SUP Technology

ALTITUDE PADDLEBOARDS – A SIMPLE PRIMER ON SUP TECHNOLOGY and Epoxy Repair by founder JB (updated 7/2/2018)

Board Construction Considerations – Construction techniques make a huge difference in board durability. Manufacturers that build their epoxy boards using molds, or sandwich & vacuum bag technologies, with thoughtful design of core materials, reinforcing layers, all backed up with a factory quality control program are going to produce a superior product that will last. Look for manufacturers that provide information on their proprietary construction specifications (NSP, Boardworks Surf). These companies truly care about and pay vast attention to manufacturing the highest quality boards. That is why we carry these brands at Altitude Paddleboards, we know how all our boards are made and we rarely see them come back to the shop for repairs. If a cheaper board found on the internet does not show construction details, assume the seller has no idea how it was made, and it may be a board that will be prone to serious damage even with minor abuse. Lower priced inflatables typically have smaller volumes, many more seams, lower quality gluing, lower inflation pressures, and funky fin systems with a paddle that is heavy and not a pleasure to use.

Epoxy/EPS Boards – This is the most common type of construction and consists of an expanded or extruded polystyrene (EPS) blank (aka styrofoam) wrapped in fiberglass cloth that is then layed up with epoxy resin. (exotic materials such as carbon fiber, and various advanced construction techniques provide varations on the theme). EPS blanks can be hand shaped but usually are injection molded or machine shaped using CAD software allowing mass production of identical boards. Benefits of epoxy construction include great durability, strength and light weight. Also, epoxy construction is a relatively green process because production of EPS foam does not involve emission of volatile organic compounds (VOCs) which are EPA regulated air pollutants. There are two main grades of EPS foam, less expensive expanded foam that is open cell and can adsorb water, and more expensive extruded foam that has better flex characteristics and is closed cell with very low water retention.

Poly/PU Boards – This type of construction, commonly referred to as “fiberglass” is the traditional foam core surfboard construction method in use since the 1960s, but is more accurately described as a polyurethane (PU) foam core wrapped in fiberglass cloth that is then layed up with polyester (Poly) resin. PU foam blanks are typically hand carved by skilled shapers. Although generally less durable than epoxy/EPS boards, their rigidity and ease of repair make Poly/PU boards a popular option especially for surfboards. The dominant U.S. manufacturer of PU blanks (Clark Foam) went out of business in December 2005 most probably due to an EPA crackdown on the VOC emissions which are generated during the manufacturing process. Other manufacturers have filled the void created by the demise of Clark Foam.

Plastic Boards – Plastic hulls, either hollow or foam filled (such as BIC) are a very durable although less performance oriented SUP construction method. Pricing is generally less with plastic boards but they tend to be relatively heavy.

Inflatable Boards – Inflatable SUPs (aka iSUPs) are a great option for portability, and are especially suited for running white water rivers. An iSUP is generally constructed of a durable waterproof PVC fabric with an internal webbing system and plastic fin(s). They come with a pump an inflation valve, if well made, can be inflated to about 15-20 psi producing a surprisingly rigid platform. A primary iSUP benefit is you can bounce the board off rocks repeatedly without damage (although your body may take a few hits). Like an inflatable raft, there may be a patch or two eventually required depending on use/abuse. Deflated, an iSUP fits into a large duffle type carry bag for transport and inflated an iSUP can be strapped on your car top like an epoxy board. An iSUP is a great choice for air travel to exotic surf destinations. Look for double seams as a sign of quality although a few single seam manufactured iSUP are very durable as well. We know which ones are good so if it is in our shop it’s a quality product and we can explain why.

Wood Boards – Wood paddle boards and surfboards can be hand-made form kits obtained online and also are available from manufacturers. To reduce weight, wood SUP boards have a hollow construction consisting of an internal framework of ribs and spars that are then covered with planking and finished with fiberglass cloth and resin to seal the hull and provide additional strength. Balsa wood and several types of sustainably grown woods can be used. Carve Industries in Lyons, Colorado produces wood surfboards and SUPs using CNS technology to speed production and reduce cost. Purchase of a well made wood board will be the most expensive option but by far the most beautiful as well.

Other SUP Considerations –

SUP Hulls – The two main hull types are planing (flat bottom) and displacement (center keel with higher overall volume).

Planing hulls – These boards look like a typical surfboard however SUPs require much more volume to “stand” on flat water. Planing hulls are generally suited for both flat water cruising and surfing on both ocean and river waves. Planing hulls can be short, lightweight, and still paddle effortlessly with a fair glide distance on flat water. Planing hulls are the most popular design and possibly the “coolest” SUP with firm roots in surfing culture.

Displacement hulls – These hulls look a little more like a boat hull and have rails that extend well above the waterline. The keel ridge will generally taper off to a flat bottom a few feet back from the pointed nose of the board. Often referred to as either touring or racing boards, they are designed for extended glide and increased speed vs. planning hulls of comparable length and width. A displacement hull is a good choice for those who like flat water performance, racing, fitness training and long distance or multi-day cruising. Some models are also well suited for heavier body weight paddlers who want the option of bringing along a dog or gear bags. (Note: for a flat water workout here in Colorado, I almost always grab a sweet displacement hull, given the choice).

SUP Venting Systems and Delamination Concerns – The opinions on vents vary by manufacturer, some claim vents are necessary and some have developed manufacturing techniques that eliminate the need for pressure equalization vents. As standard practice, care should be taken with all epoxy SUPs to minimize exposure to heating (baking) from the sun when they are out of the water. In addition to releasing internal pressure, some vents can also allow water to enter inside the hull which is especially of concern for open cell EPS foam cores. Also user error can lead to a vent being improperly closed allowing water to enter the hull. In general, less expensive, lower quality boards with or without vents can be very prone to sun delamination, especially at altitude, and higher quality boards, are less prone to delamination. A board bag is a great investment to keep your SUP from baking when you car top on a sunny day.

Fins, Traction Pads, Carry Handles and Leash Attachments

Fins – All SUPs come with either a single fin (skeg) or a thruster (triple fin) setup. The fin(s) help the board to track in a straight line. Most SUPs will accept skegs of various sizes into a built-in center box system. Center fins can be adjusted fore and aft in the box and locked in place with a stainless steel screw. The side fins in a thruster setup are generally fixed in place with an allen wrench type screw. Single fins are generally produced on longer planning hull SUPs and touring SUPs and thruster systems on planning hull SUPs designed for both flat water and surf. Fins are either fiberglass or plastic construction. On rivers it is important to use plastic or flexibile fins as they tend to slide over rocks without damage while fiberglass fins will stick and split.

Traction Pads –   Most SUPs have a factory installed foam traction pad, but some don’t, so always ask about that. A full length traction pad is nice especially when you want to bring along your dog. (Fido will want to hang twenty on the nose a lot and the pad will help her stay on board). Aftermarket pads and traction wax are second and third choices by far. A well designed pad can also help reduce foot fatigue.

Carry Handles – Due to increased width of a SUP compared to a surfboard, most SUPs will have a built-in recessed carry handle set at the balance midpoint so the board can be easily carried.

Leash attachments – This is a small plastic recess in the hull with a stainless steel crossbar for attachment of a leash. Standard surf leashes that attach with Velcro to your ankle are suitable for ocean surf and flat water only. For river use it is mandatory to modify leases with a “quick release” device attached to your coast guard approve life vest. Without a quick release, a SUP leash should never be used on the river due to unacceptable entrapment hazard.

Board Dimensions

Width – As a general rule, SUPs with a width at or near 32 inches are designed to be very stable although they will be a bit slower than a narrower board of the same hull design. When the width gets narrower down to 28-inches the board will generally feel much more tippy, however it will likely paddle a bit faster.

Length – The length factor is a bit harder to quantify. Length, width and especially volume all interact to determine how a SUP will behave. For flat water paddling, increased length can produce a smoother glide than a shorter board of comparable design. A 12-foot long SUP can be great for a heavier body weight paddler and a 10-foot long board can be great for ease of transport while still suitable for all weights (see volume below).

Volume – (thanks to Whitney Guild for the following analysis)

“Surfboard volume ratio to rider weight – Usually a shortboarder will want around 33 to 35% of his body weight in board volume. A longboarder will want a 1 to 1 ratio or 100% of his body weight. (hi performance longboard 90%). SUP board for Beginners, 2 x your body weight. Intermediates 1.7 x and Expert SUP rider, 1.3 x their body weight. (the Guild Factor). I believe this aspect of understanding volume will really help customers dial in the right board for themselves, especially for new surfers and SUPers. Examples: I weigh 80 kilos and my longboard is 72 liters= 90%, my SUP is 106 liters which is 130% of my body weight. In Volumetrics 1 liter floats 1 kilogram of weight.”

So, if you weigh 160 pounds (160lbs ÷ 2.2lbs/kg = 73kg): Beginner SUP, 73 x 2 = 146 liters. Intermediate SUP, 73 x 1.7 = 124 liters. Expert SUP, 73 x 1.3 = 95 liters

Epoxy SUP Fin Box Replacement

The following explains the steps in replacing a fin box on an epoxy SUP.

1) Scribe a rectangle around the damaged area with a sharpie pen. Use a Dremel tool to cut along scribed line through the epoxy skin layer and slightly into the eps foam. After removing the epoxy layer use pliers and a chisel to remove the damaged plastic fin box.

2) Clean out and level the excavation using a small chisel to prepare an even base for the replacement fin box. The wood stringer takes a little extra effort.

3) Center the replacement fin box and check that it is level. The bottoms of the 4 tabs should be level with the adjacent undamaged areas. The portion of the fin box above the tabs is elevated above the final surface of the board and later must be removed with a chisel (see step 6).

4) Tape securely over the fin box to prevent entry of liquid epoxy resin. Do a final check of level (N-S & E-W). Fill void surrounding fin box with slow cure epoxy resin.

5) Gently place a cutout of fiberglass cloth on top of freshly poured resin surrounding the repaired area.

6) Saturate fiberglass cloth with resin. Keep overfill minimal to reduce sanding time. After resin has hardened, use a sharp chisel to remove elevated portion of fin box.

6) Sand chiseled fin box and repaired areas smooth. Start with 60 grit, then follow with 100 grit and finish with 220 grit. Install fin!  For colored boards a painting step would follow.

If you have any questions about or corrections to the information in this primer please let us know

2 thoughts on “SUP Technology”

  1. Thank you for this information, it was very helpful. I am in the market for a new paddle board and it sounds like epoxy is the way to go. I have 2 “fiberglass” boards that each, after 3 years of regular use, really look beat up, since they are on a rack on our dock. I would like to visit your sales center, if that is possible, to shop.

    1. Jan, thanks for the comment! We would love to have you come down to the shop, but you might find our inventory is very limited at the moment, and we only have a couple of displacement hull 12’6″ boards as of right now and I don’t plan on ordering any more hard/epoxy boards for this season. Our hours are Tue-Thu 11-4 and Fri-Sun 10-6

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.