Stems

Internal stems are short pieces of wood that reinforce the bow and stern.  They are typically thin and narrow but they provide a great deal of structural support.  They’re not completely necessary and builders looking for a super light racing kayak may choose to leave them out.  Since I’m pretty sure I’ll be banging into stuff I’ll build mine with the stems.

They can be done a few ways but the most basic is to get a nice piece of wood about ½” thick and cut it into two strips that will fit the outer edge of the end forms.  It then needs to be tapered to a center point so the strips can be laid flush against it and glued in place.  The kit comes with a nice piece of cedar for the stems but unfortunately the supplier does not provide any information about what to do. 

The forms, a template and rough completed stem.

The end forms are about 20 inches long and protrude off of the ends of the strongback and the stems will need to be glued or taped to the edge.  With the forms you get thin, long pieces of particle board that serve as templates for the stems.  What I couldn’t figure out was how to put the stems on the forms and apply the strips.  Just using the stem templates on top of the forms made them protrude and that didn’t seem right. 

Without really thinking through the problem I decided to just cut the stems from the supplied cedar board and put it together.  Surely once the stems are in place it would make sense, right?  Nope.  I was wrong.  I spent four hours cutting and hand shaping the stems to fit on the outer edge of the forms.  When I had them complete I put them on the end forms but still couldn’t figure out why they didn’t look right.  I went to the computer to search the builder’s forum at CLC and I quickly found my answer.  I had neglected to cut room for the stems out of the end forms.  What a bone-headed mistake!

 

 Tracing the template onto cedar.

 

Note the two templates are cut slightly differently.  One for bow the other for stern.

The stem templates have a couple of uses.  They can be used as a template as I did or, if you are going stem-less, it can be used to mark taper lines on the end forms.  The templates are also used to trace a cut line on the end forms.  What I should have done was use the templates to mark the cut lines then use them to trace the stems onto the cedar.  Not researching the problem first resulted in wasted wood. 

 The original stem before hand shaping.

 

 The original stem after hand shaping.  Note the top edge of the form is uncut.

Original stem again.

I was unable reuse the stems because they had been shaped to fit the uncut forms.  There was enough left over to cut another stem but not two so I had to make a trip to the local hardware store for another board.  The cedar they had in stock was pretty knotty but I found some good looking aspen.  When I got back I immediately began removing the forms and accidentally broke them both.  I was able to re-glue the bow form without too much trouble but the stern form broke in two places.  The wider side broke in a difficult to repair spot and I still haven’t been able to get the glue to hold.

  

Tracing the templates on aspen.  Notice the ear form attached to the end form.  The one on

the stern form is keeping me from getting a solid enough clamp for the repair.

 

 

Stern form.  The narrow "leg" broke at the screw hole on both end forms.  This one also broke at the corner 

of the wide leg.  The repair is complicated because there is small form protruding from the backside.  

That prevents me from getting solid clamp pressure.

Not my best day but I did manage to get the bow form cut and a replacement stem shaped and ready.  I also was able to get the stern stem done but I can’t cut and reattach the form until I get it fixed.  When they’re done I’ll taper the stems and add a picture and brief description.

Rain?  Boooo! 

Alignment

It's been almost two months since my last post.  That should give you an idea of my progress - slow!  From Thanksgiving through New Years I barely even thought about the kayak but I'm picking up a little steam and hope to recover some ground on my schedule.

At this point aligning the forms and finishing the internal stems are the last items needed before stripping can begin.  Earlier I placed the forms on the strongback for rough fitting and made a few wood u-spacers.  Everything checked out without problem.  The laser cut particle boards in the kit only needed a few little spurs ground down and smoothed out.  To prepare for final alignment I removed all forms.

There are a total of 16 form ribs that mostly slide over the strongback with a few that 
will need to be glued to the protruding end forms at the bow and stern.

I then took the necessary measurements from the sparsely designed plans and marked the front of cockpit on the strongback and located the nearest form.  On this design it's #8.   Form #8 was placed in its position and I marked its placement on the top, bottom and sides of the strongback.  I then flipped the bare strongback deck side down and replaced the forms.  I secured #8 temporally then installed the remaining spacers and forms from the inside out.

With #8 secured I placed my key spacer between it and #7.  The plans call for 11.5" between forms and I left the key spacer at roughly 10.5" so there would be plenty of slack.  I then measured and placed the #3 and #14 forms in their final spots then screwed them into place before placing the remaining spacers.  I gently tapped the key spacer wedges to tighten towards the bow before finally removing the temporary screw holding #8 in place and snugging the rest of the forms from the inside out.  For the final placement of the nose forms I installed a wood screw through the adjacent forms directly into the end forms.  

 

This is the key spacer in the middle.  It's in two parts and can be expanded by hammering the wedges in the center.

It evenly snugs the forms and spacers the entire length of the boat from the inside out.

The #13-#14 spacer screwed in to place.  You can also see the screw through #14 back into the spacer.

 

Here you can see the wood screw that was placed through the #15 form.  It's ready to accept the stern form.  

You can also see the reference lines for the sheer strips and alignment.

Each form has reference marks indicating where the first strips or "shear strips" will be placed.  I used these to visually check down the length of the boat and adjusted the forms where necessary.  Very little needed to be done because the strongback is straight and the forms were precision cut.  I've clamped short strip pieces to the form following the reference line.  This will aid the installation of the sheer strips.

The reference lines and sheer strip support tabs.  Sorry for the shoddy quality.  The QC inspector was getting a little antsy about the overtime and late dinner.

This then is the final placement and alignment of the forms.  I'm finished with this step and can confidently move on to making and placing the internal stems.

Or maybe not...

Replane

I found a few hours to work on the boat today.  The afternoon was spent planing the strips I ripped last Sunday.  It really made a huge difference and I can't say enough good things about my thickness planer.  It's a well built and accurate tool.

The strips were passed through in sets of 5-7 somewhat in the order they were ripped.  They got a little scrambled after sawing last weekend so I'll need to sort them as best I can.  I used two spring clamps on the in-feed side to help heard them into the planer and built a cardboard ramp from the out-feed to a my work table.  

 Feeding from the garage to the truck.

The strips were passed through multiple times with the cutter head being lowered 1/32 of an inch between passes until they were within a sixteenth of a quarter inch.  A few strips were considerably thinner (guess I didn't do such a good job on the table saw after all) so they'll either be discarded or used in some area where thickness won't be an issue.  

The first set through was organized into four sets of four in order.  I'll need to do this for all of the strips but the rest were just bundled together into sets that were ripped from the same board.  

The markings on the end of the strips are the orientation marks.  The marks on the strip edges indicate length, set number and order.

I'm glad I decided to plane the strips.  The surface is much more smooth and I expect I'll spend less time sanding the kayak in the end.

You can see the grains are matching up nicely in this set.

I'll soon begin scarfing and actually putting the strips on the forms.