Bunks or rollers

[Eximea]

G'day all.
Rollers wore into my hull on a long road journey. (8000 Kms)
Would bunks be less damaging? I'm about to do the same trip again and don't want more holes in my hull.
Any thoughts apreciated

[Peter T]

I would definately use bunks because it would spread the load over a larger area. I am going to laminate up several ( at least 3 ) strip's of thin marine or construction ply around 200 mm or more wide to fit the hull where the bunks would sit and then line them with carpet on mine. The ply could even be fibreglassed fir water proofing as well.
My bunks are only around 50mm at the moment with that white ribbed rubber runner on them.
My plan is to cover the hull in that area with heavy plastic, laminate the ply against the hull using my existing bunks with wedges to force them in to place while the glue sets

[Eximea]

Thanks for the reply, Peter. Sounds like an interesting idea with the laminated ply. Have you had any problems with abrasion from the rubber surface on the existing bunks? And does the boat run off the trailer OK . I had bunks on a trailer I used for an 19 ft. Ply fishing boat and during one particular launch incident the aft end of one bunk peirced the hull as it dropped off the back of the trailer. Could that sort of thing happen with your existing set up?
Thanks for the pics too.

[Peter T]

Hi Eximea I actually have not launched mine as yet as I have been restoring it since purchase. I have heard some actually lower the rear bunk mount when launching / retrieving, but the original owner of mine advised me there were no problems with that. As you can see from the photo, the bunks are sitting lower at the rear anyway.
Hope this helps. Also, if the rollers are free, should not be a problem, especially if the tilt on the trailer is employed

[Eximea]

Thanks Peter.
I'm not happy with the rollers so I reckon I'll have a crack at knocking up a set of bunks. I'm heading off to the Kimberley again in a few weeks time. It's a long 8000 K return trip so it's pretty tough on boat and trailer. As mentioned, on previous trip the rollers really wore into the hull. I guess vibration and dust and grit were the culprits. Hopefully bunks will eliminate this problem. Thanks for your thoughts,
Regards, eximea

[Ozzie]

Good question Eximea. I personally have bunks as I think they distribute the load better. I built new bunks a few years back from treated pine and resurfaced them with nice soft marine carpet as the grooved plastic was scratching my hull on launch/retrieve on the old bunks.

EC3071B0-AEF2-4DF3-A631-5961E13D233C.jpeg (48.86 KiB) Viewed 4244 times

As a general thought for other newer users. Most people have found it best to lower the rear bunks for launch/retrieve as the hull gets wider in the centre. So effectively you’re squeezing the hull by not doing so. See Ian B’s comments in an earlier post. As the bunks have to be raised and lowered frequently by the regular trailer boat I always recommend using the correct sized ring spanner. The reason being, that it’s crucial that these be retightened correctly each time when the boat is on the road. Shifters after multiple use can round off the bolt heads and lead to them not being properly tightened. If your bunk collapses during cornering the resulting weight shift can really ruin your day very quickly

In regards to weight on bunks or rollers it’s worth noting that the full weight of the 563 is being taken on just the top few square centimetres of the 5/6? Rollers under the keel. The side bunks are for support of the hull only in regards of stopping it rocking . They should not be taking any real load weight.

If I were not mooring and trailered regularly I would makeup some aircraft style red clip on “warning” flags to remind me to tighten the bunks after retrieval as it really is very, very important.

If you use search function on the terms “bunks”, “rollers” “launch” there’s a few good information posts by Ian B and others on the subject.

Edit: I meant to say roller pairs for the keel support rollers.

[Eximea]

Thanks for your thoughts on this issue, Ozzie.
I notice in the photos that your bunks are short while Peter's are full length between supports. Is either better than the other in your opinion.
Eximea

[Ozzie]

Yes, true. My bunks were that size when I bought the boat so I just duplicated the original dimensions. The bunks pivot on the centre mount to change angle to conform to the hulls curved shape as it moves along the trailer. I think that’s the thinking behind the design. But that’s less of an issue if you lower the rear ones when launching. I think the long bunks obviously give a lower surface pressure per square cm which is a good thing, but you would need to be careful about squeezing the hull by maybe lowering one end somehow.

I once prepared a twelve foot tinny for return trip to the Kimberly myself and the trailer had long bunks and large wheels to spread road shock around as much as possible ( there’s a pic on here somewhere). The boat had a fairly straight bottom under the bunks though. It was bought home to me by seeing tinnies packed with heavy gear and small bunks getting deformation in the hulls . It’s happened to my little tender at times. You have the advantage on the 563 that the keel roller pairs are taking the load and the bunks are there to keep her upright.

[Peter T]

The best bunks, and the ones I am going to model my new ones off were the ones that were for " Private Eyes ". They had a 20 x 20 mm square RHS frame shaped to fit with a ply cover. They were then covered with carpet. See below. David advises me that he used to lower the rear of the bunksby about 25 mm but didnt think it was needed if he used his extendable tow bar or on steeper ramps.

[Ozzie]

This has been a good topic for reference. It’s good that these thread topics get revised after time with new input.

Just to probably add to my comments about “squeezing “ the hull. I’d suggest that what you are aiming for in launch/retrieve is to at no stage have any real weight on anything other than the keel roller pairs. If you are taking weight on the side supports at any point you may be doing harm. Just sayin’.

On that note it’s probably fair to say that the tilt (and I’ve used it and not used it at various ramps) is probably important. When you are winching onto the trailer, at one point almost half the weight of the boat is being taken on the first roller. The side tilting movements of the boat are being stabilised by the stern being in the water. By the time you have mostly cleared the water rear bunks are adding stability to the front of the boat.Tilting the trailer gets that load shared by as many rollers as possible as quickly as possible and puts less point loading on the keel. It’s a testament to the strength of the boat that it can handle this on the keel, but I wouldn’t push it. Also think about the massive load on the pull ring on the bow.

There is no doubt that floating the vessel off a completely submerged trailer is the kindest way to treat the boat but it adds the “trailer Armageddon “ issues discussed before. Just to reiterate an old ramble of mine. If you do submerge the trolley, take a moment to use the ramp tap (usually need your own hose) before you go sailing for the day as you will find the best time to get wet salt water off your gear is when it’s still wet probably not after a day marinating in the car park. Once again just sayin’.