Boiler Lagging-wood strip sanding jig

[clifforddward]

Working today on the Topaz steam plant...namely the wood boiler lagging.  As in prototype practice, each wood strip needs the sides chamfered in order to fit up closely with no gaps when placed on the boiler.  I suppose in full size practice this would be easily accomplished by tilting the blade on a table saw and ripping the wood to suit.  For model purposes sanding the edge is the method of choice, but in order to make a nice even angle a jig is necessary.  The attached photos show my "purpose built" jig cobbled together from bits of scrap in the shop.  The jig holds each 6" long strip tightly on edge, and the aluminum extruded sanding block pulled along the strip at the far side of the jig assures constant pressure and an even angle. 

Not much complicated science in this jig, but I thought perhaps the idea would be helpful to others doing lagging on a live steam boiler.

Regards,
Cliff

Cliff Ward
Cary, North Carolina
USA

[Eddy Matthews]

Just as a matter of interest Cliff, how did you decide on the correct angle for sanding? Calculation, trial and error, or guesswork?

That's not a smart-ass question, I'm genuinely interested, as I need to make a "dummy" boiler for another project I have in mind....

[clifforddward]

Hi Eddy:

Angle is pure "eyeball" guesswork.....after doing a handful and checking them up to the boiler, I can see that even with this shallow angle the outside edges of each strip touch while the inside edge does not quite meet...that means I should be able to butt them up nicely with no gap. 

Perhaps overkill, but on almost every model commercial boiler with wood lagging there is no angle on the strips and the gap is obvious...I hope my effort will prove a better result.

One interesting thing I am learning is that pear wood is quite hard....tough stuff to sand!  Should finish up nicely though.

Regards,
Cliff

[Eddy Matthews]

Thanks Cliff, I thought it would probably be guesswork - It will be interesting to see the results....

As for pear wood being hard - I've only used it once previously, and I can definately vouch for that comment being correct!!

[clifforddward]

This is my first project using Pear wood.  I started out using 180 grit sandpaper but that proved too fine for stock removal....switched over to 100 grit which worked great...a couple of swipes with the 180 grit after the angle was set smoothed angle surface ready for finishing.

I really like the nice tight grain on this pear....I'm experimenting now with stains and finishes but preliminary results look very good.

By the way, the sanding block I use has raised "safe" corners....this allows the block to slide along a guide without sanding the guide strip out of alignment.  This one was a commercially made unit, but the same idea could be made by gluing a strip to one edge of a sanding block...just enough material to raise the corner so that the sandpaper will not dig into the guide.

And I use the round self adhesive sandpaper pieces available from the big box DIY stores....the sandpaper is generally high quality on a fiber back for use on the radial sander, and the self adhesive part makes changeout on metal sanding blocks a snap...peal off, clean residue with liquid lighter fluid, and stick on a new piece.  It is easy to cut the round pieces to any size needed.

Regards,
Cliff

[crash93]

A tip given to me by Brian Martin was to heat the wood in the oven for twenty min before planking so it shrinks , that way when the boiler heats up the wood the gaps don't open to much , also on the display topaz the planks where not beveled, I asked about that as I had beveled them on another plant and he said that they will shrink and expand and they don't show as much

peter

[derekwarner_decoy]

Hi PD's....I had put this off...for a few years  ..but yesterday afternoon decided to bite the bullet ...& lagged Decoy's gas tank using ....5x1 Ramin...pre beveled & glued with 3 drops of CA on each plank...followed by sanding & cedar stain & waxing  ....24 hours later I am still descaling CA from my fingers & nails.....Sandy mentioned an option of temporary silastic...I think CA is the better option

I am OK with the result & plan to add one 50 mm band on the boiler next weekend.......just the band that is centered near deck level........

[Red_Hamish]

Exemplary work again Derek! You're quite correct util the frame of mind is set to do the task it is often better to put the task off. That way at least you know the results will bear scrutiny and be satisfying for a long time. Brilliant looks and the stain really suits the apparatus well.

cheers

Jim

[Bierjunge]

..but yesterday afternoon decided to bite the bullet ...& lagged Decoy's gas tank

No question, it looks maginficent, but...
...Why do you insulate a gas tank?
Must have something to do with the Australian climate, so we should be confident that enogh gas evaporates anyway...

Moritz

[derekwarner_decoy]

Hi PD's....well Moritz.....I understand many in Europe insulate their gas tank and the French even seem to add steam coils to mantain heat & ensure the gas does not freeze....but in OZ it is the reverse

The gas tank will reside below deck level in Decoys FWD hold & open to the sunshine..... so the lagging was to insulate & attempt to keep cool....as 40 degree C sunlight directly in the tanks black surface would have a high temperature & hence pressure increase

The second reason was to trial  such 5 x 1 planking on a round surface...[with domed ends] so the set square was of little help...if I made a mess of the gas tank I woul not try the boiler lagging

Later on during the week I will call & get a new bottle of ZAP CA standard drytime......

[crash93]

On boilers its best to use High temperature (1200 deg C) ceramic matting I know my topaz boiler was supplied with it and I am  using it on another boiler. I am removing the planking on some of my older boilers to fit it , it stops a lot of the discoloring of planking. the way one manufacturer (MHB) fits it is with double sided tape a few bands of it then a couple on top of the mat to hold the planks before the bands are fitted, I got hold of a boiler to referb last year that had been done this way and been used for about 10 Hard years and the tape was still holding the planks on (Picture)

Peter

[derekwarner_decoy]

Hi PD's .....Crash......Sandy from ACS first posted about the British "KAOWOOL" insulation material on 3/10/2005.....I did not progress beyond here

Just after this I borrowed a digital pyrometer & confrimed a true 152 degrees C at the boiler top & 143 C on the boiler sides...Sandy later confirmed these as typical of an ACS VB2 boiler...etc........ ...if I were to add another 1mm thick X the boiler diameter + the 1 mm thick wooden planking would mean new boiler bands   

[crash93]

not a lot of work making boiler bands, and its only cheap, unless you have elaborate band
Peter

[sandy_ACS]

 

Hi PD's......

From Derek....glued with 3 drops of CA on each plank...followed by sanding & cedar stain & waxing  ....24 hours later I am still descaling CA from my fingers & nails.....Sandy mentioned an option of temporary silastic...I think CA is the better option

My preferred, and suggested, method is to use THICK SUPER GLUE,.....2 or 3 small spots applied to the boiler/tank shell ,not directly to the wood, although I have seen some people use copydex or some other types of instant glue.

Thin CA (super glue) is not recomended, since, as Derek has found, it tends to get everywhere and is very messy.

Whichever glue you use remember....if you don't have a suitable under blanket (such as KAOWOOL) then the heat from the boiler will, in a very short time, render the glue useless at holding the wood in place...... every piece needs to be fully clamped by the boiler bands.
Naturally, this does not apply to a gas tank, since it should NEVER get that hot.

For marking a planking guide line on a tank with domed ends... use the same method as used for marking the waterline on your hull....a soft pencil mounted on a scribing block....hold the tank level on a flat surface and scribe the line.

For finishing the wood surface, especially on a boiler, I would recommend that you avoid using varnish....a water, or spirit based stain can be used to colour the timber to the required tone...then just use a sealer over the top.
I allways use 'TEAK OIL'.
I have tried several clear varnishes over the years and on most occasions this has started to blister and peel in a reasonably short timeframe.
I even got in touch with manufacturers (RONSEAL, JUSTINS etc) to discuss the problem, since they claimed their varnish was good for high temperatures, 150 deg C or so, and the comments received were that this was subject to application...and that in the case of some woods (PEAR ,MAHOGANY, TEAK etc) the high tannin/oil content of the timber reacted with the varnish at higher temperatures...thus causing the blistering etc...they did not, therefore, recommend their products for use under these conditions.

I used to use PEAR WOOD for all my production work, and yes...it can be tough to sand, however, it is well worth the effort.
IMHO it is a far better choice than REAL MAHOGANY.
In full size...MAHOGANY, or TEAK would normally be the wood of choice, however, if used for model size boilers, then the grain appears far to large in proportion....PEARWOOD...treated with 2 or 3 coats of TEAK OIL..... looks very much like SCALE MAHOGANY.

One final point..... in FULL SIZE practice, the timber lagging was not generally used as the insulation material, but rather more as a protective layer. The insulation layer usually consisted of 2 or more inches thickness of ASBESTOS, or laterly a CERAMIC MATERIAL (such as KAOWOOL), however, since this would be vulnerable to damage, an outer layer of some suitable material was added over the top.

Certainly, on open launches (such as small steamboats, Windermere type launches etc) this was also required to look nice, and hence, MAHOGANY or TEAK was used and the plank gaps were usually mitred, however, on most working steam boats/ships the boiler was often very rarely seen and this outer skin was often just a thin ALUMINIUM or STEEL layer.
IF timber was used, then rarely were the joints mitred.

Finally Derek, you asked about 6mm x 0.5mm thread...... this is a standard metric extra fine size.... taps and dies can be easily obtained, at reasonably low cost, from TRACY TOOLS.... they do MAIL ORDER.

'www.TracyTools.com'

OK guys, that's all for now.

Best Regards.

Sandy.

[derekwarner_decoy]

Hi PD's......thanks Crash93....& also naturally the previous & latest posts from Sandy  .........I  take on board your comments re dis-colouration of boiler cladding...but thought 152 degrees C would not cause the problem & .....

When my initial boiler temp checks [2005] were established...I trailed a wooden slat against the boiler for 30 minutes without issue

Could I ask Nick [from Monahan] if you have experienced this issue?...did your tests or customers comments rate any alarm?

I will wait for a resolution....& will lag the 50 mm high boiler band with an underlay of composite material if necessary.....

regards


Opps........thanks for the heads up Sandy on the M6 X 0.5 fine pitch.....but  & .....mother nature being the inventer of all    has created an alternative ....I will post a .jpg when completed