After a brand name foil board de-laminated/opened up behind the the foil mounting channels inside 2 years of ownership, I started looking at the structural differences between production boards, surfboards and foil boards. Basically a surfboard works on the principles of hull (hull pressure) and a foil board works on the principles of a beam (bending moments). as you can imagine, there's been a lot of ducking and weaving from both the shop who sold me the board and manufacturer over the design errors.
In the process of fixing this board, a few discoveries have been made, no vertical component to the board and no epoxy or glass reinforcing in the board. I ended up drilling holes forward and aft of the mounting channels and jacking the bottom back into place with the track screws and a bar. I then used a TIG wire to make a small passage for epoxy flow through the foam and discovered voids next to the channels. Prior to infusing epoxy, I applied vacuum to the aft hole and sucked out over 150 mls water out of the board. I then infused 250 grams of epoxy in through the front hole.
Reason for this post is, I'm considering writing a magazine article and would like some data / figures on similar failures.
I'm also tempted to push for kite board manufactures to disclose the boards strength details, i.e stringers, reinforcing and cross sectional views and information on the board, when its offered for sale.
Buy something that has a full PVC or pawlonia core, or build your own - looks like you're handy enough.
EPS core boards need to be be built with a lot of care and skill to be both light and strong, and this is at odds with the business model of big manufacturers that generally play a low-production-cost numbers game, banking on most failures happening outside the warranty period.
My home made pawlonia core pocket board weighs 2.5kg and has hundreds of sessions on it with no issue. My PVC board is 2kg, super stiff, and has a few months of hard work already under its belt. I thinks it's over-built and I reckon the next one will be 1.8kg and plenty strong.
Heaps of reinforcement at the front of the mount, tapering off towards the nose and tail.
Select to expand quotedjdojo said..
Buy something that has a full PVC or pawlonia core, or build your own - looks like you're handy enough.
EPS core boards need to be be built with a lot of care and skill to be both light and strong, and this is at odds with the business model of big manufacturers that generally play a low-production-cost numbers game, banking on most failures happening outside the warranty period.
My home made pawlonia core pocket board weighs 2.5kg and has hundreds of sessions on it with no issue. My PVC board is 2kg, super stiff, and has a few months of hard work already under its belt. I thinks it's over-built and I reckon the next one will be 1.8kg and plenty strong.
Heaps of reinforcement at the front of the mount, tapering off towards the nose and tail.
What Dojo said. Mine has been going strong for two years with zero issues. The two I shaped before from Pawlonia were equally rock solid. I only shaped another just to try and get the size down. Pocket board sizes are the way to go IMO. You build boats, so shaping your own should not be an issue.
Thank you for your responses and sounds like you guys are having great success with your boards.
Paulownia is great product, however other types of material can/are being used and structural structural integrity needs to be considered.
I,m very interested in brand name board failure data. I did't want this forum to be a name and shame discussion, maybe better to email your failures data to peter.designerboats@gmail.com.
Boat Builder - no, Naval Architect - yes.
My most used kite foil board has 800 hours on it. Lots of jumping, a fair bit of grinding the foil into the sand. The occasional whack into rocks.
According to the maker's web site:
"The board is built around a HD EPS core with a PVC deck and full Carbon wrap. ...."
My board is a custom with a little extra cloth over the rails to beef it up a little. The board has a deep tuttle box which has high density foam and a carbon structure going between deck and hull. It's super light.
Jumping with a smaller foil is a joy. Bad landings with a larger foil results in some nasty creaking noises but no damage so far.
All my foil boards (2 kite, 3 wing) have deep tuttle boxes. They are so convenient and reliable to use. I would have to be dragged kicking and screaming to consider using a track mount. I think the structure of the deep tuttle box contributes to the strength of the board.
I am 75kg and ride almost exclusively with a 95cm mast. Kite foils are about 950cm and 650cm.
I'm not surprised the hybrid board wasn't up to the task...
Best boards have double stringers supporting the boxes, all the way under the front foot.
Naish boards... the early ones creased in front of the foil box -- no stringers. My Slingshot has cracks in the front of box because the material under it compressed -- apparently that year of boards weren't well made. Been using it for three years like that though...
