Paulownia Wood for Strip Planking
Paulownia wood for strip planking is a topic important for building strong and light boards. We have discussed paulownia wood for strip planking hollow wood SUP’s and surfboards in the past and now I want to make a few more points about how perfect this wood is for strip planking. I should first make it clear that I sell paulownia lumber on my website, so I obviously have a stake in promoting the use of paulownia wood for strip planking. But the reason I sell paulownia is because I believe that paulownia is by far the best wood available for strip planking hollow wood SUP’s, surfboards and kayaks.
Hollow Wood SUP and Surfboard Structures with Integrity
Hollow SUP’s, surfboards and prone paddleboards that are built from strips of wood over a light framework all have one thing in common; a semi monocoque structure. What is a semi monocoque structure? Think of an aircraft fuselage or wing on most aircraft and you are looking at a semi monocoque structure. Other terms used to describe this structure would be “torsion box” or “stressed skin”. The loads applied to the structure determine the size and spacing of the internal framework.
Generally speaking, in hollow wood SUP and surfboards the loads are such that a fairly light internal frame can be used. High quality marine plywood is a good example of an engineered composite material with a very high weight to strength ratio and is the typical material used for the internal framework on most hollow paddle and surf craft. The skin to frame attachment is critical to maintaining the integrity of the structure; as long as the skin stays attached the structure will maintain its form which is why most hollow boards have added gluing surface attached to the perimeter of the plywood frames.
The performance of semi monocoque structures can be enhanced in a number of ways. Point loading such as that produced by a paddlers feet or the impact from going down hard on your knee(s) can be resisted by decreasing the span between the frames or by increasing the strength of the skin or both. Heavier paddlers and riders or those wanting to maximize the overall strength of the board often fiberglass both sides of the deck panel and install the panel in one piece. When single panel installations are not practical the deck panel point load resistance can also be increased by fiberglassing between the frames on the underside of the completed deck panel.
In my years building hollow wood paddle and surf craft I’ve seen many overbuilt and unnecessarily heavy boards due to a misunderstanding as to the nature of the structures involved. An over built board may not last any longer than one built to suit the loads and may not be as much fun to paddle or surf (or carry!)
Making a Wood SUP Paddle
The process of making a wooden SUP paddle has some key steps that must be done correctly in order to create a paddle that both looks and works great. The best way to start thinking about the process is to consider the different parts of the overall finished paddle as sub-assemblies that are built up, then combined to make the finished shape.
Make your own wooden paddleboard
Are you looking for a winter project? Have you got some spare time and space in your garage? If so, have you considered making your own wooden paddleboard? It might not be the quickest way to get out on the water but it’s sure to be the most rewarding. Are you up for the challenge?!
Randy Bogardus from Clearwood Paddleboards explains more about wooden paddleboards and what’s involved in making your own.
Wood paddleboards and surfboards have a long history and they have been common in Hawaii for many centuries. The modern version of “woodies” however, is something altogether different than what ancient Hawaiians were riding. With the advent of waterproof glues and plywood which became available in the 1930’s, Tom Blake who lived in Southern California began constructing the “modern” “kookbox” type of paddleboard. These were common for several decades and used by the surf lifeguards on the beaches of Southern California.
Currently, highly refined versions of the “kookbox” can be built from scratch, plans or kits and come in many forms from surf style and flat water sup’s to straight prone paddle surfboards and builders around the world have taken up the challenge of building one or several of these craft for their personal quivers. There are forums online dedicated to this type of board construction with builders from many different countries contributing to an ongoing dialogue about all of the nuances of the building process. Some woods that can be sourced for hollow board construction will yield a finished board as light as or lighter than boards of equivalent size made of foam and fiberglass, with the added benefit that hollow wood boards can and do outlast many “boards” made of foam and plastic.
I will be honest here; building your own hollow wooden SUP is NOT a quick and easy way to get on the water. You may ask why, then, would anyone want to build a hollow wood board? The answer to that question can be stated in this way: the rewards are measured in the beauty, longevity and personal satisfaction that will come with building a wood SUP with your own hands. World-wide, there is great interest in alternative building methods for “home-made” surfboards and paddleboards. What that means to a prospective hollow wood board builder is there are many different styles of hollow wooden SUPs to choose from based on your interest in the various aspects of the sport. Additionally, hollow wood boards can be built with mostly sustainable products such as salvaged or plantation grown woods and there are now epoxy resins available which are made from non-petroleum based raw materials.
The process of building a board of this type is more about a personal journey and creative expression than it is about popping out a board that looks like everything else on the water.
In the end, most builders don’t take on projects of this sort because it is easy. Building a hollow wood SUP can be learned by most people who truly want to learn the process but it is not a project for everyone. Certainly, previous woodworking experience helps. What I say to prospective hollow wood board builders is that if a board is “in you”, you will find a way to get it built. Most suppliers of kit components provide ongoing support during the building process, and as previously mentioned there are some great online resources for asking questions and gleaning insights into how the workflow should go. In the end, patience and commitment are the two main ingredients needed for you to finish a board and get it into the water.
A question many prospective hollow wood board builders ask is, “how long will it take?” There isn’t one answer to this question. It depends on the tools you have available, your eagerness to work on a woodworking project and the level of finished product you want to achieve. What can be said about building a hollow wood SUP is that it very well could be one of the most difficult but rewarding things you do in your life!
So, if you’re interested in finding out more about building your own SUP, check out the Clearwood Paddleboards website and Facebook page. Or email Randy at email@example.com.
Clearwood Paddleboard kits can be shipped worldwide.
Closing Up a Hollow Board-Tasks to Consider
Completing the assembly manual has taken me longer than I had planned and I am hearing from some “CLEARWOOD” board builders that are nearly ready to strip the bottom and close up the shell of the board. So let’s go through the basics of what we need to consider before stripping the bottom and closing up the shell.
We’ll start with the blocking that supports and reinforces the fin(s), vent and leash plug. All three of these components should be installed on both touring/race boards and surf style boards. All hollow boards should have all three of these blocking components installed prior to closing up the shell of your board.
Some builders may ask why they would need a leash on a board intended for touring. This is a fair question, but think of what would happen if you became separated from your board in really windy conditions. Boards move quickly in the wind….likely quicker than you can swim so even though you may not use a leash every time you paddle, there will be times when using a leash is essential for your safety.
The fin is obviously a critical part of a paddle board. It is essential to keeping you on course and tracking straight. The lateral loads from pressure on the fin can be quite concentrated and therefor the fin(s) needs to be securely anchored to the structure of the board. I recommend blocking both sides of the stringer (for the center fin) from three inches forward of the tail end of the board continuously to a point 2″ forward of the forward end of the finbox.. I use 1” thick material for this blocking and make the block the full depth of the stringer. This will lock the finbox/fin assembly solidly into the framework and skin of the board giving you plenty of material from which to route a pocket for the fin box. For surf style boards, the position and length of the fin boxes you choose will determine the position of the blocking so you will need to plan your fin layout and finbox choices prior to “close up”.
You will notice that in the photo above that the bottom went on first and that the deck went on last. This board was built prior to developing the “rocker tab” system. I’m showing you this photo to illustrate the blocking layout. This board is a surf style and was set up as a quad + one. You can also see the vent block which was installed the full depth of the board but in this case the vent block was notched to allow for pressure relief. This is a good example of the multiple ways there are to address any particular situation with the construction of a hollow board. In reality my system evolves. The main idea to keep in mind are the basic principals regarding structure, venting and sealing prior to close up.
The leash plug is another component that can be subjected to quite high loading. Blocking that is securely glued to a cross (transverse) frame and skin of the board is one of the keys to avoiding leash cup failure. The plugs that I make and most plastic plugs made commercially are in the range of 1” – 1 ¼” in diameter. I recommend using a block that is a minimum of 2” x 2” and is the full depth of the board at the point of placement. The placement position can vary but in general, leash cups are installed near the tail of the board on one side or the other of the stringer. Since this block and all the other blocks necessary on the interior of your board are installed after you flip the board and before you strip the bottom, you must mark the center of the leash cup and vent blocks PRIOR to installing the bottom strips. The simplest way I have found to mark the center of the leash plug block and the vent screw block is to drill though the block from the bottom side all the way through to the deck of the board. I use a 1/16” diameter bit for this hole. This hole/ “mark” on the face then becomes the pilot hole when you get to the point of drilling the pocket holes for the leash cup and vent screw body and it can’t be sanded off.
The vent screw block set up is slightly different since the vent needs to be open on the bottom (inside of the board) in order to work as a pressure relief vent. This vent is typically slightly less deep than the body of the vent screw is long. There are also different lengths of vent screw body’s so you will need to measure yours to determine the depth of the block. If the block ends up being deeper than the vent body is long, it isn’t a big problem since you will be drilling through the block from the deck side. Just remember to not make the vent screw block the full depth of the board or it won’t be able act as a vent.
At the time you “flip” your board you will have the deck and some of the rail in place. Before you begin the process of completing the rail strips and installing the bottom strips you will want to seal the interior that is now in place. From this point in the process of installing strips, the pieces should be pre-sealed since there won’t be any way to seal the inside after all the strips are in place. There are several choices of material you can use to seal the interior, from thinned epoxy to marine varnish to exterior grade acrylic polyurethane. I apply a thinned epoxy solution to all of the interior surfaces including the framework. The reason I use thinned epoxy is because it is compatible with the epoxy I use to glue the strips in place. The consideration in this regard is that the gluing surfaces on the framework need to maintain “glue-ability”. Epoxy sticks to epoxy which has penetrated the fibers of the wood but would not adhere well to marine varnish, for example. If you are using a Titebond or polyurethane product you would not want to apply a sealer to the glue surfaces on the framework since the bonding strength would then be compromised.
My system for sealing the pieces from this point to completion is to seal the strips prior to ripping them to width. By so doing, you will then have strips with fresh wood uncontaminated by sealer. If you are sealing your strips with thinned epoxy and installing strips with epoxy the surface contamination of the strips is not a problem but it is important to consider your sealers and glues as a “package” that needs to be coordinated for proper adhesion.
Another item for consideration throughout the close up process is how to keep the interior of your board clean and “rattle free”. This isn’t an issue until the point where you can no longer get the “snout” of your shop vacume hose into the board. There is no easy solution here other than vigilance. My first board was full of wood chips that I get reminded of every time I pick the board up….rattle, rattle, rattle! You just have to be really careful to keep the interior clean as you approach the point on “no return” with the vac hose.
That’s about it for this session. If anyone has further questions or needs clarification email me or call me and we’ll sort it out.