Setting up Trailer..... Questions on Bunks and Rollers

[Tin Man]

Preparing to replace and lengthen my 2"x4" carpeted bunks. Currently they are 5'. I will be adding additional bunk brackets (one to each side) and lengthening bunk boards to 7'( see my caveman drawing) . I am also going to add one additional keel roller with bell ends.

A few questions about set up.

The OEM keel roller that came with the Karavan trailer is the type below that has no bell ends. I will be adding an additional keel roller with bell ends. The purpose of additional keel roller is to spread some load as well as guide the boat as straight as possible when loading boat on windy days.

NOTE: I will also be adding guide boards to assist with loading.


My thoughts are that keel rollers serve to guide and rest keel, and not take on too much weight.
Still....how do you measure weight on bunks and rollers?

I have the one that came with trailer (no bell ends) I will place it about 2/3 forward of transom.

I will be adding the keel roller WITH bell ends near the bow area.

Questions:

1. Thoughts on additional keel roller with bell ends?
2. Thoughts on keel roller placements
3. Thoughts on lengthening bunks to 7' and placement of additional bunk brackets?
4. Should boat weight be primarily carried by bunk boards? If so, how much and how do you measure?

Additional thoughts?

Thanks

 

[MN Fisher]

After I rebuilt the trailer for the F-9 - I got all the weight of the boat resting on the rollers with the bunks basically just leveling the boat. Then I put a floor-jack under each bunk bracket and lifted to touch..then just a titch more (1/8 of a pump?) to take just a bit of pressure off the rollers.

For me, the rollers are just to help guide the boat onto the bunks...once the boat is on the bunks, the rollers should have little to no pressure on them with the exception of the forward-most roller...beyond where the bunks support.

 

[Tin Man]

Thanks MN Fisher.

My keel rollers only touch the keel at bow area (forward 1/3 of boat). The trailer's crossmembers at rear are a soft V shape and are several inches lower than keel at center, from mid keel to transom.

 

[LDUBS]

I agree with MNFisher, except I would say other than the one under the bow, no weight should be on a rear or intermediate keel roller. Like you said in your original post, add a roller towards the rear to help guide the boat. I would not add one to take any load.

Here is my reasoning. The roller is a hard point. It will be almost impossible to have the weight distributed evenly with the bunks and that rear and/or intermediate roller. Any movement (bouncing) and you risk putting a divot in your keel. Think in terms of a three legged stool. One leg too short it is still stable. Four legs with one too short and it will wobble. Your boat is in contact with two bunk boards and a bow roller (3 legs).

About lengthen the bunks, IDK other than don't the brackets normally mount on a trailer cross member? I would think Alumacraft would have some guidance. I think you already know all of this, but whatever the length, make sure the bunk extends an inch to two past the transom and that the transom is fully supported. For my boat, the maximum weight on the bunk is at the transom. That is per my boat maker's guidance.

 

[FuzzyGrub]

Agree to lengthing the bunks if the transom is not currently well supported. Otherwise make sure that the boat will actually be more supported by the longer ones. Many times the boat starts to curve on the forward section that it will not contact the hull.

 

[MrGiggles]

Those self centering rollers are the best thing ever.

On most trailers they don't even touch the hull when the boat is loaded. They're only there to make contact with the very front of the keel (where the "V" of the hull is sharpest) and center the boat while approaching. Once the boat is closer to the loaded position, the strakes in the hull will keep the boat centered on the lower bunks.

 

[JL8Jeff]

Here's my trailer setup. I have 8' bunks and the hull makes contact the entire length. My boat is a 1652 so you could probably use 8' bunks as well if your boat is a mod-v design. A deep v will be set up differently. I don't even have a rear roller but my trailer was originally set up with rollers and not bunks so the boat originally sat a lot higher. The front roller will take some weight since there is nothing else to support the boat. I'm not sure you need 3 brackets on each bunk, 2 should work fine.

 

[FuzzyGrub]

From what I saw of pictures of his boat, call it more a semi-V. A V bow to a modified V transom. With that style boat, I think it would be unlikely to have good hull contact for 8' bunks. The only downside to longer bunks and more hull contact, is sliding the boat off at shallow ramps. Some glides can help if that is an issue.

I'd want a keel roller at the back to help align and prevent the bow from hitting the cross support. Also one in the front for support and alignment, so the winch roller is not taking all the front load.

 

[Tin Man]

My trailer has V shaped crossmembers. Rollers are not feasible in rear or middle of boat, only on front tongue area.

My current set up uses 5' bunks with 2" of bunks beyond hull at transom.

I am thinking that 5' bunks, which is what comes standard on my model Karavan trailer, may be a little short for my 16'-7' boat. I'd like 8' foot bunks (1/2) of boat length, but the bunks can not be supported at this length.

I am considering adding one additional bunk bracket on each side to extend the bunks by 1.5'. This would allow me to use 6.5' bunks. This additional support, even if hull may rise slightly and is not fully sitting on bunks (for maybe a few inches of the leading edge of bunks), I believe is good for the hull...spreads the load and adds additional lateral stability while trailering.

The bunk brackets would be added as show in one of the pics below. It would mount on the trailer frame where it begins to curve towards tongue. I could mount it so that it is line with the two other bunk brackets, thus allowing the 6.5' bunk.

Thoughts?
Is my thinking correct, off, ????

Thanks!

 

[FuzzyGrub]

IMO, I think it will only provide marginal additional support. You have the transom well supported, which is key. On the other hand, as long as you don't create a point load, its not going to do harm.

Relating length of boat to length of bunk, may not be the best approach. It probably has more to do on how your boat was constructed and where it should be supported. I still have a older EZ loader, that has the old style 4', center pivoting bunks. It created no issues with a light 14' or a heavier 14' Starcraft. Those bunks are on edge, having less than 1/2 the surface area of flat laid ones.

Do you see any deformation of the hull from the current set-up?

 

[Tin Man]

IMO, I think it will only provide marginal additional support. You have the transom well supported, which is key. On the other hand, as long as you don't create a point load, its not going to do harm.

Relating length of boat to length of bunk, may not be the best approach. It probably has more to do on how your boat was constructed and where it should be supported. I still have a older EZ loader, that has the old style 4', center pivoting bunks. It created no issues with a light 14' or a heavier 14' Starcraft. Those bunks are on edge, having less than 1/2 the surface area of flat laid ones.

Do you see any deformation of the hull from the current set-up?

Thanks Fuzzy--
No current deformation of hull with current 5' bunks.

What is "point load."

 

[FuzzyGrub]

What is "point load."

If you have a high spot that puts the pressure at one particular spot vs spread out.

 

[Tin Man]

What is "point load."

If you have a high spot that puts the pressure at one particular spot vs spread out.

Thanks!

I would think that would be the case for roller trailers, no?

 

[FuzzyGrub]

I would think that would be the case for roller trailers, no?

Yes, even more critical to set-up correctly. Notorious for causing hooks in fiberglass hulls.

 

[JL8Jeff]

You might be able to put another crossmember where you're showing your extra bunk bracket but I'm not sure that would be needed. Your trailer looks a little shorter than mine if you look at where the front crossmember is and where the sides come together. I think your idea of the extra bunk bracket should work to support the longer bunks.

 

[Ronbedard57]

Hi,
All good advice here. Also keep in mind that the axle can be adjusted forward or back to adjust tongue weight if you've moved the boat back in order to support the transom at the end of the bunks. There's a formula for tongue weight vs. total weight, and it can be easily done with a visit to the junkyard scales and a bathroom scale.
Good luck

 

[Tin Man]

Unable to add a crossmember.

However....

The added bunk bracket, allowing for a 6' bunk, I believe spreads the load, but not by much.

So...... what about a 2"x6"x6' board? The added foot in length and 2" in width may be a better option.

Thoughts?