I have 3’ wide billet eps foam. I hot wire my blanks. I have made some stringer less boards. But I do not like using the carbon fiber. To me I just cant keep it straight while glassing. It becomes wavy.
I would like to start hot wiring the blanks like Greg Loehr does right down the middle and add a stringer. I like the look of a wooden stringer and I like having that reference point while shaping.
My dilemma is for anything beyond 8’ it seems challenging to find a suitable material.
In RI I can’t find any basswood. Its all poplar, cedar, oak and pine.
So a 1x8 or 1x6 12’ board of poplar here is $30. I think that’s high. Pine for the same size is $25.
I checked out 1/4’ cedar plywood but again expensive per sheet and I assume I would have to scarf joint a couple sections in order to make a 12’ stringer.
Local lumber yards are difficult since I only want a handful of stringers.
I just think it adds a much higher cost when it comes to cutting out your own blanks.
Does any one have any easier and cost effective way to make a stringer?
I like solid wood too but I cannot split boards to use the stock efficiently so it all becomes wood chips and sawdust. It is sad to see 3/8" of an inch of lumber go out the door as chips to make a 3/8" stringer from 3/4" lumber.
I have done some longer than 8 foot stringers and templates with nicer plywood joined with fiberglass cloth and resin. If it is a stringer I will stop the cloth a good 1/4" of more below the intended finished surface, taping it off like a cutlap. If I am cutting the pieces on the CNC I will usually add some sort of jigsaw puzzle or dovetail connection and markers to say which order the pieces should go.
An easy solution is high density foam 1/4" or more thick. Corcell and divinycell are both 5lb density. You would be surprised how it stiffens up a blank and makes it more workable. You don’t mention the density of you foam core? The HD foam can be cut with a knife or razor blade. epoxy or gorilla glue and clamp. Make desired lengths by piecing together in a way to make a strong continuous piece . When clark foam close I full on made EPS blanks for 18 months using wood, PVC, HD foam. The HD foam was the easiest to complete and a few customers really liked it. Also I would just glue up two halves and use a colored glue or epoxy(no actual stringer) as a curtesy to the shaper for center line of blank easy identification. On rare occasion I have taken 2 lb eps foam and used whatever width necessary to make a speciality extra wide blank of lower foam density. Wood stringers are beautiful but time consuming to mill and in my case join together to make the length.
Thanks JRandy. I didn’t even think of doing a jig saw puzzle. Not sure if I have the proper equipment to do that. Maybe I can staple and add some fiberglass and epoxy. Thank you for the link.
Corcell and other type HD foam can be found and any fiberglass supply store or marine repair service center. I would buy it in 4’x7’ sheets locally. Where are you from? You can buy it on line. 1/4" would be fine and you could have it cut 6-8" wide and 4’ or longer shipping box length to what you could afford. Longer would be better.
I can’t draw on the computer but my joints were the shape of a chair with 4" long back of chair shape matching each other on the separate pieces. With a other than ultralight glass job your board should hold up fine. I tried many combinations where to but the joint pieces thinking I would be making it stronger but never saw a difference or had breakage bring backs. All the blanks I sold to people were hand glassed and not vacuumed bagged unless I built the whole board.
The issue for me was flopping the pieces around the shop which would easily break a simple glue joint or the adjacent material. Once I added the glass I stopped having issues.
I do this with Masonite templates too. If I am doing the template by hand I just use a butt joint with glass.
Maybe make a small piece for yourself and evaluate.
PS I am digging what BB30 is saying about the foam stringers below…
Pic attached is one of my first SUP blanks I made in 2006. The board came back into my shop this year for a new handle and Casica vent plug. I made my own gortex vents in those days. This board was still super light and water tight.
This was a double 1/8" hi density foam thick stringer with resin research epoxy glue up. When I got into the foam for the handle cut I saw all the exotherm epoxy meltdown on the 1lb foam from the initial blank glue up… It was only deep in the blank. Gorilla glue you will not get a melt down and I am sure I used fast hardener because I was wanting to get them done fast and was unaware of the problem I was creating. Even that happening, the board was fixed up and sold and should last for a long time to come.
I have done 3/16"" PVC stringers on 11 to 12’6" SUP blanks. It does make the board slightly more flexible but I tend to glass 4 and 6 oz. bottoms with 6, 6 and 6 (deck patch) oz decks or decks with 1/16" balsa inlays. with no issues. I had a bunch of PVC laying around so it was a no brainer. Below is a 11’6" SUP with PVC stringers, 1/16" balsa inlay, glassed with 6 oz. under the balsa and 6. oz. over the balsa.
What do you mean by wavy, the board warps, or the carbon cloth gets wavy?
Do you want the stringer for looks, or help shape, or strength?
I’ve made more than a dozen stringerless boards. I use deck channels for strength on the longer boards, but my longest stringerless is 8’. I also glass with at least 8 to 10 oz on the bottom and between 12 to 18 oz on the deck.
Try looking at Model airplane balsa wood. It usually only gets up to 4’ long, but I’ve done a lot of boards using a sandwich of balsa 1/4" up to 1/2" thick balsa wood to get the length I want. I stagger the joints and have at least 2 pieces for the width I want, but I’ve done 3 layers.
stringer materials in addition to what’s already been discussed:
agave (century plant) stalks. Free, but lots of labor and time. Probably can’t find any in Rhode Island, and if you harvest your own it has to dry for months. Need substantial tools to cut down round tapered stalks into useful lumber.
cheap/recycled Lumber: check your local craigslist for redwood siding, recycled fence wood, old barn wood. Often quite cheap, good sizes. Cons: nails, knots, paint.
Exotic lumber:
-Paulownia (aka Kiri). Occasionally available online, Craigslist. I bought a bunch from a guy who had cut down a tree and milled it himself. Nice stuff, just scarce
-Balsa: I got a truckload free of 4’ x 3/8" x 4", because it was used as packing material around more expensive wood shipped in from overseas. The lumber importer considered it scrap. Easy enough to glue up chunks to get as big a stringer as you want. A bit labor intensive, but cheap.
Weirdness:
I recycle old carbon fiber/graphite golf club shafts and use them as springers. Route a slot, insert on neutral axis. Lovely flex.
bb30. Thanks for the info. I am located in Rhode Island. I will start looking at local businesses and see if they carry the products. I do like the idea of using a foam stringer. It will depend if it is cost effective.
Uncled. Nice work. Love the board. I typically do 2 6oz on the bottom, 2 6 oz on the top with a 6oz deck patch. Seems to be working so far. The boards are heavy but do not ding as easy as some of the 4oz boards I previously made. I have been contemplating on using volan on the bottom of boards with one layer volan with 4oz and a deck patch on the top. We will see. I will have to experiment.
I am referring to the carbon being wavy not the board. For some reason when glassing I end up pulling the carbon in one direction and screws up the alignment. I have had difficulty fixing the straightness, so I end up just leaving as is. Its not terrible, I just want it completely straight.
I like the way a wooden stringer looks, but I also want it for a reference point to measure from while shaping. Makes things easier to me.
I may stagger the stinger like you have in the picture above.
I will try and source some balsa wood. I haven’t had much luck around here unfortunately .
Thanks. I would love to find some of that wood around here.
I may mill down some shiplap. 5 bucks for 12’. I would like to try the 5# foam recommendation from bb30. I am just trying to keep the cost down for these home made blanks. I do have several sets of golf clubs that I would love to break in half after golfing. Maybe I’ll try those.haha
I used to buy wood from a local home recycling vendor. They had all kinds lumber in various sizes, and it was all old wood, so a lot of times you can find a good piece. The new lumber is not as good as wood that was cut down 50+ years ago. If you have that kind of a resource nearby check them out.
I’ve bought Balsa from this company before. https://www.nationalbalsa.com/ The other company I used to buy from went out of business.
on the real cheap and real easy… going from blank half. 4oz fiberglass/2mm cork/fiberglass/2mm cork/fiberglass/2mm cork/fiberglass… then other half of blank and proper clamping…problem solved. 1/4" composite cork stringer. Wet cork/ fiberglass out on a ping pong table then throw between blank and clamp. Will be very easy to handle by yourself, but an extra helping hand would be best.
for straight carbon stringer, light spray some glue, compatible with foam (like3m77), unroll carbon on glue then laminate it only, move slowly, use a stiff brush. alternative is to lay resin on foam first instead of glue. laminate over only after b stage or let dry.
better than ply wood, and will not gouge or chip if lay up as described is properly clamped when joining blank together. I have never done it with a stinger but I hand made 1/2" thick stuff with same lay up and when cured make other parts with it cutting with chop saw and routing.
Pic of center box plug my friend needed. Made two of these in 10 minutes. Chop sawed cork composite, ran through planer for width and drilled holes for pin and screw with plate. If I actually took my time it would be better but it was needed in a hurry.
