Dry Launch Trailer Design?

I couldn't find an appropriate category on this forum for this so putting it here. I intend to trailer my 4m s&g ply boat. Problem is lack of boat ramps. I have two launching spots in mind but the trailer cannot be backed into the water as its too deep. I am thinking a sliding dolly on the trailer that cradles the boat onto a pair of skids. A 5m+ trailer with a 5m dolly. I wonder if anyone has come up with any interesting solutions applicable to this. I would like the dolly to slide out and tilt down to contact water. A wide float under the back of the dolly buoyed to just enable the boat to float on and off the skids

Idea is to back the trailer up to the edge of the wharf, slide out the dolly under winch pressure, gravity takes over and tilts it and the winch hold it from making an almighty splash. Full extension sees the boat in a good position to unhook free of the dolly and slide off slightly and float off. Same thing with retrieval. Drive the boat between the skids and hookup. Winch the dolly back onto the trailer

Hardest thing to design that I can see will be the dollys roller/rail system for sliding out from what I can visualize of the design

 

A sketch of you idea would be helpful.

 

Will see what i can do sketch wise. Think along the lines of them table top car towing and moving vehicles. Its the table top that is tilted and slid down to the ground

 

A tilt trailer will handle this, assuming the boat is relatively light. The usual issue is dunking the engine, as the boat goes in, typically at a pretty severe angle.

 

Some thing like this but with those rails fit on rollers or something and able to slide out too
http://bigwsales.com/Hydraulic Tilt Trailers.html

 

Its either something like this or a boom fitted to the winch post. Lift the boat off the trailer, swing out and drop to the water....maybe some pulleys and block and tackle type lifting gear or even the winch itself might do the trick. Boat and motor is estimated currently to fall under 100kg

 

I think a boom or davit of some sort the better approach than a very costly hydraulic tilt setup. This may require some support stands to be placed, before you hoist and swing her out, but these could be very simple devices.

 

Google beach launch rib.

Many different options for launching in difficult areas. Some of them are very simple and are made with common hardware store components.

 

I am in agreement with you there. Monday is a public holiday here but Tue I have an appointment with the local roads and transport authority inspector about going through the handbook on tubing options and rules when it comes to home built trailers and after that I am seeing a local mechanic who will actually be building the trailer and is a bit of a genius with modifying things to fit when proper parts cant be had. I am running a 1996 Volvo 850 wagon with majority Toyota suspension parts! Lets see what this guy can input too. He does work on sugarcane trailers which have track beds and winch up a cane trian cart from the field and dump it on the railway tracks. My thots with teh sliding rack is to exploit some of that design in lighter duty but at the end of the day the boom might be more practical

 

The inspector paid a visit and checked out the boat and motor and all the parts I had picked up in Aus. Reckons 50 x 50mm gal tubing be fine. 9" skids made of 6x1 pine plank covered with PVC guttering

Long session with mechanic after that. Visited lots of yards with derelict cars to find the undercarriage parts. Found an old Suzuki 800 FWD where the rear assembly seems perfect. Solid axle with hubs and leaf springs, very tiny car. 12" alloy wheels. Made a deal on that. I am going to check what kind of fuel tank in that too

We are considering two options. Trailer with extendable ramp and a dolly on tracks or trailer with a boom. Looks like the boom will be easier to implement. Tomorrow will be testing a hydrolic jack, the kind of stuff used to lift larger SUVs and pickups to change tyres. Aim is to fit that to the boom to lift the boat of the trailer and swing out and drop it max 2m off the wharf

 

Picked up 2x 6m lengths of 50x50mm gal tubing with 1.6mm wall thickness. This is and the 50mm round gal tubing appears to the largest I can get. Boat is 4.2m so I am thinking a trailer length of about 5.5m built like this


I am 90kg. When suspend a 6m length of tubing and walk on it, it flexes. About 20cm from straight when I stand at midway. Thinking its too light and considering this shape


That is using two lenghts in a V making the drawbar

For the dry launch mechanism the mechanic and I have settled on two options

Option 1: Making a v shaped gate about 1m tall that will open and lay horizontal at the back of the trailer, in essence extending the trailer by 1m

The point of that V gate will have a fixed post about 1m high set into a swivel base. When the gate is up, the post sits horizontal over the back of the boat

The head of the post will have a hinged arm about 1.5m long (exact length of arm subject to boat balance point). When the gate is up the post and arm will be in the same plane and laying lengthways over the middle of the boat

When the gate is down, the post becomes vertical and the arm hinges down to lock and 90 degrees to the post. A 1200lb trailer winch fitted to the back end of the arm on top of the hinge area and a roller near the tip of the arm becoming a crane to lift the boat of the trailer and rotate out to drop to the water from the wharf

Option two: This time using a taller rectangular tailgate. An arm at each end of the tailgate with chain and hook at the tip of each arm. With arms up over the boat, hook up to the balance point and stand the arms up which will lift the boat off the trailer. Swing the arms back to drop the boat to the water. Dumpster truck style. Need to figure out how to connect the trailer winch to power the arms


Option two will be trickier to power in a simple manual way but more stable

 

Finally finished work on this trailer, seems to work ok. Ultimate test will be at the local dodgy ramp
TooBads in Fiji 012 289 copy by jonny.toobad, on Flickr

Painted

TooBads in Fiji 012 302 copy by jonny.toobad, on Flickr

Dolly in extended position

TooBads in Fiji 012 313 copy by jonny.toobad, on Flickr

Retrieveing

TooBads in Fiji 012 317 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 318 copy by jonny.toobad, on Flickr

Dropping the boat on

TooBads in Fiji 012 328 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 334 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 335 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 343 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 344 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 345 copy by jonny.toobad, on Flickr
TooBads in Fiji 012 346 copy by jonny.toobad, on Flickr

Whatdoya reckon