Adventures in Composite Canoe Building, Part III: Hyde and Cheryl

Randy Pfeifer maintains the Bear Mountain Boats Builders' Forum and is highly knowledgeable on the subject of woodstrip epoxy canoes. In this series, he documents his experiments building multiple canoes using composite materials, with the goal of creating a lightweight but fully functional Freedom 17.

In Part I, Randy found his first attempt came in at 58 lbs. In Part II, he successfully kept the weight manageable but wasn't quite satisfied. In the final two experiments, Randy succeeds in getting the weight under 40 lbs. 

Hyde

 For Hyde, I eliminated the outer S-glass layer and swapped the order of the first two layers (Carbon Fiber inside, Kevlar outside at the same weights as before). It was surprising to see that the combination of yellow Kevlar over black Carbon Fiber gave a greenish result.

I really like the color. The two 1/8” thick layers for the core of Jeckle created a really rigid structure. But gluing the layers in separately really took a lot of epoxy. It’s a closed cell foam but the outer cells are of course open and took on much more epoxy than I liked. I was concerned that a single layer of 1/8” foam might not be strong enough so I searched for some other light weight core. I found a honeycomb core by Nomex that is 1.8 pound per cubic foot. It’s really expensive but at this point I was more concerned about weight than cost.

The honeycomb flexes really well in one dimension but not quite as well in the other. Orienting the material on the hull the right way made it pretty easy. It stretches very easily which means its shape on the hull needed to be controlled so it didn’t shift out of place while being installed. I needed to find a way to keep it in place after installation while the epoxy set up. The prior approaches of just putting some weight on it or using the forms used to build the original hull was not going to be sufficient. Then it occurred to me that I could double-face tape it to the outside of the original hull, put glue on the inside of the composite hull and press the two back together again. I would have 100% contact across the entire surface of the core! This worked extremely well. The hull went back in place over the wooden hull easily (now back on its forms) and I pressed it down with a few ratchet straps around the hull and strongback. The biggest challenge was ensuring that I put epoxy inside the new hull in just the right places so that it contacted all of the core but not beyond it. I used somewhat thickened epoxy so it wouldn’t run out while the hull was upside-down. And yes, I used another layer of heat shrink material on the original hull to protect it.

With my new .2” thick core in place, my next challenge was to find a way to ensure that the honey comb didn’t fill up with epoxy when I wet-out the layer of cloth on the inside of the hull. To do this (and I’m not sure it was fully successful), I added a layer of .2 oz carbon fiber veil over just the core before I added internal layer of cloth. 

Instead of Kevlar for the internal layer, I decided I would experiment with 3.6 Oz Innegra cloth. It is a (relative to Kevlar) newer material and white in color. It’s available in various weights and mixed with other materials (e.g., to make interesting patterns) at various price points. It is easier with work with than either Carbon or Kevlar from a “fiber management” perspective. Easy to cut and wets out well. I used a 3.6 oz weight plain weave cloth (I think my 2.2 Oz Kevlar choice for Jeckle may have been a bit light – use over time will answer that for me). 

The Innegra cloth is available in 50” widths. This is a bit tight for the girth of the Freedom 17. I also noted that the draft of the Freedom 17 is plenty big. I decided to lower the sheerline of Hyde by about an inch to accommodate the narrower cloth. This also saved a pound on the weight of the hull. Also, recognizing that my approach to gunwales actually increases the draft of the craft about ½” I was happy with the trade. I built my gunwales at 1” tall by ¾” wide (instead of the ¾” x ¾” used on Jeckle). With slightly beefier gunwales and a stronger internal fabric I was happy with the weight savings of Hyde vs Jeckle when the hull (pre-trim) was complete. I had achieved a savings of 4 pounds so far (acknowledging that I have removed a layer in the initial lay-up).

Now to save some more weight in the trim. With a slightly lighter foam used for the gunwales, the weight of the slightly larger gunwales was actually a bit less than the gunwales on Jeckle.

Seats were a new adventure. I designed new seats using 1” x 1” foam covered in Carbon Fiber sleeves. 

Same webbing as Jeckle. Seats were mounted in Heckle and Jeckle using rivets through the hull into aluminum “angle-irons”. For Hyde, I created my own L-brackets by saturating Carbon Fiber tape with epoxy and squeezing multiple layers between two aluminum “angle-irons”. These 2”x2”x2” brackets were attached to the hull directly with thickened epoxy (with the idea that I could add rivets through the hull in the future if necessary).

I built a yoke using the same carbon fiber sleeve over foam approach. Same with thwart and handholds. The yoke was installed in the hull using similar brackets as the seats. The thwart and hand grips were epoxied in permanently.

You can see in the table below the weight savings vs Jeckle for each of the trim components. I was more careful with my measurements and included the weight savings of sanding out the hull before applying the final coats of finish. A net savings of 7 pounds… So, from my shock of 58 pounds with Heckle to 46 pounds on Jeckle to 39 pounds with Hyde, I was feeling pretty good.

 

HULL - Hyde	Delta vs Jeckle	Hyde Weight	Running total weight
Bare hull (carbon + Kevlar)	-5.5	18.5	18.5
Trim hull sheerline (1.25")	-1.1	-1.1	17.4
Outer hull weight			17.4
Core + epoxy	-0.4	3.95	21.35
Carbon Veil + Innegra	0.68	1.66	23.01
epoxy for first coat on inside	2.32	6.64	29.65
2nd coat of epoxy on inside		1.2	30.85
TRIM
Gunwales	-0.439	2.901	33.75
Seat mount brackets	-0.26	0.30	34.06
Yoke mounting		0.08	34.14
Thwart / hand holds	0.00	0.40	34.54
Flotation Chambers		0
seats (incl bolts)	-1.08	1.67	36.20
Yoke (incl brackets/HW)	-1.02	1.55	37.75
Skid plate(s)	-0.25	0.3	38.05
Hull sanding	-0.36	-0.71	37.34
Varnish - sanding	0.36	1.71	39.05

 Total Weight 39.05 pounds

A pandemic induced extension.

With a 39 pound canoe, I was quite proud of myself and ready to do some paddling in 2020 to really test the construction. As the pandemic hit, Hyde sat in the shop waiting for a paddling partner to paddle it with me…. Of course, that was a problem so it just hung there in pristine condition.

While the pandemic raged on I pondered what else might be improved. I continued to think about that core and wondered how much epoxy had seeped into that honeycomb. And how much weaker would a single layer of 1/8” foam really be. I built a couple sample lay-ups with the honeycomb and 1/8” foam and tried to bend them. My samples were really too small to provide a good conclusion but I had trouble distinguishing between them. I used glass for the internal layer so I could see how much epoxy seeped into the core (more than I liked). I also wondered if my seats were going to be strong enough. I had done some math (my son is a PhD student in Mechanical Engineering at the University of Virginia) on the amount of strain they should be able to take and had done some lab tests that seemed to support the math. But the amount of deflection across the longer seat members left me a bit uncomfortable.

I spent the year working from home and built a sauna in the back yard as a distraction.

At the end of February 2021, I retired from IBM and needed a project. I decided I would take one more spin at reducing weight and increasing strength of the Composite Freedom 17 family I was growing. Heckle – Jeckle – Hyde - …?... I needed a name first. Heckle and Jeckle as you know are cartoon crows from my childhood. You all know about Jekyll and Hyde. Then one of my favorite musical entertainers came to mind. Cheryl Crow…. Cheryl it is…

I decided I would see how fast I could build a 4^th composite Freedom 17. While I was still finishing up my exit at IBM I began acquiring materials. The day after my last day at IBM, I went out to my shop and started. A month later I was done with everything but the final finish.

I made the following changes some of which increased weight while others reduced weight: 

1. Took a gamble on the 1/8” thick single sheet of foam for the core. This started a nightly dream of massive oil-canning. But I have a commercially built solo canoe that clearly uses a single 1/8” thick core (albeit a narrower craft). I built the core a bit wider covering the turn of the bilge.
2. Used a double layer of carbon sleeve over the cross-ways segments of the seat frames. I developed a stronger means to attach pieces of the seat frames together.
3. Added a layer of Carbon Fiber to the seat brackets – probably unnecessary – still no rivets.
4. Learned to spray finishes and sprayed the outside finish creating a really nice satin finish. I found brushing the finish almost impossible to do without leaving brush marks.

The above changes produced Cheryl - almost identical to Hyde but weighs ~1 pound less. 

HULL	Delta vs Hyde	Cheryl Weight	Running Total	Comments
Bare hull (carbon + Kevlar)	0.68	19.18	19.18	After first trim to shearline – heavy than Hyde with same lay-up – inconsistent process?
Trim hull sheerline (1.25")	-0.13	-1.23	17.95	1.375 cut off
Outer hull weight	0		17.95
Core + epoxy	-0.50	3.45	21.40	1/8" foam core + ~2.3 pounds epoxy
Innegra	-0.06	1.60	23.00	3.6 Oz cloth (1.875 pounds) - No veil
epoxy for first coat on inside	-0.84	5.8	28.80
2nd coat of epoxy on inside	0.1	1.3	30.10	measured
TRIM	0
Gunwales	0.099	3	33.10	excessive weight on epoxy to install in inside fillets.
Seat mount brackets	0.084	0.384	33.48	5 layers of carbon instead of 4 (includes epoxy to install)
Yoke mounting	0.02	0.1	33.58
Thwart / hand holds	-0.13	0.27	33.85	Double layer of carbon on Thwart
Flotation Chambers	0	0	33.85
seats (incl bolts)	0.15	1.82	35.67	Double layer of carbon on cross members
Yoke (incl pads/HW)	-0.04	1.51	37.18
Skid plate(s)	0.22	0.52	37.70
Hull sanding	0.36	-0.35	37.35	less loss in sanding than expected/before
Varnish - sanding	-0.91	0.8	38.15	Spray finish on outside. 3 brush coats on inside

I kept meticulous notes measuring every pump of epoxy used and its application. A total of 599 pumps of West System epoxy was used on Cheryl. I weighed the brushes before and after to account for the weight of the epoxy that didn’t stay on the boat (this included weighing the epoxy squeegeed off as I did the lay-up).

In general, the lesson I learned is that if you measure things in grams, the pounds take care of themselves.

So now I had built 4 complete composite Freedom 17 canoes (and most of a Freedom 17 cedar strip canoe). I’ve given the heavier Heckle to my brother, paddled Jeckle deep in the wilderness. Hyde and Cheryl had yet to get wet. My brother came to visit last weekend with a friend and we were able to get a quick paddle on the lake so took the opportunity to paddle Cheryl for a few minutes in miserable weather. The water conditions were pretty calm so I didn’t get to battle any waves but I could see no signs of any oil-canning on the hull of Cheryl and the seat frames worked great (in albeit a short test). I’m looking forward to being able to spend some more serious time in the wilderness with Cheryl (and Hyde) this summer. I gave Jeckle to my brother too.

Next, I need to quickly get gunwales on the original Freedom 17 to make it more difficult to use as a mold in the future.