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Author Topic:   Adjusting Trailer Roller Height
jimh posted 01-12-2001 11:54 PM ET (US)   Profile for jimh   Send Email to jimh  
I plan to convert my trailer from a bunk-style/float-on to a keel roller style trailer.

On my trailer ( brand = Pacific Trailer) the bunks are welded in place and their current position is really pretty good. The boat sits about as low on the trailer as it can.

The limiting factor is the width of the hull and the space available between the fenders. At the moment, the boat sits with just an inch or two of clearance from the chines to the fenders.

I hope to be able to leave the welded bunks right where they are, and I will add dual rollers at each cross member. Now the question is: How to set the height of the rollers?

I had this idea:

First, launch the boat off the trailer.

Then, temporarily add another layer of carpet to the bunks. I'd do this by wrapping some scrap carpet around the existing bunks, and retaining it with some carpet-tape ( AKA duct tape).

Next, recover the boat onto the trailer. It should now sit just a bit higher due to the added layer of carpet.

Install all the rollers to the trailer frame, setting their height to firmly press against the keel.

Launch the boat a second time, haul the trailer back to the parking lot, and remove all the temporary carpet.

Go back to the launch ramp, and try recovering the boat. It should ride up on the rollers, with the clearance to the bunks just about right!

--That's the plan. Anyone have any comments?


kingfish posted 01-13-2001 12:32 AM ET (US)     Profile for kingfish  Send Email to kingfish     

Might work, but here's another idea. (What I did.)

Install the brackets and rollers right up against the keel while the boat is on the trailer, turning the bolts or nuts finger tight or a little more. Depending on your roller bracket configuration, take one or two jacks (hydraulic, barrel-type?) and put the jack(s) under the roller brackets one by one and jack them up against the keel as hard as you see fit, then tighten the nuts/bolts down while the jack is holding the weight. You kind of get a feel for how hard to jack them up as you get into it.


bigz posted 01-13-2001 06:15 AM ET (US)     Profile for bigz    
John yep that's the easiest way to do it -- make sure Jim you purchase the one piece roller brackets --- the two section type is a bitch doing it the way John outlines -- Tom
kingfish posted 01-13-2001 07:59 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Amen on the bitch with the two piece type...


jimh posted 01-13-2001 11:19 AM ET (US)     Profile for jimh  Send Email to jimh     
Using the jack-applied pressure method had occurred to me, but I thought my technique might be better.

Using jack pressure it might be hard to get uniform weight bearing on the rollers. You'd have to aim for consistent pressure against the keel. That might be hard to measure or accomplish.

Using temporary elevation of the bunks should result in more uniform weight bearing. If the boat were to be moved up, say a quarter of an inch, and all the roller brought into contact with the keel, when the temporary bunk elevation is removed, the boat should settle uniformly onto the rollers.

Of course, that is assuming you uniformly elevate the boat off the bunks during the adjustment/installation phase. That might be harder to do that it looks, too. The heavier stern section may compress the temporary carpet more than the bow areas.

Since the bunks are welded in place, I'm looking for an installation that keeps them intact. I have to fit the rollers to the crossmembers in any case, so I am trying to avoid having to refit all the bunks, too.


triblet posted 01-13-2001 01:38 PM ET (US)     Profile for triblet  Send Email to triblet     
I wonder if carpet will be too thick?
Probably depends on the carpet.


kingfish posted 01-13-2001 01:45 PM ET (US)     Profile for kingfish  Send Email to kingfish     

Keep in mind that the rollers will compress as you load them (point loaded under the keel). If you really want to go to the trouble of doing it the way you describe, padding the bunks by 1/4" won't get you where you're going. I would estimate stoltz rollers compress nearly 1/2" and at that point you've not done much more than equalize the bearing between the bunks and the rollers.


Backlash posted 01-14-2001 09:45 AM ET (US)     Profile for Backlash  Send Email to Backlash     

I have used the method John describes in replacing individual rollers, using a 3 ton hydraulic jack, and it works well.

I too question whether adding one layer of carpeting to your existing bunks will have any effect in "raising" the boat. I think your idea is sound if you can raise the boat enough on the bunks.


Backlash posted 01-14-2001 10:11 AM ET (US)     Profile for Backlash  Send Email to Backlash     

Just another thought. Using the method you describe, I think I would concentrate on "padding" the outside bunks only. Once the rollers are properly positioned, I would eliminate the inside bunks altogether. My trailer originally came with 4 bunks and the only thing the inside bunks did was hang up on thru hull fittings.

When my boat is on the trailer, I have maybe 2" of clearance between the boat and fenders.

When using my hydraulic jack to raise the roller brackets I use a short piece of 2 x 10 so that I can raise both brackets at the same time. As John mentioned previously, you will get a "feel" for how much pressure to apply to each set of brackets.


jimh posted 01-15-2001 01:06 AM ET (US)     Profile for jimh  Send Email to jimh     
I have given some more thought to the method I proposed above, and I think there is an additional problem with it.

When the boat is floated on the trailer bunks at any time before installation of the keel rollers, in order for it to be in the "just right" position it will have to be almost perfectly centered.

With just bunks supporting the boat, it is possible for the boat to get into a slightly tilted attitude on the trailer, that is, with a little list to port or starboard. This could affect the vertical height of the keel slightly, as well as setting slightly off centerline.

Since we are trying to align the rollers such that they are bearing most of the weight, even a small offset vertically could have an affect.

I may have talked myself out of this approach!

Well, there are a couple more months of winter to keep thinking about it.

I guess I should get the rollers, the center pins, and the mounting plates on order so I am totally ready for that first nice day of spring...


Hoop posted 01-16-2001 12:18 AM ET (US)     Profile for Hoop  Send Email to Hoop     
I also have a Pacific Trailer ... smaller boat, though, a Montauk. Thanks, Jim, for this post because I have been milling over in my mind exactly the same question about adjusting trailer roller height! First, though, I think I'm going to try the "silicone" on the bunks approach.

San Jose, CA

Louie Kokinis posted 01-22-2001 05:51 PM ET (US)     Profile for Louie Kokinis    
Jim, this is how I did mine

1. with your boat still on the trailer - bolt on the new rollers

2. snug the rollers up to the hull and mark the bracket height to the cross member with a permanent marker

3. take the boat off

4. raise the rollers

5. put the boat back on


Whalerdan posted 01-23-2001 07:46 AM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
Why would you want to use rollers? I have them on my trailer and their a big pain when loading. I get the boat up to hook the wench on the bow eye, and the boat starts to roll back in the water. Also, the rollers create a local pressure point on the hull and cause indentations. I think bunks would spread out the weight better and allow enough friction to keep the boat from sliding back in the water during loading.
Louie Kokinis posted 01-23-2001 02:02 PM ET (US)     Profile for Louie Kokinis    
For me it was out of necessity. We regularly trailer long distances on some pretty crappy roads and are forced to use makeshift ramps with no dock nearby. My feelings where that 4 bunks would give the hull more support than 8 keel rollers and 2 sets of roller bunks Whaler trailers offered. The factory confirmed that my CPD hull would be comfortable on either bunks or rollers, so I went with 4 – 2x6 bunks.

I quickly learned that trailers, like boats, offer their own set of compromises. The bunk system supported the boat well for trailering, but wasn’t very forgiving at the ramp. It was chafing the strakes every time I used it, and was a nightmare trying to load in a crosswind. This was happening because of the modified v and placement of the strakes. The hull wouldn’t allow for the inside bunks to be placed close enough to eliminate the bow entering between them - which would also straighten the boat in heavy winds. My options where to 1) get rid of one set of bunks (out of the question) 2) raise the boat up (no way) or 3) use smaller bunks (lose support?) 3) add rollers (not cheap) or 4) add keel guides and rollers

Since we've added keel guides and rollers the boat slips on and off with no chafing, I can now launch or retrieve my boat in the ugliest of conditions.

To date I’ve bought 8 stoltz rollers, 2 extra bunks, a couple of cross members + hardware. I think I’ve got it right….but then again :)


PS Bunks can accommodate the newer hulls and CPD boats, but anyone with a classic should read the section on trailers.

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