Canoe failure analysis

I was wondering if any of you epoxy gurus can give me insights into a structural failure that I just experienced. Here is the scenario: 1. the canoe is epoxy/ composite. 2. The canoe is 1 week old. 3. The canoe has been used three times in light ocean conditions. 5 knot wind, 2 foot swell. 4. The last time the canoe was used it was washed down and placed on padded truck racks. 6. When placed on the racks the afternoon temperature was 85 degrees and cooling. 7. The drain plug was not removed 8. The straps were not overly tightened and the canoe was transported at 35 mph a total of 1 1/2 miles. 9. The following morning the canoe- where it rests on the rear rack- had a large indentation with both lateral and longitudinal cracks in the gell coat leading from the indentation. The longitudinal cracks run from the bottom of the hull to the deck seam and two run from the indentation about three inches toward the hull. 10. The cracks definitey go all the way through the layup. 11. the hull seems soft in the area around the indentation. It will compress and leave indentations when pushed on with a finger. 12. Other areas in the hull seem soft and leave indentations.

This is the seventh canoe I have owned. The second from this manufacturer. The storeage and transportation methods have been virtually the same for all the canoes. Never a previous problem. I could use some advice so I can understand the prossible causes before I go discuss it with the builder. I am bummed out because the trades are back this weekend.

Mahalo for your help

Poidog

Submitted by poidog on Wed, 10/28/2009 - 11:43am



probably did not cure long enough???? I had a friend whose canoes went through the same problem and the curing part was the whole reason.


#1 Wed, 10/28/2009 - 1:46pm


If it was still on the racks, maybe something or somebody hit/fell/or otherwise applied a pressure/shock load to the nose or tail of your canoe. Bummers...


#2 Wed, 10/28/2009 - 2:23pm


There is one piece of information missing from your recap... what was the temperature when you inserted the drain plug? If the drainplug was inserted when the temperature was warm and not removed, and there was not another source to equalize the pressure between the inside of the canoe and the outside of the canoe (i.e. the canoe was sealed), then you have the source of your problem. A canoe that is sealed when the air temperature is warm and then allowed to cool (even in ambient temperatures), the air inside the canoe will reduce in volume, causing the canoe to collapse in on itself (i.e. the sides will be "sucked" in toward the middle of the canoe). This happens when there is no way for the canoe to equalize the pressure as the temperature drops and air volume is reduced. Always make sure your plug has a "snorkel" that will allow the canoe to "breathe" (i.e allow air to move in/out of the canoe as the temperature changes).


#3 Wed, 10/28/2009 - 4:02pm


Thank you all for your responses. The drain plug is standard issue with the snorkle. I checked to make sure the snorkle was clear. It was in place during wash down and also when placed on the racks. Temperatures have been around 82 degrees in the evening.- air and sea. The wash down water is not cold. There were no extreme temperature changes,. Nothing hit the canoe or put any undue force at stern or bow.
The uncured epoxy sounds reasonable since I have had the same problems working on boats in humid conditions and trying to go light on the hardener.
If anyone else has had this problem recently or seen this problem in other canoes- I would like to hear about it. I guess in 2006 everyone got concerned about a canoe breaking apart off Makapuu because the carbon fabric had never been saturated..

Mahalo.


#4 Wed, 10/28/2009 - 4:48pm


Second the vote that someone did a pullup on the boat then ran away.

Unless the thing was soggy wet uncured it really could not have sagged and cracked so much from its own weight and would have done do the moment you used if it was that bad. ...

Pressure differential stuff does not show up as describe either ...

Poidog, with epoxys, there is no such thing as "going light on the hardeners" You stay with the manufacture volume or weight ratios and thats it. If you do error it could be with less hardener but not for any other reason than you don't feel like putting that little bit more in and asking for trouble doing so on a regular basis. "Esters" yes but even here its to reduce cure time, not to save weight.

Sorry that thing is broken ... Call me if you want. I can help.

aloha,
pog


#5 Wed, 10/28/2009 - 5:15pm


I sense the "H" word coming up.


#6 Wed, 10/28/2009 - 5:27pm


Thank you for responses. The boat was taken out of the water, placed directly on my truck racks, driven 1.5 miles and parked in my back yard. It was not tweaked by anyone or anything.. That is why I am so amazed that this happened and wanted to put it out there to see if anyone knows why it happened. As far as hardener to epoxy ratios-I have made a mistake in ratio and could see that happening in a manufacturing process. I just do not know if this kind of failure would be due to uncured epoxy layup. In any case I will be paying for repairs but do not want to see it happen again- especially since I have no idea what caused it. Kukae happens- maybe some act of God- just very strange.


#7 Wed, 10/28/2009 - 6:51pm


That kind of damage can only be done by someone/something putting pressure/weight on the canoe tail end while it was tied down on the rack. I doubt a change in tempurature would be so specific as to only cause cracking right where the canoe rests on a truck rack.

The only other damage similar to yours that I remember is when someone had their OC-1 on tied down on their truck rack and a garbage/delivery truck backed into it.


#8 Wed, 10/28/2009 - 8:11pm


The manufacturer would like to know about this problem as they would like to figure out if it was a layup problem or curing problem(hardener???) or a use problem(pullups or garbage truck). Plus they would know best the solution. Poidog- why ask the FOrum when the builder would know best? Go directly to the builder.


#9 Wed, 10/28/2009 - 8:28pm


If its new it would be really shiny and if it was dropped or hit maybe there was a mark left where the point of impact. take a really long close look at it.

I dropped a surf ski of my truck and it looked fine but I loosen the Center board on the inside. always tie them down, mental note. also when I got over 200 ponds I put more pressure on the canoes but a new, modern one should be able to hold most people.


#10 Wed, 10/28/2009 - 8:40pm


. Wanted to find out if anyone had similar problems before I went to the builder- who I respect very much. I swear there was no structural impact- dropping, banging, hitting, hanging, surfing, etc . But that is what is going to be in the builder's mind. . The damage occured where the boat contacted the rack and I used a bungee cord to hold it down since I was driving such a short distance so there is not an overly tightened strap issue. The only response that has made sense to me is the pressure differential- I have a snorkeled drain plug and did not remove it. . The snorkle is not obstructed but may have not been of sufficient diameter to allow the pressure to equalize?. Maybe a lesson learned and to be shared. . Otherwise- manufacturing defect or a combination of both. I agree- I will have to ultimately trust the builder to determine cause and solution. If it happens again or to someone else under similar conditons? that is why appreciate being able to use this forum..


#11 Wed, 10/28/2009 - 10:07pm


Even the smallest unblocked snorkel tube will allow for proper equalization of pressure.


#12 Thu, 10/29/2009 - 2:54am


Unless that snorkel tube is bent or hull weight kinks it when it sits on the racks from roof or rack pressure (sorry JC). I saw a friends respond in the same way after transport . Not saying poidog's did but it does happen and you wouldn't know it unless you saw it before you lifted the canoe off. In my friends case the canoe had "sucked" in and when he pulled the plug it popped out. He had traveled over a good elevation change. Local repair shop fixed it nice though!


#13 Thu, 10/29/2009 - 5:04am


Yep on the tube ... as long as the air can exhange you will not have pressure damage + you gotta have some dramatic differences in temp / alititude to get major damage.

Poidog ... with that bunji on there instead of of a strap, would you say it would also allow the boat come off the racks and slam down if you hit a big bump or dip ? Is the bunji one of those multi colored ones or the contractor style black ones ?

Sorry again man, just thinking like I would if I saw it.

aloha,
pog


#14 Thu, 10/29/2009 - 8:31am


In regards to using bungy cord to tie down a hull, I've seen others use them without any problems to their hull. Granted the ones being used were pretty stretched/used already and had just enough tension to hold down and not stretch any further if you hit a bump to bounce around.

The one time I was forced to use a bungy cord to tie down the back of my hull (didn't have enough straps in the truck on the pickup point) I ended up with a 2.5 inch parallel crack in the gelcoat on the top deck just above the seam. The padded rack didn't provide enough surface support, so it actually put stress in that one point with the bungy's tension pulling it down.


#15 Thu, 10/29/2009 - 11:04am


The story is now that the bungee cord on the padded rack - traveling 1.5 miles - allowed the hull of the canoe to crack due to its movement against the padded rack as it moved moved up and down. Have carried other canoes the same way without mishap. Guess I am dealing with transporting eggshells and as a consumer I should be more careful. I will now get a padded cover. use padded saddles and make sure the straps are not too tight. Already I am feeling the pain of having to protect such a fragile craft. Guess I will go back to surfing. At least when the board breaks it was because I was having way too much fun. Not because it was sitting on my truck.
One reason I never got into wind surfing- too much hum bug. I am now feeling the hum bug coming on.

a hui hou....poi dog


#16 Thu, 10/29/2009 - 9:01pm


Poidog
I feel for you man. a new canoe too. If I had to guess . and that's guess. I would say at some point , when you were not there, or sleeping someone or something hit it. other than that it was in the curing and or making of the canoe. Its tuff but you goto get on with the repair and let the Humbug go. and get back out there.


#17 Thu, 10/29/2009 - 9:39pm


What color/kind of padding is on your truck rack and was the truck parked in the sun while you were paddling?

As noted by others, if your canoe was only a week old it may not have been fully cured and perhaps if a portion of the canoe was held against a hot enough surface it may have caused a small exothermic reaction in the uncured resin. Not normally a problem for a fully cured canoe ...

If you've ever mixed up a large batch of epoxy you may have witnessed an exothermic reaction as the epoxy heats and hardens quickly forming a molten, melty mess. Shouldn't happen to an oven baked canoe though...

Just a thought.


#18 Fri, 10/30/2009 - 3:04pm


What did the builder say?


#19 Fri, 10/30/2009 - 3:47pm


The analysis from the builder- I used a bungee on the canoe at the stern (. Have done that umpteen times with other canoes since I am only 1.5 miles from where I launch). The canoe bounced on the padded rack (surfboard pad- also used umpteen time with other canoes) and fractured the hull ! There are other soft spots but I hate to put too many dimples in the hull testing it. Heat... beitg on a padded lumber rack,,,,,uncured expoxy.... an egg shell scenario.
Proving it is a defect? ??? Like so many other responses- some one must have grabbed it....I must have hit it,,,,,etc. None of those scenarios occurred. The canoe went from wash down in perfect shape- on my rack and the next morning it looked like someone took a 2x4 to it. The gods have not been kind.


#20 Fri, 10/30/2009 - 5:45pm


Check the ex-girlfriend?? Or the ex-boyfriend of your new chick???


#21 Fri, 10/30/2009 - 6:07pm


Sounds like it could be how it was made. or your budgie is getting old. a new bump on your road,or a mix of these things.
I like those cradles and ratchet straps.
Photobucket Its funny we want canoes that weigh a certain weight that is easy to carry to the water and when we start during races it gets up and goes with ease,,, but the lighter we get the more venerable we could be making our canoes. there is the only good reason to have a cap on our canoe weight's.


#22 Fri, 10/30/2009 - 7:46pm


Hi Poidog,

Just wanted to know ...You had a bunji on the "stern" ... Very most aft part on the boat ? Or over the boat right @ rack point ?

How much over hang from where the boat contacted the racks to most aft point on the boat ?

Just wondering.

aloha,
pog


#23 Fri, 10/30/2009 - 11:04pm


Poidog. I just have to say that I have done...and continue to do the exact same thing transporting my canoes. For close commutes, I just use bungees on my truck rack w/ padded bars like you do. One bungee just in front of the cockpit area (the pedals), and one probably about a third of the way between the cockpit and stern of the boat. For longer trips..I use straps. From what I understand, there is a bit more structural integrity built into the boat deck in and around the cockpit area. I usually try to get my bungees pretty tight so the hull doesn't bounce or slide around. I pretty much try to pull them as tight as I can KEEPING IN MIND if they're too tight, I could risk cracking a seam etc. (I have to worry about this using straps too). Like you, I've done this forever (over 10 yrs). FORTUNATELY, NO problems. You do have the canoe with the deck side down on the racks, right? Once I'm at my destination, if my canoe's going to be on my racks for some time, I usually loosen the bungees up a bit....Especially when out in the summer sun/heat. I usually try to get the canoe off of the truck as soon as I can....discourage vandalism, etc. Sorry to hear about your situation. I would first think vandalism....but you seem to think this is not the case. I think if there may be construction defects, you will find soft spots, defects, etc in other areas of the canoe as well.


#24 Sat, 10/31/2009 - 2:43am


I have a truck with pipe racks. The area where the padded rack is just aft of the seat well. There is 6 feet of stern out in space from tjhe rear rack.The bungee is at the rear rack. I lay the canoe pretty much on its side so that the deck seam is supported by the pads. It was secure enough so the canoe would not slide from side to side. I hear you about having the canoe ride on its deck- that is probably the way to go. The only way for vandalism- someone came in my yard and yanked up and down on the canoe at the stern. I have no enemies and the chances of that are way remote.

As for now I am going with the idea that the damage occured in transport due to vibration on a weak part of the hull. The question in my mind- should that have happened ? After repairs are made I will treat it as being more fragile then I would have otherwise believed and see what happens from there. I realise we have all given up structure strength for lightness. The canoe is great. I only hope that this is the only anamoly I will experience with it and that any future failures show up on my truck and not out in the ocean.


#25 Sat, 10/31/2009 - 6:55am


How about snaping a few pics with the canoe on your truck and of the damaged area and post them.


#26 Sat, 10/31/2009 - 7:08am


These are some of the best straps you can buy ... And they are cheap.

http://www.nrsweb.com/shop/product.asp?pfid=1440&deptid=1188

As compared to bunjis >>>

Nice to have a little more surface to spread the load and grab the boat more ( think shifting @ speed ) at the same time.

No need to crank them down, get 'em flat, take out the slack and then just 'bump' them. They hold the boat without getting tighter and tighter.

If the boats are going to sit for more than say 15 minutes ( 5 if dark color and out in direct sun ) for sure back them off.

Poidog, I would double check with your builder about racking the boat ON the seam .... asking for trouble there too.

aloha,
pog


#27 Sat, 10/31/2009 - 9:34am


Sounds like laying the canoe on its side on the rack torqued it. Lay it on the deck- front tie down with the front of cockpit (strongest part of the canoe) on the front pipe rack secure. The back just firm should do it. Ouch!


#28 Sun, 11/01/2009 - 8:36pm


Thanks paddlefast and others offering help. I will change my ways even though no problems with carbon epoxy canoes in the past. Will be treating this one like a new born. I like those padded da kine canoe bags. Anything that helps,. Looking forward to getting repairs completed and to getting back on the water.

mahalo.


#29 Mon, 11/02/2009 - 7:34am


Hawaiian Canoe Canvas makes padded bags that are custom fit for your canoe and the snug fit and 1/2" closed cell foam offers superior protection for your canoe, even in neighbor island shipping. They are a bit pricey, but worth the extra money if you travel alot with your boat. http://www.hawaiiancanvas.com


#30 Tue, 03/09/2010 - 2:10pm


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