Strip plank hard chine hull?

The boat I want to build has a flared bow section and a tumble home transom. I do not want to use plywood on the hull and want a hard chine on the aft one third of the hull. Basically, a tradtional look combined with a modern planing hull. Boat length is 27.' I realize strip planking is reserved, in most cases, for displacement and semidisplacement craft. I like the strip plank method for a multitude or reasons and would greatly appreciate suggestions/ advice. Additionally, how do you incorporate double diagonal veneers with a hard chine design? The boat will be trailered and spend a considerable amount of time on a trailer, hence the need to veneer and glass ext hull with epoxy.

Thank you

 

Strip planking is generally used on round bilged craft, plane, semi plane and displacement modes included, but I see no reason you couldn't use the method on a chine design. The design will have to be gone over, to insure scantlings and shapes are compatible. This will likely result in modifications to the frame count and size, strip size, molded sheathing schedule, 'glass sheathing schedule, chine log arrangement, possable shape adjustments, etc.

Typical plywood, chine designs rely heavily on the ability of the ply panels to distribute loads across a large area and their inherent stiffness. You'll not be using strip planking to best advantage on a conically developed hull form, though it could be done if you wanted. Why not a molded or double planked hull? Why not plywood?

 

Strip plank hard chine?

My primary concern is the forward half of the boat does utilize all the benefits of strip plank veneer construction, however, the back half has that tumblehome aspect with a hard chine. I kind of see it as a combination of two different ideal building methods for one boat. I owned a 1956 BayCraft, 34' foot semi displacement cruiser. really liked the lines, not fast, not fuel efficient due to hull shape and weight, it was carvel planked with 7/8th Mahogany. My proposed hull shape would not be conically developed, flared bow section with tumblehome transom, precluding ply construction. I would like to use the strip plank veneer cobination, as it would accomodate my hull design with superior strength...also allowing me to use Western Red Cedar, in my opinion, far superior over plywood. My real concern is the hard chine. How do you develope the necessary strength at the chine with almost a 80 degree angle, with strip plank and veneers.

Thomas

 

I think you may be confusing strip plank with cold molding.

Cold molding builds up multiple layers of veneer to create a "plywood" hull in the shape desired.

Strip planking uses a single layer of wood strips to create the hull form.

Boats like the Buchan 40 were stripped and have lasted well. They were built of edge nailed and glued 3/4 by 3/4 cedar strips. Another more recent strip boat (with a slight chine) would be the Swift Solo. Canoes and kayaks are also commonly strip planked. Round bilge and/or chined.

A strip built boat handles a chine since the strips are placed sequentially and edge glued to each other. These days, the final finish is usually a layer of epoxy saturated glass. The Buchans were just painted.

If you want to build a cold molded hull with a chine you will need a chine log to complete the joint. It is a difficult joint and one not often undertaken. It creates a weak point in the hull that is not needed. Most boats with hard chines are plywood or composite.

 

You can see there
http://www.etoile-chantier.com/Actualites_chantier_naval.html
(scroll down to "Octobre 2005") a 53 ft hard chine powerboat built in strip planking.

There is there http://www.nexusmarine.com/odysy_const.html double diagonal planking

and there http://www.spirityachts.com/sy-power35ts.htm
double diagonal veneer cold molded over cedar strip planking.

All boats built professionally. The important thing is that the scantlings and balance weigth being computed for the choosen construction method.

 

Lindsey Lord, "NA of Planing Hulls" was one of the developers of modern strip planking, a relatively thin skin of longidutinal wooden strips with transverse stiffening from glass on both sides, a kind of sandwich where the core take longitidinal loads. Many of his planing hulls had hard chines. Mac Naughton publish a very simple scantling rules for this kind of construction.

 

Thomas,

Here are three manufacturers whose designs should give some guidance as to the validity of the process.

http://www.vicemyacht.com/construction.php

http://www.dolvik.com/boats.htm

http://www.sculleyboatbuilders.com/const_coldmold.html

Cold moulding with strips of Meranti faced BS 1088 marine ply will give you the Carolina flare you want and the tumblehome transom. Use fibreglass cloth inside and out and the boat will give you years and years of good service.

There is a cabin version and a centre console version here. http://www.boatplans-online.com/proddetail.php?prod=CS25

Of course you can use Mahogany strips, if you are reluctant to use ply, clear finished on hull and deck, to protect the epoxy from UV, like this Monaco. http://www.boatdesigns.com/products.asp?dept=240 and http://www.glen-l.com/designs/inboard/dsn-mco.html The Riveria offers the same look. http://www.boatdesigns.com/products.asp?dept=252

However, you could use ply, paint the hull and deck it with the most exotic woods you can source. http://www.glen-l.com/designs/inboard/dsn-skga.html

There are many choices out there for you.

Good luck.

Pericles

 

You can do almost anything with strip planking in shapes and its not confined to round chine hulls.

 

Hi Thomas Wick and others.

I pretty much asked a similar question on another thread (see last posts in "long range passagemaker" and post under "strongplank"). Maybe I was on the wrong thread with my questions.
I don't know if a "flared bow section and a tumble home transom" as Thomas Wick mentions is the same type of design I am talking about. At any rate, it also concerns a hard chine boat which is proposed in plywood, but for which I am wondering if it would not be stronger in a woodcore (strip plank ?) type construction. It seems we have a similar type of question. Please have a look at
http://www.chantiermer.com/presselordjim.htm
http://www.lordjimcroisieres.com/fr/index.php
and give me your impressions and critiques.

As for the combination of wood and epoxy, please check my last post on the 'long range passagemaker" thread. How do current epoxies stand up to heat and delamination ?

I will follow this discussion with much interest. Hoping to hear from you.
Greetings, LAZYJACK (Belgium).

 

The chine area of the hull will need a longitudinal load bearing member (a chine log), in the area of abrupt turn (your aft sections). This member doesn't have to go all the way forward to the stem. Dimensions of this piece and how it transmits loads to the surrounding planking and other framing members are issues that will require some engineering.

Just about any shape can be had is one of several methods of construction. Not all plywood boats have to be developed shapes, you can rip it and plank just like a molded method. I'm not sure exactly what you're asking, but your unconventional hull shape can be built will strip/veneer, plus several other methods, including plywood. The chine area will need scantling attention.

 

I will put my question differently : for a chine hull (like the Chantier Mer design I submitted and which is offered by the builder in plywood),

a/ which of the three construction methods - plywood, strip-planking or cold-molded, would give give the strongest hull ?
b/ is one method more appropriate to use than the other (I understand from Kanaka's answer that coldmolded would not be the least good candidate for a chine hull -correct?)

Am I on the right thread for this, or am I interfering with Thomas Wick's initial question?

Regards

 

There are several additional questions that could help further some stronger opinions of what my work for in the long haul
How much experience do you have with maintainance? What about boatyard service and haulouts? Have you ever owned anything in that range? Are you saying that you will purchase this boat already buiilt, or will you build it? Is this a long term deal for any heavy cruising? If so what areas of the world do you have in mind?

Cold moulded hulls, hardchine, are built every single day in many of the high speed world class sportfishing hulls.

 

If its designed for plywood, you have to make sure the strip planking + glass or other reinforcement on both sides have the same stiffness across the planking as plywood has. Otherwise you need more framing inside.

 

Strip planked hulls, built with the right scantlings, can be built without framing, allowing bulkheads, and intregal parts to form a complete hull structure. A strip plank can also be built incorporating a heavier glass that works in lieu of heavy planking, which also works just fine. If you are working with a preexisting design approved by an engineer, it goes without say to work hand in hand with the engineer. Please do not say

 

Any method can give a stronger hull. It depends on many factors. Also, you need to qualify strong. Are you talking of slamming loads, puncture resistance, stiffness, etc.?