How much load on rollers & bunks?

[ezmobee]

Re: How much load on rollers & bunks?

Hey Jim, I think the typical controversy is between bunks and rollers. Roller bunks are kinda a hybrid. They have a number of rollers closer together and I personally would treat them as regular bunks as far as the support argument goes. Just my 2 cents.

 

[109jb]

Re: How much load on rollers & bunks?

My personal opinion is that the boat weight should be on the bunks. In this particular case, the boat is an aluminum Starrcraft. I had a Starcraft, and if the construction of this one is like the one I had, the structure of the boat hull comes from lateral ribs spaced about 1 foot apart. IMO, the keel is just to close out the joint in the hull and although it is thicker than the hull skin, the ribs provide the real stiffness of the bottom of the hull. It's not built like a wood boat that has a deep keel structure running the full length of the boat. That's my reasoning. BTW, my Starcraft (16 foot Supersport) was supported entirely by the bunks and I never had any problem. As far as I was concerned, the center rollers just kept the hull (bow) from hitting the trailer crossmembers when loading and unloading..

Also, I'd like to point out that on a wobble roller trailer there is absolutely no keel support and that goes for both aluminum and fiberglass boats. I know this isn't a wobble roller trailer, but it demonstrates that keel support isn't there.

As for the roller bunks, I don't see how these are any worse than any other type of roller. The concern I would have is the number of rollers involved. It looks like there are 5 per bunk in the pictures, so you are talking about supporting the boat on 10 discreet spots. My 16' fiberglass boat had 16 wobble rollers and as a consequence it has 16 dents in the hull. The dents are measurabe and are about 1/32" to 1/16" deep in the case of my boat. Because it was a wobble roller setup the boat weight was evenly ddistributed and all of the dents are about the same. the dents don't seem to affect performance so I don't care that much but it does happen. I do prefer wood bunks to distribute the load better, and converted my trailer to do just that.

 

[Bifflefan]

Re: How much load on rollers & bunks?

I can add a little confusion to this,
Some bunk trailers dont even have keel rollers. So yes the bunks should hold the most weight.

Now, on my roller trailer, its adjusted so well that I can grab any of the rollers while the boat is on them and spin them with my hand, and not a whole lot of effort. It weighs in close to 3500 lbs.
If it was me, I would lay under it and adjust them until the boat was supported and I could twist all the rollers with using even pressure. Maybe a bit less on the keel ones.

 

[JimS123]

Re: How much load on rollers & bunks?

Hey Jim, I think the typical controversy is between bunks and rollers. Roller bunks are kinda a hybrid. They have a number of rollers closer together and I personally would treat them as regular bunks as far as the support argument goes. Just my 2 cents.

You're absolutely right about the controversy. But I think there is a difference between carpeted and roller bunks. The difference is the force exerted on the hull.

Compare a 2x4 bunk 4 feet long with a 4' roller bunk with 5 rollers. Or, about 168 sq. inches vs. maybe 10 sq. inches. Now, if the boat weighs say 2000 pounds and the 2 bunks are supporting 60% of the weight, the difference in force on the hull is 3.6 psi vs. 60 psi. Would that difference attibute to dents in the hull? I dunno and I aint gonna find out!

Compare the cheep all roller trailers vs. the better ones (like EZ loader or Load Rite) and you'll find that the better ones allow no more than about 125-150 pounds on each roller. Since they are bigger rollers and have a bigger contact area (maybe 5 in2 per), they are designed to apply no more than about 30 psi on the hull.

On my boat the 5 keel rollers are tight, but if i really push hard I can get them to move. The other 12 "bunk rollers" move very freely by hand. My keel is straight and I have no dents.

 

[JimS123]

Re: How much load on rollers & bunks?

I can add a little confusion to this,
Some bunk trailers dont even have keel rollers. So yes the bunks should hold the most weight.

Now, on my roller trailer, its adjusted so well that I can grab any of the rollers while the boat is on them and spin them with my hand, and not a whole lot of effort. It weighs in close to 3500 lbs.
If it was me, I would lay under it and adjust them until the boat was supported and I could twist all the rollers with using even pressure. Maybe a bit less on the keel ones.

Now you're talking. That's how to adjust an all roller trailer.

I don't have a problem with multiple carpeted bunks and no keel rollers. I wouldn't put that under a wooden boat, but for anything else the support of the hull should be just fine. I just would never own one like that because its just too much of a PITA to launch and retrieve the boat. My son has one like that and he's limited to using only one ramp in our area because the others are not steep enough.

 

[Azlo]

Re: How much load on rollers & bunks?

takin notes

 

[ezmobee]

Re: How much load on rollers & bunks?

You're absolutely right about the controversy. But I think there is a difference between carpeted and roller bunks. The difference is the force exerted on the hull.

I can agree with that. And I think adjusting a little more weight to the keel rollers would be appropriate in this situation.

 

[gozierdt]

Re: How much load on rollers & bunks?

Azlo,

You've got some good advice above from some aluminum boat owners, I'll admit most of my heavier boat experience is with fiberglass ones. I think I agree that the bunks should go outside the "keels". And I think there's a fair amount of agreement that the best way to do the final adjustment is to put the fully loaded boat on there, and bring the bunks up to touch plus a bit more- 1/8"? Then when both bunks are adjusted look at the boat for any deflection above the bunk rollers, and see how much the keel rollers are deflected. I noticed your boat has a "keel" like the "strake-keels" riveted to the outside of the hull. That's going to mean you'll see a lot of distortion on the three forward keel rollers because it's a very narrow blade pushing down on them. And if you bring the rear keel roller up all the way to support the transom, it'll be higher than the forward keel rollers. I don't think that'll be too much of a problem. On most ramps the stern will be floating as you take the boat on/off the trailer. And you really need that center support for the transom. So the question will be how much load to put on the keel rollers. I think you're going to have to be the final judge of that after you see how much keel roller deflection you get, vs hull deflection.

 

[JimS123]

Re: How much load on rollers & bunks?

You've got the best possible keel rollers you could ever use. Those Stoltz poly rollers are very hard, so you should see only minimal deflection.

My setup is exactly like yours. When I load or launch I back in just far enough so that the stern keel roller just touches the water, but is not sumberged. The boat slides right off, and winches back on perfectly straight becuse the keel follows the center V contour of the roller. Thus, no need to have the transom floating...in fact the retreive works best if its not.

 

[Azlo]

Re: How much load on rollers & bunks?

Ok so I just finished installing and adjusting the rollers. I positioned them outside the outer strakes. I wanted to being the boat as close as possible to the trailer. In order to do this i had to turn the roller brackets upside down. Now the boat is sitting 4" closer to the trailer and 2.5" away from the fenders.

before

after

 

[gozierdt]

Re: How much load on rollers & bunks?

Azlo,

Trailer setup looks good to me! That's going to be a really nice looking rig going down the highway. Did you paint the outside of the hull also? It really looks nice. It's so nice and shiny that a lot of us thought it was a nicely polished up fiberglass hull. Not trying to knock aluminum, just that a lot of them have telltale signs that they are aluminum. This one is just beautiful

 

[Wingpilot]

Re: How much load on rollers & bunks?

A question is asked and subsequently answered with manufacturers recommendations ( Reference Post #9 By JimS123). Admittedly, this has been a controversial subject in the past. But, I don't believe I've ever seen a post where the advice given by multiple manufacturers is not only challenged, but ignored because a member believes the manufacturer doesn't know what he's talking about! This HAS TO BE the only subject that elicites that advice. Post #13 does exactly that. Do engine manufacturers not know what they are doing when they recommend oil/gas ratios? Or maximum engine RPMs? IMO Post #9 by JimS123 is not only NOT STUPID (as it is accused of being) but the reference he provides is more informative and more to the point than any of the others.
A suggestion is made to visit a boat yard (marina) and look at some boats on/off trailers- Great idea. While there, take a look at the boats- wood, fibreglass, metal, ferro-cement- that are there in long term storage. Except for the sail boats, I'll bet you will see every one of them supported almost entirely by the keel and only stabilized to straight by the adjustable side stands. In some areas of the country these boats spend more time in storage than they do in the water. No ill effects here- no hooks, no rockers, and all through severe temperature changes.
Of course, no ones arm is being twisted to follow sound safe advice from a manufacturer but I believe it would be st**** not to.

 

[reelfishin]

Re: How much load on rollers & bunks?

I've had good and bad results from those bunk roller bars. They are fine for lighter boats and on any boat with a fairly flat rear hull section, (low deadrise).
They do tend to get hung up a bit when rolling over rivets but not bad, and most aluminum boats don't have enough weight to be very concerned about how many rollers or how much pressure is on each roller. I generally set up my boats with about equal pressure on both the bunk rollers and keel rollers. If the trailer is carpet bunked with keel rollers, the keel rollers get a bit more of the load simply because it helps the boat not stick to the bunks when unloading. Considering that many boats sit for years on three stands when off the trailer, with the forward stand being under the keel, with no damage, I doubt that the keel would suffer any damage sitting on the rollers.

One thing I would avoid is letting the boat bounce or apply sudden force or impact on any one point. Plus, damaged keel rollers can really wreak havoc on the hull whether glass or aluminum.

If the trailer is full roller, with keel rollers, it often depends on the position of the rollers packs how the keel rollers are used. I've often added keel rollers to trailers which never had them simply to prevent the keel from hitting or dragging a cross member when loading. In those cases the roller is often left just slightly above the frame and usually won't contact the hull once loaded.

What it boils down to is that you have to decide what works for your boat and your trailer. It's the particular combination that decides which is best.

 

[Azlo]

Re: How much load on rollers & bunks?

Azlo,

Trailer setup looks good to me! That's going to be a really nice looking rig going down the highway. Did you paint the outside of the hull also? It really looks nice. It's so nice and shiny that a lot of us thought it was a nicely polished up fiberglass hull. Not trying to knock aluminum, just that a lot of them have telltale signs that they are aluminum. This one is just beautiful

Thanks Goziedt, yeah I painted it. It took alot prep though. But I finally got it, I just hope it lasts. It would be dreadful to see it peel off on my splash day. haha.

 

[ezmobee]

Re: How much load on rollers & bunks?

It would be dreadful to see it peel off on my splash day. haha.

Tell me about it

 

[NSBCraig]

Re: How much load on rollers & bunks?

A question is asked and subsequently answered with manufacturers recommendations ( Reference Post #9 By JimS123). Admittedly, this has been a controversial subject in the past. But, I don't believe I've ever seen a post where the advice given by multiple manufacturers is not only challenged, but ignored because a member believes the manufacturer doesn't know what he's talking about! This HAS TO BE the only subject that elicites that advice. Post #13 does exactly that. Do engine manufacturers not know what they are doing when they recommend oil/gas ratios? Or maximum engine RPMs? IMO Post #9 by JimS123 is not only NOT STUPID (as it is accused of being) but the reference he provides is more informative and more to the point than any of the others.
A suggestion is made to visit a boat yard (marina) and look at some boats on/off trailers- Great idea. While there, take a look at the boats- wood, fibreglass, metal, ferro-cement- that are there in long term storage. Except for the sail boats, I'll bet you will see every one of them supported almost entirely by the keel and only stabilized to straight by the adjustable side stands. In some areas of the country these boats spend more time in storage than they do in the water. No ill effects here- no hooks, no rockers, and all through severe temperature changes.
Of course, no ones arm is being twisted to follow sound safe advice from a manufacturer but I believe it would be st**** not to.

1) the majority of trailers with bunks have NO rollers at all. None. Not one. Nothing supports the keel. (you know the ones expensive boats come on when you buy them)

2) if you go to boat yards you will notice that boats are either supported in multiple spots by stands or are on two bunks with zero keel support. Just like rack storage or when being transported commercially or on display at the dealer.

Now what is this solid sound advice that comes from a couple of trailer builders and is ignored by every other trailer manufacturer?

Lets see we should all follow the advice of some (of course the lower end builders) and ignore what the high end builders do and what the manufacturers of high end boats do when they order and set up a trailer.

Comparing oil ratios or max rpms isn't even remotely relevant maybe if you had info from the manufacturer of the boat in question about how you should support their boat your post would make sense.

Following generic (yes all hulls are different and a lot of them will not work at all with keel rollers anyway) outdated info and not using your brain or the solid safe advice of the people you asked a question..... STUPID!

Just cause old timers do it doesn't mean anything, it's worth listening but then you need to take that and all the info you find and use logic to figure it out.

 

[109jb]

Re: How much load on rollers & bunks?

A question is asked and subsequently answered with manufacturers recommendations ( Reference Post #9 By JimS123). Admittedly, this has been a controversial subject in the past. But, I don't believe I've ever seen a post where the advice given by multiple manufacturers is not only challenged, but ignored because a member believes the manufacturer doesn't know what he's talking about! This HAS TO BE the only subject that elicites that advice. Post #13 does exactly that. Do engine manufacturers not know what they are doing when they recommend oil/gas ratios? Or maximum engine RPMs? IMO Post #9 by JimS123 is not only NOT STUPID (as it is accused of being) but the reference he provides is more informative and more to the point than any of the others.
A suggestion is made to visit a boat yard (marina) and look at some boats on/off trailers- Great idea. While there, take a look at the boats- wood, fibreglass, metal, ferro-cement- that are there in long term storage. Except for the sail boats, I'll bet you will see every one of them supported almost entirely by the keel and only stabilized to straight by the adjustable side stands. In some areas of the country these boats spend more time in storage than they do in the water. No ill effects here- no hooks, no rockers, and all through severe temperature changes.
Of course, no ones arm is being twisted to follow sound safe advice from a manufacturer but I believe it would be st**** not to.

A couple points.

1. The manufacturer site pointed out was a trailer manufacturer, not a boat manufacturer. What is true for one boat may not be true for others which is what that website implied. Go to that site and look at their boat trailers, specifically for boats under 20 feet and ask yourself how many trailers like that you have seen. I have never even seen a trailer like those under a smaller boat like the one in question for this thread. I've seen that style trailer under much larger boats, but not the size we are talking about in this thread

2. One manufacturer's opinion or 10 does not make it an absolute. Unless ALL of the manufacturers say the same thing then there is still no consensus, and they don't.

3. There are manufacturers that make trailers that have absolutely no keel support. Look at any bass boat trailer, look at EZ-loader, Shorelander, and a host of others that sell trailers that don't even have keel rollers. Are all these manufacturers wrong?

4. Boat manufacturers don't even agree. Go to Bass Pro Shops and look at the aluminum V-hull Tracker boats sitting on Tracker trailers that have only bunks in contact with the hull and only a keel roller on the back to keep the bow from hitting the crossmember. The only keel roller on the trailer doesn't even touch the boat when fully loaded.

5. As far as dry storage goes, a boat in dry storage isn't bouncing down the road on a trailer so that is not a comparison that is even applicable. Look how I had my boat supported in my barn during trailer repairs. It worked sitting still in the barn, but I would never have trailered it supported like that.

You may think it is stupid not to follow "a" manufacturer's recommendation, but which manufacturer are you talking about??

 

[superbenk]

Re: How much load on rollers & bunks?

Look how I had my boat supported in my barn during trailer repairs. It worked sitting still in the barn, but I would never have trailered it supported like that.

That's a scary way to support your boat! What happens when someone accidentally leans on the stern or bumps into the bow? Those supports will fall like dominos! Glad it worked for you, but yikes!

As for supporting the boat on the keel or not, I have moved more weight to the bunks from the keel rollers on my trailer simply because the weight of the boat bouncing on the keel rollers was causing damage to the glass (cracking & chipping). I now support about 75% of the weight of the boat on the bunks and it feels much more secure.

I have an 18' boat on a Shorlander trailer with bunks & keel rollers.

 

[109jb]

Re: How much load on rollers & bunks?

That's a scary way to support your boat! What happens when someone accidentally leans on the stern or bumps into the bow? Those supports will fall like dominos! Glad it worked for you, but yikes!

As for supporting the boat on the keel or not, I have moved more weight to the bunks from the keel rollers on my trailer simply because the weight of the boat bouncing on the keel rollers was causing damage to the glass (cracking & chipping). I now support about 75% of the weight of the boat on the bunks and it feels much more secure.

I have an 18' boat on a Shorlander trailer with bunks & keel rollers.

The picture is a little decieving. The boat was actually very stable and I climbed in it many times with it like that. The stand at the stern was braced fore-aft and the stern has a flat area under the transom that worked perfect for supporting the boat. The front stand obviously couldn't move side to side, and as I said the fore aft was taken care of at the stern. I don't think I could have pushed it over if I tried.