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Author Topic: Laminated pine mast hoops  (Read 3902 times)

Greggy1964

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Laminated pine mast hoops
« on: October 20, 2009, 08:48:05 PM »

Here are some laminated wooden mast hoops I've been playing with for my 1/16th scale sailing trawler.

The mast will be 25mm in diameter at the base and the hoops have an internal diameter of 27mm.

The hoop body are a scale 1.5mm thick and 2.4mm deep and are 10 spiral laminations of 1.4mm pine shaved off a fine 1/4 grained 20mm x 20mm x 300mm stick.

I am currently preparing a how to article and have broken one of them in the photo so that you can hopefully see the laminations better.
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #1 on: October 20, 2009, 10:19:19 PM »

I've been playing again,

I wanted to see how much these tiny wooden hoops could take when under load so I rigged up an apparatus with some old kitchen scales I dug out of my shed and some steel weights I have.

The scales are supported by the red hardwood beam which is held to my kitchen table top by a 6" G clamp. The 22mm x 5mm section obechi beam spanning the top the  scales supports a wire sling below the scales and is able to swing freely.

This way the load is transferred to the laminated hoop and on through the wire hook, wire sling and odechi beam above it so that I can read the load directly on the scales

I wanted to mimic the load of a sail pulling at the mast via the hoop.

Bearing in mind the tiny size of 27mm internal diameter and profile of 1.5mm thick x 2.4mm deep, each ring could take an 750 gram load without deforming.   :-)) %% O0

There are ten of these hoops on the trawlers 0.367m2 mainsail and a further nine on the 0.185m2 mizzen sail so I reckon these little hoops will easily take the strain. :-))

Breaking load was found at 1500 grams! :o

The hoop took the 1500g strain for a full 5 minutes, elongating all the time until it finally broke! >>:-( <:(

I'm pretty impressed  :-)) since I used cheap white wood glue and the hoops were only made yesterday!

A post mortem of the failed hoop showed that it had de-laminated at the two points of load suggesting the lack of cure time of the glue perhaps or as I suspect a poor quality wood glue.

I'm popping out tomorrow for some cascamite to make another batch of hoops! :-))

Incidentally the little black bits on the wire hooks the hold the hoop are halves of a rubber grommet as the wire alone would have created two tiny pressure points that would not occur on the actual sailing model - I wanted to be fair! :-)
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #2 on: October 21, 2009, 05:55:17 PM »

Spotted a couple of typos in my 1st post.

The laminations are 0.14mm thick NOT 1.4mm thick and the resulting shavings are 500mm long.

I get such fine even shavings from by plane by sharpening the blade using the 'scary sharp' system of honing the blade.

See here http://dans-woodshop.blogspot.com/2009/01/sharpening-with-scary-sharp.html

The blade is so highly polished that you can see every pore in me ugly mush just like a mirror and my plane goes through pine like a hot knife through butter when set fine! :-))

I can get shavings sooo thin that they are see through but not much use for mast hoop laminations! {-) :o
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #3 on: October 21, 2009, 09:24:09 PM »

I got to studying why my first hoop was such a failure, the 1st photo shows the post mortem, clearly the hoop de-laminated to such an extent that the remaining wood carrying the load failed. <:(

I was laid in bed last night as you do - waiting for sleep to overtake me and I was pondering on my hoop load test rig and how I could improve it.

And just as I was drifting off to the land of nodd it struck me! :-)) ;)

There would be one point load where the sail was seized to the hoop, but the hoop would bear on a quadrant of the mast opposite this point. I resolved to modify my rig the following day! O0

This morning whilst in the back yard, the top of my wooden broom handle just came off in my hand - honest! {-):o %)

The broom handle is 23mm diameter, which is the size of the mizzen mast base on my new trawler, I'm going to make a 25mm diameter test mast but I'm going to have to carve this up from square stock.

What an ideal addition to my test rig even so.

Now my hoops from the same batch as my failed hoop at 1500 grams can take this load with only slight ovalation and the test rig represents a much closer setup to how things would load the mast hoops in practice.

I'm still going to use cascamite and see how much load the new and improved hoops can take :-)) :}
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #4 on: October 21, 2009, 11:04:30 PM »

I tried to be clever and speed up the drying process with the cr*p wood glue by baking the mast hoop blanks on their mandrel in the oven at 100 deg. C for an hour :-))

Only trouble was - like an over cooked biscuit, they became very hard but very brittle >>:-( >>:-( <:(

Whereas an air dried blank is tough but slightly flexible, . . . . . . . . well the results are plain to see in the photo below.

I was unable to split off a hoop from the blank without it breaking up >>:-( >>:-( >:-o

And I could crush a whole blank between my fingers and it snapped easily like brandy snap! >>:-( :((

back to the drawing board! :-)) {-) {-) {-) {-) {-)
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #5 on: October 22, 2009, 10:05:53 PM »

The back of my plane iron

scary sharp! :-))
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #6 on: October 22, 2009, 10:07:21 PM »

The back of my plane iron

scary sharp! :-))

The depth of relection is 75mm and I can get it better than that with a bit of elbow grease! O0
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #7 on: October 23, 2009, 12:16:43 AM »

Here are the new cascamite mast hoop blanks still on the mandrel.

I'm very pleased so far as I cannot see the laminations on the cleaned up end at all.

So far I have been using a blank of wood 500mm long to make the hoop shavings but I need 1065mm @ 0.14mm to get the hoop scale thickness I need.

So I have spent 2 hours today getting my plane super sharp and can now get regular and even 1065mm long shavings.

It takes a few aborted attempt to get it right but when you get in the 'zone' they come off one after another.

The longer shavings mean that after pasting them with glue I can coil them on the mandrel in one go whereas at the moment I have been using two 500mm shavings - one continuing after the other which interrupts the flow of winding the hoop blank.

I'm planning on posting a complete how to but I need to perfect the process first.

But I'm posting the development stage in the hope that prospective hoop builders will be interested in how the process has evolved.

The black line across the hoop blank is the end of the shaving and cascamite glue with muck from my grubby fingers mixed in! {-) its a messy process and no mistake!

With some fine sand paper it comes up gleaming.

The light and dark bands are the pine growth rings as the shavings come off the quarter sawn blank.

Tomorrow after the blanks are cured I'll clean them up and post some more photos.
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #8 on: October 23, 2009, 07:48:33 PM »

I think I've cracked it! :-))

I nicked a drop of my daughters clear nail varnish and varnish remover and made a thinned down sort of varnish to see what they would look like.

Here is the result.

I quite pleased.

In the 2nd photo the hoops are arranged on a McDonalds coffee stirrer to give an idea of size.

I can't get the wood grain to show up in the photos but these are 14 turns of a pine wood shaving wound around the 27mm diameter mandrel I made.

Watch this space for the comming 'How to'  ;)
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #9 on: October 24, 2009, 02:39:05 AM »

Just in case you are in any doubt as to whether these hoops are laminated here's a good close-up that I've been trying to get with my new camera all week!

This hoop is one of the original batch that badly delaminated under the thumb and index finger squeeze test! >>:-( >>:-( >>:-(

The rest of it pinged off somewhere in my kitchen and I've yet to find it! {-) :o
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #10 on: October 24, 2009, 03:01:03 AM »

Here's another close up, this time an enlargement of the previous photo :-))

How many laminations?

Care to count them? ;)
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andygh

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Re: Laminated pine mast hoops
« Reply #11 on: October 24, 2009, 01:42:30 PM »

Amazing  :-))
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Greggy1964

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Re: Laminated pine mast hoops
« Reply #12 on: October 25, 2009, 05:28:55 PM »

Thanks Andygh,

They would be if I could get those laminations to stick and stay stuck! >>:-(

In all fairness I can't put up a 'how-to' until I've perfected things, the building process works, its just the gluing that's a little wide of the mark.

The new cascamite hoops will take 1500g dead load using my test rig with slight ovalation, but they spring back when the load is released.

At 1750g the hoop go oval but are reluctant to return to their original circular shape. At 2000g the cascamite hoops last about 60 seconds before failing <:(

What this does prove is that the new hoops are stronger than the first batch using PVA glue.

The cascamite hoops are good but I think I'm using too much pressure clamping the pine laminations to the mandrel thus forcing the glue out of the joints creating a weak bond.

When I get time I'm going to make another batch with the new 1065mm x 20mm x 0.14mm pine shavings and cascamite but less holding pressure until they're set. :-))

I've also polished the sole of my plane which offers less friction while planing the shavings off the plank in using.
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