Roller to bunk conversion of my gavanized trailer

[robthompson66]

I bought this continental galvanized trailer a couple years ago for my 16 foot fiberglass boat. I don't use it that much since the boat is kept in a rack and launch but I wanted to change it over so it better supports the old hull when I do trailer it. I have seen some posts in the pasts from members looking to see conversions, so I thought I would show off my latest project!

Here is a picture of what the trailer looks like as a roller

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Rollers all removed

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Picture of the bracket with factory 1/4" holes in them

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This is the idea here, bolt the bunk boards directly to the roller brackets. They will be the same height, and fall in the same place on the boat's hull

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The bunk boards are still fully adjustable in or out same as the rollers

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[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

Here is a picture of the trailer with the bunk boards all fastened down

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Another shot

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There's the trailer all finished with the bunks carpeted. Once I put the boat on the trailer I will tighten the hardware so the don't flop around, and adjust as necessary. The entire project only took a few hours and about $40.00 in materials. The job was easier because of the pre-drilled holes in the roller brackets.

Thanks to the members of iboats for all the wisdom!

rob

 

[dingbat]

Re: Roller to bunk conversion of my gavanized trailer

I hope you have a very square, flat bottomed boat. Not sure how 8 floating supports mounted to 4 rigid support members is going to contort enough to provide the proper support at both the front and rear of the boat.

I would have set it up as 4 separate bunk assemblies to allow them to adjust to the contours of the hull independently

 

[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

Yeah, it actually fits very well, I picked the boat up today. One thing I may add though is a keel roller.

The hull of my boat doesn't have much of a contour and is very flat.

 

[JimS123]

Re: Roller to bunk conversion of my gavanized trailer

Sixteen rollers supporting a little 16" boat should have provided outstanding hull support. A Trailer Design Spec calling for about 125 pounds per roller is optimum for any hull type. The oem setup would have provided launching and retreiving in only inches of water. Now you'll need to get your feet wet.

So, what was the motivation to make the change?

 

[Fl_Richard]

Re: Roller to bunk conversion of my gavanized trailer

My guess is needing to replace 16 rollers

 

[jeffkrieger]

Re: Roller to bunk conversion of my gavanized trailer

hi,
what are you doing with the old rollers?
jeff

 

[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

The 16 rollers supporting 125 lbs. each is not enough for my 16' boat. Believe it or not, the boat without motor weighs 1700lbs, add motor 269lbs, fuel (holds 29 gallons) roughly 200lbs, a battery and gear add a bit more, so I really wasn't comfortable how the boat was supported on the 16 rollers and just feel more comfortable with it sitting nicely on 4 carpeted bunks. Everything fits better than I had expected but I did carefully plan beforehand. I didn't just tear it apart and hope for the best!

hey Jeff, I'm not sure what I am going to do with the rollers yet. Send me a pm to remind me, and when I decide in a week or so I will let you know. If you want them, I have no problem in sending them to you. They aren't in the greatest shape though, as this is an old trailer. A couple of them are split, all of the bushings are worn and the rollers were pretty loose on the brackets.

Thanks
Rob

 

[JimS123]

Re: Roller to bunk conversion of my gavanized trailer

That's a pretty hefty 16 footer. Is that actual weight or factory specs?

Regardless, if you look at trailer specs the cheaper models go up to as high as about 175 lbs per roller. So, at about 148 lbs. it seems like you're still in an acceptable range and the trailer was well designed.

I guess you must have seen dents and damage to the hull at the roller locations.

 

[jeffkrieger]

Re: Roller to bunk conversion of my gavanized trailer

hi,
they have to be better than mine since a bunch are missing on my trailer.i'll get back to you next week.
thanks jeff

 

[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

Hey Jim,

I know, I do have a fat little boat! This the actual weight, last summer I took it to a certified scale on the trailer with no batteries and an empty fuel tank and the weight with trailer came in at 2660 lbs. Needless to say, I was shocked. The trailer weighs in at 660 since I had to have it weighed to register, it is a very nice trailer and I did like the rollers for launching but I was noticing some hull damage. I know I am the cause of increasing the weight of the boat, since I added 2 gallons of flotation foam, and fully fiberglassing the floor. A couple of seasons ago I did a full restoration on the boat which included replacing the transom, stringers, adding an in floor fuel tank, and fiberglassing the floor in. I am not sure how much weight I added since I never weighed the boat before the resto, but it still has the exact same waterline and behaves very well where I boat which is the Detroit River. Today I added another 50 lbs since I just installed a cmc tilt and trim unit.

Rob

 

[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

Jim, thanks for all the info, I wasn't aware of how much weight rollers could support. I think I am going to keep them in case I decide to use the trailer for another boat one day since I added a nice winch, seals and bearings, guide ons, tail lights etc...

That's quite an impressive collection of outboards and boats that you have, how long have you been collecting?

 

[JimS123]

Re: Roller to bunk conversion of my gavanized trailer

Jim, thanks for all the info, I wasn't aware of how much weight rollers could support. I think I am going to keep them in case I decide to use the trailer for another boat one day since I added a nice winch, seals and bearings, guide ons, tail lights etc...

That's quite an impressive collection of outboards and boats that you have, how long have you been collecting?

The key to good support is having the rig balanced. I've taken pains to adjust and adjust so that I can turn each roller by hand. Thus, no excessive weight in any single place.

Over the years I've owned 2 fiberglass 16 footers. Both were bought new and since your comments piqued my interest I checked my old catalogs and one came in at 965 lbs, the other at 1150. Both were good solid boats that served me well. Thus, I would guess that your restorations are what added the extra weight.

I became a "boatman" 56 years ago, built MY first rig 43 years ago, and bought and sold for quite a few years. For the past 27 years I have been "accumulating", but haven't sold anything I've acquired.

 

[dingbat]

Re: Roller to bunk conversion of my gavanized trailer

That's a pretty hefty 16 footer. Is that actual weight or factory specs?

Regardless, if you look at trailer specs the cheaper models go up to as high as about 175 lbs per roller. So, at about 148 lbs. it seems like you're still in an acceptable range and the trailer was well designed.

I guess you must have seen dents and damage to the hull at the roller locations.

Where did you come up with the #125 per roller number? My trailer wasn't cheap and it's rated to #218 per roller. Mine is loaded @ #175per roller and the boat has been sitting on it none the less for wear for the past 13 years.

Are you sure it's not 125 PSI?

 

[dickiefl]

Re: Roller to bunk conversion of my gavanized trailer

Rob,

What kind of trailer is that? It looks almost exactly like my old(1987) Load Rite trailer except mine is for a 21 ft boat.

 

[JimS123]

Re: Roller to bunk conversion of my gavanized trailer

Where did you come up with the #125 per roller number? My trailer wasn't cheap and it's rated to #218 per roller. Mine is loaded @ #175per roller and the boat has been sitting on it none the less for wear for the past 13 years.

Are you sure it's not 125 PSI?

A few years ago I bought a new roller trailer and just for my own interest I wanted to know what they were supposed to hold. So, I went thru my 40 year collection of trailer literature and calculated the weight based on no. of rollers and rated trailer capacity.

What I found was that the companies that I considered to be "premium" manufacturer's had more rollers per capacity, vs. what I considered to be a "cheap" trailer. BTW, many of the cheepies are no longer in business.

The second thing I found was that over the years the manufacturers seem to have added more rollers. Probably because of complaints re. hull damage. As an example, I recently looked at a Lund bass boat with custom roller trailer. OMG that sucker must have had 40 rollers on it! And boy did it launch well!

Bottom line is that none of the manufacturers actually list the capacity. You have to calculate it yourself.

 

[dingbat]

Re: Roller to bunk conversion of my gavanized trailer

A few years ago I bought a new roller trailer and just for my own interest I wanted to know what they were supposed to hold. So, I went thru my 40 year collection of trailer literature and calculated the weight based on no. of rollers and rated trailer capacity.

What I found was that the companies that I considered to be "premium" manufacturer's had more rollers per capacity, vs. what I considered to be a "cheap" trailer. BTW, many of the cheepies are no longer in business.

The second thing I found was that over the years the manufacturers seem to have added more rollers. Probably because of complaints re. hull damage. As an example, I recently looked at a Lund bass boat with custom roller trailer. OMG that sucker must have had 40 rollers on it! And boy did it launch well!

Bottom line is that none of the manufacturers actually list the capacity. You have to calculate it yourself.

The increase in the number of rollers used on some trailers has nothing to do with trailer or roller designs whatsoever. The increase is the direct result of today?s trend toward paper thin hulls to save weight and materials costs.

The number of rollers you need to support the hull is directly related to the compression strength of the hull. If you hull is made out of bubble gum, you're going to need more support (rollers) than if you hull is made out of titanium.

Example: My boat weighs @ 5700 lbs and sits on 32 rollers. Each roller is 3" wide and provides ~1.5" of square inches of surface area. Collectively, the 32 rollers provide ~48 square inches of contact area for an approximate hull loading of #116 per square inch. To put this figure into perspective, a #100 lady walking in your typical 1? heels exhorts ~ #240 per square inch under foot.

From my example above, we know that a hull loading of 116 PSI, (#218 per roller) should be no problem for a well constructed boat. Why does Lund feel they need to use 40 rollers? Does the Lund weigh more than #8700?

 

[robthompson66]

Re: Roller to bunk conversion of my gavanized trailer

The trailer is a Continental made in Miami, FL. The capacity decal is present but is illegible due to years of sun exposure. I doesn't look like Continental makes roller trailers anymore but it has a nice solid frame and tows well. As for the boat...I know that the fiberglass shell at the transom is roughly 1/4" thick but I haven't measured the bottom. In hindsight I would have weighed the boat prior to dis-assembly, then weighed everything coming out, then weighed everything going back in.
I guess personally I prefer the bunks for this boat.
I almost had to get my feet wet when loading it on the trailer last week, it did require some crafty foot work but I am still satisfied. If I go up north and want to launch at a different ramp, maybe one that isn't as nice as the hard surface I am used to I may regret the conversion.

 

[JimS123]

Re: Roller to bunk conversion of my gavanized trailer

The increase in the number of rollers used on some trailers has nothing to do with trailer or roller designs whatsoever. The increase is the direct result of today?s trend toward paper thin hulls to save weight and materials costs.

The number of rollers you need to support the hull is directly related to the compression strength of the hull. If you hull is made out of bubble gum, you're going to need more support (rollers) than if you hull is made out of titanium.

Example: My boat weighs @ 5700 lbs and sits on 32 rollers. Each roller is 3" wide and provides ~1.5" of square inches of surface area. Collectively, the 32 rollers provide ~48 square inches of contact area for an approximate hull loading of #116 per square inch. To put this figure into perspective, a #100 lady walking in your typical 1? heels exhorts ~ #240 per square inch under foot.

From my example above, we know that a hull loading of 116 PSI, (#218 per roller) should be no problem for a well constructed boat. Why does Lund feel they need to use 40 rollers? Does the Lund weigh more than #8700?

Everything you said is quite true and basically backs up what I said as well. Your 5750 / 32 falls within my guidelines.

Where did you get the idea that hull compr. str. has been reduced? I'm not arguing that fact, but if its true I'm glad I haven't bought a new boat....LOL. As a matter of fact, my newest boat (2009) is aluminum and the hull thickness was 60% GREATER than the old one I retired.

I can't speak for Lund, but launching that rig sure was slick. It was an aluminum hull.

 

[aboston]

Re: Roller to bunk conversion of my gavanized trailer

Is this conversion still working for you?

I have an EZ-Loader that needs new rollers and hardware and almost vomited when I found out how much new rollers were going to cost. The rollers are for a 1" shaft, and are only available through a EZ-Loader retailer...

In this conversion, do the bunks still roll to the left and right like the rollers did? If they don't, I would like to know how you tightened them down. Also, how did you determine thh correct bunk placement? My boat is a 20' Grady White and has a preety deep V hull.

Awesome post and pics!

Here are some pictures of my situation. And my embarrassing bottom paint...:facepalm: