I’m about to start my 11’ SUP. I’ll be hotwiring my blanks from 2 lb. EPS. Normally I use PVC/ Komatex stringers. How thick should I go with the stringer, 6 mm, 9 mm? Also, is there any advantage/ disadvantage to doing a double or triple stringer? Is there a rule that the stringer width can be thinner if doing multiple stringers, or do you still need the primary width for strength and support?
Jonah,
Have you been able to find pvc foam over 10’? Otherwise do you have a plan to get the length required for the 11’ SUP?
Dave_D
Jonah…
On a board of that size I usually use a single 6 mil stringer. Anything more than that just adds to the weight, and because the PVC is ductal in strenght, bigger is not necessarly better. In order to lengthen the PVC, I extend the 8 ft material by making a dove tail in the stringer thereby adding structure to the extension.
Good luck on your project!!!
Ken
If I can’t get 11’ Komatex, would it be better to use 10’ + 1’ or 8’ + 3’ pieces? Should the dovetail be towards the nose or the tail?
Jonah…
The standard size for the Komatex is 4' X 8'. You can sometimes find 10 ft pieces, but usually only in white, (I have some 10 ft sheets) but is hard to find. As you are going to glass the board, much of the boards strength and stiffness will come from the geometry of the rails. If this is to be a SUP, you will more than likely want to add additional laminations on the rails as well in order to take up some of the damage done by paddle strikes. But back to the stringer...I would simply use the 8 ft sheet and dove tail the additional 3 ft with the joint at the nose end. Puting the joint near the fin box and riding location will tend to put more stress in the tail section. Try to find an adhesive that will stick to the PVC without cavitating the foam. I use a special water base adhesive, but it's not readily available.
I look forward to seeing some photos of your project on Sways!!!
Ken
…PVC called Sintra is good or not for a SUP stringer?
I am not familiar with Sintra. There are a number of manufacturers of PVC sheets. Keep in mind that the PVC used for surfboards is called PVC Foam, and not like your tempered PVC water pipe. I tried some of the tempered stuff way back when, and it made the board quite stiff, the material fractured, and was a general pain to work with. I use the Komatex brand, but only because it’s available. Sorry…not much help, but I will look into the Sintra product.
Ken
After doing some checking, it looks like the Sintra should work just fine!
K
…yes I supposed, but very difficult to obtain more than 8´ in a 1/8 or 1/4 thickness
…PP comes in rolls, but I only saw less than 1/8 in thickness. Also I dont know if there s a glue to glue PP to the foam…
Reverb…
You have indicated that PP is available in rolls. Poly Propalene is a material that is difficult to bond to. Nothing sticks to PP! Since you are bonding EPS foam to the PVC foam, and then glassing the whole package, there is no reason to make any major effort in using a single piece of material for the stringer. I have made over 50 of the big boards with PVC and never had a failure. Another option is to use basswood, if the concern is a jointed stringer. It is good to look at other options and materials, but I would suggest you do a test sample before risking a lot of time and effort. Al;so keep in mind that you can get a chemical or mechinical bond or a combination of both. Adhesives allow you to bond disimilar materials togeather, but the adhesive must obviously bond well to both materials.
R & D is half the fun!
By the way… I looked at your homepage…great looking boards!!!
Ken
…Airframe, I dont find basswood in that lenght right here
but still that board is in the sketch
thanks fella
The low and dirty info on a pvc stringer. Yesterday I layed out my pvc stringer for my 11’ SUP, this thing, by the way is a bahemoth! What we did, was cut two stringers long enough and then glued them together with the cuts at different ends of the stringer. The sheets we used I believe were 8ft sheets. It definently added some weight to the final product, but hey its Big Boy any who. Hope that helps some… Oh yeah, the thickness I believe ended up being 16mm or something like that, Im going to go work on it tommorrow so I will let you know for sure!
Peace,
Anthony
If weight is not an issue, then the T-Band idea is great. I would think a double 3 mil (1/8") in a T-Band configuration should be enough, but use what you have! What glue/adhesive are you using for the stringer and foam?
Ken