Lapwing

[Tom Lathrop]

After some start up software problems that kept us up past midnight, Graham woke this morning and found the problems with the computer program that runs the ShopBot CNC machine.  In a short time today, the mold sections were all cut out of 3/4" plywood.  The accuracy and fit of the sections is great, much better than could be achieved with a saw.  I will now get started on the mold.  My greatest problem is that I had already raised all my woodworking machines up in the air in anticipation of hurricanes before we left for a trip to England.  Now I have to take some down to do the work and gain enough room for the mold in the shop.  I dread it a bit since they may have to be lifted back up again it a hurricane decides to make an appearance. 

Just dog work and it must be done.  Photos will follow when there is something to show.

[Tom Lathrop]

Lapwing molds put together to day.  The fit from the CNC machine is very accurate and final measurements are very close to design values.  The view of the shop is before I dropped the table saw down to floor level to cut stringers for the mold.

I have Tom Hill's and Ian Oughtred's books on lapstrake building and will kind of blend their methods to build Lapwing.  I also ordered Brooks and Hill's book and it came today.  After a brief lookthrough, I find that there is a ton of info but their methods seem excessively (and unnecessarily) complicated.  Boats are complicated enough and I like the simple building methods when possible and practical.

[Dale Niemann]

Tom,

I know the feeling about hurricanes and flooding.  We have been very lucky so far.

The molds look great.

Glad to see you are making progress. 

I am very anxious to see how it goes for you.

Please continue to keep us informed.

Dale

[Tom Lathrop]

Picked up the last mold for the transom from Graham today and mounted all of them temporarily on the strongback.  The area I cleared out to build looks a bit small now.

Time to start watching weather waves out in the far tropical Atlantic.  Tow of them as of today.  Don't want to wish anyone else bad luck but do hope they don't come this way.  Messes up the boat building schedule.

[Tim]

Hi Tom,

Will you write instructions of your combined method for those who follow behind or do you suggest we buy both books?

Thanks,

Tim

[Tom Lathrop]

Tim,

This is my first lapstrake boat so I am not certain just how it will go.  I am learning and making it up as I go.  I started it but it's Graham's design and he will get the plans out.  We will work together and decide what works well and what doesn't work so well. 

[Doug Cameron]

I once built a Joel White designed Shellback using a plywood lapstrake design.  First I  assembed, squarde up, and screwed down the forms.  Then, beginning at the bottom, I screwed the cut plywood piece on the frame (the bottom first).  Then I planed the edges at the angle the next piece would take (with the side effect that this created a greater bearing surface for the glue).  The next piece goes down against this angle and overlapping a wee bit (this opening is filled with thickened epoxy, kin to a fillet).  The center frame on this 11 1/2 foot boat became a rib, the others were removed and the screw holes filled.  Tom, I think you saw this green and white boat with a lug sail at Cedar Key).

Doug

[Guest jopasm]

I noticed the new design is now up on the homepage.  Definitely a design I'll be keeping an eye on!  Hmm.  I guess I'm new to the board, I'm looking at building my first boat soon, which will probably be a relatively simple rowing craft of some kind, but I'm gearing up towards building a larger camp cruising/daysailer type.  The CS15 or Lapwing are looking very tempting, particularly since I'm now located in NC. 

[Greg Luckett]

I cannot find on my bookshelf the books I wanted to recommend, but one is from Ian Oughtred, "Clinker Plywood Boatbuilding Manual", and the other one is by him for lapstrake.

I just dug out from a pile by the drafting table, "How To Build Glued-Lapstrake Wooden Boats", by John Brooks & Ruth Ann Hill.

These helped me when building the lapstrake lobster boat last year.

Greg.

[Tom Lathrop]

Ray,  I don't know a John Hills as author of a book on lapstrake/clinker building.  Ruth Hill is co author with John Brooks of one though.  And then there is Tom Hill' book.  Where is the Hills book available?

[Joe Nelson CS#35]

Looked at the B&B website and the Lapwing page...looks very "salty" with the clinker construction and I expect that she will be no slouch either.  I imagine she will be very light as well.

The books you mentioned are the best I have seen, and I own both of them.  I wonder if Graham will be designing any larger boats with clinker backed with stringers?  For the effort, its hard to beat a stitch and glue boat!  I enjoy the stiffness of a hard bilged boat as opposed to round.  Hard chines also tend to have a larger bottom surface to facilitate speeds beyond what a displacement hull will provide.  I do think that the Lapwing will be a great boat for the new CNC machine.  I hope that Graham finds a strong market for kits!

[P Doug (WA)]

Hill and Brooks really do not seem to like covering a boat with epoxy.  I just started reading it and they seem to like glueing with epoxy, but do not appear to like coating with epoxy or fiberglass and epoxy. Probably just personal preference, they do give what appear to be some good reasons though.  Will the  Lapwing be fiberglassed?  And what plywood are you using?

Pretty exciting project.

[Tom Lathrop]

Everyone to their own opinion.  Around here, we have had many years of experience with both epoxy and no epoxy, in coating and gluing.  Both methods have their champions and both can produce good boats.  Graham has my copy of Brooks and Hill so I can't see what they have to say about epoxy but will look at the first opportunity.

We now coat just about everything with epoxy and, of course, glue almost everything with epoxy too.  Some fine joinery is often glued with PVA Titebond glue which is very strong and pretty well waterproof but needs tight joining surfaces.  Most epoxy naysayers fail to grasp a fundamental truth.  An epoxy coating should be looked at as nothing more than another form of paint, although one that is superior to most other paints in one important aspect.  That is, it is much less permeable to water or water vapor transfer through the coating than paints available to the home builder.  In boats, this is a good thing. 

There is the argument that some water or vapor will get through and will be trapped inside and cause rot.  In a word, that is just someone's conjecture and is just so much BS.  I have seen plywood cut from the keel of a boat that Graham built in Israel and which has spent many years in the water and crossed the Med and Atlantic and now resides in Vandemere.  The plywood looked like it was built yesterday.  Not to say that there was no moisture in the wood at all, just that there was no problem associated with it.  If the boat had only been painted, it is not likely to have survived so well. 

That said, my plan is to only coat the plywood in Lapwing and perhaps cover the garboard and second bottom strake with Xynole for abrasion resistance.  This boat, like most of our small boats, will be dry sailed and live most of its life on a trailer.  I will still use an epoxy coating because I believe it gives the best base for whatever finishing top coat is applied.  That includes epoxy as a base coat for varnish.  I have never used CPES (a very thin form of penetrating epoxy) which is claimed to be a superior base for paint by many on the forums. 

We have mostly used Awlgrip LPU (linear polyurethane) as paint but I am planing on going back to a quality "normal" paint for Lapwing due to the very high cost, tricky application and toxic nature of LPU.  LPU is great paint but I'm ready to try a more approach, particularly on a more traditional boat.

[Peter HK]

Tom said about epoxy coating

There is the argument that some water or vapor will get through and will be trapped inside and cause rot.  In a word, that is just someone's conjecture and is just so much BS.

Well said. I've heard this so many times yet it clearly is irrational. Epoxy is less permeable to water than the alternatives but the concept that the minute holes in epoxy that let water through some how have a valve effect and won't let the water back out again is ridiculous.

Clearly water in wood is bad and minimising its entry is a good thing to do. Epoxy does this pretty well though not perfectly. Let me know when something better comes along

Peter HK

[Joe Nelson CS#35]

Covering with glass and epoxy is the best way to assure a void free encapsulation...even if it is a very light cloth.  But by the time you apply epoxy, epoxy primer and topcoat...I see little room for entry of water.  There are a lot of epoxy bashers out there (traditionalists).  You will find lots of them on the woodenboat forum.  We know better!  Our secret.

[Tom Lathrop]

When is a fabric required and when not?  A case history gives a situation when an epoxy saturated cloth is needed.  Joe gave one good example.

About 20 years ago we built a trimaran with the center hull bottom laminated of two layers of juniper.  The layers were stapled and the staples were removed after the epoxy set.  The bottom was then coated with several coats of epoxy.  During the launch and sail, with TV camera crews taking video, the boat started taking on water.  Luckily, the TV people left before the boat came back to shore and the builders were saved from further embarassment.  After some cogitation, the source of the water was seen to be the staple holes. 

Anyone who has tried to fill small holes by painting has seen that the holes might appear to be covered at first.  However, the paint gradually shrinks away leaving the hole still open.  In engineering terms, its called "surface free energy" and one thing it means is that a liquid does not like to stay on a sharp edge.  A hole being a 360 degree sharp edge, neither paint nor epoxy will cling to it.

The problem was solved by adding a layer of glass and epoxy to the bottom.

Fiberglass is not the best thing to use for abrasion resistance and is only about twice as good as epoxy alone.  One layer of Xynole is 6 times as abrasion resistant as one layer of 10 oz fiberglass, which is why I use it for that purpose.

[P Doug (WA)]

Hey, sorry to turn this thread into the pros and cons of epoxy and fiberglass.  I was just relating what I had just read the the night before in the book by John Brooks and Ruth Ann Hill, "How To Build Glued-Lapstrake Wooden Boats".  I haven't even finished my first boat, so, I'm certainly not in the position to know much about this subject.  My little boat will be coated with epoxy, like I had always planed.  Thanks, for the response though, I learned from them. 

Now back to building your boat, Tom, did you say what type of plywood you are using?  I am really enjoying this thread and watching the progress.

[Tom Lathrop]

Given Tom's location of mostly sand and mud bottoms....  I fail to see any problem wiith epoxy.

Ever see what an oyster or mussel encrusted beach can do to a wood hull?

What weight xynole are you using, and where do you source it Tom?

Costs per yard?

As far as I know, there is only only one weight.  It is lighter than 10oz glass and about the same as Dynel.  It comes from Defender Industries.  It does take more resin to cover it so is heavier than the glass.  Kind of forces you to have plenty of waterproofing epoxy on the bottom.

[P Doug (WA)]

Boy am I ever sorry I brought it up!  Never again! 

[Tom Lathrop]

Raka.com sells a 4 oz xynole cloth but that is the onnly weigth theyt carry.

I was wondering if 4 oz Xynole was what you were referring to as being 10 times more abrasion resistant than 10 oz Glass.cloth

Yep,  RAKA probably gets their Xynole from either Defender or the same source.  I made some pretty exhaustive tests years go on several sheathing fabrics for abrasion resistance. 

Ray,  you may need to clean the wood dust off your glasses.  I said that one layer of xynole properly coated with epoxy is 6 times more abrasion resistant than one layer of 10oz fiberglass also properly coated with epoxy.  These tests were reported in an issue of Boatbuilder magazine six or seven years ago along with equivalent tests of Vectra polypropylene, Dynel, Knitex FG and plain epoxy.

P Doug,  This is all relevant to boat building and to what is planned for Lapwing in particular.