Trailer Tech...???

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Originally Posted by harlie

If you have skids and no rollers then the trailer must be submerged for launching - personally I'm not a fan of that. This brings me to the rust issue. Show me a boat trailer that is submerged for launching and is more than 1.5-2 years old that doesn't have rust starting in the rear end. Galvanising is a sacrificial coating that is eaten away quite quickly with regular submerging in saltwater. Personally I think these trailers are too darn expensive to treat like this - I’ll get off the soap box.

On the up side Skids will give more support than a poorly designed / adjusted multi roller trailer – but a good multi roller (with heaps of rollers and positioned directly under bulkheads ect) provides excellent support. A skid trailer can be significantly lighter.

If you are going air springs (big fan of that) have a look at the Sensa Brake system to actuate your LR hydraulic brakes, you may be able to combine air compressors…

Can’t see a problem towing on the beach but with those tyres, the narrow track of a LR axle and travel of air she will sit up unbelievably high – the guards will be well under the chines. I looked at a trailer set up similar to this (custom made by Belco) and it tilted at the front and rear to account for the height when launching and the owner commented on having problems with shallow angle ramps and surf launchings were hopeless because of the height – to get the boat to float off (as you would with skids) the car’s back bumper was in the water on the southern public ramp in Manly hbr (it has a shallow incline). The Fraser Island crowd nearly all run std 14" tyres to keep the boat a bit lower for the surf launching.

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I would have thought a good gal coating should last longer than that - especially if the trailer is hosed down (inside and out) after each use???

Maybe I have been looking at small trailers -I thought the RRC track was fairly wide by comparison? Especially with offset rims... What is a normal boat trailer track? It would be easy to cut the centre out of the axle housing and widen the track though.

The beauty of air springs is you can adjust to any height you want! I was planning on setting them low to keep the C of G as low as possible. I may even mount the air springs behind the axle, rather than on top of.

According to redbook – Disco 2 has a track of 1560 (not listed for RRC)
According to Redco’s website a trailer for a 5m Ally boat is (5m is on the cut off going to big stuff) either 1610 or 1850 BETWEEN THE GUARDS. At a guess 235/2 = 117.5 + 50 (inner side of tyre to inner edge of guard) = 167.5 each side * 2 = 335 + 1610 = a really wide track – much wider than 1560 disco.

According to Quintrex’s site – probably the worst boats available but they do list specs - a 5m boat has a beam of more then 2200 so chines at 1800-1900. 5m plate boats are actually quite big.

I know the HD trailer under my 4.2 has a wider track than the L322…

Agree with the point of adjustability of air but air allows for more (and softer) travel as well (that’s the nature of an air spring), so if you set it down low, there still needs to be height available to allow for the spring to work. I think you will find that a leaf setup will allow a lower ride hight than air because of this, but with air it can be dumped for loading. Still with a 79cm tall tyre + clearences under the chine it's high.

As for Gal. I live just above the marina here, my current boat is permanently in the water, hence I walk the dog past and through the parking area (great for kids’ bikes) most days for exercise and to check on my baby. I can say that on any given day you can count the rust free trailers on one hand, if there are any at all. My last trailer boat was 6.5m on a trailer that I built (because the original was rusted when purchased) and never submerged, painted with fish oil regularly. When I participated in club off-shore days, I was the only one with out rust, when I sold it the buyer commented on the 40 odd boats he looked at mine was the only one with a trailer in good nick. When I took it for the roadworthy for the sale the mechanic commented on how he had not seen one come in rust free before. And don’t start me on braking systems that go under…

The Gal posts holding my deck up at home have rust around the base Gal coating is long gone) from the salt air (and we don't have surf), they don’t even see the water and are less than 12 years old. Galvanising is sacrificial; it helps but doesn’t save it. I’m not saying don’t Gal just don’t believe the marketing the it will save everything - I actually have items at the Galvanisers now, currently 8 day turn around…

How about this mob Ben:D
Belco Custom Trailers


http://www.belcocustomtrailers.com.a...Camper%202.jpg

http://www.belcocustomtrailers.com.a...w%20camper.jpg

http://www.belcocustomtrailers.com.a...%20trailer.jpg

Baz.

Thinking logically (and don't get me wrong, I'm not criticizing the idea of a multi purpose trailer) but is there a compelling reason that the hassle would be worth it, such as lack of room to store 2 trailers? I would figure the cost of custom building something to do both jobs, added to the hassle and safety concerns with taking the very heavy boat on and off on land to use the trailer for a box trailer would far outweigh the benefits if any. Rego costs for a trailer in Qld at any rate are less than $100 a year, so to do it for reasons of economy is out unless your trailer regos are way more expensive. Plus the cost to build something like this would probably outweigh the cost of buying a good secondhand box trailer ($150 to $300) or even a new one (under $1000) and probably $2-3k for a good new boat trailer?

Like I say, not criticizing the idea, but it seems like the economics of it wouldn't add up.

Ben,
Im gonna pretty well ignore the box trailer thing for a one reason:
-A 5m platey off road trailer is a going to be a very specific animal, yeah you may be able to incorporate a few features to enable taking boat off and using trailer for other purposes but in reality you want to make sure you get the support for a 5m platey spot on.

Firstly, in my experience 5m platey really is above the realm of what I would call true offroadable. Unless it will be horribly underpowered you will be running something in order of 115 horses off the transom. If someone really wanted me to make them an 'offroadable' 5m platey with 160+ kg outboard I would be angling towards tandem axle setup with 14" light truck tyres and the trailer significantly wider than the hull to get the boat between the guards... which then makes it dirt road trailer not a true off road trailer??? horses for courses I guess.

In my very opinionated opinion! True off road trailers (ie take it up the OTL to west coast or drag it through 80km of mud in the wet)
MUST:
1/ track the same as the tow vehicle.
2/ run full size hubs/stubs and bearings (75/80 series fronts for tojo/patrol... disco/fender for landy
3/ have excellent support for the keel and hull.
4/ have the boat firmly attached to the trailer such that they move as one entity - no loose fitting straps... use turnbuckles and locktight.
5/ The outboard (more importantly the transom) needs to be supported in as low trim a position as possible.
6/ which generally keeps them under 4.5m and 60hp.


So, to do that your idea of using a housing is perfect-ish! It gets the track and running gear right.

Either way lets talk about your suspension. I agree with most of it, but lose the axle tube and instead build your own out of heavy wall pipe/tube, SHS or solid 50mm. Then weld on flanges that accept the landy stubs. (unless you are desperate to store spare axles in the housing I guess?) It will save some unsprung weight and enable you to better design the links and mounts. Use rear landy discs and calipers for brakes. Then run over-ride hydraulic hitch to start with, if you think you need then need electric braking - setup electric over hydraulic. Hydraulic is tough and it works.

I think running front radius arms with a panhard with airsprings would work really well.

Tinnies need keel support so run a row of 50mm diameter rollers up the keel, Run them on 100mm centres for the length of the keel.

If you do go with single axle and 235s I would definitely make the trailer tilt at the back of the A frame. I can flick a few pics of a 435 hornet trailer for a the design I came up with.

What hull you going with and what power plant... would be interesting to know!

And as an aside Harlie I concur on your assessment of Qunitrex, they use to have 'it' but somewhere along the road of mass production & cheap raw materials they seriously lost 'it'.

And similarly I agree with your comments re boat trailers and galvanizing. If you dunk the trailer... the gal will require lots of loving (think Tectyl often etc etc). The problem is most trailers are made from RHS and to gal dip a trailer it must have drain holes, which then let in the water and they ALL rust from the inside out. So either use hot rolled channel or re-build the back half of your trailer every 5 years???

In light of that and the stupid cost of galvanizing up here, repairs I make and outright builds now use 100PFC prepped and painted then Tectyl. And keep up to it!

Sorry for the ramble. Ill grab some pics of the 435 hornet rig for you.

Steve

Thinking about the mob above that I posted, having the motor attached to the boat wouldn't be a good idea, also it was only to give some ideas, I'm sure you'll work it out anyway, Steve seems to be on the right track about what you want, he would more experties than me.

Baz.

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Originally Posted by roverrescue

Ben,
Im gonna pretty well ignore the box trailer thing for a one reason:
-A 5m platey off road trailer is a going to be a very specific animal, yeah you may be able to incorporate a few features to enable taking boat off and using trailer for other purposes but in reality you want to make sure you get the support for a 5m platey spot on.

Firstly, in my experience 5m platey really is above the realm of what I would call true offroadable. Unless it will be horribly underpowered you will be running something in order of 115 horses off the transom. If someone really wanted me to make them an 'offroadable' 5m platey with 160+ kg outboard I would be angling towards tandem axle setup with 14" light truck tyres and the trailer significantly wider than the hull to get the boat between the guards... which then makes it dirt road trailer not a true off road trailer??? horses for courses I guess.

In my very opinionated opinion! True off road trailers (ie take it up the OTL to west coast or drag it through 80km of mud in the wet)
MUST:
1/ track the same as the tow vehicle.
2/ run full size hubs/stubs and bearings (75/80 series fronts for tojo/patrol... disco/fender for landy
3/ have excellent support for the keel and hull.
4/ have the boat firmly attached to the trailer such that they move as one entity - no loose fitting straps... use turnbuckles and locktight.
5/ The outboard (more importantly the transom) needs to be supported in as low trim a position as possible.
6/ which generally keeps them under 4.5m and 60hp.


So, to do that your idea of using a housing is perfect-ish! It gets the track and running gear right.

Either way lets talk about your suspension. I agree with most of it, but lose the axle tube and instead build your own out of heavy wall pipe/tube, SHS or solid 50mm. Then weld on flanges that accept the landy stubs. (unless you are desperate to store spare axles in the housing I guess?) It will save some unsprung weight and enable you to better design the links and mounts. Use rear landy discs and calipers for brakes. Then run over-ride hydraulic hitch to start with, if you think you need then need electric braking - setup electric over hydraulic. Hydraulic is tough and it works.

I think running front radius arms with a panhard with airsprings would work really well.

Tinnies need keel support so run a row of 50mm diameter rollers up the keel, Run them on 100mm centres for the length of the keel.

If you do go with single axle and 235s I would definitely make the trailer tilt at the back of the A frame. I can flick a few pics of a 435 hornet trailer for a the design I came up with.

What hull you going with and what power plant... would be interesting to know!

And as an aside Harlie I concur on your assessment of Qunitrex, they use to have 'it' but somewhere along the road of mass production & cheap raw materials they seriously lost 'it'.

And similarly I agree with your comments re boat trailers and galvanizing. If you dunk the trailer... the gal will require lots of loving (think Tectyl often etc etc). The problem is most trailers are made from RHS and to gal dip a trailer it must have drain holes, which then let in the water and they ALL rust from the inside out. So either use hot rolled channel or re-build the back half of your trailer every 5 years???

In light of that and the stupid cost of galvanizing up here, repairs I make and outright builds now use 100PFC prepped and painted then Tectyl. And keep up to it!

Sorry for the ramble. Ill grab some pics of the 435 hornet rig for you.

Steve

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Thanks Steve - all great advice! Very helpful.

The plan so far is a 5m open hull flat/clear floor platey. 60ish hp (probably 2 stroke to keep the weight down) tiller control - 4 mm on the bottom and 2 mm on the sides.

So although it will be a platey it will be a fairly simple, light platey.

I suppose you think that would be underpowered???

I can always reduce the length - you think 4.5 m would be better? If I go ahead it will be built by a mate in Brisbane who has built about 10 alloy boats before - everything from a 15ft powerboat to a 28 ft half cabin cruiser to a 40 ft sailing cat.

Quote:

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1/ track the same as the tow vehicle.
2/ run full size hubs/stubs and bearings (75/80 series fronts for tojo/patrol... disco/fender for landy
3/ have excellent support for the keel and hull.
4/ have the boat firmly attached to the trailer such that they move as one entity - no loose fitting straps... use turnbuckles and locktight.
5/ The outboard (more importantly the transom) needs to be supported in as low trim a position as possible.

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I agree with all of this, and it was what I was trying to do. The trailer/boat combo will definitely be built as a proper offroad setup, as we plan to drag it to the top of the kimberley, across to and around tassie, and maybe even to the gulf. Surely a v-shaped skid under the keep will support it better?

The box trailler idea was really just so that once a year (in winter) when I do a firewood trip I can use the trailer as well as the ute to cart wood. I have pretty much worked that out anyway - it is easy to incorporate a weldmesh floor into the design (doesn't need to be flat), and fit some temporary sides when I need to.

As much as I don't like structural components made from ally, I might have to consider making an ally trailer instead... However if I do use steel it will definitely be C or I section rather than box.

Cool all good info Ben,

Despite the fact I love working with Al, for town boat trailers its structural Al C-section all the way. But for an offroad trailer I would stick with all steel construction... the inherant flex you get between towball and axles in a boat trailer will soon kill Al, unless it was so overbuilt to negate the weight benefits.

I guess horsepower is a personal thing. I run a 40 two stroke on a 3.9m stacer. It has adequate power for what we do. A 5m standard half cab design with a 60 will struggle in northern conditions. Kimberley flood tides can push 10 knots... if you are only capable of doing 18 knots and have to work against a big current its gonna be a slow trip home. Also when you load her up with people and gear to go camping outon an island youll want neddies on the back to be safe.

Having said that a 60 yam 4st is the perfect power plant for a northern offroad boat. (this is what we run on the 435 hornet) It will use less than half the fuel of a 2st. Boat fuel gets heavy and takes up space. The extra 25kg of ourboard weight doesnt counter having to squeeze a second 44 into the tray! There are alot of boat camping spots up north where you will do big sea miles and not have re-supply for a long period of time. Carting less boat fuel should be a prioity in your planning.

If the platey was built strong but light, 60 yammie (or the new lightweight 70) on the tiller then 5m would certainly be feasible for single axle true offroad rig. When you said 5m platey I was thinking like a 5m Barcrusher or Noble... big deepVs that would make it necessary to run with the guards outside the chine.

A 20ish degree deadrise 5m LOA but relatively narrow say 1.8m wide platey would be the bomb up north. Less width means you can get away with less hp (trade off is less stability but design can accomodate some of this???) Think of a Wahoo or Hooker design in plate rather than glass. In many ways would be the ultimate northern explorer.

S