Skateboard Ramp - Bending plywood

[Hand Plane]

I have committed myself to make the grandson a skateboard ramp!
About 1m wide; 800mm – 1m high; and the ramp arc having radius of 1.4m. This results in an arc length of 1.15m, and the distance between the chord and the arc (how much the ply has to bend) about 115mm.

I'm envisaging difficulty with bending the plywood for the ramp. I'm thinking of using 6mm thick ply but examined one in a skateboard park (close in size to my intended unit, method of construction the same) where the manufacturer had used ply at least 12mm thick.

Any clues how they managed to bend ply of that thickness without it cracking?

I would expect that trying to screw it to the braces to form an arc would cause thick ply to crack.

 

[Inspector]

Glue multiple layers of thinner plywood.

Pete

 

[joshvegas]

Hunt around B&Q and you'll probably find a piece ready formed.

12mm will bend to that with persuasion and big screws, clamp it down in the middle and screw outwards. put a solid wood lip on the leading edge and lip, plywood is brital is you crash into it and ctahc the edge. the leading edge needs chamfered to because 12mm will send a skateboard flying.

But surely your grandson should be making it with a hammer and some rusty nails while you look on disapprovingly?

Is the plan to evacuate him to Ninewells or Kirkaldy when it all goes wrong?

 

[Jamesc]

I made one with my son many moons back. If I recal we use 2 layers of 4mm ply glued and screwed together. I honestly can't remember if it was to get the radius or it was all we could get. What I do recal id avoid flxy ply. We tried it first ant the first time he used it he went straight through the ply.

 

[DBC]

I made some ramps in the 1990s for a skateboard company that sold skateboard gear and also rented out the ramps by the hour behind their shop. One ramp was outdoor (2.5m ish high halfpipe) and a smaller indoor one (about 1200mm high and sort of w shaped). I used 2 layers of 9mm marine ply and (maybe) 3 layers for the tall one. They actually gave me a set of American specifications to work off. The only thing I can remember off these besides the ply thicknesses is to run the ply diagonally. I may be remembering the reason for this incorrectly but I think it was somehow safer for the skaters to try and avoid skating down the sheet joins. There was also a specialist skater’s ply that you could import from the US but as we were in NZ the shipping price made this prohibitive. Skaters also like a pipe almost completely buried in the join between the flat part at the top of the ramp and where the curve drops off. I used an ordinary galv scaffold tube I think: they may call this the transition? I dunno. Was a long time ago. I’m sure there is plenty of info about this online.

EDIT
Sorry forgot to mention that while it had to be bullied it wasn’t too hard to bend the ply into the curves. I was worried about this too. Screw as you go to avoid delamination or snapping.

Also, 1m doesn’t sound wide enough to me. If they started skating in the middle they could only deviate/wobble etc. by 500mm before falling off. Make it as wide as you can. It’s much safer for them.

 

[Bm101]

Great advice from DBC above.
When I was still in black and white I used to be a skater. *Knees creek in sympathy
We once raided a local timber supply yard for 8mm ply to build a mini ramp. Looking back it was probably a bit misjudged morally.... but skating wasn't a crime even if breaking into the local wood yard probably was.
An (older) bloke I used to skate with got sacked from his job repairing wooden train doors because of random doping test. He later became world renowned ramp builder by all accounts. So sometimes it appears, crime does pay.
A different world now....
Point being, in this day and age, there is a veritable flood of information online. Google miniramps or halfpipes and you will be inundated with plans and relevant information on everything from ply sizes and types to gradients and how to attach coping rails and plans on drop ins and etc etc etc...
Skateboard wheels are very small and need the smoothest possible surface. It's also well worth considering using a sacrificial thin surface layer if it's going to be used long term.
You are going to be a very popular Grandad!
Project pics please!
https://en.m.wikipedia.org/wiki/Half-pipe
Ps. A mini ramp and a half pipe are different beasts.

 

[Bucky]

This is what I used. Also good for veneering.
https://www.roarockit.com/thin-air-press/

 

[Ollie78]

I have made countless ramps, for BMX mostly.
I like 3 layers of 6mm ply. Two layers of 9mm birch is great on bigger stuff but bending it is tricky.
Overlap them at the point they come to the ground which creates a nice transition from flat with less lip. I know skateboarders often put a small metal strip but for bmx it doesn't need it.

I get all my thin layers cut to size (each bit longer than the one before) then fix the first one down with short screws, glue the entire surface with a waterproof glue polyurethane is quite good for this.
Then layer 2 , repeat for layer 3.
Try to put just enough screws in the under layers to hold it and offset them, then on the final layer go all up each edge and thoroughly accross the ribs, It will become a strong laminate once dry.
These don't last forever especially outside.

Proper ramps use Skatelite which is a very expensive type of HDF like valchromat but they only use it on the top skin.

Have fun

Ollie

 

[Hand Plane]

Many of the replies have come up with points of which I have already had thoughts! I must admit the bent ply in stores must be for some strange things as nothing like our project!

joshvegas – Part of the deal for the ramp is that grandson gets involved with it (once I have sorted out materials and how to go about it).

I have had both grandson and granddaughter doing projects since they could handle tools – see recent photo. They might be faster at computing/internet issues, but I can still hold my own on other things!

Someone's got to help develop their hand skills and confidence to tackle things as they don't get the sort of stuff we got at school. Imagine wanting to be a brain surgeon and never sawn a piece of wood or wondered how to put something back together!

Today's school kids miss out compared to what we did including woodworking machines (bandsaw and lathe); metalwork (blacksmith's furnace; forging; brazing; lathe; power hacksaw); science things that flash and bang! All of which helped in later life.

I think we'll go for laminating thinner sheets (not the bendy stuff) taking into account the various advice points given, increase the width to standard sheet size etc. For what looks like a simple object, it has taken a lot of thinking time!

Many thanks to all responders

 

[Ollie78]

Many of the replies have come up with points of which I have already had thoughts! I must admit the bent ply in stores must be for some strange things as nothing like our project!

joshvegas – Part of the deal for the ramp is that grandson gets involved with it (once I have sorted out materials and how to go about it).

I have had both grandson and granddaughter doing projects since they could handle tools – see recent photo. They might be faster at computing/internet issues, but I can still hold my own on other things!

Someone's got to help develop their hand skills and confidence to tackle things as they don't get the sort of stuff we got at school. Imagine wanting to be a brain surgeon and never sawn a piece of wood or wondered how to put something back together!

Today's school kids miss out compared to what we did including woodworking machines (bandsaw and lathe); metalwork (blacksmith's furnace; forging; brazing; lathe; power hacksaw); science things that flash and bang! All of which helped in later life.

I think we'll go for laminating thinner sheets (not the bendy stuff) taking into account the various advice points given, increase the width to standard sheet size etc. For what looks like a simple object, it has taken a lot of thinking time!

Many thanks to all responders

View attachment 133978

This is great, important get them doing real stuff. I try with my kids.
Even when I was at school they had decided that real woodwork and metalwork was not important and that computers were the way to go. Our school had great facilities with lathes and everything but just gathered dust.
Luckily I was let loose in my Dad's garage at home.
It is amazing the number of people around with very minimal practical ability to say the least.
Glad your grandkids will be alright in this regard.

Ollie

 

[joshvegas]

For what looks like a simple object, it has taken a lot of thinking time!

To be fair it is a device for launching a loved one skyward... It would be nice if they came back down the same condition they went up :-D