Solo expedition build

[Alan Gage]

And now for the results of the stick breaking! I'm trying to get an idea of how much strength laminating cedar with fiberglass cloth would add to gunwales. So I cut a bunch of 1/4x3/4" strips of ash, cedar, alder, mahogany, and oak.

The test went like this: I placed the strips over a 14" span and stood on a very accurate digital scale that I trust down to the ounce. I zeroed the scale and then started to press down on the center of the span with my palm. As weight was transferred to the strip it started registering negative readings on the scale (because I was getting lighter). I'd slowly press and watch the weight until the strip broke. Not very scientific but I hope accurate enough for what I need.

Here are the results of the NON laminated strips:

Ash: The little ash I have on hand is not very good quality, the grain kind of runs all over the place. I selected the best pieces I could find and cut the strips from multiple boards. Some strips were nearly flat sawn and a few were quarter sawn. They broke at:

21.5 lbs - qtr. sawn
27.5 lbs - qtr. sawn
24.3 lbs - qtr. sawn
29.1 lbs - qtr. sawn
40 lbs
30 lbs
31.8 lbs
32 lbs
30.3 lbs
32.6 lbs

As you can see it was all over the place. I'm blaming poor quality wood for the results and for this reason I decided to cut up some mahogany and oak since they have very similar modulus of rupture as ash. This will help give me something fairly accurate to compare the alder and cedar with.
-----------------------------------
Oak: All from the same board

45 lbs
38 lbs
42.3 lbs
-----------------------------------
Mahogany: All from the same board

45 lbs
42.8 lbs
45.3 lbs
-----------------------------------
Alder: All from the same board

42.1 lbs
40 lbs
38 lbs
35.1 lbs
38.3 lbs
-----------------------------------
Red Cedar: From multiple boards

16.4 lbs - completely flat sawn
25.6 lbs
22.8 lbs
20.4 lbs
21.2 lbs
-----------------------------------
Those are all NON laminated. I was very impressed with the alder, it did a lot better than I thought it would.

I then laminated some strips of alder and cedar with 6oz. fiberglass tape. I used a fast setting resin and let it cure for 24 hours in a warm (75 degree) shop and also threw them in a 175 degree oven for a while the next day. Most of the laminations looked good but some weren't perfect. That may be to blame for some of the discrepancies.

These are the LAMINATED breaking strengths:

Alder:

52.6 lbs
44 lbs
50.5 lbs
-----------------------------------
Cedar:

24.5 lbs
26 lbs
33 lbs
35.3 lbs
35 lbs
-----------------------------------

So what's the take away from this? I'm not entirely sure.

I was disappointed the fiberglass didn't add more strength. The laminated cedar is still considerably weaker than the unlaminated oak and mahogany and I'd guess that proportionally 6oz glass would add more strength to a 1/4" strip than it would a 1.5" thick gunwale. Of course we don't know how strong strong enough really is so we can't say the cedar wouldn't be strong enough, we can only say it isn't as strong.

I was really impressed with the alder. When I checked the grain of the stock I had on hand it looked pretty good. It rots easily but so does ash and red oak. My gunwales would be epoxied to the hull, hopefully eliminating the possibility of water intrusion that could be trapped between the hull and gunwale. My boats are also stored inside all the time. Even unlaminated it's close to the strength of oak and mahogany and when laminated, which I'd probably do to add some hardness, it's bests them all. It's considerably lighter than ash, oak, or mahogany at 28lbs/cu. ft (oak, ash and mahogany are over 40lbs/cu. ft)

The direction of the grain seems to make a pretty big difference. From what I could tell with my limited test pieces flat sawn and quarter sawn are bad. Somewhere in between seems to be the strongest. This surprised me as I expected quarter sawn to be the strongest.

I also expected the laminated strips to "crunch" rather than "snap" when they broke but they seemed to snap and break the same way the unlaminated strips did. Ash seemed to have the most flex and the most gradual break. The others (except cedar) seemed to have less flex and they seemed to fail more suddenly (SNAP!), including cedar.

The end result is I still don't know what I'll be using for gunwales. I talked to the local lumberyard today and found out they do have a few pieces of douglas fir mixed in with their larger lumber so when I get time I'll have to dig through the piles to see what I can find. Very strong wood for its weight. Might be a nice balance of weight, strength, and hardness.

Happy to hear anyone else's thoughts.

Alan

 

[Canotrouge]

Good work Alan... When you say laminated, what exactly did you do? Sandwich glass tape in between 2 strips of wood, or the opposite? I know that rift sawn(grain running corner to corner when looked at the end) wood is the most stable and the "strongest" you can get... if you can get it. Of course, the quality, as you know, of the wood plays a big factor regarding strength, so tight regular grain is way better than "loose" unregular" grain. that is why pieces riven from a log are so much stronger than the same pieces swan from the same log....
Anyway, keep posting the result of your testing, it is really interesting!!

Cheers

 

[Jim Dodd]

I love the lines !

Great test Alan ! I've not used Alder.

You could always try aluminum gunnels?

Those little fingers of S-glass, will scrape easier the sooner you scrape them. Best of all you won't be cutting into your main 4oz layer. !

With the test ? When did you sleep ?
Ha !


Jim

 

[Mihun09]

The 77 year old Canadian w/c canoe I have has Douglas Fir inwales. Youngest of the w/c canoes is 40 years with mahogany inwales, oldest, the Morris, at 110 years has spruce inwales.

 

[memaquay]

I really like that colour, it's great! I think I might try that at some point in the future. I'm not sure why people put that football on the exterior, I've done roughly 15 canoes now with the football wetted out underneath the main layer at the same time. Edges are undetectable, and the process is the same as just wetting out one sheet.

Have you ever worked with douglas fir before? I found it to be very resistant to bends, and quite brittle. Tried to steam some, and it was very contrary. Perhaps it was just the wood I had, it had been a big rafter in a mine for several decades.

Anyway, I can't wait till you water test this one Alan! It certainly has lots of room in it!

 

[stripperguy]

Alan,
nice stuff!
Your laminated sections would need to be more representative of a gunnel section to realize the benefit of the added glass. I didn't want to divert the conversation earlier, but I should have stated it plainly. As you know, the advantage of the glass is in its tensile strength, it needs more, uhmmm, leverage, to be most effective. Remember, I mentioned about the cubic relation of strength to height. A laminated section 3/4" thick would be at least 8 times stronger than a 1/4" section, if loaded through the 3/4" direction.
I think if you tried a 1/2" x 3/4" section of cedar, laminated with some 6 oz cloth, you would see a tremendous increase in strength over any of the wood sections.
Apparently, it didn't take you very long to do that breaking comparison, so you still can whip up some more sample gunnel sections. You don't need to rush your gunnel decision, maybe you might want to try a few more alternate gunnel sections before committing to a final configuration. Most of the loads on the gunnels come from cartopping, and from the loads imparted when the boat is in the water.
Cartopping loads are mostly in the vertical plane, and the loads are only the hull weight (plus or minus some side loads from wind, and some loads from strapping the hull to the racks).
The loads on the gunnels when the boat is in the water are mostly transverse...the hull wants to open and close at the sheer line as it passes over and through waves. The thwarts prevent the hull from collapsing ( or expanding) but the gunnels must distribute those loads to the thwarts.
When you analyze the loads on the gunnels, you will quickly see which sections should be stronger, and which sections don't need to be super strong.

Often, the optimum solution, from an engineering point of view, is not implemented due to industrial inertia and public sentiment.
Human nature being what it is, things change slowly...the true innovators are few and far between.

 

[Jim Dodd]

Another thought. I've seen where a solo was built with a full length outwhale, and just a partial inwhale that supported the seat and one thwart.. The seats were hung from the scupered inwhale. Probably reducing the inwhale weight, buy 50-60%.
It would have also made it easier to unload packs from the area without the inwhale. I've not built one that way, but the guys that did were happy with them.
It might merit some testing.
Just a thought !

Jim

 

[Alan Gage]

When you say laminated, what exactly did you do? Sandwich glass tape in between 2 strips of wood, or the opposite?

I can see where the terminology I used could be a bit confusing. When I say laminated I mean a single strip of wood with fiberglass applied to both sides. It actually wraps around so three edges are covered, just how it would be done to a gunwale that was already attached to the hull.

Interesting stuff Stripperguy, thanks for posting that.

I'd assumed that since the size and thickness of the cloth itself was proportionately thicker it would have more advantage with the thin strips than with a thicker section. But I think I can see what you're saying. Increasing the thickness of the wood is the same as increasing the depth of the webbing in an I-joist or I-beam?

I'll laminate and break some thicker sections and see what I get. If I don't kill myself in the process I'll report back my findings.

Alan

 

[Jim Dodd]

Epoxy takes several days to come to a near full cure.

I'd also be interested in the amount of FLEX your strips take before breaking.

Sorry ! If I wanted all that extra info I should do it myself ! Right ?

Jim

 

[Alan Gage]

Last night I seal coated the interior and put fiberglass way up in the stems where it's a real pan in the butt trying to get the full sheet to lay.

This morning I laid out 6oz. cloth up to the waterline with extra reinforcements at the stems:


20150315_001 by Alan Gage, on Flickr

Then a full layer of 4oz. cloth went over everything:


20150315_002 by Alan Gage, on Flickr

And presto change-o!


20150315_003 by Alan Gage, on Flickr

You guys can say what you want about the aesthetics of external stems, and I'll grant you they look mighty fine, but the internal stems sure do look ugly on the inside! Good thing they'll be covered by floatation tanks.

Funnily enough the whitish staple holes on the interior don't really look too bad. On all but the darkest cedar I think they actually blend in with the hull better than the normal, dark, staple holes. That being said they do look a little weird because it's not what your brain expects to see.

Alan

 

[Alan Gage]

Ok, so who's ready to wade through a bunch more numbers? The results of the 2nd round of stick breaking are in.

This time I cut them to just under 5/8x3/4". To measure the breaking strength I used the hydraulic press and work. After calculating the are of the pistons in the ram I was able to install a pressure gauge and accurately convert the PSI reading to pounds of force.

The span was 9". No direct comparisons can be made with the previous test of 1/4" strips because of the difference in span (14" for the 1/4" strips).

The oak and mahogany are from single pieces of wood since I only have scraps on hand. The cedar and alder were cut from multiple pieces of wood.

Results below are for UNlaminated pieces in pounds of force:

Oak - 5/8" thickness:

118lbs
149
110
141
--------------------------------------------------
Mahogany - 5/8" thickness:

141lbs
157
141
149
--------------------------------------------------
Alder - 5/8" thickness

157lbs
118
110
110
141
144
110
141
--------------------------------------------------
Cedar - 5/8" thickness

118lbs
118
110
126
118
103
110
110
--------------------------------------------------

Results of Cedar laminated with 6oz. of fiberglass - 5/8" thickness

135lbs
130
125
125
130
125
126
118
133
141
--------------------------------------------------

I also turned some pieces on edge so they were 3/4" thick (still 5/8" wide). Those results are below.

Oak - 3/4" thickness

204lbs
110
--------------------------------------------------
Mahogany - 3/4" thickness:

157lbs
165
157
--------------------------------------------------
Cedar - 3/4" thickness

141lbs
118
149
118
118
--------------------------------------------------

Cedar - 3/4" thickness and laminated with 6oz. fiberglass

118lbs
157
157
--------------------------------------------------

 

[Alan Gage]

Once again I was surprised at the variation, especially in the oak since it all came from the same board. The best cedar was stronger than the worst oak.

The oak and alder were the only ones that had a tendency to fail with a sudden POP, with the pieces breaking completely in two. Not all the oak and alder failed in that way but none of the other woods did at all. The weakest pieces of alder were the ones that failed suddenly and completely. I thought when I looked at the grain pattern I'd be able to tell which was which but I couldn't come up with a correlation. Some of the strongest were both quarter and rift sawn and so were the weakest.

And what about the increase in strength by laminating with 6 oz. fiberglass? Throwing out any readings that are grossly high or low I come up with an average of 22.5 lbs for unlaminated 1/4" cedar strips and 30.75 lbs for laminated 1/4" cedar strips, an increase in strength of 36%.

For 5/8" strips the average for unlaminated cedar was 115 lbs and for laminated was 124 lbs, an increase of 8%.

It would appear, at least from this limited amount of testing, that the thicker the wood the less benefit a single layer of 6 oz. fiberglass provides.

Mahogany, which was the most consistent of the stronger woods, gives a 20% strength advantage to cedar in 5/8" strips. With 1/4 strips mahogany was nearly double the strength of cedar.

My conclusions? Wood sucks! How the heck are you supposed to know what you're getting? There were pieces of wood I thought looked great with nice grain that turned out t be much weaker than others. Perhaps a larger sample size would make things even things out but right now I think I'm more confused than when I began. Mahogany seems to be the only wood with any consistency but a larger sample size may show otherwise. The cedar wasn't too bad as far as consistency goes.

As it sits now I'm leaning heavily towards cedar wrapped with fiberglass to add to the wearability, 3/4" inwales and outwales. I'll use something heavier than 6oz. fiberglass tape. I've got plenty of cedar on hand with a handful of boards I'd set aside because they were too nice to cut into strips. One is substantially heavier than the others. Does that mean it's stronger? I don't know but I think I'll use it it. I'll probably use different boards for inwales and outwales just to hedge my bets.

At this point I don't have any confidence that if I ordered in another species of wood, be it ash, cherry or oak, that it would be substantially stronger than trying to pick the best looking boards of the cedar I have on hand. Mahogany is the only other thing I'd consider right now but I'd want to test some other boards first to see if the consistency remained.

I'll probably order some carbon, for other uses, and when I get a chance I'll laminate some pieces of foam with it. I'll be very interested to see what I get for results with that.

I'd love to hear other people's opinions of the results or if you think the testing was seriously flawed in any way. This isn't something I normally do.

Alan

 

[memaquay]

I'm not the analytical type Alan, the numbers are interesting, but don't have a lot of substance for me. I think about things like long term survival from car topping, pry strokes, banging off rocks, trees, dropping at the end of the port. If you wanted to carry your test further to see if it any sense to continue, maybe you should laminate a three foot piece of cedar and weigh it compared to 3 feet of mahogany and calculate the weight savings and see if the trade off is worth it. With my style of kamakazi canoeing, I'm pretty sure cedar gunwales wouldn't cut it.

 

[Iskweo]

Alan, you could consider using spruce. It is very strong for its weight and was often used by the old makers for gunwales. Of course that brings up the issue of where do you get 18 foot clear spruce in your (our) area. Pretty much nowhere. But if you could get enough to laminate up some inners then maybe that would work out for you. Overlap the pieces for better strength than a scarf joint.

Soak em, clamp in place, let dry to form, pull them off and glue them up in place again ...tedious but possible.

 

[Momentum]

Hey Alan,

Great work as always. You sure know how to blast through stripping out the hull. I only wish mine took so little time. Sigh

You have certainly covered a lot of detail with your last round of testing. As you have so elequently spoken...wood does suck when it comes to consistancy and trying to base a decision on the material you had for the testing. In your tests, you didn't mention if you had moisture tested all material to ensure they were similar values. This alone could have skewed your results for either the better or worse. I'm sure you are aware that all materials will naturally become dryer the longer they sit. This may explain your 2 pieces of cedar that have very different weights.

I do like Mems perspective on use though. We always have to remember that all of these items we are building are delicate balance between use, abuse, weight, strength, cost, and of course asthetics. Only you know how you intend to use this canoe, and what you will put it through.

I would pick a material that falls somewhere in the middle of YOUR range for this build. Pick something that suits your style. Balance out all the factors above with how you will attach them to the hull, and what you will cover them with.

Keep at it, you are in the home stretch now.

Momentum

 

[Jim Dodd]

There are soo many variables with wood ! Grain, grain direction. Density, rings per inch. It's tough to make a meaningful comparison. Carbon and epoxy, might reduce your variables.

Remember the old "Super Glue " advertisements? The guy hanging from his hard hat ! How many times have you tried to glue things with Super Glue, that would NOT stick ? Wood included. I guess what I'm saying tests need to be made with a finished product .

I was always told NOT to use Red Oak as gunnels, as it is porous and will split and crack. I know of three boats that are fine to this day, as they were SEALED.

My favorite is Ash, but that's not saying it's the BEST !

I'm confident You will come up with a viable solution ! Or You could Always use Aluminum !


Jim

 

[stripperguy]

Alan,
For wood gunnels, I have settled on mahogany, the weight/strength is tough to beat.
With respect to laminated wood gunnels, remember that a good portion of the transverse strength comes from the hull section itself.
I am still struggling to come up with an easy way to prefab foam/carbon gunnels...
I'm sure you'll decide on some elegant solution, you always do!!

 

[oldschool]

SG, when you refer to mahogany, what type of mahogany are you talking about?

 

[Alan Gage]

I just ordered 12 yards of carbon tape and will try carbon over foam gunnels. It's only money, right?

Actually it wasn't that expensive. I didn't get the bias weave stuff stripperguy used, just the standard weave. It was about $70. That will be topped with 8oz fiberglass tape.

I'll laminate some pieces of foam and break them the way I did with the wood for some strength comparisons.

Alan

 

[stripperguy]

SG, when you refer to mahogany, what type of mahogany are you talking about?

Honduran, of course!!


And Alan, be sure to give enough time for the resin to cure fully before you make your assessments...test pieces that I did stiffened significantly after a few days...