EPS Stringer vs. Stringerless

OK, I know that this has been discussed in the archives many times, and believe me, I have read all of them. But I still haven’t come to a conclusion.

My question is, therefore, is a stringer necessary, or beneficial, to a #2 EPS surfboard under 6 feet?

I have read so many posts in the archives, and get alot of conflicting information. I am under the impression that a normal stringer does not add a significant amount of strength, and is in the wrong location to add performance. Bert and Greg have commented that a parabolic stringer setup is far superior in terms of performance. But others have said that it isn’t wise to build a stringerless board?

I myself have built both stringered and stringerless EPS boards, but they have been for other people, so I have never been able to ride them for a long enough time to develop a sound conclusion. I haven’t heard anything negative about the few stringerless boards I have built, so I am a little unsure about which is better.

Whats the deal??

You can build a board that is short enough (low bending moment, low strain) and thick enough ( so that it doesn’t require a stringer to keep it from snapping. Generally, in sandwich construction, stiffness increases exponetentially with increasing thickness (7-fold when thickness is doubled, 37 fold when doubled again). How about a 5 inch thick board?

I think if you are talking 6 feet plus or minus and not less than 2.5 inches, stringers are just added weight, just lines for shapers, just decoration for the glasser.

Actually, someone here turned me on to a great little book: “Understanding Airfcraft Composite Construction”. there is an antecdote about hanging a 1000 pound weight on a chain and a bungee, each capable of carrying 600 pounds. They don’t hold 1200 total. First you have to connect the bungee and let it carry say 550 pounds, then connect the chain and continue to lower the weight. the bungee has to be given a lot of stretch to carry its share of the load , but the chain does not.

Apply this to composites. Some aircraft wings are made mostly with epoxy and E glass, but with carbon on the spar caps. Carbon is much stiffer that the glass, so the carbon willl carry nearly the entire spar cap load. If any glass is used in parallel with the stiffer carbon, the glass componet is essetially wasted because it will never experience enough strain ( stretch) to carry a useful load. the carbon gets nearly all the load. Same with stringers in many circumstances. Short board don’t put a strain on the stringer. Stringers are therefore just heavy decoration. Longer (How Long?) boards do. strain the stringer.

Flex is another issue. Some like more , some less,

Please deposit $0.50 for another 2 minutes. Refunds maybe requested at the desk.

I think your going to have to give it a try yourself to see if it works for you. Greg L told me he likes 1#EPS with no stringer glassed 4/4/4 top 4/4 bottom. He said they flex unreal. So at 2# the board should be even more durable…give it a shot.

Greg, thanks for the response. I really liked the chain vs. bungee analogy…although you sound like one of my engineering professors, haha. Do continue if you had more to add, please!

J. Troy, thanks as well. You make a good point, I had heard that Greg seemed to support the idea of stringerless boards, but others seem oppossed, which i think maybe because of the idea of building a stringerless board is sacreligious to some, or make them think of a stiff popout. I don’t know???

Anyone else…I figure this would be a popular topic since so many of us are building out own blanks now…

On a side note, not to hijack my own thread, but I glassed my last stringerless board 6x6 top, 6 oz bottom. 2 # density. Is there an advantage to glassing 4x4x4 top instead of 6x6, since it all adds up anyway?? Anyone care to help me with that one??

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Greg, thanks for the response. I really liked the chain vs. bungee analogy…although you sound like one of my engineering professors, haha. Do continue if you had more to add, please!

J. Troy, thanks as well. You make a good point, I had heard that Greg seemed to support the idea of stringerless boards, but others seem oppossed, which i think maybe because of the idea of building a stringerless board is sacreligious to some, or make them think of a stiff popout. I don’t know???

Anyone else…I figure this would be a popular topic since so many of us are building out own blanks now…

On a side note, not to hijack my own thread, but I glassed my last stringerless board 6x6 top, 6 oz bottom. 2 # density. Is there an advantage to glassing 4x4x4 top instead of 6x6, since it all adds up anyway?? Anyone care to help me with that one??

They say 4/4/4 is stronger than 6/6

So youve already built a stringerless board? How did it ride?

we’ve done stringerless but since we wrap the deck balsa over the bottom balsa they don’t flex too much…

I have a concaved deck 7’4" x 22" x 1.5" thick one that does flex though but the rail isn’t wrapped… so thin it’s hard to paddle.

They feel really soft when you squeeze them but they don’t seem to flex…

For me, I prefer stringers even if it is an EPS because it is easier to shape for the following reasons: 1) the stringer provides strength when I am foiling the nose and the tail. These areas can be too thin and will flex and sometimes break while shaping w/o a stringer. 2) The stringer provides a point of reference to assure symmetry when you are cutting out your plane shape. I have a heavy shaping hand and I don’t quite have the “shaping eye” perfected yet. I am a better glasser than shaper so need all the help I can get. For weight issues and shaping ease, consider using high density foam for a stringer… just like to keep things simple.

Mahalo,

D

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Greg, thanks for the response. I really liked the chain vs. bungee analogy…although you sound like one of my engineering professors, haha. Do continue if you had more to add, please!

J. Troy, thanks as well. You make a good point, I had heard that Greg seemed to support the idea of stringerless boards, but others seem oppossed, which i think maybe because of the idea of building a stringerless board is sacreligious to some, or make them think of a stiff popout. I don’t know???

Anyone else…I figure this would be a popular topic since so many of us are building out own blanks now…

On a side note, not to hijack my own thread, but I glassed my last stringerless board 6x6 top, 6 oz bottom. 2 # density. Is there an advantage to glassing 4x4x4 top instead of 6x6, since it all adds up anyway?? Anyone care to help me with that one??

They say 4/4/4 is stronger than 6/6

So youve already built a stringerless board? How did it ride?

I built 2 stringerless boards, but unfortunately none were for myself, so I never rode either of them…the riders couldn’t really explain the flex to me…

Uncle, shaping flex was a concern, i actually have considered building a rack that would help support the board in the center…

oneula, what would you think if I were to just glass normal…no skins?? You have a ton more experience than I do, what would you think?

We have built 5 stringerless shortboards from 6’-6’6". The 2lb and 2.5lb EPS blanks were split in half, we used epoxy with black pigment to glue the two halves together. Mostly for the ease of machining/finish shaping. The boards were sent to a guy who surf’s OB (bay area) can be a little demanding! The surfer is very experianced from Kailua HI and had never ridden a stringerless board! hes still yappin about them. Says they have a nice spring to them. Not one has snapped yet. (surprisingly) The only issue was when laminating we gained some rocker. This was fixed by Gregs recomendation to lam a strip of 1" tape on the bottom of the board to help hold the rocker. I think we will be building more of these soon. Our glass schedule was 2x4 bottom 2x6 deck and 6 bottom and 2x6 deck. Kinda fun to build them no stringer drama’s…There all good different strokes for different folks.

Good luck.

Meanshapes,

Did you do anything with the glass to increase strength ie big laps, uni-directional etc? and does your client feel differences between the 2# and the 2.5#?

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Meanshapes,

Did you do anything with the glass to increase strength ie big laps, uni-directional etc? and does your client feel differences between the 2# and the 2.5#?

Same question here!!

Meanshapes, great post. Its good to see that many people have had success going stringerless…

Thanks all!!

I watched Sam, one of Greg L’s RR guys, shape a stringerless board at

Surf Expo. He told me he has done a few and has only broken one. He was

using some type of fabric material along with 4oz glass to laminate. I

never had the chance to ask him what it was. Maybe if Greg reads this

he could let us know what Sam was using and why.

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We have built 5 stringerless shortboards from 6’-6’6". The boards were sent to a guy who surf’s OB (bay area) can be a little demanding!

<span style="font-size:6px">OB -- you are saying Ocean Beach?  That place is hell on earth.  Big, cold and heavy.  That is certainly compelling if stringerless can handle that place.</span>

My thoughts are…the foam flexes more than the glass. Hit the bottom or something and you are gonna have a nice big buckle across the belly of ur board. Talked to forstall about this earlier in the week. We were talking about wood and pvc stringers though.

Syntex

A polyester laminating fabric. Sam/GL recommend 4 oz or 6 oz Syntex and 4 oz glass, and that it be used with RR 2020 epoxy resin.

http://www.oneoceankayaks.com/Abrasion.htm#syntexanch

The laminator added little length on the laps, and the 1’ strip of tape before the bottom lam to help hold the rocker. I was kinda holding my breath when we sent the boards. I did expect them to break as the OB I’m reffering to is in N. Cal. So far so good. The surfer riding them is very experianced and it is hard to get him to try something new. I think the call I got when he opened the box was. “What the F^&k! Theres no wood man! You guys forgot the stringers! We have gone through many boards together. As far as epoxy goes his flavor at least for this month is stringerless. me myself do not expect the boards to last long. The 2.5 is actually a 2.75lb EPS we used in the 6’6” board. He liked that board the least. With how excited he was when he gave me feedback on the 6’2", He said over and over he was able to make sections he normally wouldn’t. Maybe its the crooked outline? or maybe he dropped a few pounds, maybe he is surfing more cause he has a few new sticks. he has had them for a few month’s and surfs often. No worries so far. Whatever it may be its fun to try it all. Good luck!

Yeah, the syntex stuff is pretty amazing. I was really impressed with a couple of guns sammy showed me. As light as can be, and he punched them super hard to show me how durable…he didnt even dent them. Anyone know where Sammy gets his? I have reached the end of the internet, haha, and still haven’t found what I am looking for. DK?? Has Sammy given you any details??

DK, what did Steve say about stringerless…care to go into more details??

Meanshapes, thanks again…good info.

Basically I’ve been buying the 1.4lb and 1.8lb molded EPS blanks from Jim Richardson at Surflight.

So far I think I bought 6 of them.

He used to charge $45 without a stringer and $65 with a stringer. So I bought half with and half without cause I didn’t really want to shape them too much and ruin them. I’m sure the price has gone up since then.

They came out of the mold as Jeff Johnson 7’6" funboards with a slight singet to double to vee bottom about 21.5" wide and 2.75"thick. Like Jim told me if you like the design just clean off the mold and pour marks with some light sanding and you’re ready to go. The board will lose their rocker if you don’t use them right away or when you lam or vacuum them without support.

I built two wood lammed funboards with nothing but some light sanding before putting on the skins… I believe it was 4 under and 6 over on one and 6 under and 6 over on the other. Both came out super light especially the balsa one. We did one in all balsa and one in birch and mahogany. We even took the balsa down to Jim and Jeff to show them our hack work…

Eventually I found I didn’t like the ride of that shape in that weight…

You can re-rocker their stringerless blanks anyway you want if you glue in your own stringer which is what Jeff did to create a 6’8" he wanted to machine on Eric’s machine as a test but I bought that blank and made a flyer out of it. The other two stringerless 1.4lb 7’6" blanks I got at the same time, I built a 7’4" Stubb-Vector design with a more pulled in nose instead of the classic big round nose fun board design and a full on round pin 7’2" minigun I haven’t even used yet… The 7’4" is purpleheart/bamboo/sycamore and the 7’2’ is balsa/bamboo. I like to use the bamboo now as a deck patch cause it’s hard as rock after glassing.

I haven’t done a board without wood skins yet cause it defeats my goal of getting something stronger than the average bear from something wimpy like foam. So I can’t relate to what you and Meanshapes are doing. But Jeff Johnson did show us some boards they were building for Andy with no stringer under 4lbs one layer of 4oz glass on the bottom and 2 layers on top with a deck patch. Good enough for at least one heat or contest which is all the pro’s were interested in anyway… I think they are trying to get away from 1-2 heat poly boards the pros are using and get something with the same weigh and performance that lasts a couple of contests.

We also make our own blanks out of .75-1lb Lowes roofing insulation (Insulfoam) and those boards come out way light a little too light for my liking which is why I’m double layering the sandwiches now for added strength but also for more weight. We haven’t had any breakage but some delams when we used spackle versus not using it. The DAP spackled boards do come out lighter…

Everyone told me I couldn’t go bigger than 6’6" for a stringerless but we’ve gone a foot bigger. I don’t know about 8’ and above though…

In all honesty, I’m a firm advocate of a this new “composite” structure kind of like Airframe and Greg’s new blanks.

Soft real floaty inner core surrounded by a tough skin and a perimeter stringer and higher density rails to push the weight out to the rail line. In the 70’s I used to tape lead fishing sinkers to the nose of my boards to get a pendulum effect out of those big bottom turns we used to make. It looked stupid but I thought it worked great… The perimeter stringer high density rails and strong flexing skins I think are a modern version of that lead sinker technique we used to use… There’s another version Jim’s doing at Surflight which is the exact opposite which is even more intriguing but alot harder to pull off.

I think 2 bottom 3 top with a deck patch with 4oz would be fine for a stringerless shortboard. Look around for some of this new glass you can get from places other than surfshops… The fine weave airplane stuff is pretty good if you can get it…

Don’t worry though cause nothings permanent…nothing

“Anyone know where Sammy gets his?”

Call him.

You can get the number here.

http://resinresearch.net/

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“Anyone know where Sammy gets his?”

Call him.

You can get the number here.

http://resinresearch.net/

I have talked to him about it before…his answer was, “you can find it on google.” I asked if it was a secret, and he said, “no.” He said just to look on the internet. I have looked, and I haven’t found a thing…

therefore, i think you are right. Maybe its time for another trip to RR…I need more resin anyhow.

Oneula,

Great post…I really appreciate the info, and your willingness to go into all the details. Its guys like you that make swaylocks the best site in the world!!

So, I am still on the fence with the issue. I am definetely going to try a few stringerless boards myself, as well as try and build my own perimeter stringered blanks soon. Plus I plan on playing with some different glassing schedules, and some alternative cloths. Basically, I am gonna spend alot of money, and see where I end up. Luckily I have a whole willing test team of surfers, who love the idea of a free board, or a board at cost, so hopefully there will be lots of feedback!!

Lets keep this going, hopefully this thread can benefit others as well. I’d love to hear Greg’s and Bert’s input. Airframe’s and Benny’s too! And everyone else’s for that matter…I am thankful for the opportunity to learn from all of those far more experienced than me…