INVESTIGATOR 563

As per Ian’s request I'm starting a thread on my trailer repair.

Like you Ian, I’ve done winch, wheels, tyres, bearings etc last haul out As the trailer only gets used for haulout, there has not been much wear and tear there, but as Neil Young intoned “Rust Never Sleeps” and the bastard doesn’t either.

I’m unsure of the value of gal trailers. If you get creeping rust under the gal it rapidly spreads. If I was designing a trailer I think I’d use all open channels of larger sections rather than square tube. And pant it regularly. You can’t flush salt water out of closed tube and if you get even a pin hole in the weld it will get into a submerged trailer and be impossible to get out. Hot dip gal can’t get inside square tube, so no protection. Even my side open channels have rusted out under the gal .

My advice to anyone who still has a sound trailer is to drill a fill hole at the high point of your square sections and drain hole at the lowest point and flood the tube with fish oil. Then drain it out. Put seals/ screws/ bolts in the holes. But remove them after use and flush the cavities out. AND paint the whole trailer with fish oil. It will look awful but a rusty trailer looks a lot worse. The oldest known boat in human existence found by archeologists was reeds waterproofed with fish oil.

More to come.

Thanks Ozzie, I'll make a small contribution here. These are the hubs/brakes for the standard trailer:

https://sunriseint.com.au/product/9-mec ... ravan-set/

Holden HT 5 stud 63.9mm centres
Bearing LM11
My notes say 10" but the invoice says 9"
2 x HHD9HTLM Holden HT 9" Brake Drum - LM
1 x MB9P-L 9" Mechanical Brake Backing Plate - Left Hand Side
1 x MB9P-R 9" Mechanical Brake Backing Plate - Right Hand Side
4 x Mounting Bolts and Nuts for Mechanical backing plate

The kit comes with bearings, seals and dust caps.

As per Ozzie's comments, my trailer has nuts welded in to allow the rear-most rectangular sections to be filled with oil and sealed with a bolt and nylon washer. I might try doing the same for the remaining sections.

My new trailer cost me around $4000 which included all materials except wheels and tyres and also included galvanising. But no allowance for labour.
Hope this helps anyone who may be thinking about building one.

Ozzie. The last time I had hollow section steel hot dipped we had to drill sizeable holes at either end so the zinc was able to get inside and also to stop the seam of the tube splitting because of gas build up inside

Hi Ozzie, if you go for open side channel beams. I would increase the wall thickness to 4mm with 100x50 channel (3mm fine for 100x50 box sections)
Open side channels would be easier at hot dip galv plant too, some holes to drill in some corners though. (a pre-visit to galv plant helps get info) If frame is well prepared (eg sandblast, wet-blast/grinder/needle scaler) then the hot dip gal should stick like S to a blanket for decades. Just a good fresh water hose down after every salty trip.

Box sections seem ok as long as both ends are left wide open, I always fresh flush my side beams after each salty dunking. (and bearing buddy grease hubs) (at least if my new side beams started rusting inside-out, then it can be detected early at "stage 1" during flush outs)

If you need a cross beam rebuild. I would try U channel in simple \/ shape (one joint in middle).Or weld a straight beam underneath the side beam might be allot simpler, but more utilitarian looking (the original was a flat bottomed, double joint, \_/ profile, which is quite difficult to reproduce) 75x50x3mm channel should do it (it's what i rebuilt with, seems very solid)

If going to do hot dip galv (highly recommended) buy black (unpainted) steel, keep it out of the weather (in a garage) and build quick before it gets too oxidized.

Hope some of this helps, Cheers

Good info.

I bought a pair of bearing buddies but they seem to be just marginally oversized for the hubs. They have a fairly thick wall so they can't be force fitted. Any tips for how to achieve an interference fit? I don't have a lathe to bring them down to size. (I think the correct answer is send them back and buy a different brand that is 1 3/4" instead of 45mm).

PS, on galvanising, I bought a set of "galvanised" steel stringers for stairs, not knowing anything about galvanising. Turns out they are electrogalvanised or some similar inferior process. I suspect I needed to specify hot-dipped. You get what you pay for.

Hi Ian, ozzie

I'm bit weak on the fitting stuff, except use measuring callipers to get exact size to buy a fitting or bolt etc.

As a young lad got some temporary night shift work in a hot dip galv plant. Operating the acid pre-dip and hot dip galv tank with a mate. The vats are at least 9m long x 2m wide and 2m deep, thats a hell of allot of molten zinc! (and acid). Huge overhead multi-ton gantry cranes, sling I-beams etc for heavy construction projects..but also did small stuff like boat anchors/anchor chains (had frames with lots of hooks for small items).

It's definitely far better than electroplated zinc. Hot dip gets a thick layer of zinc to bond closely with the steel.

Ian S.
If you buy the stair stringers from Ingal they are hot dipped. Industrial Galvanisers (Ingal) probably the biggest in the business

Thanks for the replies. Yes, too late on the stairs. They're busy rusting away as I type. I gave them a coating of penetrol in the vain hope that might add a few years...

Thanks for all the input. I have unfortunately or fortunately as in “thank god” finished much of the work prior to reading it. I used Duragal steel as I had some on hand and purchased the rest locally. Due to health issues with my deteriorating spine there was no possible way I was able to strip the trailer down to frame and transport it for a hot dip re-gal job anyway.

In any case it’s all done and serviceable again currently waiting for Mobil trailer expert to come to fit new springs and running gear next week. I decided not to skimp or reuse anything so I have purchased new everything hubs, brakes, bearings, springs, ubolts, cables. All up over $800 in parts. I’ve reasoned that the main thing that devalued boats that people have looked at on the forum is a dickey trailer. On the road piloting over a ton of metal and fibreglass you need to be confident it’s all working. Spritzig IIs next owner may be from Melbourne, who knows? I could have probably managed to fit the new parts but I’m leaving it to a professional once again as I’m no longer up to the job. All up I’ll probably be spending $1500t-$1700 on the trailer but secondhand trailers suitable were advertised at about that anyway and would have required mods to suite an Investigator…so…I’ve got the real thing still. I few points from my bit of the work.

In constructing a complete new rear cross beam I originally tried making a template of the correct angle to cut the 50mm square section at each end. This was a mistake as even a few degrees differences in template angle was amplified after cutting and setting up the centre join. Ultimately I made a jig of sorts by marking out distances on tape stuck on the garage floor using the original rusty beam as a guide and then marking out upright cuts perpendicular to the floor with a large metal square. All good with neat tight joints to weld.see pic.All I did was tack the bits together with my arc welder till my mate could do the final proper job. Bunk brackets were reused after removal and cleanup. Why reinvent the wheel. I found getting the old roller fittings and bunk fittings off the old frame a royal PITA. Also, then cleaning the old gal off. You can’t weld over old gal and you want it well away from the new welding area as it gives off toxic fumes when heated by new welding. Getting the roller pins out of the roller brackets took all morning for two. See pic.

https://ausrollform.com.au/the-duragal-difference/
Though duragal may be different to hot dip I’m firmly convinced that trailer maintenance is far more important than either. Dunking steel, treated or otherwise, in salt water without proper maintenance and cleaning will ultimately lead to tears before bedtime. I say this after close to half a century of boat trailer ownership. My old tinny trailer was just untreated steel and got used regularly and usually half submerged at each retrieval. It got pressure washed after every use while waiting for the outboard to flush and repainted regularly. Results, zero rust when I sold it. I am about to fill my crossmembers with oil . I’m thinking not “pour in drain out” fishoil as mentioned. but fill them with engine oil and leave it in there. !!! Copious grease on everything else. The rest of the trailer I think I’ll paint with fish oil. After my mate did all the welding my wife, who’s a dab hand with a paint brush put two coats of galmet grey on all welds and new Duragal. She offered to do the whole trailer but I declined, pointing out that if you go to buy a secondhand trailer and it’s all painted in opaque grey or silver you get to wondering what was “under“ the paint. At least I do. It’s obvious on my trailer what was still quite sound and original and what was repaired/replaced. Fish oil being transparent won’t look like it’s attempting to hide anything come sale time. It was a pleasure watching my mate, a retired boilermaker welding. Neater than the original. He uses Duragal for all his projects including his own truck bodies and trailers. Also reinforced my decision not to attempt the work myself with my green shed arc welder and near non existent welding abilities.

To each his own.