Small boat trailer design w/light suspension, folding, good support?

[Ben Fuller]

I use the full length board on all of them. Sometimes you can spring the front up to get better support with rockered boats. To control point loading aft, I get the boat on the trailer then bring the roller up so it just kisses the keel. If the trailer had rollers down the middle a carpeted 2 x 4 fits neatly in those welded on brackets.

If you can move the axle a little then you can have the bow of the boat pretty close to the towing vehicle so you don't have quite such a long load.

[Thorne]

I actually don't mind the distance between bow and hitch, as it allows launching on bad ramps and beaches without submerging the car's exhaust in salt water, and gives you room to hop up on the trailer tongue to get out to the winch stand. I'm so used to the basic length of 16' boats on a trailer that my utility trailer with a much shorter tongue and distance from hitch->axle really throws me off when backing up.

[Eric Hvalsoe]

Eric Hvalsoe does this. Its not a lot of weight, maybe 100lbs I think, Steel or lead bolted to the frame of the trailer. I seem to recall he uses a fairly light weight flat bed trailer and props the boat up with fenders.


It seems that we are coming to a point: Every trailer is a compromise, much the same as the boats themselves. A light duty trailer is going to be light weight and potentially unstable in cross winds, and a heavy(er) trailer is going to be too stiff for our little boats. And the ideal suspension is more complicated than one of us could manage without some metal fabrication equipment, and the simple suspension doesn't reverse engineer down to our load level very well.

....

Oh I spose I should have been following this thread - the title was about lightweight suspension - which I've not much explored. There are several good reasons 'boat trailers', ie caulkins EZloader etc, are called boat trailers. And this is what I modify for my clients. But the minimum gross rating, at least for a Y frame, will be about #1000. I remove the standard bunks and rollers and build up a lumber platform. That adds a couple hundred pounds. It also adds flotation. So I bolt some ballast towards the rear end of the platform. With some of these trailers you can also move the axle forward to reduce tongue weight - these things are typically set up for outboard powered boats and those irritating ski doos. It is possible to juggle things and end up with a tongue wieght of 60 - 100lbs. The whole package is not particularly lightwieght - this is not a hand dolly. Practice your vehicle/trailer backing up skills. But you do end up with something that launches easily, protects the boat, and is not overly harsh on the road. My boats have been trailered successfully across the country with this rig.

The EZ loaders jumped in price the last couple of years. They are not cheap. But they are good quality with submersible lights, good tires, etc. Would love a new one for myself, I'm using a hand me down with little bitty tires. Beware of the chinese stuff, particularly tires.

[Tom Kremer]

That's an interesting site. I followed the link to the Castle Craft trailer site and noticed the 95 pound Trailex single canoe trailer (unfortunately just 200 pound capacity). So does anyone know the details of Trailex's "unique rubberized steel" suspension that "virtually eliminates road bounce? I'd love to have a 100 pound trailer with a 600 pound capacity.

After years of dragging around a rusted thing I built out of the small HF trailer, I finally got one of the Trailex singles. Much of the "suspension" comes from the low PSI that they recommend using in the tires. Fill them to rated capacity and you can dribble the trailer like a basketball but at 12-15 PSI and loaded with my Herreshoff/Gardner 17' it pulls real well. Light is good, especially if you have a compact car.

[Dave Gray]

... I remove the standard bunks and rollers and build up a lumber platform. That adds a couple hundred pounds. It also adds flotation. So I bolt some ballast towards the rear end of the platform. With some of these trailers you can also move the axle forward to reduce tongue weight - these things are typically set up for outboard powered boats and those irritating ski doos...

Eric, if you don't mind, could you post a photo of one of your modified trailers?

[jerry bark]

I found these springs, which would seem like a good retro fit possibility for a trailer that is the right dimension but to heavily sprung:

http://www.trailerpartsdepot.com/ite...c=2477&eq=&Tp=

they are rated 230 pounds each so a pair would be 460 pounds, add the sprung weight of the trailer frame/etc and a small boat and you should be in the right loading range.

Jerry

[michigangeorge]

I was watching a rerun of 'PAWN STARS' yesterday and a customer brought in a large radio control Hummer. This little thing had an amazing suspension system just like a real off road racer. That is the type of technology that needs to be applied to our small boat trailers. Any desert racers here?

[Thorne]

I found these springs, which would seem like a good retro fit possibility for a trailer that is the right dimension but to heavily sprung:
http://www.trailerpartsdepot.com/ite...c=2477&eq=&Tp=
they are rated 230 pounds each so a pair would be 460 pounds, add the sprung weight of the trailer frame/etc and a small boat and you should be in the right loading range. Jerry

Interesting! I'll have to measure my old HF trailer and see if they'd fit. Still pretty stiffly-sprung for a 100lb boat, but better than the current springs (probably 2000lbs even though the trailer was originally rated for a load of 1350lbs ).

[jerry bark]

Interesting! I'll have to measure my old HF trailer and see if they'd fit. Still pretty stiffly-sprung for a 100lb boat, but better than the current springs (probably 2000lbs even though the trailer was originally rated for a load of 1350lbs ).

Thorne,

yes the boat only weighs 100 pounds, but the sprung portion of the trailer wieght is also on the springs. so add it up: 100 + trailer frame - tongue weight = load on the springs

that's actually a slightly simplified formula ( to be precise you have to consider centers of mass and lever arms) but it will get you pretty close.

Cheers
jerry

[Eric Hvalsoe]

There is a shop in seattle that fabricates leaf springs to one's specifications, about $100. The link provided on this thread might be a good way to go for replacement leaf springs as well, cheaper if there is something just right. I am partially rebuilding my own hand me down trailer so that it will better resemble something typically provided to a client.

My 13 and 16 designs are round bottom with a plank keel. The keel is about 4" in width midships. There is good stiffness in the basic backbone structure. They will sit upright on thier keels. The keel profile has some rocker. My flatbed platform is actually flat, no need to shape it for the rocker. I simply fit several crosscleats for actual support and contact to the keel. The keel bears the weight of the boat. I have fussed with cradle sections in the past, more recently I lash a pair of sturdy boat fenders to the flatbed for additional bilge support.

For my purposes the King y frame trailer rated at 700 lbs (I assume gross) would be an attractive option.

[rkeller]

Hows this, found at the Herreshoff Museum, wood and metal with motorcycle sidecar wheels and fenders.

[Thorne]

Custom leaf springs sound good! I don't know much about the physics of springs and vehicle loading/handling, but my old Holsclaw had a lovely soft return - you could get on the trailer and bounce up and down, and the coil spring / shock absorber combo would softly even it all out.

So there is probably a lot we aren't taking into consideration here, from the perspective of actual forces acting on the wooden boat hull. For all I know it might be better to have the trailer's load be MORE than the rating on the springs, but again this could potentially cause failure in other structural parts or a worse ride -- just guessin' here folks.

Remember to make the distinction between what the trailer is rated to carry, and the stiffness/load rating of the springs. My HF trailer has what I believe to be 2000lb springs, but the trailer was only rated for 1350lbs, then later downgraded to 1090lbs.

[Eric Hvalsoe]

If I do disassemble the trailer I imagine taking one of the original leaf springs down to Craigs and have the old man tell me what he thinks of it - how he might rate it. This way he will also have the precise dimensions. The old springs are really caked with rust. I imagine the trailer frame weighs a couple of hundred pounds, lumber platform and ballast weights about 250, boat weight 200 max. Maybe springs can be ordered from the catalogue for much less. But just imagine, having your own custom fabricated leaf springs. I would guess the coil, shock absorber, torsion bar business might give you the smoothest ride of all, but I'm not going to make that much work for myself. The stock trailer, leaf spring combination seems to have proven itself cross country and in my own usage. I just might try to tweak it.
Eric

[BBSebens]

If you had properly rated leaf springs to hold the load, you could easily add shock absorbers to dampen movement. Shocks don't support weight, they just dampen the movement. You should be able to get a set of basic shocks for the rear of a small car (ie older Honda Civic, VW Golf) from your favorite Auto parts store. Mounts should be easily purchased from a wrecking yard.

[Thorne]

Lots of "should" there.

As I've said a few times in this thread, I have no interest in inventing a totally new trailer suspension design - or dealing with lawsuits and/or injuries/boat-damage if it fails at speed.

Take another look at the excellently-engineered Holsclaw suspension and tell me why it has so much more than just a coil spring and shock...



Here's my "shoulds": If it was so easy, someone should have done it already. If so, we should be able to buy it.

But apparently they haven't and we can't. I strongly suspect that there is much more to it than welding on some shocks from the junkyard...

[htom]

Links to constrain the springs and shocks to carefully limited motions. There are a lot of triangles in that trailer, and some of them might be acting as torsion springs as well.

[Dan St Gean]

Suspension is really just to smooth out the ride. Look at the popular car and motorcycle suspension types:
*leaf spring + shock--the leaf retains the axle and allows mostly upward travel although the tire will either travel back a bit or forward depending on the orientation of the leaf and shackle
*strut--used lots on fwd cars and has both a spring and a shock--doesn't do much locating of the axle
*3 or 5 link--the links locate the axle and the springs only spring while the shocks only dampen that motion
*independent suspension with seperate spring and shock functions
*there's some oddball stuff out there too
regardless, the key to all of these suspensions working well is to have a spring rate tuned to the weight it carries and shocks to help eliminate overactive spring travel, harmonic vibrations that set up hop, etc.

Most trailers are leaf spring or torsion affairs, but they don't need to be...

The overly spendy thule (rack and roll) trailer uses coilover shocks and a super simple trailing arm with no axle connecting the sides. It works because of the light loads expected won't taco the aluminum tubing.

I think light shocks would help most trailers.

Dan

[Rich Jones]

Someone mentioned that Trailex recommends lower tire pressure. How low can you go without ruining the tires? If it's just for short hauls under 10 miles, would lower pressure hurt? I've got a new EZ Loader trailer rated for 1200lbs for an 82lb. boat. I really don't want to load up the trailer with ballast because it'll be harder to hand push around the driveway.

[Thorne]

Someone mentioned that Trailex recommends lower tire pressure. How low can you go without ruining the tires? If it's just for short hauls under 10 miles, would lower pressure hurt? I've got a new EZ Loader trailer rated for 1200lbs for an 82lb. boat. I really don't want to load up the trailer with ballast because it'll be harder to hand push around the driveway.

First and foremost remember that the trailer suspension, as pointed out earlier, supports both the weight of the boat AND trailer -- so if you can get the dealer to give you the overall weight of the trailer you can add that to the weight of the boat to see how much load you place on the suspension.

Second, the bunks, bow chock, and other supports may be more important than the suspension. Did the dealer set up the trailer for that specific boat, and if so, did he use bunks instead of the rollers often sold for fiberglass hulls? Is the boat held tightly to the supports but not compressed or warped?

Third, hard to say, but from what I understand about low tire pressure, you risk overheating the tires and/or ruining the sidewalls at high speeds. So I wouldn't get too carried away with underinflation.

From http://www.aa1car.com/library/tirepres.htm -

"By far, under-inflation is a more common and serious problem. Reducing inflation pressure increases a tire's rolling resistance and hurts fuel economy. Plus, an under-inflated tire flexes more, which leads to increased and uneven tread wear. As a rule of thumb, tire life decreases 10 percent for every 10 percent it is under-inflated.

Under-inflation also makes a tire run hot. Increased flexing of the sidewall increases the temperature of the tire, which in turn increases the risk of a tire failure and blowout."

From http://www.tire-trader.com/articles/...erinflated.htm -

"The tire industry considers any tire that's been run on the road 20 percent or more underinflated to be “run flat.”

Running flat can result in very serious damage to the tire that can cause it to fail catastrophically – and without warning."


From http://www.drivers.com/article/354/ -

"...your tires will be so seriously under-inflated that driving will damage them.

One of the warnings issued by Bridgestone/Firestone and Ford after it was revealed that defective tires may be linked to as many as 88 deaths and 1,400 crashes was that under-inflated tires are likely to overheat and burst."

[Canoeyawl]

I have experimented with tire pressure on trailers and found that you can run them quite low if the load is light. A typical tire is rated for a certain load with a stated pressure. A little boat trailer may be only 10% of that rating. I run my little trailer for my old town canoe (freighter) at about 15 lbs and it has worked out well for fifteen years or so. (the tires rot before I can wear them out)
I have a little race car that the tires are rated at about 4 times the weight of the car at 35 psi and I run that at between 20 and 25 depending on conditions, works perfecty.
I don't hesitate to use tire pressure to suit my own conditions, not some generic maximum rating stamped on the side wall.

[jerry bark]

I want to comment on tire pressure, first thorne you are correct that an underinflated tire is not good. but the proper inflation pressure depend on the tire's LOAD. so the real issue is underinflated for the load if you have doubts about this point, please look at this link: http://www.goodyear.com/rv/pdf/rv_inflation.pdf which is a page where goodyear shows the proper inflation of its various trailer tires for a given load.

Also you mentioned that if it was easy, someone would have done it. But in the world of the American business economy companies do not do things because they are easy, they do things because they are profitable. A trailer such as you desire would be easy to design and make, but I do not think there is enough demand, or those few who do demand one will not pay enough, to make it a profitable venture. Its the same reason that no wooden boat manufacturers are out there building thousands of skiffs to sell, there is not enough demand.

cheers
jerry

[PeterSibley]

Here are some photos from riversailor.com of his Holsclaw suspension-

This suspension looks interesting and it's not something I've seen in Australia .I wonder how 2 motorcycle shockers would go in place of the spring and auto shocker ? Lighter but with internal springs and damping .

[Dan St Gean]

This suspension looks interesting and it's not something I've seen in Australia .I wonder how 2 motorcycle shockers would go in place of the spring and auto shocker ? Lighter but with internal springs and damping .

You just described the Thule rack and roll.

Dan

[OconeePirate]

How about air shocks of some sort? Ditch enough leafs from the spring pack on a conventional set up that with your boat the frame is close to being at risk of bottoming out then pump up the shocks just enough to lift it back to a safe ride height. This way the trailer could even be adjusted for different boats.

[davlafont]

Hi folks. This has been a great thread for me during my GIS build. The boat is light and long and I was hoping to find good advice here. I switched from reading this thread to surfing Craigslist and... voila!





My camera angle misses the shocks that are outboard of the springs on the aft face of the frame member.

The trailer was built by a boater who made his own 14' wooden rowboat. He says as-towed the boat + gear was about 200 lbs. or so. The trailer is rough; lots of ugly welds, shocks of unknown vintage, lots of rust here and there. But for $150, it gets me over a hurdle now and buys me time to either upgrade or improve it. Time will tell if the spring rates and shock damping are suitable.

I just thought I'd thank everyone for the great discussion and share my find.

[stromborg]

A while back somebody asked why off-road suspension tech isn't applied to trailers. My $.02 is that they have suspension travel needs the average trailer won't use, slamming through ditches and boulder fields with a boat behind your truck it might be handy but who does that to their precious boat? Using a solid axle limits the amount of travel too, it needs room to move vertically under the platform and most of us want the boat as low as possible for easy launching. At some point you start looking at independent trailing arms (look under the rear of your average front wheel drive car to see one in action) which is nice but not what the average boat owner "expects" to see when he buys a trailer. I suspect it is a lot easier to just keep making more-or-less "universal" solid axles that fit under a number of platforms than produce and manufacture something new that the market isn't exactly screaming for.

If memory serves, the Holsclaw is an example of a 3-link suspension. The "z" shaped bracket in the middle allows the solid axle to move up and down but not left or right. The long rods running forward keep it located fore and aft. Frees up the shocks and springs to focus on the bumps. The hot-rod and off-road guys build them for their cars to get rid of the leaf-springs.

Steve

[blisspacket]

For the doityourselfers, 2"x3" aluminum, powdercoated, used for framework throughout FL for screened pool covers seems to work pretty well. I use galv u-bolts to box it together, and an old mast also u-bolted to the main box. The extruded box structure has grooves to tuck in screening, so it's pretty stout. I probably have 2000 miles on my trailer at this point, inspect it regularly, and nothing has moved. I do slide a couple inches of 3M double sided tape between any two members. Since there's no stretching of the Ubolts or collapsing of the aluminum, I doubt it does anything.

[Frank R]

Looks like the Tee Nee trailers had a very similar design:
http://bigfinboats.com/forums/index....r-information/

[Nicholas Scheuer]

As you "trailer a lot of miles annually", consider the largest practical wheel diameter. If you end up with a stock trailer, or trailer kit, having 8" wheels, consider upgrading to larger diameter wheels and tires. Do the math to determine what the3 reduction in wheel Rev/Mile will be.

Years ago I made a nice wooden box utility trailer out of an old Apache tent camper. It had stock 8" wheels when I used it to move stuff between Duluth, MN and Rockford, IL and I experienced a lot of tire trouble with heat. This was made worse besauce one wheel spindle was bent slightly. I later converted the axle to use 13" wheels and spindles salvaged from a junk Dodge Omni. The wheels and tires can now easily handle any load the frame and box trailer can carry, for as many miles as my tow vehicle will go. Tire worry is a thing of the past.

The trailer that came with my wodden Melon Seed Skiff had the same sort of wheels and tires as the Apache Camper. Fender clearance considerations ruled out larger steel wheels, and besides, I didn't want to spend a lot of money on a trailer that wouldn't be towed very far. So I switched to a larger diameter tire for the same 8" wheel and reduced rev/mile by something like 30%.

Moby Nick

[Gary Davis]

I bought a '58 Tee Nee a couple of months ago. They're very similar but not the same suspension set-up. The torsion bar extends from one side to the other rather than being in the middle of the axle. Its in great shape - just need to replace a few pieces and repaint.

Gary

[Frank R]

I bought a '58 Tee Nee a couple of months ago. They're very similar but not the same suspension set-up. The torsion bar extends from one side to the other rather than being in the middle of the axle. Its in great shape - just need to replace a few pieces and repaint.<BR><BR>Gary

I think the "torsion bar" you mention is actually the sway bar (part number 18 in the parts diagram shown).

It seems the elements of a good trailer are:

• Trailing arms
• Coil springs
• Shock absorbers
• Sway bar

I am sure other trailer manufaturer's can be found that used similar set ups.

An option that can be considered for lightening the load capacity of the springs to handle lighter boats is to cut down the springs. I have heard this is what car guys do to get low riders. I also heard that it does not take much removal of the length of the coil spring to significantly change the capacity. Spring steel is real tough to cut so a carbide disk on an angle grinder would probably be necessary. Of course, the shock absorbers would have to be changed to match the modified springs.

Newer springs would probably be a lot easier to purchase with matching shock absorbers.

[Breakaway]

I actually don't mind the distance between bow and hitch, as it allows launching on bad ramps and beaches without submerging the car's exhaust in salt water, and gives you room to hop up on the trailer tongue to get out to the winch stand. I'm so used to the basic length of 16' boats on a trailer that my utility trailer with a much shorter tongue and distance from hitch->axle really throws me off when backing up

.

I support these comments by Thorne and add this: If you have to back through a 90-degree turn or so, a short tongue can cause the winch stand to hit your vehicle DAMHIKT


Kevin

[Brian Palmer]

An option that can be considered for lightening the load capacity of the springs to handle lighter boats is to cut down the springs. I have heard this is what car guys do to get low riders. I also heard that it does not take much removal of the length of the coil spring to significantly change the capacity. Spring steel is real tough to cut so a carbide disk on an angle grinder would probably be necessary. Of course, the shock absorbers would have to be changed to match the modified springs.

Newer springs would probably be a lot easier to purchase with matching shock absorbers.

I do not think cutting the coil springs shorter will actually give you a softer ride, if that is what you are trying to do. If you want a softer ride, you will need to use a spring with a thinner wire diameter.

Shorter springs will just reduce the amount of travel (compression) that is available before the spring starts to bottom out against itself, and this can actually result in a harsher ride.

Brian

[davlafont]

I think the "torsion bar" you mention is actually the sway bar...

More accurately it's a Panhard-Rod (-Bar, or Track-Bar). It's function is to keep the solid axle from shifting laterally from under the chassis. An automotive anti-sway bar (commonly, sway-bar) allows both wheels to swing upward together during bumps but acts against body/chassis lean when one side gets compressed while the other side extends. The resistance does come from torsion, but only when the two ends are moving in opposite directions (twisting the bar). If a sway-bar were fixed at its center, not free to rotate, it would act as a torsion bar. Torsion bars are springs in their own right, an alternative to coils or leaf. Generally mounted forward of the wheels' axes, they require some link such as a trailing arm to transfer the motion of the axle to the torsional resistance of the bar. They are often combined with short control arms at the axles to control lateral shift, but not always; the classic VW Beetle's front suspension had two sets of torsion springs and depended on the steering rack to keep the wheels from moving side-to-side.

For what it's worth...

[Tom Robb]

Face it Thorne, You're going to have to find a Holsclaw or fabricate one. How much more information do you need than has been repeated over and over here? Most of it was very good advice, IMHO.

[Gary Davis]

. . . or a Tee Nee.

[calfee20]

There are probably more Holsclaw motorcycle trailers out there than intact small boat trailers. I picked up a one on craigslist. I removed the rails, front rail bracket and extended the tongue five feet. I got a ten foot channel made up "my son-in-law is a metal worker" and will use existing brackets to mount it. I have $200 into it so far mainly because of new tires and rims. I will spend about a hundred more depending on the paint I use.

One cool thing about this is it can be converted back to a motorcycle trailer in about an hour. Only about a dozen bolts. Now I have to make up a couple of bunks that will attach to existing brackets. Lets see if I can insert a few photos.....................................Tom C

[Todd Bradshaw]

Don't forget that sway-bar, or whatever that diagonal gizmo connecting the frame and axle is. It's isolated from the brackets on both sides of both ends by thick rubber washers where the bolts go through.



Paint: It may be a very low-tech approach, but I've been amazed at how well just knocking off the big rust chunks with a wire brush and brushing on a couple coats of Rustoleum has held up - and mine sit outside year-round.

[calfee20]

I have all the pieces as the trailer was in a pile with the small stuff in a box. In fact the first question I asked the previous owner was "Where is the pan hard rod".

I really appreciate your comment about the rustoleum because I have spent more time trying to figure out the best way to paint it. Your method is the least expensive and the easiest. I think I will search this forum for some paint info or I could start a thread that may take off like this one.......................Tom C

[andrewe]

I sort of stayed out of this but...
Panhard was a French car co. that first used the axle stabilizing bar that is the Z bar noted. If you want to get some travel and softness in your suspension, stay away from the almost universal 'torsion' types. Mostly they are a square axle in a square tube at 45deg angle, with rubber rods filling the space. Crushing the rods gives the unit some spring in twist, so the arm on the end with the wheel gets a bit of movement. It satisfies the legal requirement for suspension, but mostly relies on the tyres to cushin the shocks.
Real torsion bars are steel rods that are quite progressive in load. I built a small trailer with Renault parts (Le Car, over there) Very soft, but firmed up as I loaded it. Key point is to add dampers. I now use wishbones with coil springs ( or Aeon rubber springs, as they are a bit self damping) and dampers. Built one for my Oughtred 15ft double ender. About the size of Thorne's boat. Used 80x40mm tube for the spine and cross member and smaller tube for the wishbones for the suspension. SEAT Marbella rear axle bits were cut up for the hubs and brakes, 13" tyres. Dampers were off my Espace after they failed the inspection, bit big, but free..(sort of.. after I bought new ones to pass the test)
I sent some pix to Peter Sibley, he may want to post them here.
My problem with Todd's Holsclaw is that the suspension makes it very high and therefore accentuates the sway on the highway, plus having to put it further in the water to launch. OK, it is an old design, but pretty clunky.
Couple of points on home built trailers, the pitching load is important, as is the swaying stress on long tongues caused by bumps. The actuall 'pull' load is relatively minor compared to pitch and sway.
Using wishbones and a cranked cross-member allows me to launch without dunking my hubs, a primary consideration.
A

[Brian Palmer]

If you need new shocks, these worked for my 700 lb capacity Holsclaw boat trailer:

http://www.amazon.com/s/ref=sr_nr_i_...qid=1322598615

Brian

[Todd Bradshaw]

My problem with Todd's Holsclaw is that the suspension makes it very high and therefore accentuates the sway on the highway, plus having to put it further in the water to launch.

I don't know squat about all your theoretical stuff, but I've been using that same trailer for almost 25 years now with a variety of boats - sailboats, inflatable motor boats, multiple canoes and kayaks stacked two-high and my iceboats and have never noticed any sort of sway (or any other undesired driving characteristics). It's also a hinged, tilt trailer when needed, so launching is pretty simple. If there is anything that causes concern about it at all, it's that it rides so smoothly and quietly that you have to remember that you're pulling a trailer when going through traffic. Is it the ultimate small boat trailer? I don't know, but if that's the only complaint I have with it after all those years, it's pretty close in my opinion. After all, the function of a trailer is to transport, launch and retrieve the boat without tearing up the boat or the car and without annoying the driver or being a pain in the ass to use. It has done that very well for me for decades and continues to do so. What more could I ask for?

[andrewe]

Oops, Sorry Todd, I didn't mean to put your back up. I should have said that the height makes it look as if it might have problems with sway etc. Clearly it does the job very effectively. Certainly the springing and axle location are in the best suspension tradition. Just I would have liked it to have a lower load level. Theoreticaly speaking of course.
My objections are all about the current rubbish systems that are normal and bounce around the road, giving the boat a rough ride. Problem is, good systems cost a little bit more. A bit more travel, well damped, is the way. And the 'break-back' is def a good feature to aid launching. Going back to Thorne's original brief, it would also help in reducing the storage length, by being able to disconnect the front towbar section.
A

[sailnstink]

I knew there was a reason I built short boats and drive a big truck. Have a look at the real trailer pros you don't want to know the price.

[calfee20]

Thanks for the link Brian. I was aware that the shocks were available through Amazon but this is a real budget project. I will see how the old ones work first. This trailer has taught me a lot and if I ever need another one I will probably build it from scratch using this one as a model. One thing that might be hard to find for these trailers are the springs but these should work if you could figure out which spring rate.

http://www.afcoracing.com/springs_1_78id.html

Andrew thanks for the lesson. After 62 years I now know the origin of the name of the rod. As a matter of fact the first time I heard the term I remember asking why it was named a panhard rod but no one knew. This was waaayy before the internet. That is the kind of stuff that keeps my nose in the computer way to much.

Your trailer sounds very interesting but don't talk about it photos! we need photos! I actually worked at a dealership that had VW, Porche, Audi, Renault, and Jeep. How is that for a combination?.............Tom C mechanic since birth.

[OconeePirate]

Dang it! I just typed all this out and apparently hit the wrong button!

If'n you're building your trailer from scratch, how about sort of turn the above design upside-down? Make a rigid wishbone assemble that goes from the axle to the tongue. Mount the bunks on a suspension above that, allowing the front of the bunks to be the pivot near the tongue? To tip it back for loading and unloading the forward pivot would have a pin instead of a bolt? A few less moving parts and it would increase the unsprung weight of the trailer. Higher unsprung weight would be a good thing for your lightweight boat as it would smooth the ride out. Hell, go ahead and give the thing a real sway bar in addition to the panhard bar while you're at it so that those side winds wouldn't be quite as scary.

On the issue of tire inflation... would the chalk trick some car racing guys use work? Draw a line with heavy chalk across the tread and up the sidewall, inflate the tires to where you feel they should be. After a short run check the chalk lines. If the line is scrubbed off well into the sidewall inflate the tire a bit more. If the chalk is still visible on the tread let some air out.

[outofthenorm]

A couple of points about this design and why it's a good one.

1) Coil spring and separate shock. Modern set-up in lightweight cars (for example) is coil-over-shock all in one unit. In theory it's more efficient that way, but for home-built or specialized, it's easier to engineer them separately. You can also change the coil spring with relative ease if you change the load it has to carry.
2) On an original, the spring is probably a rising rate spring, so it automatically adjusts to momentary loads and is somewhat self damping.
3) This is a true trailing arm suspension with the locating points well forward, which provides a more fluid range of motion over larger arcs than does the conventional and simpler leaf spring set-up. It's what is found under countless Model Ts and As, and works well.
4) It has a Panhard rod to locate the axle side-to-side. This is the key component in eliminating bump-steer, sway or high-speed shimmy.
5) The load carrying beam is attached at more than one point - ie: at both ends of the tuning-fork shaped frame member. A lot of trailers are a simple T shaped structure. That has to be extremely well engineered to avoid twist.

Seems to me that if you are equipped to do the simplest of welding, it would be pretty easy to self-build for a lot less than the usual purchase price.

BTW, the motorcycle trailer above seems to me missing its Panhard rod. I'd put it back for sure.

- Norm

[andrewe]

Calfee, I will get some photos up tomorrow, bit dark here now. Panhard made cars from the turn of the last century up to sometime in the 60s, when what was left went to Citroen. Later stuff was typically cranky French , good aerodynamics with a little flat twin engine around 600cc ( the tax structure encouraged small engines, virtually no engines over 2.6 lt.) suprisingly fast in a straight line. Collecters items now or rusted away, I saw a nice example a few days ago. Google Panhard 24CT for the last model. The early ones are still seen in the annual London to Brighton veterans run. Originally staged to celebrate the lifting of the speed limit from 5mph(!) and not having to have a guy walking in front with a red flag. My, how times have changed.
Andrew

Norm, your 3/ is important. The further apart the mountings the lower the stresses. And attaching the 'A' further forward much reduces the loads on the T joint.
Your 1/ is simply economics of production. Separate mounts are more expensive. OK for us with one offs, less so for volume.

I used to build a few trailers for Lotus Cars, in the days when Colin Chapman was running it. Wandering around the development and prototype shops was VERY interesting. on the edge engineering. Not for us mortals, but...
A

[outofthenorm]

should work if you could figure out which spring rate.

Doesn't make sense to try and figure that out for yourself. Call a suspension shop and they'll do it in a flash. All they need to know is the load range and the speed range. There are about a jillion off-the-shelf units available with a wide range of characteristics. They can also be fine-tuned with rubber inserts from the same sources.

- Norm

[calfee20]

I didn't know I would get so many comments about my panhard rod. This trailer came apart in a box and I have only assembled it enough to get measurements, weld on brackets and fit the boat to it. I am putting a Grumman Sportboat on it. The GSB is resting on it now. Today I got the bunks figured out and now I have to scrounge/fabricate the front bow stop, cradle? " I don't know the proper terms. There will not be a winch on this............................Tom C