Cartopping without a bow toggle

[Doug]

Okay everyone, leave the non-bow liners alone already. Just don't drive behind them.

[leong]

Oh, I thought it was all about rudders vs. skegs. Never mind.

[leong]

"Okay everyone, leave the non-bow liners alone already."

Oh, I thought it was all about rudders vs. skegs. Never mind.

[bob budd]

Think of the Space Shuttle Challenger disaster....

I can't allow this misrepresentation pass. Pressure from the white house overruled known risks with operating the solid fuel boosters in cold weather. A teacher's life was lost, she was not an astronaut who followed a career and accepted the risks. It was a shameful episode in the history of this nation.

[leong]

I can't allow this misrepresentation pass. Pressure from the white house overruled known risks with operating the solid fuel boosters in cold weather. A teacher's life was lost, she was not an astronaut who followed a career and accepted the risks. It was a shameful episode in the history of this nation.

What you say is probably true, but it's not the whole story. The engineering managers did underestimate the risk of the O-ring failing in cold temperatures. However, one of the engineers (a real engineer, not a manager) did know of the risk with the O-ring. He wrote several memos about the potential failure to several levels of supervisors and got nowhere.

Strangely, there was an editorial in Electronic Engineering Times that blamed this poor engineer for not raising the issue high enough (like to the President of the U.S. and to that poor teacher). I wish that he did, but I think he did enough. But his bosses, that's another matter!

[Brian Nystrom]

Mike, as I recall, you have a Saris roof rack on your Corolla, which is what i have. Contrary to David's ill-informed assertions, it's arguably the most solidly designed rack to ever hit the market and it makes Yakima and Thule racks look spindly and under-engineered. Sadly, Saris didn't do as good of a job of marketing it as they did of engineering it and they stopped making them a few years ago. I'm just hoping that it will work on whatever my next vehicle is, as it would be a real shame to have to shelve it.

Leon, I can assure you that there are no Morton-Thiokol O-rings in my rack. Moreover, roof-rack design is simple mechanics, it isn't "rocket science"; space shuttle design most certainly is. It's a poor analogy.

[leong]

Leon, I can assure you that there are no Morton-Thiokol O-rings in my rack. Moreover, roof-rack design is simple mechanics, it isn't "rocket science"; space shuttle design most certainly is. It's a poor analogy.

Okay, fair enough, the space shuttle is a lot more complex then a roof rack. I know this because I was a rocket scientist (if you count military surface-to-air and air-to-air missiles). As I told my friend the brain surgeon, what you do ain’t rocket science

Nevertheless, I look at it this way. I’m shouting to protect all of the poor schnooks (like me) who don’t use the Saris brand of roof racks. If I see danger and do not say danger, then I’m dangerous.

[leong]

Leon, I can assure you that there are no Morton-Thiokol O-rings in my rack. Moreover, roof-rack design is simple mechanics, it isn't "rocket science"; space shuttle design most certainly is. It's a poor analogy.

This thread is an oldie that I remembered after the following actual incident:

While refueling on the way home from Florida recently I noticed that the front Thule Load Strap’s cam buckle had let the strap slip through a few inches. Apparently, after this happened in real time, the front and rear tie-downs to the car held the kayak down and straight. Sans these two lines there could have been a terrible accident for someone behind or besides me. Note I did replace both straps before driving away. (Note to self: pick up a couple of new straps)

-Leon

PS

I did some Googling on this subject.

From here it says about someone’s accident:

“You probably set the rack up right. It's the kayak rigging that makes the rack come loose. Most other racks (like bike trays, ski racks, or Rocket Boxes) hold the bars a set distance. When we put kayaks on and crank down on cam straps to hold 'em down, we are forcing the racks together (or apart, depending on how you strap them down). This can cause the rack to push the car's roof down and make the rack's clip loose.”

The same thread also says:

"straps hold boats to the roof rack

bow and stern tie down ropes to the vehicle frame hold the rack to the vehicle"

and

“I know of no rack company that will cover rack failure unless front and rear tie down ropes are used.”

Some more good reading on the subject is here

PPS

Brian, While I’m at it I might as well address your comment that roof racks are not rocket science as are O-Rings. The Challenger Commissions Accident Report says:

“In view of the findings, the Commission concluded that the cause of

the Challenger accident was the failure of the pressure seal in the

aft field joint of the right Solid Rocket Booster. The failure was

due to a faulty design unacceptably sensitive to a number of factors.

These factors were the effects of temperature, physical dimensions,

the character of materials, the effects of reusability, processing and

the reaction of the joint to dynamic loading.”

Hmm, to this retired so-called “Rocket Scientist” it sounds like the design of a roof rack system has nearly as many concerns as there are for designing O-Rings. Roof racks must be designed to fit many different car models and factor into the design how temperature and humidity affect material dimensions and strength, corrosion, failures due to multiple reuse, forces due to driving speeds, wind speeds and passing vehicle speeds, etc.

To set the record straight I know almost nothing about designing O-Rings, or any mechanical systems for that matter. My main work entailed missile guidance algorithms; digital signal processing and data filtering; and tracking of incoming enemy ballistic missiles.

-Leon

[leong]

Yet another reason for bow and stern tie down lines. Stuff breaks!

Wasn't me, some bloke in Scotland.

[leong]

Ya think this setup doesn’t need bow and stern lines?

[Pintail]

We-ell, Sir Leon: those cars were ridiculously under-powered and he probably never used to get above 45mph...?

Now I am a non-bow-line type, myself (except occasionally, for a long trip); but I say each to his or her own taste. Personally, I do usually have two straps holding the boat on the front bar of my rack and then the loose ends are lashed to the bar, thus obviating any <reliance> solely on the actual buckle (though I have never had any problem with one, in nearly twenty years of carrying boats on the roof -- those springs have all been coated with silicone grease)

Neither am I in the slightest bit concerned about the roof-rack coming off the roof -- my car has fore-and-aft rails within the roof to which the rack is firmly bolted, which is the strongest and most reliable system of which I know. The crossbar clamps cannot come off.

Marc, I hope you have been well-entertained in this thread, which seems to have caused all sorts of long-forgotten names to crawl out into the open again...I also reckon you can quite easily devise a slip-knot to go around your monkey's fist? It'll be fine! No need to be overly-scientific...

(Here's looking at you, BrianN! Greetings, old bean)

[leong]

Now I am a non-bow-line type, myself (except occasionally, for a long trip); but I say each to his or her own taste. Personally, I do usually have two straps holding the boat on the front bar of my rack and then the loose ends are lashed to the bar, thus obviating any <reliance> solely on the actual buckle (though I have never had any problem with one, in nearly twenty years of carrying boats on the roof -- those springs have all been coated with silicone grease)

Sir Christopher et al,

You’ve already admitted that you occasionally tie a line to the bow of your kayak on longer trips. Isn’t that an explicit admission that you know that there could be some failure causing your kayak to fly off of the car?

In my penultimate post before this one, I provided this link that shows that even a Thule J-Stack kayak carrier can fail. Thus, even with failure-free roof racks and straps, a kayak can still fly off of a cartop because of a J-Stack (or cradle) failure.

Secondly, consider how you measure risk. One should be very concerned with high-consequence events even if they’re low probability events. And people underestimate the chances of low probability events because they think about Bell Curve (Normal) distributions. However, the failure statistics of a cartop system for carrying a kayak may, indeed, follow a leptokurtic distribution where extreme outcomes are much more likely than with Normal distributions.

Finally, the cost and effort of almost eliminating the risk of a kayak flying off the car is negligible; i.e. always tie the kayak to the front and back bumpers of your car.

Respectfully,

-Leon