Laminated Double Curved Tiller

[Clyde_Wanderer]

I had a peice of mahogony 150x45mm from which I want to make a tiller.
I took it to a local joinery shop to have it sliced into 8mm thick slices.
I am going to have a go at laminating it myself but would like two layers of a lighter coloured wood.
Is the mahogony suitable?
What other wood for lighter colour?
What best way to make a jig? I have searched the web but not found anything of much use.
C_W

 

[sailorman]

I had a piece of mahogany 150 x 45mm from which I want to make a tiller.
I took it to a local joinery shop to have it sliced into 8mm thick slices.
I am going to have a go at laminating it myself but would like two layers of a lighter coloured wood.
Is the mahogany suitable?
What other wood for lighter colour?
What best way to make a jig? I have searched the web but not found anything of much use.
C_W

a flat board with blocks fixed with a single screw (to allow articulation)
placed to the desired curves. cramp the laminated to the blocks

 

[VicS]

I had a peice of mahogony 150x45mm from which I want to make a tiller.
I took it to a local joinery shop to have it sliced into 8mm thick slices.
I am going to have a go at laminating it myself but would like two layers of a lighter coloured wood.
Is the mahogony suitable?
What other wood for lighter colour?
What best way to make a jig? I have searched the web but not found anything of much use.
C_W

Ideally you want to use two woods with similar physical properties as well as being adequately strong. There was an article in PBO some years ago that suggested two woods that I had never heard of!. I suspect ash is the light coloured wood normally used.
The slices are thinner than 8mm i am sure

You need to make a jig to which you can clamp the slices in many places.

From a purely engineering point of view the double curved laminated tiller is a very bad design

I don't know if I still have the PBO article. I may have kept it and I may even have filed it. I'll look for it

 

[Tranona]

For the light colour suggest Ash, Douglas Fir, or if you can get it good quality Parana Pine ( Brazilian softwood often used for window sills and stairs). As Vic says double curve can be tricky if the grain does not follow the curve. The light coloured woods are generally not as durable as mahogany, so definitely need good protection - a canvas condom does the trick - no need to go overboard on the coating. For the jig sailorman's suggestion good, but you may find it better to use short lengths of angle iron for the blocks. That sort of jig will cope with moderate curves, but if they are severe then 8mm is probably too thick for the laminates and you may need to go for a more sophisticated jig. Two side pieces in MDF making the curve and slats across to clamp the laminates against. Think of a humpback bridge and you will get the picture. Lot of work for a one off! But as there is little decent on the telly this time of year, probably a better use of your spare time.

 

[earlybird]

I think that you will find 8mm is really too stiff to form a reasonable curvature. I'd go for no more than 6mm.
If you go for contrasting woods in a tapered tiller, then, for best appearance IMHO, the individual layers should also be tapered. A difficult task to do neatly.
You need lots of G-cramps to ensure close glue lines, one every 3 or 4 inches is not too many.
Hope that helps.

 

[Clyde_Wanderer]

I may be able to make a jig from grp as the curves are very shallow/open.
Went for 8mm as I wasent sure how much would be lost from the peice due to blade thickness, but I could get them planed down. Or would it be an idea to steam them and clamp them in jig for a few days before laminating giving them time to fully dry while taking the shape?
Incidently are the "canvas condoms" available in a three pack
Thanks.
C_W

 

[john_morris_uk]

I may be able to make a jig from grp as the curves are very shallow/open.
Went for 8mm as I wasent sure how much would be lost from the peice due to blade thickness, but I could get them planed down. Or would it be an idea to steam them and clamp them in jig for a few days before laminating giving them time to fully dry while taking the shape?
Incidently are the "canvas condoms" available in a three pack
Thanks.
C_W

If they are 'sawn finish' at the moment, then you might be better to run them through a planer thicknesser to get a reasonably flat surface to take the glue.

 

[Cap'n Creosote]

As others have said 8mm is a bit thick for that, but it depends on how much curve you want. Have you tried bending one piece to see if it will bend to the required curve without breaking?
Mahogany is very susceptible to cross grain fractures, but if it will go round the former it'll be ok.

Ash for the light coloured wood will bend easily and steams well if necessary, Mahogany can be steamed but you won't get tight curves with it.
I would not recommend Parana pine, it doesn't bend well and it's durability record is appalling. Keep it for window sills.

When I made my tiller (all Iroko, no stripes) I steamed all the individual pieces to aproximate shape, then cut the serpentine shape out of a few pieces of MDF totaling 2" thick.
A couple of sash cramps across the whole lot pulled them to shape. I thought about using epoxy but I had plenty of PU glue so I used that.
A few years on it's fine.

Nothing wrong with sawn finnish, so long as it's fine & true. But if it's rough & jagged get it planed. And then roughen the surface a bit to take the polish off and key the glue.

 

[Tranona]

Depends on the parana pine. I have some tucked away in my garage from my conservatory framework of 30 years ago which bends well when I have used it in the past. Lovely red streaks in it for visual appeal. Durability for a tiller is only an issue if you don't cover it when not in use, or if it goes into a socket on the rudder head. However, not sure what the stuff you get these days is like.

 

[PuffTheMagicDragon]

5 - 6mm would be the thickness of choice if you will have at least three dark and two light-coloured laminates at the narrow end; the deeper end can receive more strips that are shorter. Have sufficient width and length of strips to allow for shaping with a plane and a spokeshave. I prefer to draw the shape full size on a chipboard sheet and having the wooden blocks with a slight curvature to the face that just touches the line. Blocks are firmly glued and then screwed from beneath. Don't forget to lay a polythene sheet on the board so that the glue doesn't stick to it. If you can obtain two thin metal strips of the same width as your wood place one inside and one outside the shape; this will give you a smoother curve and will also allow you to put even more clamps between the blocks as necessary. Resist the temptation of removing the laminates from the jig before three or four days have passed, even if your workspace is heated. All of these were learnt the hard way.

The thrill that you get when you have planed the laminates down to an even surface and shaped them to the contour that you are after is only matched when you have applied your final coat of varnish.

P.S. I used Ramin and Mahogany.

 

[Twister_Ken]

Found this!

And this. Amazing!

 

[Boo2]

From a purely engineering point of view the double curved laminated tiller is a very bad design

Why is this, Vic ?

Boo2

 

[PuffTheMagicDragon]

Found this!

Interesting bit of laminating.

To OP: Notice the metal strips in the first photo. Note also that, if you go for the moulding formers, the 'male' does not fit the 'female'. This is a common mistake. In other words each part of the pair needs to be cut individually, the two curves being separated by the finished thickness of the laminations that will go between them.

 

[Boo2]

I think that you will find 8mm is really too stiff to form a reasonable curvature. I'd go for no more than 6mm.

6mm is going to be easier to bend than 8mm but Sunrunner has a laminated tiller (see pix) and assuming it is 3 inches thick the 10 laminations visible would make them 7.6mm thick so obviously it can be done... Edit: Just measured them today and the laminations are about 5.5mm thick, not as I stated.

If you go for contrasting woods in a tapered tiller, then, for best appearance IMHO, the individual layers should also be tapered. A difficult task to do neatly.

The tiller pictured has the laminations all made from the same wood and you can see in the shot of the underside where the glue has darkened due to UV exposure. For this reason it would be better to take all the taper from the bottom of the tiller if you don't do as Earlybird suggests, that way the tiller looks OK from the top. Also try to keep any rounding within the top layer of wood for the same reason. Or use a glue which, unlike epoxy, doesn't darken with exposure to sunlight.


Boo2

 

[boguing]

Ash is great structurally, but suffers badly if water gets to it. Goes black.

Holly is good.

 

[Quandary]

Ash is great structurally, but suffers badly if water gets to it. Goes black.

Holly is good.

I cut down a couple of about 12" dia. holly trunks last year, ( supposed to be unlucky, so it explains some events) amazingly heavy dense clear white wood and they have dried out without any splits or shakes, unfortunately I did not have the foresight to leave the bits long enough for a tiller. I was going to give it to my brother for turning bowls etc. but they will probably be split for the back of the fire.
I must carry out a durabilty test by leaving a sawn bit outside for a while but do not hold your breath.

What is described as parana pine these days, (the stuff with the red flashes) is nor regarded a durable for external use in construction, though it makes nice shelves.

 

[Scotty_Tradewind]

8mm a little thick as others have said. For many hard woods which you want to bend and shape you may be wise to go to 3-5mm if you'r not steaming.

The easiest of the common timbers to bend without steaming is probably ash. I've had two tillers made from ash. The downside to ash is that it must not be left uncovered by a finish as it does rot/go black easily. Therefore knocks and breaks in the varnish on ash, should be touched up as early as possible. (boo 2 's picture of a tiller, an excellent example where if ash a touch-up of varnish need be applied)
The upside to ash is that it is a wonderfully springy timber and so small vibrations etc can be less irritating.

My son, a cabinet/stair maker and I, made up three beams as mast step supports in my last boat from european oak. The beams had a slight curve so we experimented and made the individual lamins 6-7mm.
We made up an mdf former which was fastened down to the bench. On this we dry attached the first lamin with plastic nails from a compressed air nail gun. (You can also get plastic staple guns.)
We made up the remaining beam with the lamins glued down with 5 minute polyurethane glue, again held down with plastic nails.
All three beams were finished one/night, (10-14 lamins depending on which beam). We used plastic nails the same colour as the timber, the beams could then be put through the thicknesser as the plastic nails are planeable and then 'fashioned' a little with a beltsander. Beltsanders in the right hands can produce an excellent accurate finish.
A veneer of oak was put on the underside of the beams so as to not show any sign of the plastic nail ends when finished.

If using dissimilar woods to effect a stripey effect, you may be wise to lay-up the 'softer/springier' timber a little thicker than the less soft timber, so that they are similar in flexible strength when glued up. I've seen situations where no notice of this had been taken and the less flexible less springy timber had cracked accross the grain, weakening the piece of work.
Try and use lamins with longitudinal grain, not a flowery grain.

 

[lesweeks]

You don't actually say what shape the double curve needs to be. On my ongoing 'project' the tiller needs to wrap around the mizzen and so my double curve is horizontally flat.

There is lots of sound advice given above, but imho:

1. Mahogany (Hmmm, only two true mahoganies but lots of others species sold 'as') can be rather brittle and is frequently cross grained - which might mean short grain across the layer meaning it will easily/certainly snap as soon as it is bent - so it might be a good idea to either steam it or gradually pull it into shape, dry, over a few days.
2. Ash is beautifully flexible (and is what I used) and is perfect for the job of a tiller, but it doesn't like water getting at it and so needs to be well finished and looked after. I'd use it or maple/sycamore for the light stripes.
3. 8mm is far too thick. On mine I used 13 layers of 4mm thickness and thast took some pulling!
4. I used epoxy for strength and because, when mixed with microfibres, it fills, without weakening, any small voids that might occur.
5. You can never have enough cramps!
6. Sawn surface is good - assuming it's a tipped blade on the saw and not a rip blade (rough and hairy finish).

I planned the process very carefully on paper first and then made up the various pieces for the former. In the picture below only the two lefthand pieces were screwed down to start with and then each subsequent pieced screwed in place as the bending and cramping progressed. Mine might be more extreme than yours, but the principle remains the same.

 

[stav]

Wow that is some little kink! V impressed.

However, from my woodwork days seem to recall laminate to radius was 1:200.

I have used oak for light wood in a laminated tiller. Holly would be lovely and probably pear or apple would do.

Sounds like no more than 4mm for the layers should work.
Would also second the use of epoxy or a resourcinal would do but will give dark lines.

What a nice job to do. Enjoy.

ALso make sure it is not too dry. If it has been in the garage for ten years might be worth giving it a steam from a kettle (or just pour on boiling water) or steam from a wallpaper striper. If using extramite could then just wipe off excess moisture and get on gluing it.

 

[srp]

Just made a batch of tillers for Corribees, some from solid and some laminated. The Corribee tiller has very shallow curves, so 8mm laminates, planed and not steamed were fine. Even with the shallow curves the jig has to be strong. Polythene to cover the base board, and parcel tape on the clamping blocks. Sharper curves will need thinner laminates as illustrated perfectly in lesweeks post above.

I only ever use epoxy - I haven't found any other adhesive that is up to the job long-term (and I have a personal hatred of Cascamite or whatever they call it nowadays as it has failed so many times in my experience).

My preferences for timber based on suitability for exterior marine use include Oak (English of course, American is useless), Brazilian mahogany, teak, iroko, spruce, Douglas fir, possibly elm if you can get it. I wouldn't use ash as it goes black and is very prone to rot, especially in the unseen areas like the bolt holes.

Despite the fact that I make them, I really don't like the stripey look. For a start, having two different species laminated together is not good because they shrink and swell by different amounts. Secondly, they just look so naff 1960's.

Finally, I have some sympathy with VicS's view - from an engineering point of view a laminated tiller is going to struggle to stay in one piece when a big crewmember gets thrown onto it, particularly if it has had a couple of years exposure to the elements. There is a strong argument for carrying a spare.