View topic - Canoe on roof rack: Need front & rear tiedowns if . . .?

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PostPosted: August 18th, 2017, 9:17 pm 
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By the way, Thule seems to have a much more relaxed attitude about transporting a canoe than we do! Their Canoe transport "Portage" kit includes only TWO tielines beyond the 2 that secure the canoe to the roof rack: one for the front and one for the rear! This photo,from step 11 of the kit's instructions shows the setup that Thule thinks is sufficient:

Attachment:
Transporting canoe per Thule Portage kit instructions - 1.jpg
Transporting canoe per Thule Portage kit instructions - 1.jpg [ 59.96 KiB | Viewed 1606 times ]


Interestingly, the instructions also say to keep the distance between the crossbars on the roof rack to at least 24 inches but not more than 36 inches.

From the geometry of the Thule drawing, and the fact that Thule makes no attempt to control sideways deflection, it sounds like they think the purpose of the front and rear lines is to prevent upward lift by the wind (so as to prevent pulling the rack right off of the car's roof).

It IS important to note that this drawing came with the instructions that come with specifically the Thule "Portage" kit. That kit has 4 composite blocks that install on the crossbars to "trap" the canoe's gunwales so that the canoe cannot, at least at the rack, twist sideways. This restriction on the canoe's ability to twist may be sufficient, even though there is still 6 or 7 feet of canoe protruding either forward or rearward of the roof rack. So, we should probably NOT assume that 1 line at the front and 1 at the rear woudl necessarily be sufficient if no "blocks" to sideways motion are in use.

Since Thule is professionally in the business of transporting stuff on roof racks, Thule's engineers should know what they are doing. We MIGHT be overthinking this.

Jim G


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PostPosted: August 18th, 2017, 9:51 pm 
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JimGnitecki wrote:
wotrock wrote:
2 key points are often overlooked re front and rear tie downs: (1) the rear tie point on the canoe should be ahead of the tie point on the vehicle (e.g. tie to a rear thwart) (2)Likewise, the front tie point on the canoe should be behind the tie point on the vehicle. If the rear is tied incorrectly, only friction will restrain the canoe in case of very hard braking. If the front is wrong the wind resistance will only be resisted by friction. Tied properly, tension in the ropes or straps restrain the canoe. In you pic on another page both errors seem to be made.


Note that it is NOT important for the front tiedowns to lean rearward and the rear tielines to lean forward. What IS important is that they do not lean in the same direction! As long as we vertically have a quadrilateral in which either the top or the bottom is longer than the other, we are fine. In fact, if we secure the canoe longitudinally to the roof rack via a tiedown between a thwart and the rack, the need for the differential in upper and lower dimensions disappears, as the thwart to rack tiedown prevents either forward or rearward sliding of the canoe, and the front and rear tiedowns need only keep the canoe from twisting sideways.


Jim, you are pointing out what I think is one of the best things about tying to the rack for the fore (and aft) movement. The need to have those end lines do two different jobs - sometimes not easy to do - is removed.

JimGnitecki wrote:
From the geometry of the Thule drawing, and the fact that Thule makes no attempt to control sideways deflection, it sounds like they think the purpose of the front and rear lines is to prevent upward lift by the wind (so as to prevent pulling the rack right off of the car's roof).

Since Thule is professionally in the business of transporting stuff on roof racks, Thule's engineers should know what they are doing. We MIGHT be overthinking this.

Jim G


Yup! We might be.
OTOH we are the ones with our goods and our safety on the line. And in enough miles driven there are too many things that *might* happen. And I think it is important to remember that we might make a small miscue on one part somewhere: too loose, the wrong angle, canoe a few inches off the "usual" place, or whatever. Sometimes I find that snugging them in the wrong order can leave you with a problem. Then having it all set up to be perfect - with just the necessary lines - is no longer adequate.

Jim I think the system you have described gives you great security: lines have one job to do, and can have some backup from others in the case of a slack line, knot working loose, lines stretching when wet, or any of the other things that can happen all the way to breaking. In fact I am going to use your note above to review what I do.

Reverting to first principles, at least when traveling at high speeds or long distances is not a bad thing, IMHO. (I have moved a canoe around my neighbourhood with only two super-heavy bungee cords, and not had an incident, but that does not mean its a good idea.)

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PostPosted: August 18th, 2017, 9:59 pm 
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I think we both see advantages in "multiple safeguards"! As humans, we often make mistakes when distracted or fatigued, and having multiple safeguards gives us a degree of protection when we screw up.

Jim G


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PostPosted: August 19th, 2017, 10:51 am 
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I use a setup at the front like KipawaRob.

I have cross bars attached to factory rails, without those centering portage pieces you're talking about.

I have a bow tie down line which is a rope through the handle of the canoe down on each side to Thule hood straps using the truckers hitch. I use a strip of electricians tape around the edges of the hood so the straps don't wear down the paint. It will leave residue that you'll have to clean off. The stuff KipawaRob mentions would be superior; the whole front of my vehicle is covered in it, just not around the edges. Before I thought of the electricians tape it did wear through paint after a few years on an older vehicle I had.

I've never used a stern tie down, but it's always been tied to a van or SUV so the rear strap is fairly far back on the canoe.

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PostPosted: August 19th, 2017, 11:20 am 
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GRS Riverrider wrote:

. . .

I've never used a stern tie down, but it's always been tied to a van or SUV so the rear strap is fairly far back on the canoe.


Yes, that is an advantage of an SUV or station wagon, or a pickup truck with a rear supporting crossbar frame right near the tailgate.

Jim G


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PostPosted: August 21st, 2017, 3:48 pm 
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I'm not grokking those 2 key points wotrock ... got a picture?


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PostPosted: August 21st, 2017, 4:08 pm 
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Prospector16 wrote:
I'm not grokking those 2 key points wotrock ... got a picture?


He means that:

- The front and rear tiedowns should not be perfectly vertical, when looked at from the side of the car, AND

- They should be parallel AND opposed to to each other, when looked at from the side of the car. i.e. One should lean forward and the other should lean rearward.

The reason is that if they are either vertical or not opposed to each other, they won't stop a canoe from sliding forward under hard braking or being swept back by the wind at highway speed. The "opposing" ensures that they won't let a canoe slide EITHER forward or rearward.

However, I pointed out that another way of securing the canoe against forward or rearward sliding is to tie a thwart horizontally to one of the roof rack bars.

His method is better though in that besides preventing the cnaoe from sliding, 2 non-vertical and non-parallel sets of tiedown lines will help to control the canoe better if the canoe comes loose from the roof rack or the roof rack comes loose from the vehicle (surprisingly common apaprently due to poor mounting to thin metal roofs on some vehicles).

Jim G


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PostPosted: August 21st, 2017, 5:16 pm 
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Oh wait I just saw the posted picture now and get it. OK.


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PostPosted: August 21st, 2017, 7:44 pm 
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JimGnitecki wrote:
Note that it is NOT important for the front tiedowns to lean rearward and the rear tielines to lean forward. What IS important is that they do not lean in the same direction! As long as we vertically have a quadrilateral in which either the top or the bottom is longer than the other, we are fine. In fact, if we secure the canoe longitudinally to the roof rack via a tiedown between a thwart and the rack, the need for the differential in upper and lower dimensions disappears, as the thwart to rack tiedown prevents either forward or rearward sliding of the canoe, and the front and rear tiedowns need only keep the canoe from twisting sideways.

Jim G


I think the word you were looking for was trapezoid rather than quadrilateral. While it is technically correct that a trapezoid with either the long side down or the short side down would do the trick, in practical terms it's quite hard to get the front ties far enough back from the bow to make an angle big enough to offer much restraint.

I have tied a rear thwart or seat to the roof rack on the van, making the rear tie down unnecessary, but generally find it easier to tie lower down on the rear of the vehicle.

The other comment I'd make is that 2 ropes or straps are needed in front to keep the canoe from yawing, whereas 1 is sufficient in the rear(unless you expect 1 hell of a tailwind! :D )

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PostPosted: August 21st, 2017, 9:41 pm 
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wotrock wrote:
JimGnitecki wrote:
Note that it is NOT important for the front tiedowns to lean rearward and the rear tielines to lean forward. What IS important is that they do not lean in the same direction! As long as we vertically have a quadrilateral in which either the top or the bottom is longer than the other, we are fine. In fact, if we secure the canoe longitudinally to the roof rack via a tiedown between a thwart and the rack, the need for the differential in upper and lower dimensions disappears, as the thwart to rack tiedown prevents either forward or rearward sliding of the canoe, and the front and rear tiedowns need only keep the canoe from twisting sideways.

Jim G


, , ,

The other comment I'd make is that 2 ropes or straps are needed in front to keep the canoe from yawing, whereas 1 is sufficient in the rear(unless you expect 1 hell of a tailwind! :D )


You're probably right, but I keep imagining a very unaerodynamic truck going by in the passing lane at high speed and generating a horrendous buffeting side wind, and figure better safe than sorry . . . :)

Jim G


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PostPosted: August 27th, 2017, 10:31 am 
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If you tie the front of the canoe to the front of the roof rack and the back of the canoe to the back of the roof rack, the canoe should not be able to move backwards or forwards.

Solid rope a couple of good knots (e.g. bowline and a trucker's hitch) work well for this purpose.
(edit: posted from previous page after clicking on view unread posts - it seems I missed a lot! Have not read a lot of replies: apologies if already said)


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PostPosted: August 27th, 2017, 10:42 am 
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Ghost wrote:
If you tie the front of the canoe to the front of the roof rack and the back of the canoe to the back of the roof rack, the canoe should not be able to move backwards or forwards.

Solid rope a couple of good knots (e.g. bowline and a trucker's hitch) work well for this purpose.
(edit: posted from previous page after clicking on view unread posts - it seems I missed a lot! Have not read a lot of replies: apologies if already said)


Yes, beyond tieing the canoe to the rack to hold it down onto the rack, everyone has agreed that tieing a thwart to one or both crossbars to prevent forward or rearward sliding is important. I say "tieing a thwart to one or both crossbars" because IF the thwart happens to be right by one of the crossbars, tieing it to that ONE crossbar will prevent both forward and rearward movement. However, if the balance point of the canoe does nOT align a thwart with a crossbar, you need TWO tielines to the rack to prevent both forward and rwarward motion.

Tieing to the rack is beneficial even when both bow and stern non-parallel tiedowns are in use, as those tiedowns still allow a little forward or rearward movement because they are ANGLED and more vertical than horizontal.

Jim G


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PostPosted: August 27th, 2017, 11:25 am 
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So .... have you had the new boat on the water yet????


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PostPosted: August 27th, 2017, 12:00 pm 
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open_side_up wrote:
So .... have you had the new boat on the water yet????


Got the last of the required tiedowns and the cart the other day, so now have all the gear! Plus, my wife finally has a few days off starting today. So, will have it on the water early this week!

Debating whether to go to a nearby lake (15 miles each way) or to the much nearer (either 1 or 3 or 7 miles) coastal shoreline, or to the "urban area" lakes 18 miles away each way. I have pre-scouted all 3 possibilities.

All 3 are reached via paved road, but:

The coastal shoreline (east coast of Vancouver Island) would mean no hills or obstacles to transport the canoe over, and would probably not require bow and stern tiedowns (max speed would be 70 kph on the coastal access road) but would require attention to and limitations of the tides (our low tides put the water a full kilometer or more from the high tide line, over muddy sand, and high tide only comes every 6 hours at times that change daily and are not great for us right now!). Plus I would need to do a complete washdown of EVERYTHING (canoe, shoes, PFDs, paddles, etc) in the underground condo garage after each outing to get the salt off. Plus more attention to weather and tide currents, as winds from the east or NE can build too much wave action for me to handle with my low skill sets.

The lake is at a provincial park, would not require any washdown, is "safer" because it is a small lake, and the water level and therefore access is always the same, but the access is not good. I either have to park and unload/load the canoe right on the highway shoulder and navigate the canoe on the cart past multiple deadfall tree trunks, or park off-highway but actually have to take the canoe down a fairly steep hill with "rustic stairs" to a pebble beach. The lake is also unusable whenever the wind is from the west and is moderately strong (more than 10 kph), as the lake is small but long and narrow and lies east-west, so wave action is significant at the east end. (East wind is not relevant as there is no launch area available at the west end).

The next nearest readily accessible lakes are in Nanaimo (urban area), where parking and water access are easy and short, but where motorboat action is too high and where both the scenery and sound level are too urban for our tastes.

Still debating which location makes more sense given our novice level experience and the logistics for each . . .

Jim G


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PostPosted: August 27th, 2017, 12:42 pm 
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4 Pages!!!
Jim.... go paddling.

You're engineering this to death.
Too many hypotheticals can discourage you beyond repair.

We just came home last night from a six day trip to Kidprice Lake.
Two very lightweight solos (with lots of tumblehome) on the roof rack, 80kms of highway speed (at 100kph), another 80 kms of dirt road with washboard, potholes, and overloaded logging trucks that drive like they own the road.

This is with two hull straps and one front tie down per boat. We stop at intervals to check up on the boats.
The only thing we've ever discovered (in all our years of boat transporting) was the foam pads starting to move out of place and this has only happened on our round roof Tercel that had no roof rack.

I'm getting worried that this may be one of the boats that I regularly hunt for. 8)

Like Starsky said... "Do it, do it"


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