rollers or bunks which carries the weight

[belairbrian]

So the boat I recently purchased has 3 rollers under the keel, two 6 foot bunks and a v pad above the bow hook.

Boat is a 15 foot grumman aluminum center console with a 48 Spl . Weights hull around 480 motor around 190.

My question is should the bunks carry the bulk of the weight and the rollers only a little?

Currently the middle roller is split and the keel is down in the split, the rear is not touching and the forward roller is resting against the keel?

I plan to pick up new rollers tomorrow. Since the roller brackets are adjustable, should I loosen the brackets and lower the rollers placing all the weight on the bunks, then replace the rollers and just bring them up into contact with the keel?

 

[batman99]

Re: rollers or bunks which carries the weight

I was told that for better even "weight distribution", bunks are much better than rollers. Rolls tend to provide "point load" weight contact and bunks (when properly set), apply much better distributed weight support. In winter storage or parked, there's no major difference in the boats hull pressure points. But if pulling a boat / trailer down bumps roads, then bunks are much better to have (so I was told). If trailer parked, I wouldn't worry about a diffective roller. Simply replace deffective roller before towing the boat.

 

[WIMUSKY]

Re: rollers or bunks which carries the weight

I plan to pick up new rollers tomorrow. Since the roller brackets are adjustable, should I loosen the brackets and lower the rollers placing all the weight on the bunks, then replace the rollers and just bring them up into contact with the keel?

That's what I would do.....

 

[Maclin]

Re: rollers or bunks which carries the weight

In my opinion you are on the right track. I believe the keel rollers are to help center the boat and ease the way "up" to the bunks, and also to keep the keel from hitting bare cross brace. Ideally they should not have any weight on them when the boat is winched up and fully loaded in my understanding.

 

[bonz_d]

Re: rollers or bunks which carries the weight

What you have is not as criticle as a larger heavier boat. What this is, is a keel roller bunk trailer and the keel rollers should be supporting some of the weight.

Yes, pull the rollers and replace. On these types of rigs I like to move the rollers up to were I can just turn them with a little effort while the boat is sitting on them. Also with 3 keel/spool rollers if there is room I prefer to add a 4th. What I did with my last one of these was while the boat was off I took a straight edge and laid it on the rollers to assure it was making even contact with all rollers.

Hope this helps.

 

[dingbat]

Re: rollers or bunks which carries the weight

The keel is structurally the strongest point on the boat. The hull is one of the weakest. Which one do you want supporting the weight?

 

[Maclin]

Re: rollers or bunks which carries the weight

I'm thinking the keel rollers themselves are not designed to be weight bearing.

 

[bonz_d]

Re: rollers or bunks which carries the weight

I'm thinking the keel rollers themselves are not designed to be weight bearing.

How many of these trailer have you used? A 6' bunk does not a bunk trailer make. I've owned 5 and have used many more of these size trailers. Though you're free to believe what you like.

 

[V153]

Re: rollers or bunks which carries the weight

On that particular trailer I'd think most of the weight should be on the rollers. Read: Keel of the boat. However I have seen rigs with multiple bunks that didn't have any rollers?

 

[Maclin]

Re: rollers or bunks which carries the weight

How many of these trailer have you used? A 6' bunk does not a bunk trailer make. I've owned 5 and have used many more of these size trailers. Though you're free to believe what you like.

Bonz, your own recommendation in post #5 was for the rollers to not hold the weight, so what is your point here?

 

[JimS123]

Re: rollers or bunks which carries the weight

Boats used to be wood and were kept in the water. The 1950's and 1960's were the golden age of the "trailer boater". When I got started I talked to some old fogies at the marinma, plus I went to the library (OMG do they still have those?) and got a book on how to set up a boat trailer. Been doing it the same for 45 years sucessfully so I guess the old fogies didn't steer me wrong.

Yup - keel is the strongest part.

First of all, go out and buy a set of yellow poly Stoltz rollers. You won't be sorry. The black rubber ones will fail just like the ones you have now. Next install them and level all of them in a straight line (boat off the trailer), then drop the bunks down. Put the boat back on and let her sit on the rollers. Raise the bunks so they just contact the hull, positioned to the boat is level side to side. Finally, raise the bubks up about 1/2" each to support the hull firmly and prevent any side to side sway.

When you launch and retreive the boat will effortlessly glide up on the rollers. If the bunks support the weight, you'll be inclined to have to back in too far because you can't push the boat off without breaking your back. You'll still break your back and get wet feet besides.

 

[bonz_d]

Re: rollers or bunks which carries the weight

Bonz, your own recommendation in post #5 was for the rollers to not hold the weight, so what is your point here?

Think you misinterpreted what I was trying to describe, or my discription was misleading. Guess my idea of a little effort and your idea of effort is greatly different. 1st of all the total weight of this boat and motor is less than 1000#. With that I think that even the way JimS123 describes the way to do it I would still be able to turn the rollers. Which is also why I suggest adding a 4th roller to even still distribute the weight move evenly.

Now having said that, my Lund is appx. the same weight and I could still easily push a puddy knife between the bunk and the hull. Also when launching the boat all of the rollers turn which is what they should do so there must be some weight on them.

Also the OP was asking how to change them while the boat is still on the trailer as best I can tell which is why I suggested to do it the way I did. Otherwise the way JimS suggests is the same procedure I use though the boat then has to be removed to do it. With the acception that I do not then raise the bunk as high as 1/2" after it's set.

I too would have to reccommed the Stoltz rollers. They are a bit more exspensive but last twice as long and yes I learned the hard way.

 

[Maclin]

Re: rollers or bunks which carries the weight

Good discourse, thanks for allowing me to catch up so to speak... I was hung up on the rubber constructed ones, and them thar rubber rollers can't take it in my view, just the general design and materials are not for holding lots of relative weight. The harder material rollers are designed for more, and I would allow more weight to rest on those as adjustments would allow.

 

[bonz_d]

Re: rollers or bunks which carries the weight

I'm thinking the keel rollers themselves are not designed to be weight bearing.

I think we are on the same page now.

Actually those black keel/spool rollers were designed to carry weight, they just don't do a very good job of it. Not sure when Stoltz came out with their rollers but before that all there was were those black rollers. The black ones crush and develope flat spots even after just a short time period. Or at least the ones being sold these day do.

The trailer I use now is rated for 1660# and it is a full roller trailer with 3 spool rollers which are the black ones. Worst part is that they also only use a 1/2" axle shaft and when I bought this trailer two of them were bent. So when the season is over they will be replaced with Stoltz rollers with 5/8" shafts. Which I've also found roller shafts that have grease fitting in them which I think I'm going to try.

 

[Silvertip]

Re: rollers or bunks which carries the weight

I've had many boats and both bunk and roller trailers. I always come back to a full roller. I think it is relatively clear that the keel is the strongest part of the boat. Therefore it can handle the "so called point contact" which really isn't point contact but rather a contact patch just like the tires on your car. The side bunks can indeed handle part of the load but their primary purpose is to stabilize the lateral loads. With that in mind, a good roller trailer (one that actually has some "design" to it and on which the rollers are properly adjusted) cannot be beat for ease of launch and retrieval. The black rollers can leave some black marks but again, if that is happening in a big way, they are not properly adjusted and the boat is moving around on the trailer.

 

[belairbrian]

Re: rollers or bunks which carries the weight

Thought I'd come abck wiht where I am so far. Read through everything here and went out and did some further looking. The keel was sitting on the front and middle rollers. as well as the bunks. Rear roller had about a half inch gap.

I loosened the middle roller clamps and the boat came down to where it was sitting on all three rollers. So I conluded that the rollers must have been carrying a good bit of the load. If all the weight was on the bunks the boat would not have moved down. I believe the bunks were in contact enough to stabilize the boat as it does not move on the trailer when going down the road. I can watch it in the rear camera. even when dry teh boat will move on the bunks if you turn the winch ( i moved the winch post forward a while back and cranked the boat up into place with little effort.

However the middle roller is literally split in two down the middle and needs to be replaced. I locked for the Stoltz rollers but all I found locally had 5/8 shafts. So far haven't found one online for a 5" wide 1/2" shaft. So likely I will have to go with the rubber ones form Academy for now.

I can easily take it to the river and moor at the dock while I replace the rollers as long as I do it on a week day. That said I'm still a bit fuzzy on the process. So I'll spell it out what I am thinking and you guys can suggest changes.

1) Unload Boat
2) level trailer front to back using a 4 ft level over cross braces.
3) install rollers and level rollers to each other. Using the front one as a baseline.
After this Is where it gets fuzzy.
It was recommended that I lower the bunks and support the boat on the rollers then raise the bunks to contact plus 1/2 inch.
Seems the boat is going to lean to one side when I pull it out. So How do I get it vertical to adjust the bunks?

And how to I get the bunks to move up the 1/2 inch after they are against the hull? Jacks?

Guess I could use the guides while bringing it to the lot a the top of the ramp.

 

[JimS123]

Re: rollers or bunks which carries the weight

Actually, you can do it all at home. You just need to be able to crawl underneath the trailer.

In the Summer all I do is cut grass, cause it has to be done. The rest of the time I'm in the boat. Replacing rollers and such are best left for Winter when the boat is in the garage and you got spare time.

To replace the roller, just loosen the bolts and it'll drop down. Then take it off. 5/8" shaft - so what. Drill out the bracket and buy a new shaft or use a bolt. Or order one online and you'll have it in 4 days.

When you replace it, put a car scissors jack under it and raise it up to the proper position, then tighten the bolts.

Same with the bunks. Just stick a pair of socker balls between the trailer and the hull to level it up. Or use the bunks and go up one side at a time until the boat is level. Then use the jack to push the bunks up one end at a time.

 

[bonz_d]

Re: rollers or bunks which carries the weight

Let's look at what's available.

http://www.iboats.com/Seachoice-Spo...16763943--session_id.986648361--view_id.47814
http://www.iboats.com/5-Keel-Roller...16763943--session_id.986648361--view_id.65069
http://www.iboats.com/SeaSense-Poly...6763943--session_id.986648361--view_id.343874
http://www.easternmarine.com/5-yates-thermal-plastic-spool-roller-1-2-id-510y-4
http://www.easternmarine.com/5-stoltz-polyurethane-keel-roller-1-2-id-rp-55
http://www.easternmarine.com/5-heavy-duty-keel-roller-black-rubber-5-8-id-5244-105ec

If you have to use a black type then I highly suggest the last one listed here.
If the bottom of your Grumman is flat like my Lund I think you will find if you raise the bunks 1/2" after contact you will be lifting the keel off the rollers. So check that out.

 

[belairbrian]

Re: rollers or bunks which carries the weight

Let's look at what's available.

http://www.iboats.com/Seachoice-Spo...16763943--session_id.986648361--view_id.47814
http://www.iboats.com/5-Keel-Roller...16763943--session_id.986648361--view_id.65069
http://www.iboats.com/SeaSense-Poly...6763943--session_id.986648361--view_id.343874
http://www.easternmarine.com/5-yates-thermal-plastic-spool-roller-1-2-id-510y-4
http://www.easternmarine.com/5-stoltz-polyurethane-keel-roller-1-2-id-rp-55
http://www.easternmarine.com/5-heavy-duty-keel-roller-black-rubber-5-8-id-5244-105ec

If you have to use a black type then I highly suggest the last one listed here.
If the bottom of your Grumman is flat like my Lund I think you will find if you raise the bunks 1/2" after contact you will be lifting the keel off the rollers. So check that out.

I'm thinking the next to last one the Stoltz RP-55's.

I'd describe the hull as a shallow V there is a definative keel then the hull goes up at a shallow angle.

Not a great angle to see it but I don't have one from the stearn handy

 

[belairbrian]

Re: rollers or bunks which carries the weight

Finally got time to get at this. Wanted to come back and let everyone know what ended up happening. There was a lot of good ideas here and want to thank everyone for there inputs. Some suggestions didn't fit for my situation so don't think I don't appreciate the input.

What i found was the entire weight of the boat was on the rollers. I could move the hull back and forth slightly due to space above the bunks. This was being masked when I towed by the two over the hull straps I use.

I squeezed on a bunk only to find it would compress in my hand. AKA rotten. SO now I have 2 bad bunks and a split keel roller.

I made a transom support from wood and raised the boat up. Replaced the mid and front rollers and got the level but the back one needed to be higher as the keel slants up at the rear and there is about an inch difference between there and the middle. SO the rear got set higher.

I got the boat centered on the rollers, level to the trailer using straps, lowered it, then pushed the side bunks in to steady it. Removed the rotten bunks and built new ones. I found the old ones had not been angled on top to match the hull, so the hull was riding on a corner only. The bunk brackets have to go up at an angle or the bunks would come up under ribs. So I ran the boards through the table saw and now have bunks with a side to side contact patch of 2".

I brought the bunks up flush to the hull. Marked the brackets and brought them up another half inch. Now have full bunk contact and the rollers can be turned with a very firm twist. Still plan to put the Stoltz rollers on when I get them.

Also extended the bunks the extra 5 inches needed to get to the transom.