Carrying a composite kayak on roofrack

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sprockerdog
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Carrying a composite kayak on roofrack

Post by sprockerdog »

Can anyone advise is there an ideal or minimum distance between roof bars for transporting an 18' composite kayak?

I have Thule Aero bars and Thule Dockglide supports for my RTM Tempo, and wondering (hoping) that these will be OK for my next kayak, but unsure if the distance between the roof bars will be enough.

twopigs
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Re: Carrying a composite kayak on roofrack

Post by twopigs »

Composite sea kayaks are usually carried on J-cradles rather than resting on the bars ..... composite racing kayaks are usually carried on V-bars. I have set my roof bars as far apart as possible on the roof rails.
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sprockerdog
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Re: Carrying a composite kayak on roofrack

Post by sprockerdog »

twopigs wrote:
Sat Oct 09, 2021 12:12 pm
Composite sea kayaks are usually carried on J-cradles rather than resting on the bars ..... composite racing kayaks are usually carried on V-bars. I have set my roof bars as far apart as possible on the roof rails.
The Dockglide system cradles the hull so it doesn't actually rest on the bars.

https://www.thule.com/en-gb/winter-and- ... roof-racks

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Re: Carrying a composite kayak on roofrack

Post by pathbrae »

Try to get the support under the bulkheads (usually front of cockpit and between day hatch and rear hatch) to minimise the squish on the hull.
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Tricky Ricky
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Re: Carrying a composite kayak on roofrack

Post by Tricky Ricky »

I think Thule recommend no less than 700 mm btw bars. A few mm when it's someone else's kayak should be grand. Lol.

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Re: Carrying a composite kayak on roofrack

Post by charleston14 »

I use the dockglide system for composite sea kayaks, bars as far apart as they will go and a bow and stern line down to a towing eye.


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adventureagent
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Re: Carrying a composite kayak on roofrack

Post by adventureagent »

Racks by mfg's like Thule specify where to place the rack towers on the car. I think this is to minimize effects on doors, minimizing noise, rain dripping into the car. Some vehicles have small triangles to assist located racks.

That being known, I use a verticle bar on each rack cross-bar. I mount the towers, as far as reasonable apart. This is how I've come to know about water and noise and door closure issues.

Further, I mount my boat ON EDGE, as I think this is the strongest way, given that the re-inforced seam, on edge, is a curve. I can give quite a strong pull on the "over-straps" without them deflecting the boat. I have taken standard foam kayak blocks and cut them to the profile of the boat as it meets each cross-bar. That prevents direct contact with cross-bars.

Two small, strong cords are at my bow so I don't have to tie on at each paddle launch. I tie the bow to each side of the front be means of nylon webbing attached to the car by means of the bolts that hold the fender on. I tie the stern to a single webbing strap which is attached to some body member (not human) in the storage area.Two straps aft seem inconvenient in my case.
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Chris Bolton
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Re: Carrying a composite kayak on roofrack

Post by Chris Bolton »

There are two issues with supporting boats on roof bars; to ensure the load is stable and to avoid damaging the boat. Putting the bars as far apart as possible helps with stability. There's a secondary effect for a long boat with the bars close together, any longitudinal pitching of the boat causes an increased load at the support points. That's why long delicate boats like racing K1s are usually carried on V bars, which include a longitudinal bar that spaces out the support points on the boat. Tying the ends to the vehicle helps with stability of the load, but don't tie them tight, as that pulls the boat down onto the bars.

I have always carried composite sea kayaks, downriver race kayaks and slalom kayaks on their edge seam, supported against uprights, with no padding on the bars, and have never had any damage. Paddling allows the boat to move a bit, by squashing it, so I prefer to strap the boat tight to the bars and know it can't move.

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Re: Carrying a composite kayak on roofrack

Post by sprockerdog »

I'm thinking at 800mm spacing my roof bars are not going to be far enough apart. Another thought I've had is a length of aluminium extrusion clamped longitudinally to the roof bars, with J bars at each end. This would in effect lengthen the distance between support points.
This may get me through the next six months until my car is exchanged.

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Re: Carrying a composite kayak on roofrack

Post by adventureagent »

Chris Bolton wrote:
Mon Oct 11, 2021 8:45 pm
There are two issues with supporting boats on roof bars; to ensure the load is stable and to avoid damaging the boat. Putting the bars as far apart as possible helps with stability. There's a secondary effect for a long boat with the bars close together, any longitudinal pitching of the boat causes an increased load at the support points. That's why long delicate boats like racing K1s are usually carried on V bars, which include a longitudinal bar that spaces out the support points on the boat. Tying the ends to the vehicle helps with stability of the load, but don't tie them tight, as that pulls the boat down onto the bars.

I have always carried composite sea kayaks, downriver race kayaks and slalom kayaks on their edge seam, supported against uprights, with no padding on the bars, and have never had any damage. Paddling allows the boat to move a bit, by squashing it, so I prefer to strap the boat tight to the bars and know it can't move.
As my webbing over the boat, to and from the rack are each in the smaller section of the boat, fore and aft, the amount of movement is miniscule. Fore and aft shifting is virtually elliminated. I do this with care, as in the past, had boats leave the rack on car braking. Very risky to others' property.

My long, downward pull on the straps pretty much puts the edge of the boat on the bar with little room to move up / down (nil). The long pull is steady, not jerky, as here too I have in the past exerienced boats cracking. This method seems to work very very well.

Bow and stern lines (dyneema) are taught, not over-tightened and virtually unnecessary.

I use a red flag at the stern, with reflective material attached, for the fools drunk or doped, who may not see the boat, and it dangles about mid-windshield height.
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adventureagent
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Re: Carrying a composite kayak on roofrack

Post by adventureagent »

Another thing I did with a previous boat was to make a square frame. The length was such that I could mount standard kayak foam blocks on the ends. The ends were at the point where the boat's bulkheads meet the hull.

This way the hull didn't get deflected . In practise, however, sometimes the boat was pushed just ahead of or behing the bulkhead. Still, closeness to the bulkheads seemed to minimize deflection of the hull. This was a simple, bolt-together rig and it served well until I decided to take another boat alongside. This needed room and rather than "J" racks, which mean a higher lift, I installed my old straight-bar, verticals that I used to use for my whitewater boats.

At all times, I try to remember those lessons of the sound of cracking resin. I've had epoxy boats (Sana Extreme) FULLY rotate in the rack/ropes. the resin cracked, but the Kevlar was not affected. Virtually destroyed the boat, really, but it remains a reminder of what a passing truck can do, so I'm pretty good at tying my boats.

Seems as if something could go wrong, it happened to me. Fifty years after starting kayaking, I'm still learning! Yay !!
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Chris Bolton
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Re: Carrying a composite kayak on roofrack

Post by Chris Bolton »

Bow and stern lines (dyneema) are … … virtually unnecessary.
There are not necessary for stability if your rack bars are a good distance apart, but I use them for two reasons. If you have a failure of a strap, upright to rack or rack to car fixing, they may prevent the boat coming off the car, avoiding potentially fatal consequences to boat and anyone it hits. Secondly, the instructions for my (Thule) bars require them for long loads, and in the event of an accident, it's possible that failing to follow the instructions might be considered to invalidate my insurance.

eskapist
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Re: Carrying a composite kayak on roofrack

Post by eskapist »

Chris Bolton wrote:
Tue Oct 12, 2021 3:27 pm
Secondly, the instructions for my (Thule) bars require them for long loads, and in the event of an accident, it's possible that failing to follow the instructions might be considered to invalidate my insurance.
Chris Bolton's concerns about any insurance issues can also apply to the location of the roof rack/ roof bars and the maximum static load being carried which must be according to any instructions given in the owner's/ driver's manual. It's better to fit the bars correctly and if necessary attach a framework to suit the load. I have a quite short car and this is my low cost lightweight solution.
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Re: Carrying a composite kayak on roofrack

Post by Tricky Ricky »

+1 Chris Bolton.

adventureagent
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Re: Carrying a composite kayak on roofrack

Post by adventureagent »

eskapist wrote:
Wed Oct 13, 2021 12:46 pm

Chris Bolton's concerns about any insurance issues can also apply to the location of the roof rack/ roof bars and the maximum static load being carried which must be according to any instructions given in the owner's/ driver's manual. It's better to fit the bars correctly and if necessary attach a framework to suit the load. I have a quite short car and this is my low cost lightweight solution.
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This is similar to what I refered to when I said I made an aluminum frame, whereas yours is wood. In my case, the frame extends fore and aft. U bolts hold it to the rack and allow to adjust forward or back to compensate for boat overhang. And as I said, such that the foam blocks are under the bulkheads to lessen the deflection of the hull.This is important if you leave a "plastic" boat up for a long time. It also allows more snugging of tie downs.

Yours is a really nice, neatly fitted unit. Beautiful. Maybe you should set the plan out somewhere on this site so others could do their own.

Your comment re insurance is something I hadn't thought of, though. Of course the industry would look / find ways to find fault with the owner/operator. That's just logical, as that's what their business requires of them. Never thought of it. Thank you.
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Re: Carrying a composite kayak on roofrack

Post by fergus_finn »

We had a similar issue. Short car / long kayak. In this case 0.8m between the bars and and a nordkapp HM. We made a couple of short trips using just padding on the bars and it was not good. Deflection of the hull and pitching. Very bad for the boat. Our solution was to use the hull as a male mould for 2 fiberglass cradles. These were laid up using cheap polyester resin and CSM. Carpet was also laid over the hull prior to layup. The finished cradles were then attached to the bars using 2*6mm bolts with holes drilled through the bars. A small mark on the hull means that the boat is always in the same place on the rack. The cradles have been a huge improvement. No hull deflection when tieing down and solid as a rock on the motorway. I appreciate that this is more work than just getting J cradles but I like knowing that the boat is supported & secured as well as it can be. I also do front & back tie downs.
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