Hollow Wood SUP and Surfboard Structures

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.

SUP fishbone 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.

SUP building in progress

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!)

Sustainability in SUP and surfboard production

Sustainable SUP and Surfboard Production

Building a hollow wood SUP can be a great way to build a board with a low carbon footprint. Tom Blake started building hollow wood paddleboards in California the 1930’s and they were the standard surf rescue craft for several decades. The good news is that hollow wood SUP’s are now available to paddlers inclined to build their own board and they have become much lighter and more durable as a result of the use of epoxy resins, fiberglass cloth and paulownia timber. Hollow wood boards can now be built that weigh no more than, and in many case less than, fiberglass covered foam boards.

Paulownia 2

The SUP’s we ride when we go paddling are made in several different ways, typically involving fiberglass covered foam but the boards we ride on any particular day are probably not something we give a lot of thought to in terms of how they are made. Board construction methods and the question of sustainable construction is typically not something most paddlers think about. The idea of sustainability in the construction of SUP’s has been in the mix of industry topics for years, and now with the huge numbers of SUP’s being built worldwide, it might be something for us as to consider. Should we, as SUP paddlers be concerned about this?

Although not a practical choice for everyone, many paddlers have embarked on the path of building their own hollow wood board from paulownia timber which is plantation grown in Spain, New Zealand, Australia, China and many other countries around the world. The carbon footprint we leave in our wake can be reduced, and for paddlers wanting to build their own board, building a hollow “woody” is a viable option for limiting our carbon footprint. Paulownia timber for those of you not familiar with this species of wood, it is the wood of choice for building hollow strip planked SUP’s, and it is now available in the UK from Paulownia timber is the wood of choice for several reasons; it is plantation grown and can often be sourced without being shipped great distances, it has the highest weight to strength ratio of any hardwood on the planet and has beautiful grain character. Paulownia timber is also “reluctant” to absorb water and grows to maturity in approximately 15 years.


What makes a hollow wood board a “sustainably” built board? Most of us that live around the sea have seen and appreciated the classic wood boats we see that are still in good shape after decades of use. Wood SUP’s are similar; hollow wood boards can be used for years if properly built and maintained. Of course board shapes change, but quality designs with a fit paddler aboard will perform well and look great for a very long time. Plantation grown timber combined with some of the new epoxy resins such as “Super Sap” made by ENTROPY RESINS will produce a beautiful board with a low carbon footprint that is fun to paddle. Paddlers that are interested in building a hollow SUP have numerous resource available. Online forums such as are great sources for information on how to build a hollow boards. There are also teaching environments that are dedicated to the craft of building hollow boards.

Paddlers interested in building their own board but who are not ready to take on a project of this nature without guidance can now do so via several schools scattered around the world that have been set up specifically for the purpose of teaching the skills and build methods necessary in crafting their own hollow wood SUP. In the UK, James Otter at is now offering classes for SUP builders as well as Patrick Burnett in South Africa at In New Zealand, Ben Godwin is setting up a school environment for building hollow SUP’s and he can be reached at

Doug and Ben - Copy

Paddlers not inclined to build their own board can still reduce their carbon footprint when buying a new SUP. Recycled foam blanks are increasingly available worldwide and local shapers that have access to these recycled foam blanks can be a great option for “keeping it local”. A knowledgeable local shaper will be able to customize a shape that suits the size, ability and local conditions of a particular paddler with the added benefit that buying a board from a local shaper supports a local craftsman. A board that is shaped for a specific paddler will most likely be a board that will be paddled for many years thereby reducing the number of boards sent off to a landfill. Is sustainable board construction something we should be concerned about given the quantity of waste and mountains of refuse created globally? Is the contribution of our leisure activities make to this problem something that matters? We as individuals are the only ones that can answer these questions. The good part of the sustainable board construction story is that there are options available to us should we be concerned

17′ Unlimited Length Standup Paddleboard

17′ Unlimited  Length Standup Paddleboard


Unlimited launch




The 17′ Unlimited length SUP board by Clearwood is now ready for production after a year of designing, building and testing. We’ve been paddling the board in a wide range of conditions varying from glassy flatwater to wind chop, and in both upwind and offwind conditions. I also raced the board in terrible, rough ocean conditions and still had fun, but had the most fun in more protected water. The Unlimited 17′ x 27 1/2″ stand up paddleboard went upwind well in 10-12kts of wind and was really swift off the wind. This is definitely not a “downwind” board in the sense of doing “downwinders”, but more a fast cruiser which will be suitable  for paddlers up to 260 pounds handling a wide range of conditions.



Ron 3 Ron 28


Conceptually, the development of this board has been to accommodate bigger paddlers that still want a board that performs well. The Clearwood Paddleboards 17′ Unlimited length SUP board will be a great board for extended touring with the ability to handle sizable loads or will be perfect for the larger paddlers out there that just want a great board under them.

The 17′ Unlimited length SUP is based on the very successful and swift “Cascade” lineup of boards. We’ve added length, and reconfigured the rocker line and think we’ve created a fun and fast platform for paddlers wanting to paddle a longer board. The board is designed with the same reliable “fishbone” style frame with a few added structural elements to give the board a very solid and stiff feel. The prototype board came in at a very respectable 42 pounds using paulownia strips with salvaged redwood pin line and features.

I’m really looking forward to paddling this board with a gps on board so I can see what kind of speeds we’re getting with the prototype. But I can tell after paddling the board that it sure seems like I’m going fast!

Wood SUP Paddle Making

Getting Ready for Glue Up   At this point in the process you will have your paddle shaft glued up and milled to size (1 1/4″ x 1 1/4″). This is the point in the process where you will cut the long miter in the shaft that will form the bend at the blade end of the paddle. I’ve created a simple jig that slides in the slots in the top of my table saw. The jig is set up so that the shaft will slide through openings in the jig which is then passed over the saw blade. The long part of the shaft is held in place by cam clamps that are set up to apply pressure to the center line of the shaft and this holds the shaft in place while the saw cut is made.  I’ve laid out 9, 10 and 11 degree marks on the jig which makes it simple to clamp the shaft down to the sliding jig at the desired angle. It’s important to layout the long miter carefully so that you end up with a shaft miter that is the proper length for the blade you want to create. I lay this miter out on the squared up shaft with a pencil and a large protractor so that there is no guesswork when you fire up the saw. I have made the mistake of not getting this right and the blade end miter came out short! So know what will happen and how the parts will go together prior to making the cut.     shaft 4   shaft 3   Once the cut is made, the short, blade end of the cut is rolled over and becomes the mitered piece that is glued to the long part of the shaft. If you are using epoxy for the adhesive (recommended) this will be a very strong joint. At this point in the process I round over the long part of the shaft leaving the grip location square so that I can glue the grip parts onto the shaft. The cut off blade end is also left square. I round over the shaft with a 5/8″ roundover bit on a router that is housed in a shop made router table. It is easiest to round over the part of the shaft that isn’t adjacent to the grip of the blade before the grip is glued on.     shaft roundover 2   shaft 2   The miter has additional reinforcement provided by the blade which is glued to the side of the shaft.   shaft 1   shaft glue up     We have all the paddle parts laid out, dry fit and they are ready to glue up for a nice laminated wood SUP paddle. All of the pieces are sawn to the same 1 1/4″ dimension of the paddle shaft cross sectional dimension. You can use up any scrap you have with consideration for the weight of the species of wood you choose. I tend to use paulownia wood for most of the surface area of the paddle blade for its good weight to strength ratio, with some accent wood strips mixed in. The glue up process is quite straightforward and simple. I always lay out the parts to be glued up, on a sheet of waxed paper which will prevent them from sticking to the work surface. I prefer using epoxy glue for all of my adhesives for many reasons and one of them is that you don’t need high levels of clamping pressure. Also, the nature of a well shaped paddle blade means that some of the parts of the blade will be fairly thin so the importance of using an adhesive that you have confidence in is critically important. Once the blade is shaped, it is then sheathed with fiberglass cloth. I use the same 4oz (3.7 oz actual) that I glass my board with since there are always cut off corners which are perfect for glassing paddle blades. blade   grip   The technique for using epoxy is the same as you would use for any situation where epoxy is being used for an adhesive. I pre-saturate the mating surfaces with mixed epoxy/hardener then add a structural thickening agent which is then applied to the mating surfaces. This assembly is then lightly clamped. In the photo above you can see that I’ve created a “platform” which has been clamped to the shaft. This provides a secure surface on which the grip parts can rest while the adhesive is curing. The grip I’ve used for this paddle is solid paulownia wood. I have made grips with multiple laminations of different woods but I like the workability of paulownia so am trying one with just one species for this paddle. You will also see in the photo of the grip that I’ve rounded over most of the shaft prior to assembling the parts. Here’s a YouTube clip of the setup on the workbench.