Setting up Trailer for MilPro Mark V

[AlpinetoOcean]

Hi RIBNet Community,
I'm a new owner of an older (1993) Zodiac MrkV HD. It came on an U-built trailer that has seen better days. Renewing the old trailer doesn't look practical. For one thing it is painted steel which I assume was chosen for its original life in freshwater. Here on the Pacific coast it has rusted heavily. So I found a used galvanized trailer that looks to have potential as a replacement.

Knowing that there was no way I would be driving the old trailer on the road, I had the Zodiac lifted onto the new trailer as a first step. It is a tight fit. The transom was ~8 inches aft of the end of the bunks so I added a longer length of 2x6 on top of the bunks to support it. You can see the end of the new wood in the photo below.

Once the Zodiac was on the new trailer the other issue that became apparent was that the main tubes are resting on the wheel fenders. Not too heavily, I'd say by about 1.5" or so.

So my plan is to set up a new pair of bunks and take the trailer to the boat ramp and get it off the trailer, park the boat in the marina and run the trailer home to fit the new bunks on the trailer and then retrieve the boat.

I have all the parts: 12" bunk brackets, U-bolts, new bunk carpet, stainless staples etc... I'm not sure if the 12" brackets will lift the tubes high enough off the fenders so I'm toying with the idea of laying down 2 layers of 10 ft lengths of 2x6 to get an additional 1.5" height. I know that's unusual but I also imagine this will give the bunks enough heft to better support the transom and the overall weight is no where near the 2200lb capacity of the trailer.

My specific questions concern the placement of the bunks. Currently I have the bunks about 48" from outside edge to outside edge. That puts them just inside the speed tubes. (I cut the fore end of the temporary bunks at an angle to accommodate the forward end of the speed tubes). This leaves about a 40" gap between the inside edge of the bunks athwartships.

- should the bunks be positioned inside the speed tubes as I have?
- is 40" too wide to support a SIB over the long term?
- should I consider adding a second set of 2x4" bunks close to the keel to better support the hull?
- would the additional friction of another pair of bunks (albeit narrower 2x4) impede the ability to winch the boat up onto the bunks?

I suppose some of these questions are conjecture because until I put the trailer in the water I won't know how high the boat floats relative to the bunks. Still any insight into this would be greatly appreciated. Thanks RIBnetters
Phil

[jonp]

Any boat I ever buy, I set the trailer up so I can quickly and easily drive the boat onto the trailer. Setting up the v bunks with plastic bunks that line the boat to the centre makes life so easy. Most of the ramps I use will have several hundred boats launch and retrieve in a day, so most people have similar setups to mine. The tubes shouldn't come in contact with anything on the trailer.
I also opt for marine grade aluminium c section trailers these days as galvanised box section trailers have limited life in comparison and require more maintenance.

[Pikey Dave]

Originally Posted by AlpinetoOcean

Hi RIBNet Community,
I'm a new owner of an older (1993) Zodiac MrkV HD. It came on an U-built trailer that has seen better days. Renewing the old trailer doesn't look practical. For one thing it is painted steel which I assume was chosen for its original life in freshwater. Here on the Pacific coast it has rusted heavily. So I found a used galvanized trailer that looks to have potential as a replacement.

Knowing that there was no way I would be driving the old trailer on the road, I had the Zodiac lifted onto the new trailer as a first step. It is a tight fit. The transom was ~8 inches aft of the end of the bunks so I added a longer length of 2x6 on top of the bunks to support it. You can see the end of the new wood in the photo below.

Once the Zodiac was on the new trailer the other issue that became apparent was that the main tubes are resting on the wheel fenders. Not too heavily, I'd say by about 1.5" or so.

So my plan is to set up a new pair of bunks and take the trailer to the boat ramp and get it off the trailer, park the boat in the marina and run the trailer home to fit the new bunks on the trailer and then retrieve the boat.

I have all the parts: 12" bunk brackets, U-bolts, new bunk carpet, stainless staples etc... I'm not sure if the 12" brackets will lift the tubes high enough off the fenders so I'm toying with the idea of laying down 2 layers of 10 ft lengths of 2x6 to get an additional 1.5" height. I know that's unusual but I also imagine this will give the bunks enough heft to better support the transom and the overall weight is no where near the 2200lb capacity of the trailer.

My specific questions concern the placement of the bunks. Currently I have the bunks about 48" from outside edge to outside edge. That puts them just inside the speed tubes. (I cut the fore end of the temporary bunks at an angle to accommodate the forward end of the speed tubes). This leaves about a 40" gap between the inside edge of the bunks athwartships.

- should the bunks be positioned inside the speed tubes as I have?
- is 40" too wide to support a SIB over the long term?
- should I consider adding a second set of 2x4" bunks close to the keel to better support the hull?
- would the additional friction of another pair of bunks (albeit narrower 2x4) impede the ability to winch the boat up onto the bunks?

I suppose some of these questions are conjecture because until I put the trailer in the water I won't know how high the boat floats relative to the bunks. Still any insight into this would be greatly appreciated. Thanks RIBnetters
Phil

Trailer setup is a bit of a black art & needs time & patience to get it right. A poorly setup trailer is at best a PITA, at worst down right dangerous. The basic principles are, in no particular order:-
1, Boat transom wants to be flush/slightly overhanging the rearmost support
2, wheels as far forward as possible, whilst still maintaining adequate nose weight, too little nose weight will cause trailer "wag" & is VERY undesirable.
3, boat sat as low as possible on the trailer, whilst maintaining sufficient clearance under the keel so that the keel doesn't catch any part of the structure during launch/recovery. This clearance will alter depending on the angle of the slip & depth of water, so make sure the clearance covers all eventualities.
4, Hull needs to have maximum support, distributed evenly along the trailer/hull length.

That's for starters, get to that stage & "tweak".
It's fairly easy to drop the boat off the trailer on dry land to get the basics setup, I do this regularly as it makes servicing the trailer easier without the boat on. I've posted a "How To" if you do a search. This allows you to get into the right field before you go to the slip.

Here you go
https://www.rib.net/forum/f8/droppin...den-76830.html

[AlpinetoOcean]

Thanks jonp, yea aluminium trailers just aren't a thing here. It's galvanized square tube all the way. And they do seem to last. It may be the cooler climate with a LOT of rain to wash the salt away but either way it's just what's available.

Thanks for the note on keeping the tubes clear of the trailer. I have made up a pair of new bunks with longer brackets and my best estimate that once it's all set and the boat is on it the main tubes should lie proud of the wheel fenders.

As mentioned in my OP I'm mainly curious what people's advice is regarding supporting the soft hull of the Mark V specifically. I don't think V bunks would be adequate. If I am going to go to the trouble of adding additional support I think a second course of 2x4 bunks longitudinally would provide better support. I'm just curious if there's a consensus as to whether that is necessary our if the one set of 2x6 bunks is adequate?

Cheers
Phil

[AlpinetoOcean]

Thanks Pikey Dave,
There's a couple of key bits of advice there I will bear in mind. I like your procedure for getting the boat off the trailer. I have a large Douglas Fir stump right alongside my parking/work area that is most definitely the sort of immovable anchor that would work to anchor the boat to.

I am curious whey you would keep the vehicle connected to the trailer when you winch the trailer back under the boat? That seems like it would add unnecessary strain on the winch.

Also you mention letting he transom overhang the bunk but I don't know that that is ideal for a SIB where the stress of that weight would then be transferred straight to the tubes. I can see with a RIB that would be fine but a soft hull not so much. The new bunks I have made up are set up to support the transom.

I have to weight now for the Provincial insurance corporation to process the trailer transfer and I'll be able to get on the road.

Cheers
Phil

[Pikey Dave]

If you don’t keep the trailer attached to the vehicle during the “recovery” phase, it will result in the hitch being 6’ up in the air until you get the weight forward of the wheels.
Agreed about the transom, my method was aimed at a RIB setup, I’d missed that yours was a SIB. Get the bunks just under the transom & let the cone ends of the tubes overhang. This will make launching easier as you get the buoyancy from the tube overhang sooner and it will take the weight of the transom.

[AlpinetoOcean]

Originally Posted by Pikey Dave

If you don’t keep the trailer attached to the vehicle during the “recovery” phase, it will result in the hitch being 6’ up in the air until you get the weight forward of the wheels.

Roger! I can picture that. Thank you.