Boat trailers

I know this might not be the forum for trailer design, but I assume you guys have a lot of experiences with trailers anyway. I have been using european trailers for years, and I've been so disappointed in their design that I've been thinking about making my own. However, what are the features of a trailer that makes it stand out from the competition? Any experiences on the differences on hub and disc brakes? Just anything. I'd like to hear your opinions.

Yours sincerely,
Lars Fadum Haugstad

 

Just my 2 cents worth, use c-channel (galvanized) or aluminum I-beams for the main rails and cross members. Don't use box tubing, this is flimsier, and will rust out from the inside. Use 2 big heavy bunks from midships to transom, with the after bunks overhanging the trailer frame by 2 feet or so (2/3 meter?? ) to prevent the bow contacting the trailer frame while driving on. Mount a smaller set of bow bunks set inboard of the after bunks, and overlapping by a foot or so, to catch the bow and center the boat on the trailer. Centerline rollers should be the clear variety with snubbers on the outboard sides of the roller brackets. This prevents the hull from contacting the brackets, and clear rollers don't scuff the gelcoat the way black rubber ones do. Can't help you with brakes as down here they only last for 2 or 3 dunkings before they start rusting up and quit working. I'd imagine stainless disc brakes of the surge type would be best, and of course the most costly. Definitely have a flushing system for whatever kind of brakes. I've seen a few boneheads put electric brakes on boat trailers, figuring if they disconnected them before dunking, they'd be o.k. Probably don't need to tell you how that came out. I like leaf springs better than torsion axles because you can see what's going on with them, and they're relatively easy and cheap to replace, but everyone loves the new thing and lots of trailer manufacturers here are switching to torsion axles. We'll see how they hold up in the brine. Finally, a short set of side guides, or my personal favorite, a pair of 1 1/2 inch PVC pipes upright at the aft end of the trailer mounted on pipe/brackets that allow the PVC to rotate make driving on a snap. I also mount my trailer lights and license plate on the bracket the PVC slips over to keep them out of the water. (It's a Texas thing) These are the features I look for (and usually have to add on myself) Good luck!

 

i've seen a sort of lengthwise torsion independent wheel suspension system enabling a lower center frame and CG. i liked the electric winch multiwheel canting config for my V bottom powerboat, ofcourse it all depends on the load, i've seen many overloaded and bended trailers also so make it strong but not too heavy. let us know what you did and didnt like also please

 

A lot depends on the size, weight, configuration of the boat and conditons where it will be used. Different boats call for different "best" trailer solutions. What kind of boat are you talking about? I've been trailering boats from 150 to 4500 lbs for many years and find that most of them needed something different.

Glen-L has a book on trailer design and construction that many have used to build good trailers.

 

Thanks for some excellent feedback. Lots of good comments there, Corpus Skipper!

Yipster, I have a few friends in the Netherlands, and it looks like you guys have the same problems that we do in Norway - American trailers aren't road legal. Is this the case, and do you know why they're not legal?

Tom, I will try to make a trailer with a 2500 lbs capacity.

 

Lars, i had the electric brakes made to mechanical on that one. tandem (2) axes and tilting frames are legal, quit a bit of law on the subject though but did not know american trailers aren't road legal here.

 

As Tom has pointed out, trailer design needs to be matched to the boat. A poorly fitted trailer can damage a boat. The boat I'm working on now was trailered 300 miles to me and arrived with the port bunk pushing 6" into the planking. It had popped all the fastener along the garboard and broken over a dozen frames. This trailer was a very poor fit, didn't have bunks in the right location nor long enough to do the job.

I also like to center the bow, but do it with guides mounted on the trailer frame rails or a "V" mounted on the centerline. PVC guides aft, make much easier loading, amber rollers with S.S. tubes hold up a lot longer, can handle much more weight and don't mar the finish, like the black "WalMart" types with the Teflon sleeve rather the a metal one inside. You can't have enough rollers. Mounting the trailer lights high is a southern thing, not just the great state of Texas, all the folks who use their boats regularly and have replaced reasonably new light assemblies, mount them on the guides or as I've seen sometimes on the boat. Keeps things dry and easier to see in traffic.

I've seen small trailers with torsion springs, but none in larger sizes. I'm sure they make them, but I'd be wondering about the frame flexing too much on a big tandem or triple. The extra few inches would be nice down here in shoal land, but I'm not sold on the idea yet for rigs over say 3000 pounds. My Chris needs twice that, an extension and still gets the rear or the truck wet at launch. Life in the shoals . . .

Can't think of why American trailers aren't legal there, maybe lighting requirements, but a trailer is a trailer and the beast can't be much different in European trim. Brakes could be an issue, electrics suck bad, for any usage.

 

Lars, Since trailers are so different from each other, I also assume teh legal issue is a difference in lighting requirements.

For a 2500 lb boat I would want a tandem axle trailer with brakes. At this point after fighting surge drum brakes for a few years, I'd try the stainless disc type. The tandem axle kind are much more stable and forgiving on the highway even if the weight is legal for a single. I think this weight is ok for aluminum but an aluminum trailer should be well overrated to minimize flexing which can stress the boat. Galvanized steel is much stiffer than aluminum and I echo the use of open channel and "I" beam sections to minimixe corrosion failure.

Lights mounted on tall trailer guides are fine. I prefer float on trailer bunks to the roller type for boat protection. Bunks should fit the bottom of the boat, both longitudinally and in deadrise angle. The bunks should be placed so they are under the strongest structural members available in the boat to avoid hull distortion.

Finally, I advocate tying the boat firmly to the trailer. For a sailboat that might be the bow eye and jib winches with a separate STRONG tie leading aft from the bow eye to prevent shifting forward in an accident. For a powerboat I like ties from the trailer to the transom or motor mount of an outboard.

There are a lot of other good things to add, like a wide board to walk on the trailer to hook up with dry feet and/or solid plywood cover on the trailer to protect the boat from road debris.

 

As usual I've arrived at this discussion after much of the good advice has already been given but I do have a couple of suggestions, with the caveat that I speak from Oz, so laws may be different....

Brakes. My ski boat (at aroung 3300lbs combined boat & trailer) runs stock standard overide discs on the front axle of its tandem trailer. Combined with bearing-buddies (an absolute must on any boat trailer) I've never had a problem.
Our dive boat (at around 9500 lbs) has vacuum-assisted discs on all four wheels. Ideally the boat should have a tri-axle trailer. We've had several different braking systems. When we bought it, the trailer was equipped with simple overide discs on the front axle.....woefully inadequate. We then installed an electro-hydraulic system to all four wheels which used a little gyro to sense braking effort anf thus provide some sort of proportional braking to the trailer. It was ok, but there was a considerable lag time between applying the brakes in the tow vehicle and when the trailer brakes actuated. Finally, we moved to the current system (made by Sensa-brake). It too provides proportional braking, this time from a pressure sensor attached to the brake pedal. It provides instant response and we a pretty happy with it.
As far as the discs themselves go, there are discs and then there are discs.... Beware of supposedly stainless discs - most (all in fact that we've seen) still use steel pistons. And no matter how carefully you wash down your trailer after each dunking, salt water always finds its way in and before you know it the brakes are siezed. The only ones I would recommend are made in New Zealand I think and are entirely made of Bronze....I'll get back to you with the manufacturer if you're interested.

Here in Oz, we appear to do things a little differently to elsewhere in the world. Only the cheapest trailers use longitudinal carpeted support beams. Most decent trailers use a combination of lots of rollers and pvc or teflon guides.

 

Lots of good advices and feedback. Let me summarize with a few questions..

1. Brakes.
Are disc brakes really the only real option? I want it to be as rust-resistant as possible. What is the best actuator-option?

2. Suspension.
Leaf springs? Slipper type leafs? Rubber torsion suspensions? Any ideas?

3. Tip-function.
I am not sure what to call the function, but I've seen trailers that have a rear frame that can tip up for the boat to get on the trailer easier. Any thoughts on this?

4. Materials.
What is the best material to use? I have heard you guys mentioning aluminium and galvanized steel. From what I've gathered here, galvanized steel is stiffer and has a stronger rust resistance. Is galvanized steel the only way to go if dealing with salt water?

5. Rollers/bunks.
I personally believe in rollers. I've never used a trailer with bunks, but I couldn't even imagine not being able to roll the boat onto the trailer. Am I mistaken on this one? Should I consider bunks? Are some types of rollers better than others? Also, with rollers the boat gets placed pretty centered on the trailer. I guess bunks will do the same thing to some extent..

6. Axles.
Where can I get axles of excellent quality that will be stainless/galvanized? Any experiences with some good axles? Do I have a variety of options here, or is an axle an axle - and that's it..?

7. Lights.
I have to look into the laws and regulations on this one. I guess LED lights are superior, and they'd have to be water resistant. When doing it "the southern way" (I used to live in Georgia), do you have a seperate lighting system from the trailer that you remove and put on the boat or the guides when in use - or is it permanently attached?

8. Tongue Jack Wheel.
Should this weel not be aligned on the center of the trailer in a perfect world? I wouldn't think that would be completely impossible to do. Does it even matter if it is slightly off to the side like most trailers are? Should I just leave it like that, or is it worth working on getting aligned to the center?

9. Tires.
Should I go for automotive tires or trailer tires? What are the differences? I guess the rims would have to be galvanized steel too? Can you get good looking galvanized rims..?

10. Options/goodies
I am considering an electric winch. Any downsides about having such a winch? Will the standard electric system drawn from the little plug in the car support such an electric winch - or do you have to have some other juicy setup for it? Do the winches last for years, or do they break down after a season or two?

I was also thinking of welding permanent strap holders to the trailer, so you won't have to haul around a dozen straps. It makes strapping down the boat easier and quicker, and I think it would be a good feature.

A good stepping plate over the wheels would be a good thing. Perhaps even extend it all the way back so you can easily walk around on the trailer without getting your socks all wet.

It was a good idea about the cover for road debris. How will this affect driving the trailer if there's an horizontal metal plate protecting the boat? Is road debris a typical problem? I have never seen a trailer with this function, but it does sound like a good idea. However, the thin layer of metal that would make up the cover would rust through easily I guess?

What about flushing kits? Are there any really good kits out there? What needs to be thoroughly flushed after use? I understand the axles and brakes, but how about the rest of the trailer?

Will, if you could provide me with information about the bronze brakes. How do these brakes perform compared to regular brakes?

Thanks for all the help guys!

 

Drums work o.k., but get gunked up and rusty faster than discs, but they are cheaper than disc (don't know why, drums are more complicated!!!)

If you're going in salt water, with a 2500 lb. boat, assuming you have a substantial tow vehicle (1/2 ton pickup or better?) surge hydraulics are more than adequate, simple, and easy to maintain.

Par makes a good point about torsion axles giving a low slung trailer for easy shallow launching. The jurt's still out on longevity, but like I said, around here most of the trailer manufacturers are switching to torsion. I like leaf springs simply because you can see them and know when they're due to be replaced. Can't see that torsion axel inside the tube. Just something to think about.

For a boat as heavy as yours, I think I'd leave that out of it. 2500# is a lot to tip. Biggest boat I've seen with a tipper was a 17' Whaler the guy surf launches, but it looks cumbersome and takes at least 2 people to do it.

I believe aluminum I beams are best, but galvanized C channel works very well, and lasts a long time when kept washed off after every use. But like tom 28571 says, if you use aluminum, build it HEAVY, I've seen aluminum trailers crack, and it's harder to find someone to weld aluminum than steel.

I think this is a matter of personal preference and local conditions. We don't use rollers here because the water is hypersaline, and the rollers freeze up. The only rollers are the center rollers for the keel, with bunks for the rest. Put teflon strips on top of the bunks and the boat will glide on and off slicker than snot. Bunks seem to make better drive on trailers than rollers which can sometimes make it hard to center the boat, and seem to stand taller than bunks as well (if your concerned about boat height on the trailer)

Even the aluminum trailers I've seen have galvanized tube axels (for spring suspension) so I guess that's all there is? I think aluminum would have to be too thick for axels, and how to attach the spindles?

Permanently attached, though some folks use bungee cords and attach their lights to stern cleats and string the wire along the hull with a wrap around the bow cleat and down to the trailer tongue. They'll never get wet, but I think it's a pain to string up the lights and take them off everytime you launch.

Yup! They are too wobbly to me if they're mounted to the trailer frame. I would make the tongue long enough to accomodate the jack. One of those swing up types that bracket mounts to the tongue is fine, doesn't have to be EXACTLY on center.

TRAILER TIRES!!!!! Radials don't like being twisted around like when cornering with a tandem axel, the belts separate.

Don't know. Never had one. (drive on trailers only)

Boater's World has trailer brake flushing kits. It's nothing more than some flexible plastic tubing that hooks up to a fitting on your brakes dust shields, and a garden hose connector. As far as the rest of the trailer, a thorough rinsing/washdown of the whole thing is all that is required. A friend used to rub his trailer down with engine oil, but I'd imagine this isn't the best practice nowadays, putting oil in the water. One more thing (whew!). Par said

A guy I know just had a custom aluminum trailer built for his 46' Harley twin diesel, with quad torsion axels.

 

I pretty well agree with Craig on his points.

I do have an interesting thing to relate about aluminum trailers. I have a tandem unit that carries a 2200 lb boat which has a center of gravity further forward than the usual power boat. This has created a problem with getting tougue weight down to a reasonable level. One thing I did was to move the spare tire from the tongue to under the starboard bunk all the way aft. The light trailer actually floats up on that side, making retreival more difficult. Solution is added weight in the spare wheel.

This trailer came with drum brakes and a washer system which was used at every opportunity after retreival. It seems like it did not even slow down rapid rusting and failure of the brakes. I replaced them with galvanized brakes and will wait to see when they fail. They have already worked past the life of the original set.

And I like your test for determining whether your *** is too small.

 

I will check on the legal issues with hydraulic actuators. I fear they are illegal (for some absurd reason) in Norway. I was thinking hydraulic myself.

As for choosing between I-beams of aluminum and C-channel galvanized steel - which one will last the longest without reducing structural integrity and corrosion/rust? Can you successfully paint aluminum and galvanized steel? (I like painted trailers far more than the steel look of unpainted ones.)

I am not really sure how the bunks works, to be painfully honest. I always thought you'd have to sink the trailer down totally, drive the boat onto the trailer and then drive the trailer and boat out of the water with the boat sitting on the bunks. I never thought you could winch a boat up on bunks. Perhaps I am mistaken..? I would think the friction would be too great. Perhaps bunks are to be considered then? I have never had any problems with corrosion/rust on rollers. However, bunks are a lot cheaper I would think.

Will I find lights that can be sunk into salt water every now and then without having difficulties with them? Here, we always take the lights off when launching. I would prefer to have a permanent light system I could just leave on - even when submerged.

From what I gather, aluminum is lighter than galvanized steel - but not as stiff, requiring thicker aluminum beams. Would the weight then be about the same as if I were to go with galvanized steel?

When designing the trailer, is AutoCad the program to use - or do you have better suggestions? I am not too into this engineering thing. Sadly.

 

Rollers put most of the weight distribution across a very small patch of roller (1/8" by the length of the roller), leading to much higher stresses in those areas. They are nice for lazy launching and retrieval, but hard on the boat. Planked boats, or simulated lap boats shouldn't use rollers at all. Best way to spring a plank is to drive a boat onto a trailer not in quite deep enough and crunch the frames, planks, etc.

Trailer lights should be attached to the trailer, or guides. Removable lights have no real benefit, unless you have more then one trailer and are to cheap to spring for lights on both.

Aluminum is the way to go if you can afford it. It holds up much better then steel, but is prone to stress cracks from flexing, so most over size the rig. This causes you to lose the weight savings, but at a ton and a 1/4 you shouldn't miss much over steel.

I beam, C channel and box rail construction will be sized for the loads expected. I beam and C channel will live the longest with the same amount of care, because they are self draining.

You can paint anything now a days. Rhino coating an old steel frame could add many years to a trailer and pretty her up a bunch.

Personally, I'd not try to engineer this trailer yourself. Your questions and comments show quite clearly that the skills necessary, calculations needing be performed, understanding of the variables - including a solid background in the materials and construction techniques, typical of most trailer design is well out of your grasp, as yet. This doesn't mean it's rocket science, but you'll have quite a difficult time of it without a much better knowledge of the principles, dynamics, techniques, construction methods, materials and their properties.

There are several books available on the subject, with free trailer designs in them. If you don't stray to far out on the design limb, with under-engineered design changes to one of those supplied, then you'll likely fare well. It would be a shame to look in the rear view mirror, after a slight tug of the wheel, just to see your pretty craft doing cartwheels down the shoulder of the lane, because you didn't understand the algorithm necessary to calculate a specific loading and took a "good guess" at it.

 

I have a galvanized trailer which carries a load of trailer and boat of 5800 pounds. It is production model. Bending the metal or welding for a trailer should be done by a professional. After all you have a trailer which is carrying your expensive boat. I have 4 bunks and can winch the boat into position without a problem. The ramp I use is fairly steep and I only get the back tires at the water edge. No need to go swimming with the truck. If you are launching on a flatter ramp then rollers would work better. I have only heard of a few people building trailers as they were custom design for loads of 12,000 pounds and it would seem cheaper to buy a production made trailer if there is one available to suit your needs.
I have surge brakes on all 4 wheels of the tandem axle and think it is safer than a single axle. My trailer empty weighs approx 1100 pounds. I have been using it in salt water for 9 years. The lights get submerged every trip and they are working great. I do have a water flush system on the brakes which seems to work well.
Hope this helps