11' Kayak "Loggerhead"

Yup, it's another kayak. There is nothing with this kayak that I would consider unique when compared to the other builds that I have posted here. I think everyone loves to see a build so I will include it here. The special quality with this kayak is the fact that I am doing it with my 15 year old daughter to introduce here to boatbuilding and to generate a bit more personal ownership as it will be her kayak when all is said and done. That being said, the design was developed with simplicity in mind so that it coiuld be built by an individual with a limited amount of experience. Bear with me if this looks like a rehash of other build threads that I have done.

The design name is taken from the loggerhead turtle. The back of my previous build struck me as being very similar in appearance to the loggerhead when viewed from behind. No perversities please. I incorporated the same styling into this build to use the name. I was tempted to do a play on words and name it "Lagerhead." I fear my beer drinking days are over so I'll stick with the original name.

The build has already started and I'll include pics shortly. For now I'm posting the lines plan from FS and a PDF file of the panel developements. I will need to update the PDF as I've had to modifly on the fly to get the panels to come together with limited difficulty.

 

This kayak has grown from it's first inception. The first iteration was 9' and I felt it was too pudgy. 9 feet turned into 10' that turned into 11'. Some of the on the fly modifications were a reduction in the curvature of the forefoot (and aftfoot?) to ease the plywood stresses in those areas during construction. Ease of build criteria. The chine edge of the upper strake was trimmed to match the shape presented by the garboard strakes when positioned to the frames and bulkheads.

I'm finding that FS has trouble in accurately defining the flat-plates in the bow and stern with a deeply vee'd entry/exit. I used to think that was a bit of casualness in my construction process. My forward bulkhead is located 1' aft of the bow and the chine in the upper panel was falling 5/8" below the chine set by the garboard panel. I had to assume the garboard panel was correct as it was placed by the forward bulkhead and it was taken directly from the modle in FS. I took a batten through the new point and faired it backwards and forward to create a new chine edge and trimmed it. It was uncanny the the forward sections fell together afterwards.

 

A few pics of the hull wired and "tack" fillets in place.

The first photo is a shot down the length of the kayak. The level and the straight edge are in place to asure that there is no twist in the hull. The molds keep each of the stations oriented properly. I let the rest sort itself out.

I like using this method as the stiches are removed before full filleting takes place and there are no remnants left in the build.

Leveled and true.


The bow tacks. These tack fillets are smaller than the final fillet so a little sloppiness is acceptable.


Shimming the keel line. Low spots (inverted) get tapered shims to spread the seam and pull it into alignment with the rest of the keel line. The tacks will keep it aligned through the fillet and tape application.


Transom tacks.


Wired, shimmed and tacked.

 

I'm attempting a different approach on this build. In the past, I've filleted and taped the frames and bulkheads at the same time as I've done the chines and keel. This time, I left the frames unglued when the tack welds were done. I'm relying on the tacks to hold the hull in shape while the frames are removed. This gives me/us a clean shot of the interior to do a continuous fillet and tape. stem to stern.

Action photo of the hull being masked for filleting.


Fully masked.


Stem, stern, keel and chines filleted taped and epoxied.


Prior to filleting, the keel line was inspected once more for undesired humps and hollows. There was one hollow noted and the tack in the location was released. The hull aligned itself to the surrounding areas when the tack was released so nothing else was done before filleting. There is one very minor hump that I think we'll just plane done fair when we get to that phase of the build.

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I estimate that the fillets and tape add about two pounds to the overall build. They may be overkill, but I'm wanting to put some really large radii into the chines for improved performance through better waterflow around the hull. Most likely, we'll start with a chine chamfer that penetrates the full thickness of the plywood and maybe into the fillet from the outside a bit.

 

The next step was adding the shelf to the shear. We had cut the shelves last week, but I wasn't feeling energetic about installing them and I am glad we chose to wait. Further inspection of the sheer revealed some humps and hollows that needed fairing prior to adding the shelf. If you look closely at the photo below, you'll see a dip just forward of the stean followed by a hump that goes past midships. Also, it gave me time to think about the details at the bow and stern and the quest for simplicity with this build.



The existing shear edge was simply the flat pattern output from FS with no real corrections added. If you look at the first post with the lines drawing, you'll see some bow to the sides and bottom. I was originally exploring a tortured construction and failed to remove the bow when I created the flat-patterns so there is some operator induced error with the flat-patterns I'm working with. I've since changed my thinking about tortured flat pattern creation, but that's a different thread. The shelf made a great batten for drawing the new shear and it was replicated on both sides. Maybe you can see the new shear through the PVC clamps.



Instead of trying to make a close fit in the ends and maybe have trouble with filling the voids with thickened epoxy, I decided to cut them short and leave plenty of room to fill the area easily.



The shelves went in very nicely. The inside sheer edge was coated with thickened epoxy for the full length. Position marks had been made earlier and the aft end of the shelf was aligned with this mark and clamped. The forward end was allowed to exten over the side until the aft end was in place. With the aft end secure, the forward end was sprung into place in the bow. Since the shelves were cut short, they were clear of the epoxy along the sheer and didn't try to smear it out of place. At this point, clamps were added starting at the stern and working forward until the entire shelf was clamped in place. Working one side at a time, the excess was scraped up and used on the opposite side. The excess from the second side was scaped up and used in the ends.

 

The epoxy has set along the sheer and the clamps are removed. The sheer has a nice, natural shape as it sits without any of the frames or bulkheads in place.



The goal is to keep the sheer natural looking as it gets pushed around a bit as the internal components are added. The bow components are not so much the problem as the aft components. The turtleback stern widens fairly rapidly and causes a bit of stress as things curve around back there.

Today's endeavours are to install the bow and stern bulkheads and also the fore and aft frames. These components will get small fillets with 1" glass tape, but today, the various clamps in use obstruct free access to all areas so we will be filleting the accessible and ensuring that all frames and bulkheads will remain fixed once the clamps are removed. Once removed, full filleting and taping can be completed.



We had the foresight to cut the openings in the frames prior to gluing them. :idea: Previously, I had to use a router set-up to go in and route frame opening after it was installed in the boat. Prior to is much easier and can be done as bench-work. The cut-outs will again be used as bulkhead door panels for the associated frame. There is also a mold that fits in at midships. I have check it's fit and the natural shape of the sheer passes outside of the mold by 3/8"-1/2" on either side. I left it out at this stage and will put it in place prior to final filleting. If pulling the sides in to meet the mold causes any unfairness in the sheer, the mold will be tossed in favor more natural lines.

 

Aaaack, you're making me look bad, again, LP. I can't believe how fast your boats come together! Nice work as always!

 

CT-thanks for the complementary words. This is just a fast (and simple) method. At least in the early stages. I worked to keep the details simple as possible so as to not discourage my daughter with her first boat build.

Finally, time and energy! This weekend, we finished filleting the bulkheads and frames. The first fillets were refilleted so as to have a nice bedding for the 1" glass tape. I like the way the tape presses into the thickened epoxy and holds it in place while the unthickened goo is brushed on. Oh yes, all of the bulkheads and frames are taped also.

Three coats of sealing epoxy have been hot coated this weekend and a couple of breasthooks have been installed. This boat is ready to flip and start working the bottom in preparation for sheathing. I'm going to agressively radius the chines on this model so I have put together a test piece to simulate the chine joint. The test piece is to check the extent that I can be aggressive with the chine. I may look to additional layers of cloth at the chine if I find weakness with the joint. I plan to radius right through the ply until I hit fillet material on the inside of the kayak. I purposely made larger than normal chine fillets for this purpose. Fingers are crossed.:!:

 

Some overdue photos.

6 oz. cloth wetted with epoxy a week ago Thursday. Note the chine radius and the dark central stripe that is the inside fillet showing through. I have done a test panel for this chine design though I have not done any testing with it. The test panel feels strong, but I will take it to failure to determine the weakest component of the chine.



Three hot coats of weave filling epoxy. Friday morning, Friday night and Saturday morning.



Curing and sanding and filling and sanding and coating and sanding and fairing and sanding is next.

 

I had the same problem with a Wee Lassie design. At first I noticed that the two bottom planks on each side appeared as if they could be replaced by a single wider plank so I merged them into one. The developments looked very strange, with a concave bottom edge and a sort of notch at one end. I did a mockup of it, but I didn’t believe the development so I straightened out the curve and faired the notch. The single bottom plank went together but the rocker was several inches more than designed.

I suspect that is what happened in your boat, which also raised the chine.

When I restored the original much narrower plank width the development had a straight bottom edge and the mockup went together perfectly with the designed rocker. The planks are twisted almost 90 degrees from midships to stem. Presumably with the wider plank this put so much distortion into the plank edges that FS was unable to resolve the 3D shape into a 2D development. Just because the software will provide plank developments doesn’t mean they will work . . .

 

Hey Terry,

I must have missed your response. I think that as a panel departs from developability in FS, it (FS) loses track of itself and starts to output bad data. I think that the surface and edge errors need to be lower than previously assumed to get accurate output. I was trying to get FS to give me some panels for my "tortured" panels and I was getting some major departures from the equivalent untortured panel. In my mind, I think that my tortured panels need to be drawn in conic form with estimations added for the final panel shape. I'll be doing cross-checking and error checking of developed panels in the future, even on conics, just to be sure. I haven't done this yet, but a comparison actual station dimensions with station dimensions of developed panels is a start.

It's been all work and all play with little boat building since the last post. Admittedly, the Keys are nice this time of year. (Gloat)

The progress report is: sanding, sanding and sanding. The weave fill coats are sanded. A coat of thickened epoxy is scrapered over the hull to fill all of the low spots and sanded again. An additional layer of 1" tape was added at the chine.

Here is a piece of test panel showing chine cross-section.



Test panel after stress test. Note failure of epoxy fillet.



I took another test piece and added a layer of 6 oz. cloth to the inside and outside of the fillet. No pictures yet, but this time the failure occured in the ply adjacent to the fillet. I have added the additional layer to the exterior chine and will add the interior layer when I start working the topsides again. This will make a total of (2) 6oz. layers of glass cloth at the chine both inside and out. The second layer of cloth serves two purposes, now. Strength and added abrasion resistance at the chine.

 

It's hard to see but it looks like the test sample had glass inside the fillet, which has pulled away from the fillet. That could be an adhesion problem rather than a strength problem.

However I don't have experience of using glass so I could be wrong. So far all my builds have had chine logs; it's a simple matter to calculate the cross-section for a chine log that will ensure it is stronger than the ply, then test it.

As far as FS is concerned, when I go back through my records I find I have never built a boat that required me to use FS developments without first making a scale model to check that the developments are correct.

My next build is going to be the Wee Lassie; I made a card model at 1/12th scale which went together well but suggested the build will be sensitive to accuracy, so I am going to build a 1/6th model using aircraft ply so I can work to closer tolerances.

The older I get, the more persnickety I get . . .

 

I don't believe there is an adhesion problem. The glass was laid into the fillet while it was still "wet". To me, it looks like the fillet fractured and leveraged the glass up off of that portion of the fillet.

 

Now I see what happened. The glass was under tension during the test and the fillet was also under tension and pulled apart. Rounding the outer surface of the chine reduced the depth of the fillet which in turn increased the tension in the inner glass layer. Fillet failure may not have happened if the chine had been left square.

I would imagine that, when rounding off chines to this extent, a filler that adds tensile strength to the fillet mix is needed, but since the boat is already built the extra glass layers shoudl take care of the problem.

It's good to see boat builders test samples of their work!

 

It's been a while since I did anything with this.

I did a test float in it several months ago and then got wrapped up in other projects. The float test went very well. I was pleased with the kayak on all points. It moved through the water easily. It's stability is aggreeable. Tracking was great.

This is pure speculation, but I feel like the radiused chined have a lot of influence with it's ease of motion. It glides really well. It reminds me of one of my one-sheeters. in this regard. The one sheeter had radiused corners and almost no wetted surface. Once it had drifted down to a fraction of hull speed, it seemed like it would coast forever.

Stability was right on target. It's was less than my earlier project that needed more, but it was still reliably comfortable. You still knew though that you were sitting in a kayak. I think I could make a design with less initial stability and still be comfortable though.

Tracking was perfect. I don't think I would build a kayak with out a skeg. Granted, this falls into the cruising category and quick maneuverability is not a requirement. Straight tracking is. I find it tiring to continually be making course adjustments when paddling in a straight line and just a little bit of skeg keeps the bow pointed where you want to go. When needed, a couple of strokes on one side and you've made a slight course adjusment. The skeg helps with weather vaning also. When under way (paddling) the wind has little affect on my skegged kayaks.

The only detraction from all of the good stuff was the location of the forward frame. For me, it is located too far aft and I have to put my feet through the frame to fully straighten my legs. My daughters legs aren't quite so long so this wasn't a negative for her.

On to pictures:

My ugly mug with adjusments made for balance.



Deck panels coated with epoxy.



Support structure for forward deck. The fore-n-aft stringer is a standard component of my kayaks. It gives strength to the deck and also prevents the bow "divit" the occurs in the bow sections of the deck if left unsupported. The upright component at the frame is a temporary frame support. The frame itself is not strong enough to support the deck as it's wrapped over the frame during construction. Once the deck is installed and the frame is filleted to the deck, there will be sufficient support for the deck elements. The cockpit ring will also give additional support to solidify the deck stucture.