I just bought a used Hullavator for putting boats on my car. I'll put a link down below so you can see how it works. It lifts 40lbs of boat up on top of the car. The gas springs which provide the lift are worn out and I'm thinking of replacing them with higher poundage springs. Since it lifts 40 lbs and has 2 springs I'm assuming each is a 20lb'er. I'm thinking of swapping in 30 or 35lb springs to give it more lift. Anyone have experience with gas springs in applications like this and know if it would have any problems with stronger springs. My kayaks weigh at least 65 lbs
It looks like McMaster Carr has the stronger springs.

Thule 897XT - Hullavator Demonstrated by Rack Outfitters - YouTube

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You mean the gas struts, right? A gas spring is a different beast.

Going with larger struts could cause a problem...remember how old hoods used to have those massive springs on the hinges, and how some hoods would bend when closing them? You could be asking for the same issue here, and the possible projectile that is shot out when it breaks would be dangerous.

I would find a way to strengthen the brackets and platform prior to adding stronger struts.

If you are able to reinforce the brackets, then get longer, as well as stronger struts...it will lessen the snap that will happen with only going stronger.

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1987 560SL
85,000 miles

I think I would try it with the knackered springs. It doesn't look like it would be that hard to do with no help the way its designed.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Gas springs appears to be the standard designation: McMaster-Carr

I need the lift of the gas springs because these will end up on my Fuso Camper and I'll be trying to lift a 70lb boat while standing on a ladder. The existing frame of the mechanism is heavy steel.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Oh, I see. It didn't look too hard with the guy standing next to the compact suv.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

This is what I think of when I think of gas springs, due to the amount of die work I've done over the years...sorry about that.

My advise still stands on reinforcing the brackets...

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1987 560SL
85,000 miles

stronger springs = catapult???

Might be a unique way to 'launch' the boat...

I would spend the money on lighter boats...

Hoping to get one of these in the spring. 33lbs

Design Specifications
http://www.rawsonboat.com/

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On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

Nice boat. Even 30 lb boats are not easy to get up on the Fuso.

Attached Thumbnails

 

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Is the difference between a 20 and a 35lb spring enough to turn it into a catapult? I'm thinking the difference is fairly minimal.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Nice rig!!!

I would think not, especially when you have a heavier boat on it.
I was being a wiseacre...

How much is a set of springs?
I would try the heavier capacity ones and see.

The Rawson boat is made right here in CT and is a forward cockpit design, which I believe would give a tall guy like me a better chance at not ending up tail down in the water. Seems like all the other boats I have paddled, I end up moving the seat as far back as it goes so I have room for my legs, then the nose comes up... Can be a real drag paddling across the wind.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

Springs are only about $18 each.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I would just buy 'em. Maybe just pull one side down at a time and make sure they lock though.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

What kind of slide in camper is that? I like the popup feature.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

It's a Texson TS1000, now sold as a Northstar TS1000. Has the bath and shower. One feature I really like is that the pop up canvas has windows and screens all the way around which can be opened. Very nice for viewing scenery and sleeping with a breeze thru the windows and across the bed. I can crank up the top with 3 boats up there. I turned a sailboat winch handle into a crank handle to get some extra length for leverage.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I don't think that is necessarily a safe assumption. The gas springs aren't lifting the mass of the boat directly in a straight line. Instead, they are applying force through the mechanism as a whole - so mechanical advantage (or mechanical disadvantage) may come into play, based on the geometry of that mechanism.

I think you might want to be thinking about the distance over which the gas springs are applying force (in a straight line) compared to the distance that the boat is being lifted during that action.