new kayak project research

Builder's Forum
1

Hi all, 

am working out the details of my latest build and wanted to ask any of our forum members about their experience with paulownia.

the remit for my latest boat is very low weight day touring boat.  as i get older, light weight gets more and more attractive.

so the basic idea is something like a petrel play hull with a new deck i am currently designing built out of 1/4 inch or 3/16 inch thick paulownia glassed in 4 oz s-glass.

currently calculating out a total weight of between 26 and 28 lbs depending on some options i am still working through.

anyway, the essence of the question is really about paulownia and 3/16 vs 1/4 inch.  and can i go with 3/16? and how do people see the risk/tradeoffs on this question.

thanks in advance for your thoughts and ideas.

h

2

it's warmed up here in the DC region and i have started the project in earnest.

the last two days were about setting up the frames and making the adjustment for the custom deck.  this was a tedious process and doing it the old fashioned way with a petrel play hull and a customized, low profile deck.  the low profile deck takes some volume out of the ends but does not impact the general cockpit volme.

the picture below shows the desired profile and a reference line for sorting it all out and a draw-over on the original petrel play hull profile, so you can see generally what i mean by taking some volume out of the ends.

as i mentioned, below the water line, there is no difference from the petrel play but i took some spring out of the shear and thus there is a new shear line and the first and last couple form are signficantly cut back.  for most of the paddling i do which is flat or flat and windy, this should have no negative impact....and probably a positive one.  in trying to hit 25lbs everything matters so a little less volume on the ends adds up to taking about 120 square inches of skin out of the boat and yields back 7.09 oz of weight saving, and less windage.  interestingly enough, the tweak in measurements adds a bit of knee room (about 1/8 inch) and takes out a bit of foot room (about 3/16)

anyway, it was a long day but all the adjustments were made to the forms 

the next picture is what the forms in the bow looked like with some premeasurements in place (prior to cutting).   so these are the original petrel play forms...but the blue tape line shows the new deck profile that i am going to cut and the pink line is the adjustments to deck height on back that needs to be worked in as well.

so after all the tedious cutting.....here is what it now looks like:

you can see in this picture the downsloping deck now along the pink line and the recut bow form.  forms 1 - 5 all needed to be adjusted for the new slope of the deck.

the same exercise was performed on the rear of the boat as well impacting forms 11-14.

anyway, going to call it a day.  but i think it looks on track.

h

3

just a quick update on the project.

the shear strip is in....it's a white piece of cedar.

a lot of hours just getting the first strip all perfect and centered and symetrical.  but looks good.

and now for the first strip of paulownia.

so my first impression of the paulownia (3/16" X 3/4" x 8 feet) is that this is very easy to work with and relatively soft compared to cedar.  the wood that i had prepared for me is very clear and even and not visually interesting....but the objective of this boat is light, high-performing, easy to carry.  so now that the first strip is down i should be able to accelerate.  this is not bead and cove....so its a bit slower as each piece needs to be beveled....and i am using Nick Schade's robo bevel tool...so seems like pretty quick work.   

one thing is clear is that i will need to pay very careful attention to alignment and sanding as 3/16 thick does not leave a lot of room for errors and a ros sander can easily bend the wood between forms.   so i am thinking of some creative was to ensure i can get the finish/fareness i need.

h

4

i thought a little update would be in order....i have accellerated the stripping and making good progress

the petrel play hull strips pretty fast except to the point you get to in this picture where from about the rear of the cockpit area half way to the back of the boat you have a hard chine that needs a little bit of attention and some careful cutting to get around this corner.  that said, i will make the turn tomorrow and the the bottom then will be relatively quick.

i thought i would comment some more on using paulownia wood to this stage.  first, it is very consistent grain very similar to balsa wood and a bit more flexible and soft than western red cedar.  so i am finding it very easy to work with and the robo plane planes it very easily.  so stripping is striking me as relatively easy compared to cedar.

i am a bit concerned about how easily dented it is pre-epoxy.  i was also concerned a bit with its ease of flex.  but now that i have six strip edge glued and the petrel has a nice curvy line to it, everything is stiffining up quite nicely compare to how an individual strip felt.   i don't intend to bang this boat around as its target weight remains ~ 25 lbs....but i do want it to be able to take normal bangs....so i guess we will wait and see.

on the kayaking front, i am getting out two to three times a week with my 33 lb petrel.  all i can say is making it light makes it really easy to go paddling...so i hope i can hit the mark of a sub 30 lb boat with this modified petrel play.

h

 

5

just moving along on the hull.....one half of the bottom to go then we can start the deck.

the paulownia is very easy to work with....i am very interested to see how it glasses up.

h

 

6

   Now that you've built with bead and cove, and bevel, which would you prefer?   Is one better than the other?

I'll be using paulownia.

7

Hi Ross

Great question.

The first strip boat I built was cove and bead and, looking back at the skills I had at the time, I don’t think I would have gotten a great result if I had tried the bevel technique.

But now I handle a plane like a good musician handles their instrument and turning out a bevel boat is just as easy as working with cove and bead.  I don’t really think about it….i pick up the plane, visualize what I want to do, and it just goes right and the gaps are just as tight as cove and bead.

So right now, I tend to build the cove and bead or bevel technique based on the wood I happen to have acquired.   If its cove and bead, that’s what I will use.  If I am having it custom cut, I usually go with rectangular pieces and do all the beveling myself.

Fwiw, I picked up a lot of my planing skills building my first strip built….even a cove and bead boat requires a fair amount of beveling…..but it sort of eases you into it.  the robo bevel, which I used for the first time on this boat, makes it even easier.  The first bevel boat I built was before the robo bevel.

As mentioned in my remarks above.  I am finding the paulownia very easy to work with.  It does not have the strong grain of cedar….so less tear outs or rough cuts.

Attached is latest picture of the hull.  Closed it up this afternoon and this evening pulled the staples out.  So we will see how it sands up tomorrow.

h

8

   hspira

Question, what is a roto bevel?

Had another question, but realized it doesn't pertain to this style of boat building

9

   apologies,   i meant to say Robo-bevel.  see the link below:

https://www.guillemot-kayaks.com/catalog/boat-building-tools/robo-bevel-strip-built-boat-beveling-tool

it really speeds stuff up if the tool happens to work for you.  in some cases, the hull shape is such that the tools is not very effective (tight radiuses/curves).  but if you have a lot of straight/long runs....it definitely takes some work out of planing by hand.

h

10

   WOW, cool tool!

I can see where that would make things easier

Don't think I'll ever build a strip kayak, but thanks for enlightening me

11

i thought i would update you all on the build as i came to an interesting juncture on this boat's construction ...and got to try some things out that i had not done before.

my most recent task was the external stems....and historically, with longer, pointier boats, the stem bends were gradual enough that i could bend wood with, at best, a little bit of muscle,  and at worst, a little bit of heat from a heat gun and some muscle.   but after breaking a couple pieces with these two techniques, i finally surrendered to the realization that this was going to take steam.  and so i dutifully set upon the internet to find a steam box that i could quickly assemble.

after several hours of research i declared myself unsatisfied with the proposed solutions and started about rummaging throuh my favorite place (and my wifes least favorite) the kitchen,  for a solution.

i was greeted with a 'what are you cooking?' (her birthday's tomorrow.....) and promptly and proudly (becuase i spent no money) displayed that i had conscripted our turkey roasting pan and steamer platform into boat building duty and was happily 'steaming'  the cedar strips for my stems.

this did not prompt any particular reaction from my wife, but as she realized this had nothing to do with her birthday, she quickly lost interest and returned to her hobby playing with the family cats....refusing my entreaties to engage her in a conversation about everything i had just learned about bending wood and how it was so similar to cooking brisket.

anyway, enough about the family....

the next picture shows how relaxed the wood became after about an hour of steaming (hence the brisket analogy) so i temporarily held the pieces on the stem forms while i busilly attached their kin to the boat:

and here is the final step with them now attached to the boat:

anyway....the goal tonight is to start to fare these stems in....and work on overally sanding of the hull.

in summary, a turkey pot is a great way to steam small wood strips without making an investment in a specialized steam box.

h

12

time....for an update.  its been going a bit slower than i had hope.  part of the challenge is i don't have my regular work shop and very little room....so i have a lot of re-arranging of things after each step.

also just trying to be careful as i a key objective of the whole project is to see how light i can build - target 25 lbs...and so you have to be careful.

anyway, this is the hull after sanding and faring.

 compared to cedar, you can see that the paulownia is not particularly visually interesting.  it has a very much balsawood kind of grain and color.   i also had to take some extra time sanding it with very new/clean sandpaper as i am only using 3/16 strips, so they bend if you push them....you need your sandpaper sharp and just need to be carefu.

i have not totally sorted out how i want to finish the boat...i have been thinking about painting....but i also know if you want that stained look, its got to go on under the glass.  so i have elected to take a bit more time and stain it with my signature look (see the night heron in the pictures) so i have the option to do that or can paint over it if i want.  so that ate up some days.  interestingly, it stains well but is more difficult to stain than cedar becuase since there is little color difference in the strips themselves, you have to be a bit more attentive to the stain density across the entire boat for it to look nice.  with cedar, the variation in color in the underlying wood means you can be a bit looser on the stain consistency.

anyway, stained, and applied 4 oz s glass and will complete fill coats tomorrow.   the s glass is pretty expensive stuff so i am also being vary careful laying it out and minimizing wastage.  i bought only 10 yards of 60 inch wide so have to get both a hull and deck piece/inside and out so the material needs to be carefully cut in its width with little wastage to make it all work.

for lazlo, if you are reading this, you can see my white sheer line and stem lines which is basically just carefully masked off stain.   worked very well on this.

i have also been measuring all the epoxy used so far....and seem to be on track for the calculated weight.....

h

13

  flipped over and  started working on the deck.  so far, so good :)

14

thought i would provide a little update on the project.  the last two nights i cut the hatches and tonight will glue in the spacers and platform.

for this strip build i took the liberty of buying some pre-cut pieces special ordered from other designs to help me with places that i did not want to build up from scratch.   the two areas i went for were the cockpit sill, risers and coaming and hatches which i like from my night heron experience.  i was thinking about different hatch experiences i have had and trying to sort out looks, weight and water-tightness and have found that the night heron hatch set with six toggles per hatch can look real nice in a wood build, are incredibly water tight and not too heavy when you weigh out all the components.  my previous boats have been combination of straps vs toggles....and toggles win hands down for creating really tight waterproof hatches....   anyway, here are the pictures.

the first picture is scribing the hatches uses the spacers to help keep everything aligned.

there was a lot of time pre-fitting everything before i actually started cutting carefully 100% by hand with a japanes bonsai saw.....

and here after a couple more hours is after the cut:

the cuts were pretty clean and i was happy.....just went very slow and carefully.

the other thing that was happening along the way was marking the rigging, bulkheads (will use minicell bulkheads are about 3 inches thick) and footbrace locations and skeg actuator.....to make sure that the location of all of them do not accidently interfere with one another...before the hatches are cut.   this is a bit of the planning that needs to be done when you are customizing ......have to think ahead to the finished product to avoid problems.    the white stain also introduces some challenges about order of operations to preserve it in places i want that color.

anyway....that's the update.

h

15

   Is it available in your area?

Sounds like an interesting wood species

https://www.wood-database.com/paulownia/

16

i am in the washington DC metro area.  i am looking at using https://clearwoodpaddleboards.com who sells milled strips that can be shipped within north america.  they appear to be based out of oregon.

 

17

I built my last kayak using 3/16" Paulownia strips. I used the paulownia for the hull and cedar for the deck.

I was able to buy 1"x6"x16' paulownia exterior siding at a lumber yard near me. The siding had quite a few knots so I ended up painting the hull, and at that point made the decission to use cedar for the deck. The paulownia worked quite well for the hull and I would use it again as  it is strong, light and isn't difficult to work. 

18

hi walt, 

could you share some more details about your project that you did with paulownia....what kind of kayak?  any pictures?  what glassing schedule...how has it held up? 

many thanks

h

 

19

Hi folks, 

just thought i would update forum readers on the project i am working on.  may look like i am a forum stalker but have been at my computer all day working on the design of the 'new boat' and looking up a lot of reference material and making some decisions.

as i mentioned, the remit of the boat is a lightweight day tourer sea kayak - inspired by some ideas i have been reading a lot about.   for example, designing to be efficient (fast) at cruising power is not the same as designing to be efficient (fast) at maximum power.  and a boat that is designed to be fast at cruising power is often shorter, counter-intuitively, than a boat designed to be fast at max power.  or another way to think about it is, a shorter boat can be faster than a longer boat at low (cruising) power.  i have also thought a lot about the mission and, notwithstanding all the great adventures i read, about, what does most of my paddling look like? (e.g., i take day trips, and bring a lunch.  i rarely go overnight camping self supported out of my boat).   anyway, when you distill it all down, if I think about it like that, and want to make it easy (e.g., keep the boat light), i think the right answer is a boat that can do the job at ~ 26 lbs without doing anything really fancy.

so i thought i would share a picture and some calculations.

so the first picture is the boat:

the hull is based on the petrel play with a custom deck that i will be fabricating.  i have been doing a lot of work studying the petrel play and i think its hull is the right hull for the job.  i am going to take a little volume out of the ends above the waterline as i am not really expecting to use it in the surf the way the original petrel play was designed.  the orignial petrel play is 14" loa....so this will be about 13"6 with the same waterline but with the ends a little less tall we are going to lose about 6 inches  of overhang and loa.

the next picture is the calculations of the bill of materail weight (e.g.,  the ingredients and their individual weights).  i analyzed a couple different hull buildups and am going with the 3/16 palowinia (hence highlighted in yellow).  the time by the computer today was sorting out all the weights and it suggest a build coming in at ~ 26lbs fully rigged.

anyway, i thought it might be interesting to share.  the last time i built a customized boat i was within a pound of the calculated weight.....so it can be reasonably reliable if you are careful with the math and a careful builder.    happy to hear any feedback.   material has started to arrive so i expect in March the building will be starting.

h

20

as i think about spring coming and it warming up enough that wood glue works (> 50 degrees), my project for a 25lb lightweight touring kayak has started in earnest.   

the other day i picked up the petrel play forms from CLC (plus a couple nice T-shirts that were on sale).  today, my 1000 linear feet of 3/16X3/4X96 inch paulownia strips arrived.   big thanks to Randy Bogardus at Clearwood Paddleboards for sorting through his inventory and rejecting the 'heavies' to mill me the lightest strips.

i was impressed with a really tight packing job and everything appears to have come through shipping in great shape.  my initial impression is the paulownia, compared to cedar is not visually interesting.  very consistent color and grain.   pretty much a balsa wood kind of look....so am curious to see how we will approach the finishing steps and how stain and paint will work with this.

next steps are to buld a new workbench in the garage and get the strongback set up.....i expect the stripping to go faster than usual as, like a lot of folks, i am working out of the house for the next several months  so i can covert commute time stripping time.  

h