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Old 23 June 2016, 13:32   #1
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Country: UK - England
Town: Cornwall, UK
Make: Quicksilver 430HD
Length: 4m +
Engine: Mariner 20Hp 4s
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Seeking suggestions for trailer modifications please

Hi All,

Got an issue with my new SIB and trailer. I know, it's a "Classic" issue, but I'm specifically looking for suggestions on how to tackle it for my setup. The dreaded bouncy castle trailer ride has got to stop! I've been looking at my trailer and boat then scratching my head as best approach. I have used the search facility and found some posts and ideas, now I want to work out what to apply to my situation. The trailer has two bunks that the outer tubes sit on fine, but the keel has two small ones and only the forward one touches once the boat is on the trailer. Cue pictures to save the thousand words..

I also wanted to pop my proper post cherry..

So this is the boat.


and this 20hp 4stroke heavy lump hangs on the back. Never owned a 4stroke, I'm still amazed at the weight!


But the transom on the trailer looks like this...



I'm happy to approach a local fabricator who has many years of marine experience, or DIY it. However I want a decent solution either way. Also I'd quite like to incorporate the facility to attach the trailer board to whatever I do.

Do I:
  1. Change the central bunk for one long-un that reaches past the transom and also enables me to support the engine?
  2. Get some extendable arms made that slot into those holes in the box section that supports V shaped across the transom and again, support the engine?
  3. Use a "Tansom Saver" type option or just block of wood and luggage strap?
  4. Anything else you good people suggest?

Thanks in advance,

Dan
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Old 23 June 2016, 13:44   #2
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I'm far from being an expert on towing but I'd start with the tyre pressures for bouncy castle.
Is the trailer very nose heavy or light with boat on it? Maybe adjust boat position to improve c of g.
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Old 23 June 2016, 14:15   #3
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What exactly is bouncing? Is the boat trying to bounce off the trailer, or is the trailer itself trying to bounce off the pavement? Or are you seeing the motor doing the pendulum thing while everything else is OK?

For the first, you might try moving the side bunks in a little so the spot where the floor material, the tubes, and the floor itself all come together, which will eliminate the weight sitting on big balloons. You can also pick up the transom with these bunks.

For the second, not much you can do (as far as I know) aside from playing with spring rates on the trailer suspension. I never found that tire pressure made a lot of difference other than causing weird wear patterns.

For the last, you need to transfer some weight of the motor to the trailer frame, and preferable triangulate the motor against something more solid than the tubes. I used a transom saver that mounted against the rear trailer crossmember, and tied the (tiller steered) motor so it wouldn't turn from centripetal acceleration on curves.

As long as the flooring is supported, there isn't a big need to support the keel, as the only weight there is the inflatable keel and floor material. My SIB trailer did have a centerline bunk, but like yours, the only contact was the front just before the bow upsweep. Not really sure you'd want a whole lot of weight on that anyway, as the load would be carried solely by the keel tube.

jky
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Old 23 June 2016, 14:39   #4
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I have the same boat as you T4S ..and will agree 100% with all jyasaki said.

I donít trailer with the outboard attached ..but the boat is often loaded with a lot more than 52Kg of weight. (Outboard weight 52kg) If your bunks support the tubes..that is where your bounce is coming from. The bunks should support the floor at the edge of the tubes. I donít have bounce in my setup.



I have a bunk runs down the centre of the trailer..and the keel only touches it at its lowest point..which is up near the bow. I let all air out the keel to recover the boat.. so there is nothing supported by the mid bunk...its redundant

I would use a transom saver if trailering with the outboard in position.. but I prefer the OB in the car..as it makes launch and recovery easier for me. Im not to keen putting the trailer in the sea now..its getting too rusty for that as its not galvanised.

Its a great SIB..you will have a lot of fun with it once it is in the water..but it is a heavy brute on land
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Old 23 June 2016, 14:44   #5
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I have a similar boat Mercury 365 (3.8 with shortened cones ) with a 25 hp 4 st I put a keel bunk in coming just past the transom for support two ratchet straps to the trailer off two eye bolts through the transom and one strap round the engine to the trailer.winch on the bow holding it slightly down.rides perfect.

Cheers
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Old 23 June 2016, 16:06   #6
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Sorry should have been a bit clearer, it is the weight of the engine bouncing an unsupported transom that's my issue. The trailer tows sweet, its just that bouncy load.

Thanks Mr G, I didn't realise that the bunks shouldn't be under the tubes. That's a good start.

I think Jeff what you're doing is going to suit me best, it's sort of what I had in mind with my point no. 1. Didn't think about strapping the boat down at the transom. Makes total sense.

When I used it the first time I used luggage strap to the trailer and a wood wedge to keep the engine up a little but that transom support was missing.

So is there an acknowledged method to make and cover a central bunk? I'll start a search....

Cheers all, thanks for sharing in my cheery popping
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Old 23 June 2016, 17:11   #7
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I differ from others not saying I am right but had no probs my bunks are on the tubes off of any joints always done it with no probs the keel you could have just a transom pad under the engine I carry lots of kit in the boat so support all the way. The engine I put a composite block between the engine and clamp just to stop the tilt mechanism from strain and strap down.
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Old 23 June 2016, 17:16   #8
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Cheers Jeff, ive been and had a look. There is a pad at back but the boat doesn't come far enough forward. It needs extending at one end or the other! It's nicely balanced to boats probably in the right place.
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Old 24 June 2016, 03:46   #9
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sounds like your 99% there extend make sure its taking the weight straps on job done.
the boat will bounce a bit naturally especially if the bow can move with mine the keel is like a shock absorber with the winch holding down. keep playing with it you will sort it for your own needs.

cheers
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Old 24 June 2016, 07:00   #10
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Cheers Jeff and yes, I think I'm sold on the route to take. I'm going to introduce a middle bunk from the axle back to the rear cross member on the trailer and on beyond the transom a wee bit. Unless someone can point out a really big hole in my thinking...

Does anyone know if you can buy the galvanised trailer box section anywhere?
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