SE5 Prop: Clean and Polish

[Gabriel]

Hello fellow forumites,

Many thanks to everyone who has been generous with their time and advice following my many questions about caring for old propellers and specific questions concerning SE5 props. In particular, to Bob Gardener for his sage advice and wide ranging knowledge.

So, now I can now hopefully share my own experience. I have just collected a four blade SE5 prop, pattern T28096 to fit the 200HP Hispano Suiza. As far as I can make out the prop is untouched since manufacture, still the with original fabric on the prop tips and nothing done (no varnish etc) to the woodwork. It has obviously sat for long periods on the blade tips rather than been hung on a wall as two of the tips have suffered a little bit and cracked, the two opposite the manufacturing stamps (ie the prop stored leant up against a wall with the hub stamps uppermost to easily be read). See attached photos.

[Gabriel]

So, here it is after cleaning. I just used a very weak soap solution (literally a couple of drops of washing up detergent in about 3 litres of warm water) and gently wiped over being careful not to leave the prop too wet.

Once dry I’ll start with the beeswax polish.

[Bob Gardner]

Hello Gabriel,

Thank you for these photographs. I look forward to seeing the end result.

With kind results,

Bob

[Bob Gardner]

An afterthought, but not for the frequent viewers and cognosceti amongst us.

It looks as though it might take several episodes to remove the ingrained dirt from the prop. Don't worry about the damage to the tips. It may well have stood on these two tips for a hundred years, which is part of the history of the prop. If you wish to replace the fabric in due course, it is relatively easy to locate some second-hand Irish linen to glue in place.

With kind regards,

Bob

[Dbahnson]

An afterthought, but not for the frequent viewers and cognosceti amongst us.

It looks as though it might take several episodes to remove the ingrained dirt from the prop. Don't worry about the damage to the tips. It may well have stood on these two tips for a hundred years, which is part of the history of the prop. If you wish to replace the fabric in due course, it is relatively easy to locate some second-hand Irish linen to glue in place.

With kind regards,

Bob

On the other hand, if you don't do anything to it except to preserve its present state, just think how unique it will be 100 years from now.

[Bob Gardner]

Yes! Indeed! A very valid observation.

Bob

[Gabriel]

So, I’ve done a bit of a halfway house. I’ve cleaned the prop as much as I dare without damaging anything. I used a weak soap solution and also a quick wipe with denatured alcohol (methylated spirit on this side of the Atlantic) to further clean the prop and remove any contaminants. Note, this was a very quick wipe as I didn’t want to affect the original green paint which is still on the back of the prop boss.

Some of the original protection (I assume it was a varnish applied after manufacture?) has come away leaving bare wood so I am keen not to cause any more damage. In other areas though it is in quite good condition, see below.

So, one application of beeswax so far and another one in due course.

[Gabriel]

Also, I have a question about my prop.

If you look closely at the photo below, you can see a line of four small bumps under the fabric and again a row of three in the blade about 4-5 inches back from the edge of the fabric. These are on all four blades in the same position and almost look like small wooden plugs approx 4-5mm in diameter.

Being under the fabric (which as far as I can tell is original) I am assuming they are there from manufacture - but what are they? I wondered if they were to add small lead weights to aid spanwise and chord wise balance, but were things that advanced in 1918?

Any suggestions gratefully received!

[Dbahnson]

Some early propellers had dowel reinforcements across the planks, and I suspect that's all you're seeing under the fabric. (The planks shrink across their width, but the dowels shrink less across their length, a characteristic of all wood. So the dowels end up protruding a bit from the surface of the planks.)

While a few props may have had weights added to balance the blade, the preferred method was to arrange the wooden planks in a balanced layout and then do a fine balance on a knife edge by applying extra varnish on the lighter blade. I have a photo of that varnish balancing somewhere, and one catalog describes the method of laying out the planks to match wood grain and weight.

[Gabriel]

Some early propellers had dowel reinforcements across the planks, and I suspect that's all you're seeing under the fabric. (The planks shrink across their width, but the dowels shrink less across their length, a characteristic of all wood).

That makes sense, the slightly raised bump is only on the front face of the prop and not on the rear (thrust) face, which suggests the dowel runs chordwise across the laminates rather than perpendicularly through them.

[Bob Gardner]

These are the dowelling which hold the laminations of overlapping wood together. Wooden dowels were fitted to holes drilled through overlapping laminae. This prevented any movement or creep of the laminations during manufacture. It was only used by the British prop makers and the practice fell into disuse towards the end of the war.

With kind regards,

Bob

[Dbahnson]

That makes sense, the slightly raised bump is only on the front face of the prop and not on the rear (thrust) face, which suggests the dowel runs chordwise across the laminates rather than perpendicularly through them.

Another possibility is simply that the dowel occupies a full 3/4" deep hole in the rearward plank and a much thinner front piece, so the glue anchors the dowel in the back but there's not the same holding power on the thinner front piece, where shrinkage in the dowel thickness may even further reduce the holding strength. All speculation, of course.

One of the reasons that dowels are not good joinery technique is that the amount of effective grain contact is low since it's passing perpendicular to the end grain on the plank for much of its surface area. End grain makes a very poor gluing surface.

Dowels are good for pinning joints like a mortise and tenon where they prevent shearing, but they're not very good where they are used to prevent tension, such as where you might choose a lag screw, for instance. The normal expansion and contraction of wood also tends to break down the glued against the end grain.

[Gabriel]

So, here is the finished prop. This is after three episodes of thorough polishing with beeswax. Note, after much research I used a beeswax sold by a small independent producer containing only pure beeswax blended with a small amount of natural turpentine to soften it and make it easy to apply.

Following Bob G’s advice I used the beeswax on both the wood and the fabric and it has brought both to a very satisfying deep lustre without being too shiny. I’m very happy with the result.

[pmdec]

Hi,
The simpler way is to made the wax yourself: Beeswax can be bought from a beekeeper (or from Amazon!) and turpentine from supermarket. You have to put the solid wax in a closed jar with some turpentine until the wax become soft enough (time=some days).
The trouble with this way is the wood remain sticky for some days. I think that there are more volatil solvant(s) than turpentine in commercial preparations.
If you add around 5% of carnauba wax, the wax coat will be more resistant, quickly less sticky and glossier. Beware: to made the mix, you have to heat until ~50°C and it is VERY flamable!
Regards,
PM

Remark(!!!): I don't myself use wax on propellers, only on furniture... and on wooden floor...

[JR44]

It looks great.