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Damon Linkous
1992 Hobie 18
Memphis, TN
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Catamaran trailer with three cross arms?
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Posted: May 31, 2012 - 03:54 PM
Ever seen a beachcat trailer with six single rollers on three cross arms? Neither had I until this Hobie 18 was posted for sale. Pretty interesting approach for spreading the load. Not really needed on a tough H18 but could be a good idea for lighter built boats.
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Damon Linkous
1992 Hobie 18
Memphis, TN
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Posted: May 31, 2012 - 04:33 PM
I do not think the 6 rollers would have near the supporting area of 4 cradles, but I think its a good and cheap idea.
I moved my front cross bar pretty far forward on my trailer. The long bows have too much leverage on the front cradles of many cat trailers in my opinion. Moving the cross bar forward made a big difference in the over all stiffness without making the set-up any longer. It does make loading very slightly more difficult, but as long as the bows will reach the front cradles before the boat gets too far past its balance point on the rear cradles, its ok.
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Greenville SC
Offering sails and other go fast parts for A-class catamarans
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Posted: May 31, 2012 - 05:37 PM
It would be even better if the forward rollers were ganged in pairs on a single pivot. That way they would distribute that load evenly between the four rollers, similar to how the suspension on the Mars rovers work.
Tom
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Tom Benedict
Island of Hawaii
P-Cat 18 / Sail# 361 / HA 7633 H / "Smilodon"
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Posted: Jun 01, 2012 - 07:46 AM
Three rollers will not necessarily support evenly, as there is no way to ensure all three supports will align properly. Two of the roller sets will almost always support more of the load than the third set.
I also think distributing the load over a greater area will be more beneficial than adding 2 more point loads. I have cradles on the rear and bunks up front.
I estimate the area supporting my boat is more than 500 square inches, if the boat weighs 400 lbs, that results in the hull, over the support carrying 0.8 lbs/sq. in. (static, dynamic loading is higher on the road). Using rollers, assuming the contact 4 points on the same boat are 0.5” wide by 2” long (that is a generous assumption for a soft roller), the static point loads result in each hull, over the roller, carrying 100 lbs/sq. in. Increasing the number of rollers by two, to six total (using the same rollers) will yield a load of about 67 lbs/sq. in. Three double rollers set ups will further drop this to about 33 lb/sq. in., and may alleviate some of the problems with the triple support I metioned earlier.
The drawback to cradles is that they have too much friction for loading and unloading. My plan is to reinstall the rear rollers, use them for loading/unloading and then place the cradles under the hull for transport.
Edited by presto99 on Jun 01, 2012 - 07:49 AM.
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Jeff
Houston TX
1986 Hobie 18 Sail# 13031
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Posted: Jun 01, 2012 - 01:53 PM
Huh! I like that idea!
I wonder if it would be possible to set up a roller/cradle arrangement so you can crank the cradles out of the way, roll the boat on and off, then crank them back into place for travel. That way there's not much wrench work to get them in and out of place. Something like a good solid cam lever would be nice for this.
Nice analysis on pressure and loading, by the way. I've got rollers in back and cradles in front at the moment. I might revisit my trailer at some point.
Tom
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Tom Benedict
Island of Hawaii
P-Cat 18 / Sail# 361 / HA 7633 H / "Smilodon"
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Posted: Jun 02, 2012 - 08:18 AM
I have cradles on both beams; came that way when I bought it. As long as I keep the hulls waxed, easy on, easy off.
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Eric C
Force 5 project boat
Unnamed
Previous boat
1980 Nacra 5.2
"Double Vision"
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Posted: Jun 03, 2012 - 04:08 PM
I agree with Jeff about the 3 cross bars being hard to evenly distribute the weight. Seems like you would either only be supported by 2 cross-beams, or worst case you would be pushing the middle beam up into the hulls by pulling the bow and stern down to their beams. Since most hulls are not straight on the bottom this makes alignment tricky. I think cradles and/or double rollers are best, but for most old style boats the single front and rear roller is sufficient unless you trailer a lot of long distances. The only major problem I have seen is someone leaving a trampoline on the boat and have a lot of snow buildup on it in the winter.
Cradles and 2 rollers per beam are a nice upgrade but for us with boats built like tanks not needed. My brothers Supercat 20 has cradles on all 4 corners and they work great as long as they are in the water when getting the boat on and off the trailer. If you try to do it with the cradles out of the water you don't stand a chance getting the boat positioned.
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Scott,
‘92 H18 w/SX wings
‘95 Hobie Funseeker 12 (Holder 12)
‘96/‘01/‘14 Hobie Waves
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Posted: Jun 04, 2012 - 09:37 AM
I have to agree the triple would likely end up with a double (mostly single on the middle bar) point load unless the boat is in the exact same spot every time and the install was done very carefully.
On my H-18 double rollers in the rear and cradles in the front. On the N-5.5 Uni cradles all around, it is much easier to load the Hobie with rollers. The 5.5 came with cradles all around so I am not changing it. I did put a winch on the mast cradle at the front and just winch it on once the fronts of the hulls are on the rear cradles and the boat is stable. I have considered putting rollers on the rear of the Nacra trailer but have been too lazy to do it. The other issue is the hardware (spin) on the front of the Nacra, getting to the middle of the boat to load it is a pain, so the winch is easier. JMHO, YMMV, Richard.
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Lake Perry KS
H-18
N-5.5 UNI +spin
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