I've heard of/read about certain woods being used for patterns, and used some as well. I've heard of mahogany, white pine, cherry, poplar, hard and soft maple. I've used the last 4, as well as birch plywood. I'm wondering what other kinds of wood are in use here. I've wanted to try Sapele - looks like mahogany, is hard, mills well, and is semi-reasonable for buying - unlike the fabled mahogany...
The pattern making timber in Australia was Jeulatong: milky pine logs soaked under water in running streams for a couple of years until it was nothing but cellulose fibres and then dried. It was fabulously expensive and these days MDF rough machined and then coated with epoxy resin before final machining to shape works pretty well: it soaks up epoxy like a sponge and machines like plastic afterwards.
The epoxy I used is 24 hour cure which takes an hour to begin to set, it went in about 6mm or 1/4" but seemed to soak up as much as I could apply with a brush. MDF does have a grain: layers parallel to the flat surface it was pressed in so I have had it split in layers and had to drill holes and glue with epoxy. The moisture resistant MDF is exactly that: resistant but it will take up moisture and swell, just less than normal MDF so epoxy is necessary to seal and reinforce. On a lathe it machines like plastic with long streamers of material shearing off the tool bit.
Want an especially runny epoxy, then, like the stuff used for gone-rotten wood, perhaps? As in used for "rot repair?"
I just use a 5:1 boat builder's fibreglass epoxy, it is runny, water clear and yellows a bit with age. Any generic fibreglass epoxy on Ebay would do nicely.
Seems the "penetrating epoxy" sinks deeper, but does not get as hard as the 5 to 1 - and one wants hard in a pattern, as hard goes with smooth as a rule. Perhaps dosing initially with penetrator, and follow up with 5 to 1?
It's used for boat hulls so I would imagine hardness is part of the requirements, not sure what penetrator is. Usually with epoxies, the ratio of the mix is an indicator of inert fillers added like styrene, a 1:1 ratio epoxy has a lot of filler and a 1:5 epoxy would have less filler but still have some according to the label. The resin I buy has a slow/medium/fast part B component and being in the tropics I use the slow component. If the resin was cooler then the cure time would be slower: Arrhenius' law states that for every 10 degree C hotter a chemical reaction is, the speed of reaction doubles so it wouldn't have to be too much cooler to get very long cure times and give the resin plenty of time to soak in. The viscosity of the fibreglass resin is about that of engine oil, but once it begins to cure it suddenly gets runnier and behaves like diesel viscosity. I find it's perfectly usable like that and doesn't waste resin, If I wanted deep penetration, I'd use a vacuum chamber.
"Total boat penetrating epoxy" - an example of "penetrator?" "WOOD HARDENER FOR ROTTED WOOD: two-part epoxy system seals, hardens, preserves, and protects all types of wood by stopping rot. Makes finishes like paint and varnish stick better and last longer. Easy to use treatment has no VOCs or harsh fumes..."
your choice of wood for patterns depends on how you are making them, hand carving, you will probably want Tupelo wood or white pine (sugar pine) poplar is a fair choice, Mahogany if you expect it to take a beating , Mahogany, cherry and Maple are good for turning larger patterns , because of price and availability I almost always work in Poplar and Plywood, I have alot of 3/16 Ply it's almost always the back of a plaque (minimum casting thickness) , I keep 1/16 , though honestly a cereal box works as a replacement for that the shamrock in the bottom of this piece is a cut out from a cereal box https://www.instagram.com/p/CHn1zVhj1y8/?utm_source=ig_web_copy_link Simce most of my work is produced using a disk or drum sander, I try to stay away from Mahogany , it's sawdust iritates my skin (might just be me ) but i use Mahogamy for Plque backs on custom pieces Hope some of that helps V/r HT1
Birch plywood - stuff with lots of layers? (Like I prefer for stuff That's sorta like furniture and patterns?)
unless it is really thin, 5 Layers minimum, 3 layer is seldom stabile, it will warp you can do hobby plywood by https://midwestproducts.com/ which is the exact same stuff as Revel's hobby plywood, this is good stuff, but often overpriced shop around I have had good luck buying marine grade Plywood drops off of ebay just search marine grade plywood most recent I purchased this item very good stuff https://www.ebay.com/itm/3-16-PLYWOOD-4-ply/283908897105?hash=item421a49f951:g:-1MAAOSwPGBfp0Ut If you really want quality you can get aviation grade ply https://www.wicksaircraft.com/shop/birch-and-poplar-plywood-aircraft-grade-mil-p-6070/ with plywood, watch out for shipping rip offs V/r HT1
Yeah, I know about the shipping. (Plywood less than three, shipping close to nine!) 3/16 ply - I like to use it for patterns; seems I'm not all wet, then - can sometimes be purchased locally in "better" hobby shops. I've bought it in those, when I could find it. Never done business with Wickes, though I've heard of them. I have bought stuff at Aircraft Spruce - mostly steel and aluminum, thus far. (Shipping is cheaper, being on the west coast.) Don't have a disk sander of real size - yet.
I use Baltic birch plywood as the main component of my patterns. It is the same stuff high-end wood toys are made from. I buy it in 3/16, 1/4, 3/8, and 1/2 thicknesses. It is practically void free and is not very expensive bought in 60x60” sheets. It is very dimensionally stable and takes a good finish. For solid wood trim pieces I like yellow cedar as it’s grain is so fine and it is pretty hard. But it is pricey. I also have used poplar (Very soft), fir, and bass wood. To harden the surface of wood where it is likely to get bumped and bruised, I use thin cyanacrylate glue or epoxy. Denis
totally forgot about Bass, great for hand carving, but expensive expecially in larger pieces, and gluing up pieces and then carving is inviting a disaster V/r HT1
Hardwood is more expensive than steel in the UK and birch plywood isn’t cheap either. I’ve made a couple of flasks recently using pressure treated decking timber off cuts. Might have a go at making aluminium ones as there are plenty of very good posts on here about them.
Sounds like a very good idea for flasks, then. Perhaps make several sizes of flask-panel, and then mix-and-match as required?
Just need to build up my depleted aluminium stocks and 3D print some patterns. Just not enough hours in the day at the moment. How did I ever find the time to work for a living.
I make my plaque patterns with a CNC. I've used Baltic birch up to 3/8" but I've made quite a few from 1/4" PVC sheet stock. In the sign trade it's actually considered foam. It's certainly not "foamy" but the interior is much more porous than the smooth outside surfaces. I use a polymer coating on it that seals the pores for a very smooth finish and also softens sharp interior corners and edges. I can't say the PVC is super tough, but it works well for flatbacks. Pete