new project - kayak couture

i thought i would send a picture of my in-progress project for my wife.

first, thanks to Mark Nye (consistent forum contributor) in florida for sharing a lot of ideas with me.  the design requirement began with a new boat for my wife at 105 lbs.  a high-performance, easy-for-her-to-carry, good looking boat.   basically 'kayak couture'.

not a lot of stuff in the commercial space for petit folks....and after a lot of consultations, i am building on Mark's idea of a 90% frej (15 feet by 19 inches) with help from CLC cutting the forms from the designers files and selling all the materials san's some specialty items.

now here is the trick on this build.   a goal of a complete, outfitted build weight of 22 lbs.

i have some experience doing light builds ( i have a 30lb petrel)  so i am not totally off my rocker....but the jury is still out.  based on a detailed bill of material spreadsheet and layup and checking all the figures....that's what the engineering says is theoretically possible.

so what are the key ingredients?

  • tight stripping with minimum gaps that only gain weight
  • 3/16 thick strips
  • minimilist layup schedule and will use s-glass (vs e-glass) with minimal patches for abrasion (becuase it is light enough to be carried).
  • excrutiating attention to the upcoming epoxy work
  • dispose with adjustable foot peg system  (amazingly heavy when you are a weight weenie)  and use closed cell foam for bulkheads and foot rest system
  • no screws or metal fitting
  • occasional strategic use of carbon fibre and kevlar

anyway....so far a very interesting project and am glad that i finally got started.

my wifes current boat is a Chesapeake 14....very nice....but it was time for an upgrade:)

will keep you all posted.

h


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RE: new project - kayak couture

All I can say is -- Wow! That is going to be quite the boat! Fast AND light! Keep us posted.

Years ago I built my wife a 10' skin-on-frame kayak that weighs about 25 lbs. Light weight makes all the difference in the world when a woman is trying to get her kayak on top of the car.  It's the difference between a boat she can enjoy using and one she cannot.

RE: new project - kayak couture

Hello h, Thanks for the kind words.  I believe that using 3/16" strips and all WRC will go a long way in regards to your weight goal.  My wife's boat weighs 39# fully rigged, but I carry it!  I used 1/4" strips and the Alaskan White is actually about 25% heavier than WRC.  It has a Happy Bottom Seat, adjustable foot pegs and a sked (from KayakSport).  One suggestion that may run counter to your weight target is to add a skeg.  Bjorn suggests one and I find that this boat tracks very loosely, even on flat water.  Power on, an intermediate paddler easily controls this boat, but as soon as you stop paddling, it goes where ever it wants without a bit of skeg.

 Now some questions for you.  My next will be a lightest possible Mystery for racing.

1.  CLC is cutting the 3/16" strips?  Are they bead and cove?

2.  What weight E-glass are you using?  Single layer?

3.  I have been using the CLC hatch kits with delrin toggles and stainless hardware.  I am convinced that this approach is heavy.  What are you doing for hatches?

4.  Similarly, what are you using for the cockpit rim.  I used stacked Sapelle ply which is very pretty but heavy.

Thanks for the help!

 

RE: new project - kayak couture

Hello h, Thanks for the kind words.  I believe that using 3/16" strips and all WRC will go a long way in regards to your weight goal.  My wife's boat weighs 39# fully rigged, but I carry it!  I used 1/4" strips and the Alaskan White is actually about 25% heavier than WRC.  It has a Happy Bottom Seat, adjustable foot pegs and a sked (from KayakSport).  One suggestion that may run counter to your weight target is to add a skeg.  Bjorn suggests one and I find that this boat tracks very loosely, even on flat water.  Power on, an intermediate paddler easily controls this boat, but as soon as you stop paddling, it goes where ever it wants without a bit of skeg.

 Now some questions for you.  My next will be a lightest possible Mystery for racing.

1.  CLC is cutting the 3/16" strips?  Are they bead and cove?

2.  What weight E-glass are you using?  Single layer?

3.  I have been using the CLC hatch kits with delrin toggles and stainless hardware.  I am convinced that this approach is heavy.  What are you doing for hatches?

4.  Similarly, what are you using for the cockpit rim.  I used stacked Sapelle ply which is very pretty but heavy.

Thanks for the help!

 

RE: new project - kayak couture

Hello h, Thanks for the kind words.  I believe that using 3/16" strips and all WRC will go a long way in regards to your weight goal.  My wife's boat weighs 39# fully rigged, but I carry it!  I used 1/4" strips and the Alaskan White is actually about 25% heavier than WRC.  It has a Happy Bottom Seat, adjustable foot pegs and a sked (from KayakSport).  One suggestion that may run counter to your weight target is to add a skeg.  Bjorn suggests one and I find that this boat tracks very loosely, even on flat water.  Power on, an intermediate paddler easily controls this boat, but as soon as you stop paddling, it goes where ever it wants without a bit of skeg.

 Now some questions for you.  My next will be a lightest possible Mystery for racing.

1.  CLC is cutting the 3/16" strips?  Are they bead and cove?

2.  What weight E-glass are you using?  Single layer?

3.  I have been using the CLC hatch kits with delrin toggles and stainless hardware.  I am convinced that this approach is heavy.  What are you doing for hatches?

4.  Similarly, what are you using for the cockpit rim.  I used stacked Sapelle ply which is very pretty but heavy.

Thanks for the help!

 

RE: new project - kayak couture

Hello h, Thanks for the kind words.  I believe that using 3/16" strips and all WRC will go a long way in regards to your weight goal.  My wife's boat weighs 39# fully rigged, but I carry it!  I used 1/4" strips and the Alaskan White is actually about 25% heavier than WRC.  It has a Happy Bottom Seat, adjustable foot pegs and a sked (from KayakSport).  One suggestion that may run counter to your weight target is to add a skeg.  Bjorn suggests one and I find that this boat tracks very loosely, even on flat water.  Power on, an intermediate paddler easily controls this boat, but as soon as you stop paddling, it goes where ever it wants without a bit of skeg.

 Now some questions for you.  My next will be a lightest possible Mystery for racing.

1.  CLC is cutting the 3/16" strips?  Are they bead and cove?

2.  What weight E-glass are you using?  Single layer?

3.  I have been using the CLC hatch kits with delrin toggles and stainless hardware.  I am convinced that this approach is heavy.  What are you doing for hatches?

4.  Similarly, what are you using for the cockpit rim.  I used stacked Sapelle ply which is very pretty but heavy.

Thanks for the help!

 

RE: new project - kayak couture

   Sorry about multiple posts.  Notsure how that happened.

RE: new project - kayak couture

Mark, 

thanks for the questions. 

point noted on the species of cedar...other than a trim piece, i will be using 100% western red cedar....and it will have a skeg....agreed, boats of this hull form without a skeg are not very manageable.

the 3/16th i bought from CLC were straight cut and very reasonably priced but special ordered....they gave me a an offer that was based on them cutting them  from scraps (will be staining...so no problem).    my 30 lb petrel was done with 3/16 that i bought as 1/4 inch bead and cove and planed down with a thickness planer to 3/16.   bead and cove is easier to work with.....but the extra difficulty of a straight cut was manageable given the prior experience.

s-glass (not e-glass)  4 oz inside and outside. not quite as clear as e-glass.  and you could do e-glass deck if that was a problem on the deck.....second layer of s-glass patches on bow and stern water lines ares for a bit more strength there....but no 'rub strips'.  the goal is light enough that you will pick it up and not carry it.  s-glass is a specialty item that i buy from jamestown...more expensive than e-glass...but workable like e-glass and about 40% stronger.

aghhh hatches....i think this is a bit of a toss between strap approach or delrin....but where i focus on saving the weight is the structure below.  no marine ply...i do everything with western red cedar and shaping to minimize fillet sizes and weight.  in general to avoid metal i do hatches or rigging with redfish style loops that go through the hull (soft padeye approach) ..incredibly light vs using marine stainless steel.

coaming and cockpit rim will be all cedar.  extra work but can get the same strength for less weight.

other elements that i did not mention:

- the bulkheads with be mini-cell.

- the skeg/skeg box will be custom built using cedar core, carbon sandwich.   i have a design i will adapt....but wish CLC would pick one of these designs and knock the pieces out with a CNC machine....would be a great kit option.

- any gaps (on the inside) will be faired out with epoxy and microballoons

- will use 'skim coat' approach to epoxy work as appropriate to prevent too much epoxy from being pulled into the wood.

hope that helps...happy to answer any questions.

h

 

RE: new project - kayak couture

below is picture of the petrel i was referring to at ~  30lbs

its a bit hard to see...but all the strapping is with soft-padeye approach saving the weight of (bolt, nut, washer)X24...and looks very sleek.  this boat was also done with the layup schedule and techniques described above.  However, it does have adjustable foot braces.....so a fair bit of extra weight there and an after market skeg kit (kinda heavy) and toggles that were a heavy plastic.  

when i do the square feet of area on a petrel vs the frej 90...plus imrovements based on what i learned here....i am reasonably confident i can find my way to ~ 22 lbs. 

 

RE: new project - kayak couture

   two other techniques on the petrel that helped for a couple ounces apiece:

- end pour and toggle through hulls created prior to deck fitting with epoxy/microballoons only where they absolutely need to be ...so the amount of materail is quite small,

- inside boat the hull/deck seamed neatly with two inch kevlar tape....the kevlar is lighter weave than e-glass-based tape so less epoxy weight  but incredibly strong.   the technique also involved some painters tape which was removed prior to the epoxy kicking off so the overspill/overpaint weight of the epoxy was removed from the boat (basically the kevlar went down the lane of painters tape with 1/2 inch margin edge on each side...and then once the kevlar was set, the painters tape was removed)

RE: new project - kayak couture

   I like s-glass hspira, over the cheap E-glass. Great choice. Next question, are you planning on using vacuum bagging on any part's? This alone will cut over 30% from weight.  

RE: new project - kayak couture

great question about vacume bagging.

the short answer is no.....one of the factors that is a big part of my equation is 'workability'....that is the ability to do something without specialized tools/facilitites.   so for me, vacume bagging is sort of where i draw the line with respect to what i am willing to invest in this hobby.

i might consider vacume bagging a small part (like the fin) which is relatively straight forward compared to a large part.

i would also point out, that while i agree with 30% weight savings....you can only apply that savings against the epoxy weight component of the bill of materials...not 30% against the whole bill of material (e.g., wood, minicell, glass, etc).   the reason i like s glass is i can go with 4 oz which is pretty shear so it already takes a big slice out of the epoxy weight because it is so easy to wet out and keep the epoxy layer thin.   interestingly, that is why, if you don't have vacume bagging at your disposal, carbon fibre is heavier typically than s or e-glass becuase without vacume pressure, it just holds a lot of epoxy.

based on some scenario analysis i have done...for this boat....low 20 lbs is about what i think you can do without resorting to anything 'exotic' and that is still plenty strong.

that said, if you have some ideas on how to do vacume bagging easy ...i would love to learn about it.

h

RE: new project - kayak couture

Hspira - Thanks for the info.  Any chance that I can get close up pictures and/or description of how you do the "soft payeye approach" for the hatch straps?  Thanks   

RE: new project - kayak couture

    Vacume bagging is not easy or cheap. One time I needed two vacume sources and quickly turned my air compresser into one by reversing the line from the head, worked great. The mold was 8'x12' and carbon/kevlar and honeycomb. The rest of the materials needed are not very expensive, bag, peel-ply,bleader cloth, sealant tape (dumb dumb), old air hose, and cheap vacume guage. If you draw vacume from a tank and it's set to shut off you will need a check valve (one way) from the tank to head, or let it run until it's dry.

The foam-core bulkheads is why I asked you about this. Vacuuming these is really the proper way to do them.

I have 30 years in Aerospace design and Race car fab. Just finished a five million dollar car. Google- Troutman and Barnes Special , the car is white with number 8 on her. This car was the first scarab that inspired carroll shelby to build his cobras. And he raced her.

Ask away and if I can help anyone do this, to make it easier.

RE: new project - kayak couture

   My user name didn't show up

 

Happy hooker.

RE: new project - kayak couture

mark 

soft padeyes are described here:

http://www.redfishkayak.com/softpadeyes.htm

they are a bit of work but really slick in my view.  like a lot of details, first one seems to take forever and then you rapidly pick up speed.

only caution from my perspective is that they are, like a lot of things much easier to set up (the holes that is) prior to putting the deck on.  i would describe the approach as being a more sensitive to pre-planning than through-bolting becuase the 'washer' in this technique is a bit more glass immediately backing the hole.

and as to Happy Hooker's comments, the foam i was referring to for the bulkheads is mini-cell closed cell foam...the same material used for seats.  it's a firm but spongy foam and not a structural foam that you would use in a typical composite.  that said, in kayak building they make totally serviceable bulkheads and have the advantage of allowing a certain amount of hull flex if you happen to go over the top of a rock.  the hull can compress without splitting becuase as you ride over the obstacle, the bulkheads (being soft) doesn't act like a lever to crack the hull the way a stiff bulkhead does.  they also have the advantage of being very light.

btw...your composite experience sounds great.  i used to hang out at TPI composites in rhode island.  i used to be into high-tech sailboat racing hulls.

that said...post a link to your car...would love to see it.

h

 

RE: new project - kayak couture

   H--A very interesting thread, I have it all saved in a Word document. I plan to paddle a few boats when CLC does their west coast tour and may try to build a strip kayak using some of these techniques. I would love to build a boat in the 30 pound range. I found soft padeyes on the web but could not find a good reference for your 'skim coat' approach to epoxy. Do you have a link the elaborates on that process. Mike

RE: new project - kayak couture

   Hspira--You indicated that the s glass is not as clear as the e which impacts the appearance of the kayak. Would using s glass on the interior and e on the exterior of 3/16 inch strips provide enough strength?  Mike 

RE: new project - kayak couture

was out of town on holiday....so just getting back to the thread.

on the skim coat question....basically, after prep sanding and the stage where you would do glassing, instead of glassing, you pour a small amount of epoxy onto the surface and rapidly wet/coat the surface as fast and as thin as possible.  i usually use a squeegee for this.  if you do this right, the wood will still look unfinished (not shiny) but you can tell it has had an epoxy wipe.  let it cure (6 hours)....then proceed with normal glassing.   you will be surprised how little epoxy it takes to wet down the whole surface if you move fast and use a squeegee to move the epoxy about.

the idea is this... block the pores of the wood with as little epoxy as possible.  if you let a large pool of liquid epoxy sit on the wood (i.e., the amount required to wet out cloth), a lot of epoxy gets drawn into the wood and makes the boat heavy.

you will find that you use a lot less epoxy when you do the glass over the skim coat then you would use if you did not do a skim coat.

 

on the question about s or e-glass on the exterior.....i do s glass on the hull and typically e-glass on the deck.  what i have noticed is that you can't usually see the difference between the two unless the glass is exposed to direct sunlight....and typically only the deck is going to see the direct sun.

i would do a sample with both so you can see what i mean and decide for yourself.    in my view, it is not easy to distinguish the difference between s and e unless you are really looking for it....your eyes are close to the boat and you have a lot of light.

h

 

RE: new project - kayak couture

Thanks Hspira, I am considering trying to apply all of the above to a microbootlegger with the goal of a lightweight tandem for my wife and myself. If I am pleased with the results I may follow up with a petral play. Mike   

RE: new project - kayak couture

i was off on a two week holiday and returned to get going again on my frej project for my wife.....and my goal of 22 lb boat..... and thought i would update folks.

so i finished stripping the hull and have now flipped it over to start on the deck.  am very happy in looking in the inside that i was able to keep the seams tight.  so there will be minimal weight given up to filling core irregularities with anything denser than cedar.

there is one other weight saving bit that i am giving a go on this boat that i wanted to point out.  there are no 'internal stems' or 'sterns'.    these are wood structures inside a strip build on the ends that stay with the hull and don't come out when you 'pop' the forms out to take the hull off.

one of the things i have noticed as a place where i apear to give up weight in the past.... is overly generous fillets that are required to cover these structures and allow the glass to fit neatly into the ends.

so without these structures i will make up a 'whipcream' of microballoons and epoxy and make the smallest fillet possible prior to internal glassing.

so in the hull stripping, i just extended the strips beyond the normal end of the internal stem and glued them to one-another.

i am not concerned about strength here given there is still going to be an outer stem and an extra layer of glass on the inside and outside of this seam.

there is some adjustment to construction order and care to ensure that the placement of the outer stem doesn't accidently 'open-up' the ends of the boat.....which is not a typical concern if there is an internal stern.

so far i am impressed with the curviness of this design.....  and how little number of strips i have used to get this far.   as soon as i finish the deck and complete the external sanding, i will report of the weight of the unfinished core....and we will see how we are doing.

h

RE: new project - kayak couture

   I really love the hspira one! Is just amazing! So shiny and I bet is fast!

RE: new project - kayak couture

just thought i would update progress with a picture of the hull now fully stripped.

after i get most of the staples out i will be starting sanding.  

i am curious if i am on weight target but, at least by calculation the results are encouraging and on plan.  right now we are at nine 'ten packs' or 720 linear feet of 3/16"  (with a lot of little bits leftover).  i figure after sanding we will average 5/32 or a tad thinner.  if you use 23 lbs per cubic foot of western red cedar and the full 720 linear feet that would calculate out to a between 12 and 13 lbs for the core....which is on target to get to 22 lbs.

as soon as i can, we will weigh the result....and confirm if it matches the engineering plan i made up prior to start of the project:)   but for now it seems to be 'on target'.

 

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