Thread: paddleboard trailer

Hi, if you were to make the base the same length as the supports for the boards you could make it as an A frame on each end which would give the stability required, on the frame run a diagonal brace from top of the A to bottom to give it support. In regards to the draw bar I would make it an A rather than a single, it makes it much stronger. Galvanized RHS would be an ideal way of making it, finish the welds with several coats of cold gal paint. Will you be MIG welding or arcing the frame? Make sure that you have no slag enclosures to start the rust process.
Kryn

Hi Kryn,
OK thanks for those comments - here's version 2, with A frame drawbar. I can't do a vertical A frame to the uprights because the 'shelves' need to be open all the way to the centre, so instead I added some braces on the bottom 'shelf', which could be diagonally braced as well if needed. Regarding welding, good question - with gal, I'd definitely tack up with MIG, but would be torn between stick and MIG for welding - probably MIG. My main issue with gal steel, is not painting the external joints, but how to prevent rust on the inside of the RHS along the weld lines. That's the main reason I started thinking aluminium (which would be TIG). This thing would see a lot of salt air.
Cheers
- Mick

trailer2.PNG

I like version 2, but a couple of points...

The width of the cross bars at 1645mm looks much narrower than the guards/wheels/axle, and therefore would make quite a wide trailer.
Would also mean leaning over the width of the guards to load the boards from the side, especially the top ones.
Your bottom cross rails are raised off the main chassis, and if you made the height of these rails level with, or slightly above the top of the guards, you could run a chassis width of 4' (1220mm). Firstly, this would mean an "off the shelf" axle length (same as a 6 x 4 box trailer), Secondly, the overall width outside the guards would be 1690mm (assuming standard 9" guards) meaning it would be similar width to most tow vehicles, less issues with roundabouts and tight corners.

Tapering the rear of the chassis so narrow, leaves little room for mounting taillights and number plate.

Excellent points Yonnee - I'll work on version 3...
thanks
- Mick

Hi Mick, in regards to rusting inside the welded areas, drill a hole close to the welded joint and paint the inside with the cold galv spray, you might be able to get a can with a flexible nozzle or use a spray gun, these holes will also allow any moisture/water to drain out. As you can't make the frame an A, use something like 75X50 or wider on the flat to make it a bit more rigid.
Following Yonnees advise about loading the upper levels, you could make the guards out of Ally checker/diamond plate and bolt them on. Using the plate will give a support to stand on with grip.
I wouldn't taper the end to a point, as Yonnee said, you would have no where to mount tail lights etc., instead I would trim the end where the upright finishes and put a diagonal brace from bottom front to top rear, this will well and truly brace it. My main concern would be bracing sideways movement, which is why I suggested the RHS on the flat.
A reason that I prefer steel over aluminium is that should you find a crack in it anywhere, welding repairs can be made anywhere, using three car batteries if required. To the best of my knowledge, this can't be done with ally.
Hope this helps.
Kryn

OK fellas, here's my next version. Width of chassis is reduced to 4' as a wide one would most definitely be a pain. The back of the trailer is squared off for lights, etc. to attach. I've left the overhang at the back as the paddle boards would overhang the brackets by about this much. So it's a protection/overhang thing. I've added some gussets on the outside of each upright which in combination with the legs on the bottom shelf brackets would give enough bracing? I haven't drawn it, but yeah, I think orientating something like 75x50 so it is wider laterally would also be the go (is this what you meant Kryn?).

Drilling holes to allowing painting of the inside would work, but cleaning the inside (flakey zinc, etc.) would be a bit of a pain - I wouldn't be confident of fully protecting the areas where the gal had burned off. Remote area repairs aren't a real issue for me. Still thinking about aluminium too.. what size materials do you reckon?

Thanks

- Mick
Capture.PNG

Those gussets at the base of the verticals is what I was going to suggest, as I don't believe the legs on the ends of the bottom rungs would do much in terms of lateral strength.

Originally Posted by KBs PensNmore

Hi Mick, in regards to rusting inside the welded areas, drill a hole close to the welded joint and paint the inside with the cold galv spray, you might be able to get a can with a flexible nozzle or use a spray gun, these holes will also allow any moisture/water to drain out. As you can't make the frame an A, use something like 75X50 or wider on the flat to make it a bit more rigid.
I hate to be the bearer of bad news but that won't work. 75X50 RHS is not Galvanised, but rather a product called Duragal. Duragal is only a Zinc enriched coating and even then is only present on the outside of the section. The inside is black steel. I have seen a hole drilled in the steel section and a couple of hundred mls of oil poured in and the hole then welded up leaving the oil to slosh around inside preventing corrosion. This only works if the sections are welded air tight so the oil cannot leak or be forced out.
Following Yonnees advise about loading the upper levels, you could make the guards out of Ally checker/diamond plate and bolt them on. Using the plate will give a support to stand on with grip.
Major corrosion issues here. Ally and steel are not happy bedfellows.
A reason that I prefer steel over aluminium is that should you find a crack in it anywhere, welding repairs can be made anywhere, using three car batteries if required. To the best of my knowledge, this can't be done with ally.
Very valid point
Hope this helps.
Kryn

Alluminium gains its strength from tempering. Tig welding while a beautiful process, tends to produce a soft weld in ally due to its greater heat input when compared to mig. Building an aluminium trailer is more involved than taking a steel design and substituting an aluminium section for the steel. Thankfully, the weights involved with this trailer are minimal, so that simplifies life somewhat. I really wouldn't be too concerned using steel if salt air were the main concern. As long as the exterior is painted with a good paint, (even if using Duragal, which doesn't stand up to salt air well at all compared to galvanising or even cold galv with chlorinated rubber top coat), you should have few issues. You will not be immersing the whole trailer ala boat trailer so water ingress is a minimal issue. Duragal touch up paint is crap too. To get decent protection from it, cold galv must be used underneath.

Karl, I've only worked with the smaller gal steel sections (which have definitely had at least some zinc on the inside)... I didn't realise the larger ones didn't - that's good to know. I wouldn't be complacent about rust through - up here everything rusts. I lived down in Hobart for about 8 years and was amazed at how little things rusted there (lower temps, less humidity, dominant offshore wind), but having moved back to the beach in northern NSW, rust is always a biggie. The oil idea had crossed my mind, I've done that on some other projects and they've lasted well. If I went with steel, I think I'd go this way with the oil and take the time to ensure all the ends were sealed up. I have done the hole and spray thing before, but I've never been able to clean the affected area well enough to get a good coat on.

Since I haven't done a trailer before - what would be the key design features that would need to be changed if it was aluminium? See, the thing is - I just love aluminium!
Karl - Are you referring to issues with distortion due to excessive heat input, or cracking at stress points? Or both? well... I guess it would be both. It would be good to get some pointers on specifics relating to aluminium trailers.

Rustyarc - I agree regarding the little legs - probably superfluous, I almost deleted them in the last version.

Thanks

- Mick

I found some pics of something which looks pretty close to what I was thinking. Although as noted earlier I might add a small locker and water tank and have more overhang at back. The boards on this trailer are exactly the same size as I'm looking at.

7569557.jpg7569051.jpg7569049.jpg

You're right, sections up to 50X50X1.6 from memory are available in true galvanised inner and outer. Duragal runs parallel to these lines, so check before purchase. I have, except for one occasion only seen true galvanised in 1.6mm thicknesses. The one occasion was some imported 50X50X2.5 SHS. We sold as many slings of that as we could get.
Duragal is a good product, but if placed in a salt air environment will fail, (did you realise that there is a clear polymer coating applied to protect the zinc enriched surface below?). A previous employer of mine got caught out when Duragal was first introduced. We built a big set of cattle yards that were sent to King Island. I don't think the cheque had cleared before the rust started coming through the Duragal!
Anyhow back on track. When fabricating with steel, we can pretty much butt two sections together, weld them and call it good. The weld will effectively hold what the section is capable of and the tensile properties are not overly reduced. With Mr Aluminium, when we produce a weld, we significantly soften the heat affected zone and produce a weld softer than the parent material. This means that if we butt out two sections together and weld them, we may experience cracking in this area when placed in service. Aluminium also does not like vibration - if it moves it cracks. I fabricated all the access stairway handrails for the Woolnorth wind farm towers, these were made from 40X3 Al tube. within a month we were getting phone calls to say they were cracking through, not near the welds either. The wind was so strong, (I guess that's why they put a wind farm there, that the Aluminium was being worked until it cracked.
So, back to our Aluminium trailer. It is a good practice to think of Aluminium fabrication as similar to building a timber house. The design provides the strength, the nails stop things moving. IE. Truss on top of post, nailed to stop it sliding, not truss nailed to the side of post with the nails bearing the load. If you look at an aluminium tipper body, they are built like ikea furniture, this bit slides into that bit and keys into a third bit. The welds are only a glue to stop things moving and the upper sections transfer weight directly to the lower sections if that makes sense.
For your trailer, you would want a design where the two main runners with the suspension mounted, had the crossmembers stacked on top, (transferring the weight directly with the welds only preventing movement), all open ends capped. You would be best served using eye to eye springs and ensuring that the mounts were gusseted to prevent them ripping the bottom wall of your main runners. The drawbar would need to qo right to the spring hanger (and could form the front gusset), being welded only longitudinally as is standard procedure anyway. Your uprights would need to be braced so they dont wave in the breeze, factoring in wind buffeting from other vehicles and road bumps. Said bracing needs to be extended high enough that you don't just chase the cracking to the top of your bracing. A good soft suspension will help you out a lot as well. If you ran 7 leaf springs for example, I would near guarantee you that your trailer would self destruct in a short time. Only use enough weld. Overwelding softens the section even more.
I too like Aluminium, it is actually cheaper to fabricate with ally in many cases due to the elimination of painting, (particularly if labour rates are factored in).
Hope I've made sense.

Originally Posted by WelderMick

I found some pics of something which looks pretty close to what I was thinking. Although as noted earlier I might add a small locker and water tank and have more overhang at back. The boards on this trailer are exactly the same size as I'm looking at.

7569557.jpg7569051.jpg7569049.jpg

From what I can see of the design, that would actually work quite well with Ally provided you do away with the bend in the side rails in front of the spring hanger - that will fail. I would make a sub frame for the suspension and mudguards then place the main frame on top, (you can fine tume your balance this way too - just load the trailer up and try the axle in different positions until you find the balance you desire then weld it off). Despite not strictly abiding by the stack the sections rule, it is well braced and if 100X50X3 RHS was used, would have ample strength I feel. The only potential issue may be the horizontals in the "christmas tree" carry your bracing out as far as you can and you should be good. The welding in that design is also in places where the reduction in tansile should not bother you too much either.
If you put a water tank on, don't forget to baffle it. A half full 60L tank equals 30Kg of sloshing every bump you hit.

Great info in both of those post Karl, although I've got a soft spot for aluminium (pun intended), I'm swaying towards steel. I'll ponder it a bit more. The aluminium analogy with timber is a good one.
In your last post were you referring to the design in the photos?
The water tank would be low and flat with baffles and placed say 1m forward of the wheels. I'd probably down size it to more like 40L max.
I worked with the Hydro when I was down there, so I know what you mean about the wind!
- Mick

Yes, I meant the one in the photos. The drawbar seems to come back in a taper and then has been notched and welded to bring it back parallel for the suspension to mount on. Questionable with steel on all but the lightest trailers and a definite no no with Ally.
Ally is definitely a very accessible material to work with now the only real downside remains that there are few sections that sleeve nicely.
I can see a real case for ally in building that trailer provided you can get the sections you require and formulate a suitable design. Hot dip galvanising would be nice, (duragal hot dips beautifully by the way and is often cheaper than painted rhs), but expensive and all sections must be ventilated.
There are some really nice two pack paints around that will stand up well, (I don't like painting duragal much, even with an etch primer and a good sanding adhesion seems to be a real issue). Stone chip will always be a problem though.