Bloody hell Al.. Waddya doin to ya self... Looks like some primitive form of acupuncture.... .. Or possibly you are practising up on a bit of voo doo majic by jamin chunksa 4x2 through ya pinky.
I'm a bit dissapointed you showed evryone just how evil plywood can be... Its gunna set back the good reputation of Bondwood as the van restorers product of choice...
Now that people have seen what it is capable of they will be signing up for bauxite and fobbergross vans
Tis one of those situations where i dont think even lightweight gloves would have saved you. Just do what any tuff bondy owner would do. bite the end of the wood with your teeth and spit it out... NO NOT YOUR TEETH... the piece of wood
Now get back to work ... and .. oh yeah.. watch out for splintery edges.
P.S... you are allowed to swear in these sort of events...
I've decided to start a new punk vin vanners group. No sissy safety pins or silver studs for us. It's splinters through every digit, or it's not on!
Sid Vicious? - Pah!... Amateur! Just wait'll ya see 'Vic Insidious'! Tomorrow I'm getting G-clamps on my earlobes, and a couple of slot head screws through my nipples. Am I gonna look tough, or what?! (ummm...just don't come near me with a heavy duty magnet, ok? )
This is gonna take bondwoodage and discipline to a whole new level!
Post by Franklin1 on Sept 28, 2011 17:52:27 GMT 10
Yeah, it makes me squeamish every time I look at it too!
I've toned it down a bit. If anybody still finds it 'puke-ish', I'll substitute a photo of my new G-clamps when I get them fitted. (I can't show the slot head screws through the ni :-Xs though. This is a family forum, after all. )
Post by jodel1050 on Sept 28, 2011 21:31:17 GMT 10
Only a small crime. I served my apprenticeship over 40 years ago with RR, and they would only allow 1 and 1/2 thread's in safety, yours are way too long, it will never fly, or maybe you don't want it too? Great job though.
Post by Franklin1 on Sept 29, 2011 19:21:50 GMT 10
You'll have to explain to me what "1 and 1/2 thread's in safety" actually means, and why having long bolts is a "small crime". ;D
Building the walls:
Each side of the van requires three sheets of ply. I'm having an amateur go at making a Claytons scarfed joint between the three sheets. (How old do you have to be to remember Claytons?)
My first attempt was to cut two sheets at 45 degrees using my jigsaw...
But when the sheets were folded out and butted together, the cut was crap. It looked alright here...
...but here you can see where the jigsaw got the wobbles...
...and here you can see where the jigsaw has 'run off' the line...
Clearly a jigsaw is not stable enough for this job. If you've ever used a jigsaw, you'll have noticed how the motor housing has a bit of play in it, relative to the jigsaw base. For the precision cutting required for this job, I needed something a lot more stable.
On went the thinking cap. And out came my trusty little Makita 61/2" power saw. I drilled some holes in the base, and screwed the saw to a piece of ply left over from the flooring job. Then I fitted a couple of grab handles to the ply...
A bit of talcum powder was sprinkled on the surface of the ply sheets to make it nice an slippery...
Then I could run my contraption along the straight edge by holding the grab handles rather than the saw handle. That kept the ply base flat on the ply sheet...
This attempt was "much more betterer", but still not perfect...
I think there is a miniscule bow in the straight edge I'm using (the straight edge is another full sheet of ply). You wouldn't think a half millimetre bow would be a problem, but when you fold the sheets out and butt them together, any error is doubled. So, a half millimetre bow becomes a 1mm gap. I think I can sand the bow out of the edge of the sheets, but I'll be unscrewing my fingers and putting them in my pocket before I touch any sandpaper again.
I think I'm on the right track with the job. I just have to find a straight edge that is absolutely perfectly straight.
Last Edit: Sept 17, 2018 20:14:07 GMT 10 by Franklin1
I wonder whether it is worth doing a 45 degree scarf joint? Especially in the light of the difficulty you have shown us. But well done on your ingenuity!
When I did a bit of training to fix plywood gliders we had to make a practice joints with a 16:1 gradient. We just did it by hand, using a sanding block and the different colours of the ply layers and the glue between them to help guide the process. A 45 degree has only a 1:1 gradient. I dropped it back to a 8:1 ratio when I scarfed in 8 patches on an old sailing dinghy.
As far as I undersand the scarfing is to do with making sure there is no weak point, or stress line, as a result of the join. But with a double skinned wall on a caravan wouldn't a simple butt-joint, reinforced by being supported by a batten along the joint, be plenty strong enough?
It would think it should be easy to make, fill and sand to give an invisible joint when painted.
But I must admit I have not attempted such an invisible butt-joint on my old vans as yet. I Have done the joint many times when replacing sections of rotten cladding, but have not bothered to attempt to make them disappear behind the paint.
I am interested to hear what you, and others, have to say about the underlying theory here.
Last Edit: Sept 29, 2011 19:56:21 GMT 10 by millsy
You'll have to explain to me what "1 and 1/2 thread's in safety" actually means.
in jodel's absence, i'd reckon he means that only 1-1/2 threads of the bolt should extend beyond the nut, to ensure that the extended bolt thread doesn't become a "catch point" (oh&s and all that stuff) - in your case, nothing that an angle grinder can't remedy, (although i don't think that messrs rolls or royce would be particularly happy with that solution).
Post by jodel1050 on Sept 29, 2011 21:36:22 GMT 10
Geoff & Jude is (are) partially correct, (OH&S did not exist back then) it is just too long, - yes one of those rare occassions when something is too long. For jet engines it was just a weight issue & one of space constriction. From memory our sockets were not that deep & with two wobbly's & three extension bars to reach the errant nut a bolt or stud that long just would not have worked.
So it is just a weight/access problem & saves you time. Apologies I should have used the metric 1.5, damned fractions...
Coming along nicely Al, I once performed timber acupuncture on myself also, bloody thing was as thick as a match and about one and a half times as long, went in just above the last knuckle of my pinky and along the edge of the hand, left a tidy looking hole when I pulled it out , worst part about it was it was Treated pine damn did it hurt, for a couple of days at that.
If you get an email telling you that you can catch Swine Flu from tins of ham then delete it, it's Spam.
Post by Franklin1 on Sept 29, 2011 22:19:18 GMT 10
You've put forward a lot of good information.
An old 2007 brochure I've got from Hancock Plywood (I think they recently stopped making plywood) shows the scarfed joint to be 8 x T (where T is the thickness). They wouldn't scarf less than 7mm ply.
A lot of what you say makes sense. I may well be wasting my time doing it the way I'm doing. I just thought it would be interesting to see if a 45 degree "scarfed" joint (which I probably should more correctly call a 'mitred' joint) could actually be done by an amateur. And whether it would look better than a filled, butt joint.
I was actually planning to glue a cover strip of ply on the inside of the joint, which as you say would make it stronger. My van is only a single skin wall, so the cover strip will be routered to give a pencil-round appearance.
If I can't get the result I want after a bit more mucking around, I can always fall back on the butt joint method.
Thanks for your thoughts.
G'day Geoff 'n Jude, and Jodel,
Well, well, well...the things you learn on this forum, aye?!
Obviously there weren't too many inspectors in the caravan building industry in the 1970s, because my non-vintage van has oodles of bolts underneath that are "too long". So too did another '70s van I had for a short time last year. I must look under my '56 Franklin and see what length the bolts are under there.
No way am I getting back under the chassis of the project van to cut the bolts shorter with a grinding wheel. If any fool wants to crawl under there and get their eye poked with a long bolt, then let them.
I'd like to say that an enormous amount of research went into bolt selection, but it was more a case of me nonchalantly wandering in Bunnings one day, when "Pssst...over here!" was heard. I turned to see where the call was coming from, and it was from a box of bolts on the clearance table ...
200 bolts for ten bucks.
Me and my wallet made good friends with that box pretty quickly. ;D
Last Edit: Jun 5, 2019 15:12:10 GMT 10 by Franklin1
I had another go at cutting the 45 degree cuts on the sheets, this time using a full sheet of Laminex Aquapanel I had in the shed. Aquapanel is 3mm thick laminex (used in bathrooms), so it is pretty strong and straight stuff...
I'm much happier with the look of the joint when two sheets are butted together...
Next step was to cut some 50mm wide strips (or "straps" as they are apparently known, when used in a "strap joint")...
These strips/straps were then rounded on each edge with the router...
After a bit of research, I've decided to use Bote-Cote products for glueing all the plywood together. I bought the handbook that explains everything...
...and which includes a diagram of a couple of typical joints used in boat building...
Just to be "different", I've decided to make a combination of those two joints, and use this version...
I've never used Bote-Cote products before, so this will be a learning curve. The handbook says to use this product if you are doing this step, except if you are doing that first, then add this other thing into the mix before starting, but don't add that stuff if you want to be able to do this other thing later. All pretty simple really.
Is there anyone on the forum who has first-hand experience with using Bote-Cote and plywood? Surf Tragic and beetlesbailey don't seem to be on the forum anymore, so I'm looking for an unpaid "technical advisor" to help with questions.
Last Edit: Sept 17, 2018 20:17:35 GMT 10 by Franklin1
The timber straps were coated with a sealing coat of Bote-Cote:
...and so were the edges of the wall sheets:
A strap was glued to one side of the wall joint:
And then the first and second wall sheets were glued together:
All those steps were repeated before joining the second and third wall sheets:
Then came the tricky bit of drawing the outline of the van onto the wall sheeting. Trying to transfer a diagram from a sheet of graph paper to a full-size sheet of plywood is not easy. Lots of time was spent with a piece of string tied to a pencil, and drawing various curves in all four corners...
Eventually I got to a point where the outline looked somewhat like the original van shape, so then it was a matter of taking the plunge and cutting out the shape:
Now I'll spend a bit of time sanding the edges to make sure all the lines are nice and smooth and curvy.
Last Edit: Sept 17, 2018 20:20:14 GMT 10 by Franklin1
The other wall for the van has been constructed. I laid the nearside wall on top of it and traced around the outline...
But while I've got the nearside wall on the floor, I need to do a few things to it in readiness for future steps.
I had to make a timber jig out of scrap plywood, which would fit onto the bottom of my router...
This jig would allow the router to straddle the timber strap glued to the sheet joint...
...and would allow me to router the timber strap down to the wall ply level. This section of the wall sits flat against the chassis edge, so the timber strap had to go...
In order to maintain the strength of the joint in that section, I'm proposing to put a patch of fibreglass across the joint. Is there a fibreglass expert in the house that can tell me if that is a sensible idea or not, or should I be doing something else? I don't want the joint to end up splitting in that routered section.
Last Edit: Jun 5, 2019 15:17:51 GMT 10 by Franklin1
Post by atouchofglass on Nov 4, 2011 16:57:18 GMT 10
Hey Al You just wanted me to weigh in on this one. ;D ;D ;D
If you decide to go with fibreglass. You will need to resin coat the ply before glassing. So mix up a hot mix of resin..... IE two or three times the recommended amount of catalyst to resin. Timber retards the resin so to get it to go off in a decent amount of time it needs more catalyst. Paint it on and let it go off before thinking of glassing.
Once it has set remove any high spots with a quick sand... 28grit. Cut/tear your fibreglass to size and coat the ply again with resin. This time with the recommended amount of catalyst. Put the fibreglass over and wet the glass out. Smooth with an aluminium roller and let the glass go off.
Do the same on the other side.
I'd be inclined to use at least one layer of 600 or two of 300 fibreglass. Up to you.
Someone else out there with more experience may have a better grasp on what you need to do.
Don't you try and trick me with all that fancy fibreglass talk. I've got L-plates firmly fixed to my chest, you know.
The Bote-Cote range of products must be different to the ones you use. There are the core products of resin and hardener, and then there is a thinning liquid that is added to the mix for the first coat applied to raw timber. This thinned mix soaks into the timber and seals it ready for subsequent coats, or for glueing, or whatever.
The Bote-Cote handbook also says in bold type: Adding more hardener does not speed the cure, rather it stops the epoxy setting properly!
It also goes into great detail about the relative strengths of the fibreglass matting available, and says that matting with the strands running at 45 degrees to each other is better than 0 and 90 degrees.
The sections I want to do are hidden out of sight in the finished project, so I might muck around with putting a patch of matting over the joint and see what happens. Whether I put glass on the outside of the joint is something I'll have to think about later, because I'd have to do the whole height of the joint on that side, I presume.
...And so I mucked around putting fibreglass patches on all four areas of the walls. Needless to say, I'm still very much an amateur at this fibreglassing game, so lucky the patches will be out of sight.
I cut some fibreglass sheeting up at 45 degree angles to give me the patch size of 90mm x 90mm...
Stuck it into position and applied the coats of resin as required...
And here's the offside wall patched up and coated with resin in the areas that will butt up against the chassis edge, and the mudguard...
If you are thinking of using the Bote-Cote products on your van, here are some tips I've discovered in the short time I've used it...
1. Brushes and Applicators: It's a pain to keep brushes and applicators clean after using them. The Bote-Cote handbook says to soak them in brown vinegar to remove the hardener out of the mix (...Who would have thought?! ). But, you are still left with the resin in the brush...
I gave up on that and ended up cutting some jumbo size "fish fingers" out of a block of foam and using them instead. Foam is cut easily with one of those electric carving knives. Use the fish finger once (or twice if you're lucky - both ends), and then chuck it. Worked well for me...
2.Measuring and mixing cups: There is a standard 250ml cup available from the Bote-Cote supplier. Works well for medium to large jobs. Cup is re-usable. Cured resin is removed by flexing the cup and the resin peels away...
But, for really small amounts of resin, it's difficult to judge the correct ratio down in the bottom of this cup. For example, I only need 7.5mls of mix to coat the patches with one layer of resin. I stumbled across some medicine measuring cups in a cupboard in the house. Eureka! These are graduated to 30mls and are made from the right plastic...
The only thing you need to do is cut the three lugs inside the cup away with a sharp knife, otherwise the stirring stick snags on the lugs...
3. Stirring sticks: Packs of paddle pop/popsicle sticks from the Discount store are marvellous...
4. Disposable gloves: It can be a messy job. Some people can even be allergic to the ingredients. These gloves mean no sticky fingers...
5. Removing excess cured glue: If you don't manage to scrape off all the excess glue before it has cured, fear not! Bote-Cote softens between the temperatures of 55 and 75 degrees (which means you should never take your van into the Simpson Desert in summer ). The handbook says you can use a hot air gun and scraper to soften and remove the excess. I discovered you can also use a 40W soldering iron as a heated chisel to do the same thing...
So there you go. Never too old to learn, aye?!!
Last Edit: Jun 5, 2019 15:21:52 GMT 10 by Franklin1
Thanks seeshell and jamesandbel for your comments above. Jamesandbel, I think you'll be well and truly finished the way you're going, long before I could even think about heading up your way.
This week's progress report:
Both walls have been constructed and cut to shape. Now I have to build those lamination thingys that are glued around the perimeter of the walls (so the roof can be fixed to them).
I did a couple of trial laminations, just to get the hang of it and to see how it all happens...
The two trial blocks will be used in the seat framework in the rebuild, about where the circle is in this photo...
Now I'm in the midst of the main event for the laminating. All members of the Clamps Regiment have been called up for active duty from the shed. All leave has been cancelled, and significant amounts of overtime are being worked by many of the clamps.
The formwork is being progressively cut and shaped as I work my way around the perimeter...
...followed closely behind by the laminating process...
Eighty four strips of ply are required to do the job for both walls. Yep, 84 strips of ply to be cut, sanded, and glued together to give a block 7 layers thick. Boy will I be "over it" by the time this part is completed!!
I'm using Aquadhere PVA to glue the laminations together, and I'm using cling wrap under the laminations to stop them getting glued to the wall. I have to be able to lift the laminated block back up when it's completed, so I can glue it to the wall with the Bote-Cote stuff.
Last Edit: Jun 5, 2019 15:25:57 GMT 10 by Franklin1