WOOD vs. METAL Trailer Wall Construction

[JPK]

I am guessing that these procedures are not used by any trailer builder JPK. Thank you for telling us how and what you were talking about. Pretty amazing to say the least. My guess is that these are boats that cost in the hundreds of thousands of dollars. More a work of art than anything we build.

The 65'er would run near $3 million if the interior is what I suspect it is (the engines and drive line would be around $1 million.) But there are plenty of much more utilitarian charter boats built the same way, and many smaller boats, all the way down to center consoles, skiffs and canoes. Cold molded construction is very cost/price competitive.

The cold molded construction ought to be used, that's the point. Cost effective, stronger, lighter, not subject to fatigue, quiet... Can be done at home as well.

Plank on frame with epoxy is nearly as good, and adaptable as well. Some loss of inteior cubes, but no different than any other material that requires framing.

JPK

 

[JPK]

For comparison, here is a more traditionally built plank on frame boat - but with epoxy as well. Fasteners are used, but I'm unsure of where and howm many. This boat was built by a fellow to be hs charter boat in the Oregon Inlet area of the Outer Banks of NC, in Dare Co., where many wood boats are built. The last one, the 65'er was built there as well, Wanchese in in Dare Co.

Imagine building an off road tear drop with this method or cold molded.... Strong, lightweight,....

Here is the builder shaping a frame.

The beginning.

Progress on the frames.

More progress on the frames.

Juniper planking, juniper because of its light weight, dimensional stability and its impervious to water characteristics. The juniper planks are edge glued and I believe mechanically fastened to the frames. If mechanically fastened, probably with bronze screws to prevent corrosive expansion of the fastener in the case of contact with sea water.

Often plywood is epoxied over the base planking for additional strength and to ease fairing and finishing. No photo of this though, and this boat may not have had plywood applied, though it probably did.

Finished hull, glassed over and at least partially faired. The interior would be at least "pickled" with epoxy, meaning well sealed with epoxy thin enough to soak into the wood some. Those plank on frame boats I been below decks on were also painted. Some had glass mat in the engine room or other places where wear and abrasion could be expected.

Finished hull shot, faired and painted.

The boat running, its called Marlin Fever.

In plank on frame boats the frames stay in the finished boat, adding weight and also taking up some interior cubes. Still, the end result is a very strong boat up to running off shore daily for decades.

Either the more traditional technique, with modern materials - glass, epoxy, structural epoxy putty fillets, etc. or cold molded.... Great choices. Or the "Stitch and Glue" method shown by Heifer Boy would make a great trailer...

From what I have seen, tear drop builders build more along the lines of plank and frame, especially the roof. If they are not using boat building techniques they ought to. Stronger, lighter, waterproof quiet...

JPK

 

[bob]

The only way that would happen is on an individual basis. The cost overall would be too much for the average off roader to pay I think. If I had the tools I would try it, but not only the tools holding me back. These are artists compared to what we build. I doubt I know anyone that has those skills, and if they did would not be building a few off road vehicles.

It is obvious the craftsmanship is far beyond what any of the manufactureres are doing. :Wow1:

 

[JPK]

The only way that would happen is on an individual basis. The cost overall would be too much for the average off roader to pay I think. If I had the tools I would try it, but not only the tools holding me back. These are artists compared to what we build. I doubt I know anyone that has those skills, and if they did would not be building a few off road vehicles.

It is obvious the craftsmanship is far beyond what any of the manufactureres are doing. :Wow1:

With plank on frame construction, for the frames. Not the rest. But if SoCal and others are already making frames - and the photos I have seen says they are, it would be a small step to employ epoxy and epoxy putty structural fillets. In any event, the frame sizes and the relatively simple lines and curves on a trailer don't require the skill that a plank on frame boat would. And don't forget the structural gap filling epoxy putties...

And not for cold molded construction. If you can use an electric drill, a skilsaw, a jig saw and a mason's trowel you can git 'er done. Lofting a jig takes some skill though, but nothing a good carpenter couldn't handle, and an easy chore for a cabinet maker. And jigs are re-usable.

Stitch and Glue would produce a fine trailer, and that technique is made for the home builder, let alone a small production shop.

Don't confuse the finish with the build. The finish looks great, but the build is what is important.

Just think of the plank on frame boat. The guy's proffesion is fishing. Not carpentry or cabinet making, fishing, and he built his own boat. Not uncommon in NC in the recent past, though becoming less and less common due to longer fishing seasons and more travel to fish.

JPK

 

[Heifer Boy]

Amazing boats JPK. I read a fantastic bass boat build a while back but haven't been able to find it since. The construction was incredible and when you see these bigger boat builds it really opens your eyes to what's possible.

When you scale a build down to camper/trailer/teardrop size I think plank on frame would take up too much internal space. The main benefit for you guys in the US with a frame it gives you somewhere to put your insulation which is something rarely considered over here. Unless you are buying high end caravans or Kimberly Campers etc, heaters and airconditioners are an unkown. If it's hot you go outside, if it's cold you wait until the sun comes out!!! We are camping after all...

I agree it would be a small step for SoCal and the other tear builders to add epoxy glue and fillets to their build processes and I think they would soon find that amount and sizes of frames could be reduced because of it. I can't understand why some of the methods used haven't evolved past bits of pine and staples. If the requirement for a structural frame is removed from the construction then it can be reduced to the barest minimum and used for just mounting points and edging for insulation. Very simple, flat surface building. Then it's just assembling.

The gap filling qualities of epoxy vs PU glue and the strength it provides can't be underestimated. The great thing about S&G construction is it rewards bad carpentry!! A bigger gap becomes a stronger joint so anyone can build well It really is true that if the joint to too precise it won't be that strong. Simple tools and skills are all that's needed. The finish is totally up to the builder and some of the teardrop 'Weekenders' prove you can throw something together in a weekend and then use it. Production is whole other story.

BTW - the cost of the canoe shown is generally about US$180-$200. $3m is not even on the same planet LOL!!! For a camper it is very cost effective though and very few materials needed. Clever pattern layout and cutting means a lot of the same material can be used in many different places. The 1 and 2 sheet boats builds are a classic for this and I did some tricky layout and waste reuse on my build to save buying more sheets.

 

[JPK]

I'm not so sure that a frame would be so cube's consuming. Think laminated frames 1" "tall". Not much room eaten in width, just 2" overall, but tremendous strength. Ply wood for "planks."

But I really think that either cold molding for more complex shapes or stitch and glue are the routes to take. As far as I have seen, any tear drop shape could be matched with stitch and glue. But re-usable jigs would make commercial shop production easier and cheaper in the long run I think. Most of the Carolina yards are small shops, and their production is cost efficient compared to bigger "factory" producers.

Interesting note regarding stitch and glue seam fit.

Also, the $3 million for the 65'er includes power. Near $1 million for engines and transmissions at what I'm guessing is about 1,450hp a side. But when you add the power plant for the canoe, that price soars beyond the yacht's. One human power plant is priceless!

$200 is less that you can purchase a plastic or aluminum canoe for here. 16' plastic, new, ~$600. I may have to give that canoe a try, if tight fitting seams make it weaker, mine would be strong as hell!!!

JPK

 

[Ozarker]

Great thread! I too have an all steel utility trailer with a tilt bed. I want to build a module that will slide in and out out of wood. I intend on using boat buildint techniques, glass the seams and paint it. I'm thinking of using small steel plate on the corners and critical areas. As I have posted before, I'd like for the module to attach to amas, or pontoons providing acabin for a small catamaran about 24' long. Due to the nautical nature the cabin will need small ports (windows) and an entry hatch. For you boating types, I'd like something similar to a Jar-Cat or Cato, maybe the Jeff Gilbert cats. Going this route will save time and money from building a boat and a trailer without duplicating a small living space.

Another solution is to just set the cabin in a Gunther bow (snub niosed like a John-boat) with a flat bottom, primarily for lakes and rivers. This is a much simpler soultion. Back to the topic, steel angle could be used for the frame and ply bolted in it. Yes, it would be heavier. I'm not that concerned about weight so long as it floats (LOL) as my truck will have no problem pulling it. A small 10hp outboard will push it along for cruising, it's not to ski behind.

The teardrops would be great and a metal interior frame seems to be an option as well, just over a dozen welds at a shop might do it.

In a boat, the seats and storage hatches are part of the framing, I think the same should apply to a trailer.
I'll stop, but what do you all think about a comination of steel and ply?

 

[Heifer Boy]

Do you mean like this...
http://www.mikenchell.com/forums/viewtopic.php?t=46755

 

[Heifer Boy]

If the resin to be used is epoxy then I've no idea if they're compatible or not.

You can use epoxy resin over polyester resin but not the other way around. Generalisation to follow -

Polyester resin doesn't stick too things very well (including itself once hard). It's great for making 'fibreglass' components like boats and sub-woofer boxes and spoiler kits and BMX helmets. It's mixed with fibreglass chopped mat and wrapped around or blown into or over a mold. It hardens really hard and brittle which is why it shatters when it impacts anything. But those components then need to be attached to something it's done with an epoxy resin mixed as a glue.

Epoxy resin bonds to just about anything except plastic. It can be mixed with a large number of different fillers to build up surfaces and joints (ie fillets) or thinned to penetrate surfaces for waterproofing (wood, concrete, stone etc). I'm about to spray the outside of my concrete block house for this reason. Garage and workshop floors are often epoxy coated too. In boats, deck hardware like winches and cleats and pulleys are attached using epoxy resin. The hole for the screw is drilled over-size and the hole filled with thickened epoxy. The hardware is then screwed to the deck while the expoxy is still wet and it produces a totally waterproof and incredibly strong attachment. Sails put many, many tons of strain on these attachments and they don't let go. It's way beyond any force a camper would ever encounter. Epoxies are also great for laminating fibreglass (or carbon fibre) cloth to things (like boats and campers) for strength and abrasion resistance. This creates super strong composite structures and panels. Sometimes the substrate used for these is wood but it is often foam or a honeycomb structure. But wood is very common for home builders because it's cheap, easy to work and is self supporting while building. It doen't mean it's not the right material for the job though. Fully encapsulating the wood in epoxy makes it impervious to rotting too. Epoxy resin is also used for repairing fibreglass boats

It's really important to differentiate between polyester and epoxy resins. A fibreglass boat is NOTHING like a wooden one built with epoxies and fibreglass cloth. These aren't fibreglass boats - but composite boats. This is misunderstood and they are often seen as the same things.

The same applies to campers but as Bob said before - it's doubtful any commercial builders are using these techniques. The construction doesn't need to be anything like a large boat build but a few simple techniques and importantly, the right materials, and it would make a big difference to a camper.

Just my 2c.

 

[Woods]

Pretty good description. It leads to the following question. Why would anybody ever choose polyester resin over epoxy? Two reasons that I know of. Generally speaking epoxy is more expensive and more UV sensitive. An example, I'm currently building my galley. I wanted to use a clear finish so I chose a "Bar Top Finish". It's, a hard, clear, self leveling, high gloss epoxy finish. Though it has UV inhibitors built in, it is not for use in daily direct sunlight. One quart covers about 8 square feet (not very much) and it cost me $30.

You can use epoxy resin over polyester resin but not the other way around. Generalisation to follow -

Polyester resin doesn't stick too things very well (including itself once hard). It's great for making 'fibreglass' components like boats and sub-woofer boxes and spoiler kits and BMX helmets. It's mixed with fibreglass chopped mat and wrapped around or blown into or over a mold. It hardens really hard and brittle which is why it shatters when it impacts anything. But those components then need to be attached to something it's done with an epoxy resin mixed as a glue.

Epoxy resin bonds to just about anything except plastic. It can be mixed with a large number of different fillers to build up surfaces and joints (ie fillets) or thinned to penetrate surfaces for waterproofing (wood, concrete, stone etc). I'm about to spray the outside of my concrete block house for this reason. Garage and workshop floors are often epoxy coated too. In boats, deck hardware like winches and cleats and pulleys are attached using epoxy resin. The hole for the screw is drilled over-size and the hole filled with thickened epoxy. The hardware is then screwed to the deck while the expoxy is still wet and it produces a totally waterproof and incredibly strong attachment. Sails put many, many tons of strain on these attachments and they don't let go. It's way beyond any force a camper would ever encounter. Epoxies are also great for laminating fibreglass (or carbon fibre) cloth to things (like boats and campers) for strength and abrasion resistance. This creates super strong composite structures and panels. Sometimes the substrate used for these is wood but it is often foam or a honeycomb structure. But wood is very common for home builders because it's cheap, easy to work and is self supporting while building. It doen't mean it's not the right material for the job though. Fully encapsulating the wood in epoxy makes it impervious to rotting too. Epoxy resin is also used for repairing fibreglass boats

It's really important to differentiate between polyester and epoxy resins. A fibreglass boat is NOTHING like a wooden one built with epoxies and fibreglass cloth. These aren't fibreglass boats - but composite boats. This is misunderstood and they are often seen as the same things.

The same applies to campers but as Bob said before - it's doubtful any commercial builders are using these techniques. The construction doesn't need to be anything like a large boat build but a few simple techniques and importantly, the right materials, and it would make a big difference to a camper.

Just my 2c.

 

[Heifer Boy]

Both those things are true but also add that polyester resin goes off a lot faster. I think in about an hour and you can sand it etc. Using epoxy is also known as 'slow welding' because it takes at least overnight before you can work it. It can be quite temperature sensitive too but different hardeners can be bought to cope with that.

Some of the 'Quick Canoe' builds (like my example before) used polyester resin when they are built really fast. Funnily enough, these canoes are also known as 'Cheap Canoes' or 'Disposable Canoes' because they were orginally designed as a one season thing. They were not designed to last longer so were built with cheap materials and polyester resin and finished in house paint. That tells you something.

Sometimes even a hot glue gun is used to 'tack' a canoe together too. Then once the structure is held in place it's perminantly fixed with epoxy. Sound familiar to you welders out there :Wow1: It's a handy thing to know when you can't clamp something or don't want filled screw holes showing afterwards.

 

[indiedog]

Great discussion. A couple of years ago I explored using Stitch and Glue for a teardrop inspired trailer. I got great feedback from the Wooden Boat Forum. The link is attached below. If you read that you'll see that the guys actually suggest that the tongue could also be made of fibreglassed ply, so in fact almost no steel is required if done correctly. I thought that would be a bit much for the licensing guys to get a handle on though! The very last image shows how the structure of the ply enclosures developed with the feedback. If anything I'd now continue the bedhead panel all the way up and do cutouts for storing stuff behind the bedhead.

http://www.woodworkforums.com/f32/my-upside-down-boat-wheels-111423/

There's some great information about how to glass most panels on the flat before assembly and if this method is used then construction is much easier. Also some great feedback on how to incorporate good structural stiffness.

I haven't built the trailer indicated as it no longer suits our needs but the information gained will certainly help me on my latest design which will start construction next year.

A quick question, for the cold moulded timber, how is it shaped and/or attached to the jig? The concave bending of the timber would require some reasonable fixing I would have thought.

 

[JPK]

Pretty good description. It leads to the following question. Why would anybody ever choose polyester resin over epoxy? Two reasons that I know of. Generally speaking epoxy is more expensive and more UV sensitive. An example, I'm currently building my galley. I wanted to use a clear finish so I chose a "Bar Top Finish". It's, a hard, clear, self leveling, high gloss epoxy finish. Though it has UV inhibitors built in, it is not for use in daily direct sunlight. One quart covers about 8 square feet (not very much) and it cost me $30.

From Envi Boats, a plan and material supplier:

"It is important for the resin to have similar characteristics of elasticity and strength as the core material. In the case of cold-mold construction, the core is, of course, marine plywood. Epoxy fits the bill nicely. Less expensive polyester resins cannot be used as they will delaminate. As tempting as it is due to cost... "Just Forget About It" [Obviously Envi is a Carolina company, cold molding in the Carolinas means plywood, but in Florida some builders still use mahagany strips.]

Also from Envi:

"Why do I have to use more expensive epoxy resins in cold-mold construction when polyester-based resins are significantly cheaper?"

Answer: Epoxy resins have much better properties of elasticity and can handle and "match" those properties of the core material much better than the comparatively brittle polyester-based resins. For this reason, they are very well suited to cold-mold. If you choose to use polyester resins (which are well suited for solid fiberglass lay-ups) rather than epoxies, the boat will likely suffer from delamination problems in relatively short order.


Lots of questions answered here: http://www.enviboats.com/home/boatbuilding/boatbuilding-faqs

 

[JPK]

... A quick question, for the cold moulded timber, how is it shaped and/or attached to the jig? The concave bending of the timber would require some reasonable fixing I would have thought.

Attached to the jig via an easily removable means - like brackets and screws... - are the keel, other structural members like stringers and battens or ribands. The plywood stripping or mahagony stripping, as the case may be, is glued and screwed to those pieces. When the epoxy has cured the screws are removed... The battens (also called ribands) stay with the structure, as do the keel, etc. When the structure is flipped the jig comes out first, but the battens, keel, stringers, etc are now one with the structure of the hull.

Battens and other parts that become part of the structure are fitting to the jig in notches, and as mentioned held in place via a means which can be unfastened when it is time to remove the jog and flip. You can see notched in the jigs in some of the earlier photos I provided. The one shot of a jig from a non-sportfisherman shows notched very well.

JPK

 

[Heifer Boy]

@JPK

That Envi site answers the questions in a much more knowlegable way than I did. Good stuff.

@indiedog
!!!bleepinggodam$$&***bleepbloodyindie***&&&^%%$$$bleepindogbleepbleep!!!:violent-smiley-031:

I've had a teardrop idea in mind since I started building my camper box and you have just posted up EXACTLY what is in my head!!! Your drawings are way better than mine though. Line for line it's the same (except for the spare) and more importantly, your using the same design philosophy too. Single skin epoxy build, raised sleeping platform to create torsion box support structure, lightweight 'ribs' for roof support. A cross between a T-Van, a teardrop and boat. The scary thing is I also refer to it as a 'an upside down boat with wheels'. Now that's spooky :yikes:

I've got loads of profile doodles in pieces of paper scattered around the house and have gone from curved shapes to squared off shapes and back to curved again. I'm thinking mine will be like a reverse Benroy shape for interior spaciousness. I even plan to drill holes in the ribs like you have. Nothing like a bit of industrial steampunk-ish style to finish things off. That's why my camperbox has the cutouts in the shape they are. Just add some leather and brass to yours and even Captain Nemo would be proud of her.

10 days ago I fired up SketchUp and came up with the rough drawings below. I was going to start a design thread here but there is no need now after your thread. You even got advice and feedback from Michael so not much more to add there. On Monday night I came to the conclusion that I would build the roof curve on a jig and attach it to the walls after so you've stolen all my thunder. Grrrrr!!! Mind if I build it?

http://i1101.photobucket.com/albums/g423/Heifer-Boy/Simple Camper/SimpleCamper4.jpg
http://i1101.photobucket.com/albums/g423/Heifer-Boy/Simple Camper/SimpleCamper6.jpg

On a serious note though. I really think we need to sit down around a fire in a bush camp somewhere with a few beers, a pen and some paper and design the world. Maybe halfway between us somewhere - Youldales Hut? Feb/Mar sometime? I'm even happy to talk about architecture