How to build a diving board

Build Your Jump

(22/05/2007)
We’ve all been kids, and we’ve all played jumping over a curb, a log, or a rock. Now let’s take it up a notch with a jump.

Last time, we saw how to build a grind box. It was pretty straightforward since it consists only of flat, rectangular surfaces. Now, we’re going to look at how to build a ramp and a jump.

A ramp is an inclined plane that allows you to practice jumps and can also serve as a landing. A jump is curved to induce a transition in the angle of the jump. It can also be used as a landing, but that becomes more complicated.

So, in increasing order of difficulty for jumps, we have:

jumping from a ramp and landing on a table, jumping from a jump with landing on a ramp, jumping from a jump with landing on a jump.


As usual, sadly, we have to include a disclaimer. This means that neither VTTnet nor the author of this article will take responsibility if you smash yourself on the jumps you built yourself, even if you followed the few misguided tips below carefully. So you build them and use them at your own risk. Got it?

Plan and Dimensions

First thing, the dimensions of the ramp. This will depend on your level, mainly what you can jump flat. There’s no point in building a monster that will scare you, or worse, hurt you. And it’s not very useful to build a ramp the height of a curb; your sidewalk can suffice for that.

I recommend that you get on various obstacles with your bike (not necessarily the living room table) and see if you feel comfortable at that height, if you feel capable of jumping it (dropping). Also remember that a jump will send you higher than its own height, so it’s better to aim too low than too high.

If you’ve already built the grind box from the previous article, its height may be suitable, as this will give you a take-off and landing table. This is the basis I started from.

The ramp doesn’t present too much difficulty in planning. Laterally, it’s a triangle. Just be careful with its inclination. We often tend to overdo it and end up with something too steep in the end, and thus unusable.


Personally, I used a slope of 60%, which is about 30°. For a height set at 45 cm, this gives us a base of about 80 cm and a landing length of 90 cm. For a BMX with a wheelbase also of 90 cm, this may be suitable, although it is borderline. I certainly wouldn’t use it as a landing without something like the box in front. For a mountain bike with a wheelbase of about 110 cm, this is not suitable at all, and it needs to be lengthened. I also think that the slope is a bit too steep for a beginner. Something like 20° would be more reasonable. So a good rule of thumb for the length of the landing is to DOUBLE the wheelbase of the bike.

Now for the width. The width of a jump matters little if you are just jumping straight, meaning without rotation like a 360. If you can ride straight, a jump 40 cm wide can suffice. However, the landing must be much wider: you wouldn’t want to land next to it!

For a beginner, a wide landing means that small deviations in take-off won’t lead to a major crash on landing. For someone with a higher skill level, a wide landing means more ease in tricks. So everyone wins. 60 cm is a minimum, but if you can build a width of 90 or even 120, that’s even better!

You can keep the same dimensions for length/height/width for the ramp and the curved jump. The only problem with the curved jump is finding the right transition, that is, the right curvature. For that, no secret: it’s trial and error. But to save you too much trouble, you will find in this article the graph and even the equation that will give you a good transition. It’s up to you to adjust it for the dimensions of your jump.


What I found best for the equation giving the curvature of the jump is the foot of a Gaussian curve. This makes sense if we consider that the jump in its entirety is a Gaussian and that the jump is its base. This is where everyone bursts out laughing (or tears up) at how freeriding leads to mathematics! N.B.: this can also help a math teacher in need of inspiration to motivate his students.

Materials

For the frame that constitutes the skeleton of the jump, I used square section pine posts of 5 cm on each side. Strangely, what is referred to as 5 cm is actually only 4.5 due to sanding (there’s no small profit, carpenter’s saying?).

The side panels are made of plywood (5 layers) with a thickness of 1.5 cm. Plywood has many advantages: excellent rigidity for a reasonably thin thickness, good resistance to weather, and elasticity that prevents it from breaking under repeated impacts.


For the curved jump, the top of the jump (its skin) consists of two panels of 3-layer plywood and 0.75 cm thick stacked on top of each other. This allows for a curvature without generating too much tension in the layers and breaking them. This makes it possible to deform the panel without excessive force.

The screws are wood screws made of steel, 4 cm long, with a countersunk head. I needed about a hundred of them for two jumps. The curved jump consumes a lot of them. We will see the reason for this below in the assembly section.

With all this, I spent just under 100 euros. For a tighter budget, you can always look for reclaimed materials, leftover wood, etc. But I don’t think it’s worth it. As for tools: a drill/screwdriver is essential, a circular saw for cutting the panels, and a jigsaw for curved cuts are welcome.

Assembly


Assembly is child's play for those who know how to handle a screwdriver. However, you should keep in mind that the screw heads must not protrude from the wood, otherwise, you could burst your tires or, worse, injure yourself. There’s no need to countersink the screw holes you’re going to drill since the heads will sink themselves into the wood. However, it’s better to pre-drill the screw holes because, without that, your pine posts may split along their length.

If the frame of the ramp shouldn’t pose a problem since everything is straight, it’s good to think a little about the curved jump. You can no longer use long posts for the curved part; you need to use small sections spaced regularly (see photo and sketch).

As mentioned earlier, the skin of the jump consists of two stacked plywood sheets. The flexibility of the material allows for imposing curvature. The first sheet is directly screwed onto the side reinforcements, and the second is screwed through the first onto the stringers. Be careful to mark your spots to hit the middle of these.


To avoid having too thick an attack edge at the start of the jump, I let the second plywood sheet extend beyond the first at its base. This allows the jump to be used with smaller wheels like rollers. For a skateboard, the 0.75 cm thickness of the sheet will still be too thick and will cause it to hit. So you need to place a metallic sheet with a fraction of a millimeter thickness at the base of the jump.

A few tips

Before screwing, drill a smaller diameter hole in the wood. This helps reduce the stress in the posts so that they don’t split when you place the screw.

Carefully mark your holes with a pencil before drilling, check that two screws do not cross in the wood.

Cut out the two triangles of the ramp and the curves of the jump by overlapping two panels. This will give you better symmetry.

Take all necessary precautions when you’re DIYing.

Before calling all your friends to come try your new jumps, first check that they are solid, test them (on foot), jump on them, see if the posts don’t move, add reinforcements if necessary.

Always anchor your jumps to the ground, check that they don’t slide back or tip over when you jump. Some loading pallets can work to secure the jump to the landing, or you can use the box to create a table (see photo).

Next time we will see how to build a quarter-pipe, but here we’re bringing out the big guns!

Building Your Ramp

(22/05/2007)
We've all been kids, we've all played jumping over a curb, a log, a rock. Now let's take it up a notch with a ramp.

Last time, we saw how to build a grind box. It was relatively simple as it consists only of flat rectangular surfaces. Now, we will see how to build a ramp and a jump.

A ramp is an inclined plane that allows you to try jumps and can also serve as a landing. A jump is curved to induce a transition in the angle of the jump. It can also be used as a landing but that becomes trickier.

So, in increasing order of difficulty for jumps, we have:

jumping from a ramp onto a table, jumping from a jump landing on a ramp, jumping from a jump landing on another jump.


As usual, we unfortunately need to add a disclaimer. This means that neither VTTnet nor the author of this article will take responsibility if you crash on the jumps you’ve built yourself, even if you have scrupulously followed the few tips mumbling below. So you build them and use them at your own risk. Got it?

Plans and Dimensions

First thing, the dimensions of the ramp. This will depend on your level, mainly what you're able to jump flat. There's no point in building a monster that will scare you or worse, hurt you. Also, it’s not very useful to build a ramp the height of a curb; your sidewalk can do the job for that.

So I advise you to go up various obstacles with your bike (not necessarily the living room table) and see if you feel comfortable at that height, if you feel capable of jumping it (dropping). Remember that a jump will send you higher than its own height, so it’s better to aim too low than too high.

If you have already built the grind box from the previous article, its height might be suitable, as it will give you a table for takeoff and landing. That’s the basis I started from.

The ramp doesn’t pose too much difficulty in planning. Laterally, it’s a triangle. Just be careful with its inclination. We often tend to exaggerate and end up with something too steep in the end, thus unusable.


Personally, I used a slope of 60%, which is about 30°. For a height set at 45 cm, this gives us a base of about 80 cm and a landing length of 90 cm. For a BMX bike with a wheelbase also of 90 cm, this can work although it's on the limit. I certainly wouldn't use it as a landing without something like the box in front. For a mountain bike with a wheelbase of about 110 cm, this is not suitable at all and needs to be lengthened. I also estimate that the slope is a bit too steep for a beginner. Something around 20° would be more reasonable. So a good rule of thumb for the landing length is to DOUBLE the wheelbase of the bike.

Now for the width. The width of a jump isn't that important if you're just jumping straight, that is to say, without rotation like a 360. If you can ride straight, a 40 cm wide jump can suffice. However, the landing must be much wider: you wouldn't want to land next to it!

For a beginner, a wide landing means that small deviations in takeoff won’t lead to a major crash on landing. For someone at a higher level, a wide landing means more ease in tricks. So everyone wins. 60 cm is a minimum, but if you can build a width of 90 or even 120, that’s even better!

You can keep the same dimensions length/height/width for both the ramp and the curved jump. The only issue with the curved jump is finding the right transition, that is, the right curvature. For that, there’s no secret: it’s trial and error. But to spare you too much trouble, you’ll find in this article the graph and even the equation that will give you a good transition. It's up to you to adjust it for your jump's dimensions.


What I found to be best for the equation defining the curvature of the jump is the foot of a Gaussian. This makes sense when considering that the jump as a whole is a Gaussian and that the jump is its base. This is where everyone bursts out laughing (or breaks down in tears) seeing how freeriding leads to mathematics! N.B.: this can also serve a math teacher suffering from creativity block to motivate their students.

Materials

For the frame that forms the skeleton of the jump, I used square-section pine supports measuring 5 cm on each side. Strangely, what's referred to as 5 cm is only 4.5 due to sanding (there's no small profit, a carpenter's saying?).

The side panels are made of plywood (5 layers) 1.5 cm thick. Plywood has many advantages: excellent rigidity for a reasonably thick material, good resistance to the elements, and elasticity that prevents it from breaking under repeated shocks.


For the curved jump, the top of the jump (its skin) consists of two layers of 3-ply plywood 0.75 cm thick stacked. This allows for a curvature without generating too much tension in the layers and breaking them. It thus becomes possible to deform the panel without excessive forcing.

The screws are wood screws made of steel, 4 cm long and countersunk. I needed about a hundred for two jumps. The curved jump consumes a lot of them. We'll see why below in the assembly section.

With all that, I spent just under 100 euros. For a tighter budget, you can always look for recycled materials, leftover wood, etc. But I don't think it's worth it. As for tools: a drill/screwdriver is essential, a circular saw for cutting the panels and a jigsaw for the curved cuts are welcome additions.

Assembly


The assembly is child's play for anyone who can handle a screwdriver. However, you need to keep in mind that the screw heads should not protrude from the wood, or you could burst your tires or worse, injure yourself. It's not necessary to countersink the screw holes you are going to drill since the head will sink into the wood by itself. However, it’s better to pre-drill the screw holes because otherwise, your pine supports might split along their length.

If the frame of the ramp shouldn’t pose any issues since everything is straight, it's good to think a bit for the curved jump. It’s no longer possible to use long supports for the curved part; you must therefore use small regularly spaced sections (see photo and sketch).

As previously mentioned, the skin of the jump consists of two stacked plywood sheets. The flexibility of the material allows implementing the curve. The first sheet is screwed directly onto the side reinforcements, and the second is screwed through the first onto the stringers. Make sure to get your measurements right to land in the middle of them.


To avoid having a leading edge that is too thick at the onset of the jump, I let the second plywood sheet extend beyond the first at its base. This allows the jump to be used with smaller wheels like rollers. For a skateboard, the 0.75 cm thickness of the sheet will still be too thick, and it will bump against it. Thus, you need to place a metal plate a fraction of a millimeter thick at the base of the jump.

A Few Tips

Before screwing, drill a smaller diameter hole in the wood. This helps reduce stress in the supports and prevent them from splitting when you place the screw.

Mark your holes clearly with a pencil before drilling and check that two screws don’t cross in the wood.

Cut the two triangles of the ramp and the curves of the jump by overlapping two panels. This will give you better symmetry.

Follow all the usual safety precautions when doing manual work.

Before calling all your friends to come try your new jumps, first check that they are sturdy, test them (on foot), jump on them, see if the supports don’t move, and add reinforcements if necessary.

Always anchor your jumps to the ground, check they don’t slide back or tip over when you jump. Some pallets can serve to secure the jump to the landing, or you can use the box to create a table (see photo).

Next time, we’ll see how to build a quarter-pipe, but now we’re bringing out the big guns!

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