Micro sled version 2.0

[jhl.verona]

Hello Woodtalkers,

I know, I know, all I'm doing is publishing designs - nothing built yet. I suppose that never happens to you...

The original, built 15 years ago is here.

The sketchup for the new micro sled (any similarity to Star Trek is intentional):

Rear view:

Two side views:

As seen from underneath:

and, of course, the sketchup file: micro-sled.skp

This is tea tray technology™ - the thing is about 14 1/2" by 14 1/2".

One interesting point: an Australian friend tells me that wooden sleds are prohibited there, plastic is fine apparently. I'm checking here in Italy, but finding the right person to ask is tricky...

This is the jig I'll use (thought police permitting):

Bottom jig (the sled is built upside down):

Top jig:

Both jigs together:

and again, but wireframe:

Sketchup file here: micro-sled-jig.skp

I didn't draw them in (too difficult for me) but there will be pass through bolts to clamp the top and bottom jigs together, and the 'floating' wing blocks left and right.

I've asked on an Italian WW forum and they suggested polyurethane glue, and a polyurethane epoxy finish - going to get some abuse on the slopes.

I'm trying to find something like your birch ply for the body - three laminations of 4mm (say 1/8"). The runners will be three 5mm strips of hard wood (about 1/5") - any suggestions for the essence here?

Any thoughts you may have (critical or otherwise) greatly appreciated...

TIA

John

[iSawitFirst]

Good looking sled and well thought out. Can you get bendable plywood there? That would be the way I'd go. If not, maybe try 1/8" wood laminated.

Will the "wings" have LED lights?

Good luck!

[jhl.verona]

Good looking sled and well thought out. Can you get bendable plywood there? That would be the way I'd go. If not, maybe try 1/8" wood laminated.

Right now I can't seem to find anything even remotely approaching what I would call plywood. In Italy there only seems to be either the "Big Boxes" Marlin-Le Roy or Brico (and it's all poplar), or commercial building suppliers (still poplar, just bigger pieces).

The stuff I'm looking for is very similar to your Baltic Birch, or Finnish Birch. I can can get very thin pieces (even down to 1mm) with very thin layers, about 0.5mm or less, from model shops, but they only keep very small pieces - and they're not letting on as to where they get them. Still it's amazing to see five ply 3mm plywood!

The worst curve is for the wings - they're 45 deg on a 20mm radius in my sketch. Don't know if that's really possible, so I'll have to do some experimenting - which will be the fun part. I can always start the curve earlier and use a larger radius, or go to 3mm and four layers.

Will the "wings" have LED lights?

Good luck!

That's an optional. But if you order the power steering and SatNav, then they're suppiled free

John

[iSawitFirst]

Maybe the curved pieces could be cut from solid wood and connected with splines. That would leave only the seat and runners to be bent which could be done with thin pieces laminated.

I suggest you put a radius on all the corners for safety. It'll give it a more sleek, sensuous look. More like a Jem 'Hadar Attack Ship.

[jhl.verona]

Hmm, things aren't working out quite as well as I thought...

Maybe the curved pieces could be cut from solid wood and connected with splines. That would leave only the seat and runners to be bent which could be done with thin pieces laminated.

I bought some 3mm Baltic Birch - it's called compensato di betulla avio in Italian - in fact it's used to build aircraft, not just models, but ultralights too.

It's a small panel (actually got it from a model shop) here:

I tried to show the side, but my camera's not really up to it - the board is at the bottom, I used some balsa to try to convince the camera to focus on that - didn't work too well :

Anyway there are six plies in it. It's actually two 1.5mm 3 ply boards glued together! How do they do that?

Unfortunately, it's also incredibly strong. I can just about get it to follow the seat curve. Not a chance of it bending to 45 degrees in anything like a 20 or 30mm radius.

I suggest you put a radius on all the corners for safety. It'll give it a more sleek, sensuous look. More like a Jem 'Hadar Attack Ship.

Yep, the corners will be radiused, I just couldn't convince Sketchup to do that - it refuses to carve away pieces on a curved surface.

So - plan B. I looked around for 'bulk' purchases of 1.5mm ply (which will bend more easily), and found some USA side of the pond at $16.75, a bit more than €12 but of course the shipping would cost a fortune. But lo, they have a European channel too, same product code and all. Unfortunately something got lost in translation because here it costs €19 a sheet. Hmm, I'll end up way over budget.

Not giving up though. I'll keep the cost down by using a sandwich, ply top and bottom and kerfed hardwood in the middle. I'll look for something like 10mm x 50mm from the big box stores - it can't warp that much over a 400mm length, surely.

But to attach the wings I'll have to cheat, using a small piece of bent duralumin which I'll surface with the 3mm ply - that will bring me to about 9mm for the wings, and 13mm for the body. Hopefully it will still remain light weight, and not bust the budget.

It's becoming a sort of modelling project I'm afraid... Still I have finally managed to find some 18mm Baltic Birch for the television table...

John

[iSawitFirst]

If you need to you can cut very shallow kerfs across the ply to help it bend.

I'm not familiar with Duralumin but it sounds pretty cool. Just the thing for this application.

Post pics of your progress.

[jhl.verona]

The build begins...

Warning: the equipment used for this project might make you wince

I never can cut straight in vertical, so this time I used a small piece of 'L' shaped aluminium as a guide - worked well, and stopped the tenon saw from bruising the plywood:

(yes I use a chair as a saw horse)

The three centre pieces of the jig, clamped together with screws, being squared up:

I couldn't convince Sketchup under Linux to print - just got a lot of black pages, so... DYI pantograph:

Starting the curve cut. I used a hack saw. Didn't bind once, so I think a band saw can cope with this curve:

I've run out of image space - I'll continue in another post...

[jhl.verona]

... 45 minutes later (who needs to go to the gym?):

The results, not perfect, but good enough, after all this is a jig, not the finished product. The cut off I did by eye, and yes it's not square, maybe next time:

A little bit of cleaning up those rough surfaces, cut the two base plates for the jig. Done for today - I'm exhausted, 4 hours sawing, 2 sanding... zero watts of electricity consumed!

John

[jhl.verona]

The saga continues...

I used a sharp knife to score the start of the kerfs for my saw...

I had to make a kerf every centimetre to get the curve I wanted. An interesting experiment (and another hour in the gym). You've got to be really careful with the depth of the cuts, too deep and you see a prominent line on the 'good' side.

Still, the two jigs lined up much better than I had expected:

Finally a little hardware for the clamping system, and I can now pronounce the jig complete:

For the actual sled I had to go to the not so local big box - it's called Brico here. They had a vast choice of two types of strips, Kotò (they called it Coto) or Mahogany. Well a sort of dark brown wood anyway. The Kotò came in 5mm thicknesses, so that's what I bought.

A quick search on the Internet tells me that it's a couple of grades above box wood - used mainly for the internals of modern furniture. Sigh.

Well it's light in colour and weight, and very hard (using the calibrated thumb nail indentation test).

Cut into lengths of 350mm and I was hoping it would bend, just a little. No chance. It has a not very pleasant odour, and the saw blade binds in the saw dust. Probably full of silica or resin or something.

But I'm not giving up yet. Done kerfing, but I don't have a steam bath handy, so... First test is going to be a good soak (hour or two) in hot - as in boiling - water, followed by a couple of minutes in the microwave. I kid you not. Off to the kitchen...

John

[jhl.verona]

Success noticeable by it's absence...

Take three 20mm strips, boil for an hour, then cook in the microwave for three minutes at 1000W. Place the pieces in the jig for a day, then let dry out thoroughly for two days. Delicious with whipped cream...

View from the front: "Kotò has interwoven fibres" I read somewhere - they weren't kidding.

View from the side: What happened to that curve?

Right now I've glued up three more (without going anywhere near the kitchen) using a polyurethane glue, hope it holds, we'll see tomorrow:

So the sled body has had to undergo some drastic rethinking. I purchased some poplar plywood (it's difficult to find anything else here), three layer, 5mm. Three sheets cut to size bend in the jig (I tried earlier today). But poplar plywood is not exactly the hardest of materials, so I want to go composite - two layers of plywood and the bottom layer in Kotò. Put this little cocktail in the jig, added 80Kg of weight, but only got about half the necessary curve. I wanted to add another 20Kg, but the dog wasn't having any of that.

So, step down off the jig, take the 80mm width strips of Kotò and cut them down the middle. But I'll have to wait until I can free up the jig, tomorrow.

Anyone know where I can buy cheap plastic sleds?

John

[jhl.verona]

Today the barometer has swung from 'depression' towards 'moderately optimistic'...

The 20mm slips that I glued up yesterday seem to be holding.

I prepared two channels on each side for the angle brackets I'll be using for the wing supports (couldn't find any Duralumin in the end, the brackets are 90 degrees, but I'll bend them back to 45):

Even with the body strips resawn to 40mm, the thing only gets to half the curvature. So... ferret around in the cellar and bring out the big gun - my cheap and cheerful plunge router.

Using a 6mm bit and cutting depth of 2mm, I cut a few blind dados - works like kerfing. Noiser but gentler on the muscles:

The dry build worked out fine:

Now it's in the jig. Tomorrow will tell if things are now running in the right direction.

I've put the glued up thin strips on top so you can see the result.

Funny stuff that polyurethane glue. Seems to produce a tight bond, but the squeeze out foams up similar to polystyrene though a bit more rubbery. Fortunately a sharp knife gets rid of it.

John

[jhl.verona]

Big day for me, removing the sled body from the jig - difficult to do with your fingers crossed...

The results:

I'm going to call that a success - much less loss of curvature than I expected. Obviously a very good glue.

Matches up with the one runner I've built so far:

The success went to my head, so I took a few 'mockup' photos of how it will look in the end:

Another plus is that the all-up weight will be just about 1Kg:

which is half a kilo less than the original.

John

[jhl.verona]

A truely memorable day...

I was ruefully contemplating rasping away at all those bits of wood, with vivid memories of all those planes in my father's garage... Couldn't bare it.

So I when down to the cellar and rooted about in the cardboard boxes that I had sent over from the UK when I sold my parent's house.

An hour and a half unpacking stuff that's been there over two years now, but it was worth it. Found two old friends:

Now they aren't exactly Lie-Nielsen, but they certainly bring back plenty of memories.

So they need some TLC which they'll get shortly, but just like finding an old car that's still got some oil, water and fuel, I couldn't resist.

Set the block plane to the pieces and thoroughly enjoyed myself for over an hour, and everything is beautifully finished (at least by my standards).

I know that the block plane is a great unknown, but what type of plane is the bigger one? It says Bailey on the shoe, and it's 9 1/2" long.

John

[jhl.verona]

First prototype ready for finishing...

I forgot to photograph the wings being glued up. I'll try to capture that on the next sled. There are some lessons to be learned here for me...

I had originally planned to glue up the runners in the jig. But... I'd already glued the wings on, so it won't fit. Looked at the jig, looked at the saw. Nah...

So I gathered together all my clamps, that's four if you include the spring clamps. Did the job though:

You can see the mistake (well the bigger mistake) in the first photograph. I just didn't get the right angle by eye for the wing - and didn't have enough patience. Going to have to build me a sort of shooting board, me thinks. The joint is quite tight on the other side. Repeat after me, polyurethane glue is not a filler glue...

Ok, so I spent an evening with the rasp file and some sandpaper (120 grit) for some soothing 'zen' sanding. Do you contemplate life, the universe and everything when your sanding? So I've snapped a few photographs (I'm actually quite proud of the results so far - I've never been this good before):

One last minute modification was to saw the wings so that the sled lies flat upside down. Looks a bit sleeker, thought about people then sitting or standing on it that way up - hope not.

If you're tired running after the kids, it makes a great 'cushion' on the snow. Wood's also a good isolator, and you don't get your behind wet.

Next I need to think about finishing. Here's some ideas using acrylics, black is definitely out, it doesn't absorb evenly:

Lessons learnt for the next one:

1. Shouldn't have cut the dado closest to the front edge. I trimmed that edge back with the plane so I don't know how much wood is left, and I couldn't put a good round corner for fear of cutting into the dado.

2. Must take more time over the wing angle, plus make the dado for the brackets longer. Planing the angle reduces the length. I had to hack saw off a couple of millimeters from the bracket.

3. Get as much of the glue off before it sets. The polyurethane foams up due to the high humidity in the air (compared to the wood). Need to dig out my acrylics spatula for that.

John

[PaulMarcel]

I got behind on reading this work-in-progress thread. Nice documenting and great pictures. Makes me miss sledding; the best you could do here in Arizona is sand-boarding (nothing to do with water-boarding )

You didn't get much spring-back at all especially considering that you were using real ply as opposed to a bending ply.

Are you planning on painting the underside or leaving that natural? Seems like the paint will wear off quickly even though snow is pretty slick. One mogul and game over (for your butt, too).

[jhl.verona]

I'm a little behind myself...

I got behind on reading this work-in-progress thread. Nice documenting and great pictures. Makes me miss sledding; the best you could do here in Arizona is sand-boarding (nothing to do with water-boarding )

Ah, yes, snow is a required feature I'm afraid. The youngest recipient (5 years old) is in Doha, Qatar, right now, so this may not be such a brilliant idea as a Chrstmas present. They have ice rinks though - perhaps I can rustle up a hockey stick? Got any plans? Last time I played (got a friend who still does) though, we used these.

OT: So you're an ice hockey fan living in Arizona? Gooood planning

You didn't get much spring-back at all especially considering that you were using real ply as opposed to a bending ply.

No I didn't, that surprised me too. Damn good glue is all I can think.

I'm still a bit depressed that I can't find a 'serious' wood supplier round here, been on the road about 8 hours in the last month searching. It's either Big Box (hardly any 'wood', most of which is uncertified, Kotò, Samba, ecc, or poplar ply, or premade fir table tops), or wood merchants - hunk of wood, remove the creepy-crawlies, plane and edge. Just need to find somewhere that'll give me some boards pre finished, not easy.

Are you planning on painting the underside or leaving that natural? Seems like the paint will wear off quickly even though snow is pretty slick. One mogul and game over (for your butt, too).

I'd like to leave them natural (otherwise I could have made the thing out of fibreglass or something). I've found a pretty tough varnish, similar to marine varnish. Won't stop the scratches, but I'm expecting that. The bottom will be waxed (ski wax) which provides some extra friction protection. This is not heirloom stuff, be nice if it lasts 5 or 6 seasons though.

Ah, the moguls. That's the really fun bit, any fool can go down a slope on a sled (me, for example). But to crash spectacularly in a flurry of powder after becoming airborne attempting that giant mogul - now that takes great skill! I've awarded artistic points to my (then) kids many a time - all covered in snow (9.4), depth of the landing crater (9.7), apparel - one glove lost, goggles skew-whiff, and size of cheesy grin/smile!

I've also noticed that while a traditional sled tends to keep going to the bottom of the slope - with child/parent in hot pursuit, the micro sled (version 1, of course) stops pretty quickly - without the weight on top it soon spins or flips over

[jhl.verona]

I've just put the fifth sled in the jig...

There were a few mishtaks, I didn't take enough time over the second glue up, the result:

- that one's going to have an unusual curved front and back - there's not enough material to plane it all away (because of the internal dados). "No two the same"TM - couldn't if I wanted to.

Now I tape up the corners, it stops the laminates slipping when I bolt down the jig.

Some pictures of the wing preparation. Cleaning out the slots with a 2mm drill bit (also used as a file - it works):

Preparing the sides:

The 45 degree shooting board in action:

Bending the steel angles, start:

... and finish:

The finished angles:

Bending with the clamp, one side stays flat, and one has a curve. The curved side goes in the body, that way the joint is a little lower which helps bring the wing into line with the top of the body because of the 45 degree angle. So the 10mm wing at an angle of 45 degrees is 14.1mm long which matches the 15mm side (near as dammit).

John

[Bobby Slack]

It looks like you will be ready to use this soon. It just started snowing in the mountains in California, I am assuming the Alps are getting some white stuff these days.

[jhl.verona]

Absolutely. Some of the higher altitude slopes are already open. So "time is of the essence"... Five down, three to go.

Although parts of Verona, Vicenza and Padova (Padua) have been flooded by torrential rain (and it's still raining), this probably means that it will be a good year for snow. At least according to the black cloud/silver lining theory.

John

[jhl.verona]

Just a quick rundown on getting the wings installed.

Firstly, a small success - using tape to keep the laminations together before going in the jig - works:

Also an apology for the quality of the photographs. I think it's the lens, but it could easily be the organic material behind the camera...

Using an angle to 'break-in' the mortises:

... and getting the damn thing out again:

... sometimes more persuasion is required:

With the 45 degree angles inserted:

The joint from the top (this is really tight by my standards):

... and the bottom:

There will now be an assembly and sanding pause - of about ten days probably...

John

P.S: I changed the images, the others were truly appalling.

[jhl.verona]

Progress (of sorts) report...

63 20mm strips:

have become 21 runners:

for the other seven sleds (getting their wings glued up):

Seems the snow gods are appreciative of my efforts:

John

[Bobby Slack]

Oh yeah! the sliding season begins! I like your tropical/winter garden. You have to post a video via youtube on the first slide ...

[jhl.verona]

Today I finished preparing the last sled - that was a lot of sanding, seven evening's worth, I've almost run out of zen...

First, the traditional ultra detailed tutorial (my notes for a future build).

Once the runners are glued on the sled looks like this:

Using my new Ryoba (the small one, which I'm really enjoying - the big one is still pretty scary to me) cut away the angles:

Then smooth over the cuts with the rasp:

Next grab the sandpaper, and use much zen:

Finally, the results to date:

In formation:

Low level fly over:

Ready for vertical lift off:

All your base are belong to us!

John

[Vic]

Today I finished preparing the last sled - that was a lot of sanding, seven evening's worth, I've almost run out of zen...

First, the traditional ultra detailed tutorial (my notes for a future build).

Once the runners are glued on the sled looks like this:

Using my new Ryoba (the small one, which I'm really enjoying - the big one is still pretty scary to me) cut away the angles:

Then smooth over the cuts with the rasp:

Next grab the sandpaper, and use much zen:

Finally, the results to date:

In formation:

Low level fly over:

Ready for vertical lift off:

All your base are belong to us!

John

Looks cool, John! Those are for packed snow, I'm guessing?

[iSawitFirst]

That's the best for sledding.

Great job, John!