Can I add a stringer to my Stringerless 7 surfboard?

General Discussion
1

Can I add a stringer to my Stringerless 7 surfboard?

I recently bought an 8ft. 7s superfish III carbon fiber surfboard.

8’ long x 23"wide  x 3" thick = 61 Liters volume

It does not have a traditional wooden stringer. I love the board. That’s the good news.  The bad news is that within 3 months from purchase the board has completely snapped in half once and buckled twice. I have had the board professionally repaired each time.  The repair shop did an amazing job. I notice no difference in the performance of the board. But the repair shop and I believe the board is just too fragile in the 8ft long dimmension for the surf conditions where I live.  I would like to strengthen it to prevent the almost certain future buckle or snap.

Could I route a channel in the board 4 inches from the center fin box to about 4 from the nose? Then glue both sides of the stringer and insert into the channel. Then glass over top and bottom.  This way I do not have to cut the board in half.  Since I am retired and kind of a handyman  I would enjoy turning this board into a project board. I know it will change the surf carchteristics of the board but at this point one more break and it’s going to be a coffee table. Am I crazy?

Any suggestions/advice?

I am an intermediate level surfer, 56 years old 6’1, weigh 185 lbs. I have been surfing now for about 2 years. I live and surf in  Dominical Costa Rica 3 days a week in approximately head high surf. When it gets 2-3 ft. overhead I do not go out because I wish to surf another day. I am so glad I discovered this sport!

2

…hello; I do not know exactly the way that that brand of pop out boards are done; in the case of the NSP s the other day I was checking ones that have a Coconut fiber outside that seemed hollow at some points or overall; however, not in the lighter side; similar weight to the PU boards in that range. Without disrespect, I think that is not possible to obtain an intermediate level in 2 years at that age. Possible not beginner but still a rookie; more if you are saying that surf smaller conditions and the board condition; in fact all these type of boards are stronger for knee dents etc. You have several buckles… no way you can have those buckles because you have a radical board or surfing style…so is because your level and as you says, those beaches conditions. Ok, if you are a handyman, is better to shape or build a new board from scratch but if you want to do it with these types of boards; you ll need to use vac bagging equipment and then after all the sanding, paint over with car paint; that s the way they make them. Will be too heavy and too rigid; so more prone to break again and the ride would be no better.

3

If the stringer is not solid from top to bottom, they will be just vineer’s.

Solid stringer is like an I-beam.

Sounds like a lot of work for a board that WILL still break.

Sorry if I’m being a Debbie Downer.

4

Routing wood strips into the top and bottom will create a faux stringer like those found in 60s popouts. It will add no strength and probably make the board worse in many ways. You might want to think about getting a better board from a reputable manufacturer. Although, these days many so-called ‘top name’ boards also snap with ease. You may be better off with a Wavestorm, in fact.

5

Thank you for taking the time to read and reply to my post. 

“Without disrespect, I think that is not possible to obtain an intermediate level in 2 years at that age. Possible not beginner but still a rookie “ 

No disrespect taken.  Maybe “beginner improver”?  Rookie, yea, definitely yea, I included my level of experience only to paint the picture.  I am sure that some of the damage is due to my lack of experience. 

Routing wood strips into the top and bottom will create a faux stringer like those found in 60s popouts.

If the stringer is not solid from top to bottom, they will be just vineer’s.

Solid stringer is like an I-beam.

Understood, I was not clear.

The stringer I had in mind would be from top to bottom.

  • **The plan would be something like this:**
  • **Cut the slot in the surfboard.**
  • **Plane a wood board the thickness of the slot.**
  • **Insert the wood board into the slot.**
  • **Draw trace lines onto the board.**
  • **Remove the board and cut according to the  trace lines to  shape of the stringer to match the boards profile.**
  • **Apply adhesive to both sides of the stringer and into the slot.**
  • **Insert the stringer.**
  • **Clamp the board with gentle pressure with bar clamps and let cure.**

After the above I would start the glass process which I realize involves a lot research and many patient steps.  Plenty of advice about that on Youtube.

**I think my real question is: Can a top to bottom stringer be added without cutting the board entirely?**

**How might it change the performance or integrity of the board?**

As I said this board the board is one wave away from becoming a coffee table. I am retired so I have the time.

And of course I will be getting a new board.  As soon as my wife will let me.

6

Seriously?

With all due respect to my fellow Swaylocks participants, I disagree… routing a slot in the deck and bottom with glassed in partial thickness stringers will definitely add breaking strength. Saying it would add “no strength” is just plain wrong and some simple loading tests on sample panels would prove this quite easily.

A basic understanding of sandwich composite/I-beam theory would reveal that even a strip of wood on either side, especially when reinforced with fiberglass inside the slot, will enhance the strength of the tension and compression sides of the sandwich.  Just a simple glass layer on either side of the foam core adds a lot of strength and stiffness but slots, wood and ‘3-D’ fiberglass shaped inside the slot add additional strength and stiffness.

Lots of stringerless boards are being made these days with slotted rails to achieve a corrugation effect in the glass job.  The boards with slots alone are definitely stiffer than a ‘flat’ glass job.  Adding wood strips to the glass inside the slots?  Stiffer still.  

I’m not an engineer - the extent of the strength increase would be determined by the depth of the slots and thickness of the wood. There really shouldn’t be any doubt that there would be an improvement.

The slot/stringer installations would of course need to be ‘capped’ with additional layers of glass. Although more for water proofing, even these additional capping layers would impart some additional strength.  

 

7

OK - I remember surfing Dominical, Costa Rica - that is a serious wave.  I remember getting my ass kicked on an 8’ day there…  There are a lot softer waves in that area…  If you go surf Manuel Antonio or one of many other breaks around there, you are not likely to snap the board in half and can actually surf 2x overhead waves. :wink:

I stayed in Dominical the first time I went to Costa in the 90s.  Since then I have mostly surfed in the northern Guanacaste pinunsula.  I like Nosara…  But the breaks around Tamarindo are pretty good too…

8

John is right. Rout at center and instead of wood laminate UD glass mesh. Don’t need to go deep about 3 to 5 mm, same width. Center part of a stringer only experiment shear forces with low intensity compare to tensil/compressive forces at skin. Most decent foam are able to take this shear load. That’s basic of flexural work…

9

Could you post pics of the board and the repairs it has had so far?

 

10

Thanks again for all the helpful replies.

da5id

“OK - I remember surfing Dominical, Costa Rica - that is a serious wave.” 

You are right about that! I grew up in Florida near Daytona Beach and I used to body surf there. But when I got to CR. I was surprised/shocked how powerful Dominical Waves could be.

Magic Seaweed spot guide for Dominical 

3-12 Swell Range

Dominical is a laid-back surf city, less developed than Jaco and Tamarindo, with a highly consistent, strong barrelling beachbreak at Playa Dominical. It can hold serious size without closing-out, gets bigger near Rio Baru rivermouth, but broken boards and drownings are frequent here.

johnmellor

“Seriously?

With all due respect to my fellow Swaylocks participants, I disagree… routing a slot in the deck and bottom with glassed in partial thickness stringers will definitely add breaking strength. Saying it would add “no strength” is just plain wrong and some simple loading tests on sample panels would prove this quite easily.

Also

Lemat

John is right. Rout at center and instead of wood laminate UD glass mesh. Don’t need to go deep about 3 to 5 mm, same width.”

The above sounds like a better more viable solution I am going to do more research on the UD glass mesh.

Also

Partial cut and past of Green light surf supply’s response to my question

Thanks for your interest in Greenlight.

Yes, you can certainly route a pocket down the centerline of the board on the bottom and shape a stringer to fit both the deck and bottom curves. 

You’ll want to glue or epoxy the stringer in and fiberglass over the bottom again. 

It will keep the board alive for more surfing fun!

 

Newschoolblue

Could you post pics of the board and the repairs it has had so far?

Yes I will do that.  Also if I choose move forward and add stringer/Stringers I will document and post results.

“Measurement is the first step that leads to control and eventually to improvement. If you can’t measure something, you can’t understand it. If you can’t understand it, you can’t control it. If you can’t control it, you can’t improve it.” 

― H. James Harrington

11

I’ll throw another idea into the mix and suggest you do another layer over each rail for the length of the board. Go Carbon if you want it fancy. It will stiffen the board up but also strengthen it without cutting into the integrity of the core.

12

Your idea sounds workable enough. I might suggest trying to use a foaming glue like gorilla glue if you have it available in order to fill any gap and help make solid contact with the core.  Light clamping would be wise just to make sure it doesn’t widen the slot (and the board).   It also strikes me you could leave your stringer material slightly proud of the groove while gluing, then bring it down nice and flush with a block plane and sanding block.

 

13

I made post stiffner on a batch of board that buclkled. At that time i try to make stringerless boards with reinforced rails, some with carbone other with glass, deck buckled on massive impact, waves here are strong too. So i route a slot on deck, at center on top of crown, and laminate in UD mesh then cap with a 2" 40z glass tape.
Some board resist well better after.

14

Hola D-

What if…the stringerless construction allows the board to bend past the point where the carbon fiber is failing?

I would be concerned that the surface repairs are just stress risers at this point. So, if one could ‘uncouple’ the bad and ‘recouple’ in some goodness…

Add the stringer, strip the carbon 2" off the rails, glass whole thing like a new board 2 layers 4oz each side with healthy laps.

Now the key structural members (rails, stringer, shell) are fresh and unified and the old carbon and repairs are a lesser part of the system.

I am only 10 boards deep so take this for what it’s worth, ramblings meant to inspire thought…

EDIT: I just saw the added pictures of the board in question and read the manufacturer’s write-up online. The board is not carbon fiber cloth, it is stringerless EPS with carbon fiber ‘vector’ net on the bottom. I like Wrcsixeight’s post for a ‘been there done that’ point of view.

15

“I might suggest trying to use a foaming glue like gorilla glue if you have it available in order to fill any gap and help make solid contact with the core.”

That is my first choice if I go with the wood stringer and I can get GG it here in CR.

“leave your stringer material slightly proud of the groove while gluing, then bring it down nice and flush with a block plane and sanding block. “

Excellent advice!

How many inches /mm  beyond the stringer should I glass and how many layers?

Any thoughts on that?

16

“instead of wood laminate UD glass mesh.”

 

Did a search for “UD glass mesh” but not getting much on it.  Can you please direct me to where I can get more info for it? 

 

Thankyou

17

I had a 9’3"x22x3 pintail that was about to snap in half with stress cracks over much of the bottom. When I rode it with a smaller fin, I decided I could not let it snap in half.

 

I routed 1/4" deep slots, deck and hull over the stringer.    Next to the fin box, I added two unequal length stringers full depth , but tapering to zero in the foam… 30 and 40 inches long. Under the 3.5" wide  deck plank, and 5 inch wide hull cedar plank was a layer of 6 oz cloth saturated with epoxy.

 

Once both sides cured, I sanded the cedar flush, and the bottom got a 6 oz strip covering the plank + 1 inch either side. and the hull rehot coated.

 

The deck, I routed 3/4 inch wide strips rail to rail about 3 inches apart nose to tail, trying to not go through both layers of  original 6oz cloth.  Into these recesses, I pulled prewetted carbon fiber roving  tightly, which ‘bridged’ the massive and many heel dents.  After sanding the edges of the CF, I glassed the deck, no rail wrap, with 4oz cloth pulling it tightly, Not so worried about the ridges over the CF.

It gained about 4 Lbs.  It lost a flot of flex.  I do not miss it.  I ride the Piss out of this board upto double overhead.  Underwater cartwheels bearhugging the thing, I have no fear of it snapping underneath me.  The ‘I beam’ strength effect on this board is rather absurd.  I was afraid the extra weight and extreme reduction in flex would kill the way the board rode.  My first surf post reinforcement I left the water laughing like a maniac, and I have put many many miles on it in the 4 years since…

 

The rails continue to get beat up, but the deck is not getting any softer.  No delams.  I have had to fix one ding on the deck where the glass cracked next to the CF strips.

 

When I inlaid the planks I was afraid the board might split along the length .  the CF strips rail to rail were initially ntended for holding the two halves together, but then I went a little overboard bridging the soft spots.  It has shown no further stress.  The former stress cracks on the hull  have not reopened.

 

Making a new board would have been Way less work, but the board was the 3rd I ever shaped, back in 1997.  It was from a 10’6" blankI intended to be a noseryder, but Hurricane Linda came and went, so I cut into it deeply to get it to a narrow thin 9’3" pintail, meaning it is soft.  It was also my first glass job.

Very imperfect, but very fun to ride.

 

If you are going to inlay a plank with a router, You can add a little 1/2 or 3/4 deep partial ‘stringer’ to it to add more strength via the half “I beam” effect.

 

 

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Yes you can do all of the above. It will certainly add “some” strength.  How much is questionable.  I’m surprised that somewhere along the line in the numerous times you had this board repaired; the person doing the repairs didn’t recommend a wooden insert.  Lowel

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One gallon or five gallon paint sticks and a quarter inch router bit do the trick.

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Pics of repairs  Bear in mind I told the repair shop I did not care how the board looked cosmetically. 

The area with the carbon fiber X’s are the buckles The area to the right of the X’s is where the board completly snapped.

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