mahogany drops I had left over. Worked well.

[Oscarvan]

wearing only grass skirts and sandals

Sandals? SANDALS? What happened to barefoot?;)

[Thorne]

What Bruce said.

I guess I need to rephrase what I said earlier. What I was **TRYING** to communicate is this:

If someone wants to build a trad boat with trad materials, the easiest way to do it correctly is to only use trad processes/materials.

Once you start making changes or considering alternate materials and processes -- you'd better know what you are doing, and clearly understand the dynamics of the materials and designs.

In other words, it is far easier to say "For a trad boat, use trad materials and processes.", than it is to answer hundreds of questions and discuss every possible variation and modern material possible.

Otherwise you end up with a loooooong string of negatives, like: "Don't use beech biscuits.", "Don't fiberglass over carvel construction.", "Don't use Elmer's White Glue for planks.", "Don't use sheetrock screws.", "Don't mix bronze, steel and SS fasteners.", "Don't dramatically change the sail rig without also changing the centerboard/hullshape.", etc etc etc.

I have no problems with modern materials on trad boats -- but I've either followed the advice of experienced folks on this Forum, or regretted it...

I used Vulkem116 for caulking/sealing the lapstrake planks on my dory skiff, and CPES on the slightly-rotted bottom planks and hull exterior -- all of this has worked really well. But I also stuck to all bronze and copper fasteners, as the boat was already fastened that way.

[Jon Etheredge]

I also agree with Bruce Hooke.

Biscuits are designed for interior joinery work. The material is rot prone. I would also be concerned that the compressed material that biscuits are made of will eventually cause problems from expansion. Even if they are glued in with epoxy, they will eventually expand and have the potential to cause splits in the softwood planking that is usually used for a dory bottom.

Or maybe I am wrong about that. But why take the risk when edge gluing, half lap, tongue and groove, or splines will achieve that same result with much lower risk?

Ok, so you can glue up multiple planks with epoxy and you will end up with this monolithic piece that will work the same as the single wide plank did in the past. What are the benefits and risks with using this monolithic piece?

When Gardner wrote about using a single wide plank in the past, he was more than likely talking about boats that would be kept in the water all or most of the time. The single wide plank worked fine under these circumstances and it was faster (cheaper) to build the boat this way.

There are risks that a monolithic plank will split if the boat goes in and out of the water periodically though. The plank probably won't split as it swells but it may split when drying out and shrinking. Actually, I think it will split if the moisture content of the plank is allowed to get too high and then it goes through a long enough drying cycle.

A caulked seam will serve as an "expansion joint" and will reduce the risk of the planks splitting from wetting/drying cycles. Plywood will eliminate this concern completely.

[Todd Bradshaw]

If you're interested in this type of project without breaking out the modern glues and sealers, there are a couple of boats you might want to look up for construction references. If you can find a copy of WB#32 (Jan/Feb 1980). On page 29 there is an article by Bob Baker on building the "Westport Skiff" (I think the WoodenBoat Store still sells plans for it). It's a 1980 replica of a 1942 Fred Tripp flat-bottomed, flat-sided, 11' skiff that despite it's rather simple comstruction and lines, is a really charming little boat. The sides are big solid planks, but the bottom was 3/4" cross-planked cedar boards. The article isn't great for construction details, but the bottom planks would either have to be edge glued in some way or calked and it would not have been done using modern goo in a tube, fiberglass, epoxy, etc. I haven't seen the WB builder's plan for it, but assume it would explain the bottom construction details, which could also be used on most planked dory bottoms.

The other interesting boat is the "Yankee Tender" which was shown in a series of several step-by-step building articles about the same time. As I remember, it was also cross-planked on it's flat bottom, but it was done with two layers of planks with a thin layer of cotton fabric between them which had been saturated with something like roofing tar (I'm going from memory here, but it was some sort of tar-like stuff). I believe the WB store still sells the plans for this one as well.

For someone who wants to build a flat-bottomed boat and for one reason or another avoid breaking out the resin and 5200, these boats might be worth looking at for construction information. Cross-planking obviously works and obviously has been around long enough to be considered traditional. Sure beats hunting around for a single 42" wide cedar or pine board.

[neilm]

OK, lets forget about the biscuit joint idea. But if I butt join or spline the bottom together with White Pine, Cedar, Spruce, or D. Fir will is split? Let's say for argument sake a 16ft Swampscott Dory LOA.

Neil

[Thorne]

No telling. So many factors will determine this, including the wood used, woodgrain orientation, age and quality of the wood, the way the planks are joined, amount of time in the water, on the trailer, bumpy roads, freezing/thawing, etc etc etc.

Pick a plan and build to it -- that's best. You can always stuff some cotton caulking into any bottom plank seams that leak after a day or so in the water.

You seem to be asking for much too definite of an answer to very general questions. Sorta like asking, "I'm going to buy a new Toyota Corolla LE and drive it cross country. When will I need my first oil change, and where will I get my first flat tire?"

After all, you said that you thought building a trad dory would be a hoot. Part of that 'hoot' is discovering how traditional materials interact, and what happens when you build something this way or that way. I've learned to enjoy it with my Chamberlain dory skiff, and am sure you will too -- the uncertainty is part of the experience.

[boatbear]

OK, lets forget about the biscuit joint idea. But if I butt join or spline the bottom together with White Pine, Cedar, Spruce, or D. Fir will is split? Let's say for argument sake a 16ft Swampscott Dory LOA.

Neil

Each of the timbers you mention will have a range of movement with expansion and contraction due to changes in moisture content. A bit of research will sort out the different rates. If you build in the traditional manner, the movement must be taken into account and flexible sealants used. The alternative is to seal each piece with epoxy to arrest further movement. There is a case for doing this particularly with a dry stored boat.

Is the Hammond 16 footer the one you are interested in? It is a fine looking boat. I built the 18' One-design from Chapter 15. It has a wider transom but is otherwise pretty similar in most sections. The Hammond is pretty narrow aft and would be very nice to row.
Charlie