Something stirs in the Undergrowth

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IslandPink
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#2641 Re: Something stirs in the Undergrowth

Post by IslandPink »

A few more details done, including two coats of varnish inside. The next piece may go on later, it's already cut to size.
Once it gets to 80cm , I'll get the driver and start doing some listening tests as I did with the folded horn.
Horn1p9m_assembly2.JPG
ps. I'm proud to be maintaining my status as one of North Wales' premier horn-recyclers.
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IslandPink
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#2642 Re: Something stirs in the Undergrowth

Post by IslandPink »

My predictions were correct - the next piece did go on.
Note also a small piece of dowel inside, to reduce panel flex as much as possible. I'll do this on subsequent pieces.
Horn1p9m_assembly3.JPG
The next step is to look very closely at a big table of numbers, and decide which pieces of wood and what shape, are going on next. I think I'll keep 18mm ply going on the side pieces for another 40 or 50cm if possible.
I have just been thinking that if the larger pieces, later, that I might make from 13mm fibreboard, are not rigid enough, I might go to the car shop and get some fiberglass mat and polyester resin. The fibreboard would be an ideal substrate. I think it would be less work than trying to double the thickness of the fibreboard and get it all in contact.
"Once you find out ... the Circumstances ; then you can go out"
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IslandPink
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#2643 Re: Something stirs in the Undergrowth

Post by IslandPink »

Slow going, what with the emergency fridge issues. One further side piece finished and fitted. The other side piece nearly finished - that one had to be made by biscuit-jointing two smaller pieces of 18mm ply together ! ( I am trying to be very frugal ).
Horn1p9m_assembly4.JPG
"Once you find out ... the Circumstances ; then you can go out"
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Paul Barker
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#2644 Re: Something stirs in the Undergrowth

Post by Paul Barker »

Very ecological and t quote Ray Mears talking about his paddle madein the woods, “when Iv’e finished with it I’ll give it back to the woods”.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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IslandPink
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#2645 Re: Something stirs in the Undergrowth

Post by IslandPink »

Nice one - yes !
I am also seeing a noticeable reduction on the number of pieces of wood stacked in the hall, so I'll keep this going.
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IslandPink
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#2646 Re: Something stirs in the Undergrowth

Post by IslandPink »

Make a flip-book and watch it grow !
Horn1p9m_assembly5.JPG
Today it crossed the line between 'manageable' and 'cumbersome' .

I ordered some glass fibre cloth ( woven ) on EBay a couple of days ago, let's hope I got the right weight. I chose 300g/sqm.
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Ray P
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#2647 Re: Something stirs in the Undergrowth

Post by Ray P »

300gm/sq M is middling weight for glass cloth. What resin will you use? How will you be laying up the lamination?

Woven cloth will give a superior laminate compared with chopped strands (what most people will think of when you mention fibreglass) because weight for weight you get a much higher ratio of glass to resin.
Sorry, I couldn't resist!
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IslandPink
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#2648 Re: Something stirs in the Undergrowth

Post by IslandPink »

That's what I figured. I used it years ago for something totally different ( not a boat ). It also looks a bit more classy than the CSM.
I will be using polyester resin as it's easy to get and not too expensive, I have some from the car shop.
This is really just a quick way of making 13mm fibreboard into something harder and more rigid, for the outer ( bigger ) parts of this horn expansion.
I can add the fibreglass layer on the inside ( first ) and on the outside, if necessary.
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Ray P
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#2649 Re: Something stirs in the Undergrowth

Post by Ray P »

Personally I would have used a low viscosity, slower curing epoxy resin as you would get better absorption into the fibre-board.

I've used this outfit for composite supplies a few times. Good quality and a reliable supplier in my experience.

https://www.ecfibreglasssupplies.co.uk/
Sorry, I couldn't resist!
vinylnvalves
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#2650 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

Epoxy is not compatible with general glass fibre matting or rovings it does not wet out, the binder in the matting doesn’t dissolve in epoxy. Generally rule polyester for glass fibre - epoxy for carbon fibre. There are exceptions with more exotic resins, but they aren’t available to the general public. You could primer the wood first with epoxy-however the wood repair stuff like ronseal wood hardner which is polyester resin will work just as well.

Rays recommendation for a supplier is who I have used in the past, there is another in NI that have some good deals from time to time, their name escapes me
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Ray P
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#2651 Re: Something stirs in the Undergrowth

Post by Ray P »

I agree that with chopped strand matting you should stick with polyester resin but in my experience epoxy and glass cloth works perfectly.

For my model yacht hulls I normally use both carbon and glass; 200g carbon on the inside for stiffness and 200g glass on the outside to make the hull more 'ding' proof - glass is better for that and a lot easier to work with than kevlar!

Anyway, here's a snip from the website of the supplier I mentioned;
Capture.PNG
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IslandPink
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#2652 Re: Something stirs in the Undergrowth

Post by IslandPink »

When I used weave before I did use epoxy. and it worked OK, but that was 35 years ago, for a telescope mounting fork.
I suppose if you're using it for something serious like a boat, then the pros/cons can be discussed in more detail.
Anyway, this is academic, because (a) I've bought the cloth and the resin and
(b) this is only a rough test-bed unit again, doesn't need to be perfect.
I'll take Steve's advice and wet the fibreboard with the resin before I put the cloth on.
I will probably do a test-piece first to see how well it adheres.
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Ali Tait
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#2653 Re: Something stirs in the Undergrowth

Post by Ali Tait »

Have you tried kerf cutting Mark?

I’d have thought that would be a quick way of prototyping, bend to desired radius and use maybe Plaster of Paris to form a smooth horn mouth?

Haven’t tried it myself so no expert. :D
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#2654 Re: Something stirs in the Undergrowth

Post by IslandPink »

I don't really need go to that trouble, Ali, thanks - I have a lot of unused 13mm fibreboard from the double horn prototype, it's flexible enough and I think it will only be necessary to lightly curve two or four panels of this, to do the last 60cm. My idea is to just cut some curved formers 'spars' (? ) out of ply or MDF, and tack the fibreboard to those, then reinforce with a single layer of glass cloth either before or after fitting the thing together. The exact shapes are still to be worked out based on the numbers. I think the horizontal expansion can be conical, but at a greater angle, for the last 30-40cm, while the bigger upper and lower panels can be curved.
If it doesn't feel solid enough, I have an option to add more spars and/or another layer of glassfibre on inside & outside.
The only other complication I have in mind is that it might be worth the extra effort to make this last section removable :confused3:
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SimonC
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#2655 Re: Something stirs in the Undergrowth

Post by SimonC »

There is a difference in glass mat properties between the US and Europe:
In the US most mat (woven or CSM) is made with a binder that holds the fibres together, this makes it easier to cut and handle as it holds its shape without fraying. The binder is dissolved by the solvents in polyester resin and it then goes floppy and easily conforms to the shape of the mould. Epoxy resin doesn't have these solvents and you have to force the resin through the fibres to get it to saturate the mat. Quite often the lay up will have a milky look to it as the binder goes into suspension instead of dissolving. It doesn't make a lot of difference to the strength, but it makes it harder to work with.
In Europe mat is made without binders, so it harder to cut and shape while dry as it frays and moves around. The advantage is that it works equally well with either poly or epoxy resins and you can pick whichever one you want depending on the job at hand.
All the reputable suppliers will be able to tell you if its made with or without binder. ECF are one of the biggest suppliers in the country, I've used a lot of their products and would recommend them. Another good supplier is Easy Composites, they are geared more towards the low volume end of the market and are generous with their knowledge and advice. Their EL2 epoxy laminating resin is a bargain for what you get.
Woven vs CSM is more down to choice. High strength+low weight=woven, if bulk isn't a problem then a few layers of CSM is usually a more cost effective way of getting a result.
A cheap trick for adding strengthening ribs is to spilt some pipe insulation (the stuff that looks like a pool noodle) length-ways to make a U shape and glass this into the structure. Another one is to use offcuts of garden hose. Just lay them on and slap a couple of layers of mat over them. Crude but surprisingly effective for quick prototypes.
Have fun :)
Simon C
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