Rooftop canoe weight calculation

I’m switching my canoe transportation vehicle from my Dad’s pickup truck to an SUV (which I am currently shopping for). My canoe is a 17’ Old Town Ranger that weighs in around 80 pounds.

One vehicle under consideration is a 2018 RAV4, which has a rooftop carrying limit of 100 pounds. My questions: Besides the weight of the canoe itself, are there any other forces I need to factor in that would make a 100 pound carrying limit insufficient? If so, what are those forces? If a 100 pound max is not enough, how much would I need?

Downforce from wind, and weight of any extras in your canoe. I once got my Dumoine home safely at speeds to 70 mph on my pickups rack without strapping it down. Definite oopsie moment, but demonstrated the strength of wind caused downforce. I always had the bow behind the windshield, preventing upforce and as I found, creating downforce. Your Rav and long canoe will have driving creating upforce, wind off the windshield aiming into the hull. That being said, TommyC1 who used to frequent this forum, went from a Ford F series to a Rav4 years ago, and I’m sure he often had 2 canoes on the roof. I’ve paddled with quite a few small suv owning canoists traveling interstate with 2 canoes on the roof, and racks with tennis balls on the end so you didn’t gash your head open bumping into them.

100 lbs is pretty thin aluminum. These days roof bars seem more like decorative skegs.

I’ve always assumed that a hull-up canoe gets some aerodynamic lift just due to the airfoil shape, but the front gets a lot more upward force than the rear due to to deflection off the windshield. So holding the bow down is critical. Question in my mind is how many pounds of force get added by tautening bumper tie downs, and do auto engineers take that into account when they publish weight limits?

If your want to carry canoes on a RAV, I would forgo the factory rack and use either Yakima or Thule towers and bars. They would be more sturdy and stable. On a RAV I think the best bar spacing you can have is about 4 ft between them and that means you have about 6.5 ft over each end if you have a 17ft canoe, so you will need to firmly tie down to he bars and both ends.

If you google car roof rack load limits you’ll find some good info.

This summary says that you should add a safety factor of 1.5 if driving off-road, presumably because the dynamic loads will add to the static weight. Manufacturers aren’t expecting you to do a full engineering analysis and calculate aerodynamic loads…they are giving you a (conservative) static load limit.

Car manufacturers will have some sort of safety factor built into their design so if it’s rated at 100 pounds it’s not going to fail at 101.

Another summary I saw pointed out that your rating is the lowest of everything involved, meaning that if the roof is only rated for 100 pounds and you add a rack that’s rated for 200 pounds you’re still limited to just 100 because of the roof.

A RAV4 with a 100 pound limit should be OK for you if you don’t plan heavy off-road use and you don’t throw your canoe onto the car. But if the 100 pound limit is the roof itself then don’t get an aftermarket rack with long bars and carry two heavy boats. Hopefully the rating is for the factory rack which can be replaced with something stronger.

There is a bit of confusion on this topic online. Using the factory crossbars the limit seem to be about 100 lbs., but some sources say the roof rails have a limit of 165 lbs., in both cases with the load evenly distributed. A friend of mine has a Rav 4 and has been carrying 2 kayaks with long Thule bars for years with no problems that I am aware of.

Lots of owner’s manuals are available online. The manual for the 2018 RAV4 says the limit for the factory crossbars (not the roof itself) is 102 pounds. While the factory system may be fine you’d definitely benefit from an upgrade to a Thule or Yakima rack.