After seeing the highly informative article here, I remembered talking to a very famous Russian - actually Ukrainian - modeller, Yakov Mazniak many years back who was complaining that it was so hard to get materials other than carbon in Russia. In particular he was talking about tooling resin.
However with typical Russian ingenuity they had found a solution: Cement!
To make a nice durable, hard faced tooling resin, they simply mixed powdered cement with the epoxy.
I tried it, and given the normal precautions of allowing the bubbles etc to dissipate, it works very well. So for those of us who simply don't have the need to buy large quantities of expensive tooling resin, just nip down to your local building site with a Tupperware pot (Don't tell "she who must be obeyed") and slip the lads there a sheet or two.
Nastrovia!
JH
About release agents (wax)
Over many years of making props (and epoxy bedding rifle barrels) I have come to the conclusion that Kiwi Neutral Shoe Polish does a great job, readily available and not very expensive https://www.rimfirecentral.com/forums/showthread.php?t=339769
Maybe worth a try 🙂
Danny
I have had just about every kind of failure that you can have with composites.
I don't find props very demanding on the release system but I don't hot cure the props, I do a warm cure (30 to 40 deg C) then demould and do a full controlled post cure.
I will look at the Kiwi polish, I think we might even have some of that stuff in the cupboard.
Over the years the cost of the really good release systems has come down in price, there are some magic systems sold over here.
Jim
Good tip on tooling epoxy, I often make my own tooling gelcoat by mixing in aluminium powder and silica, what do you use as a backing material on your glider wing moulds?
B.
HeyBarrie, I use "Poraver" - a kind of plant pot pumice stuff. Light as a feather - some of those glider wing moulds are very large.
Cheers,
J
G'day Barrie.
Your topic caused me to dig out my ancient Aeromodeller's (Feb/Mar 1983) and when I re-read the prop making articles I was reminded about the advice to include a glass core under the carbon, it was supposed to increase 'toughness'.
I still have a mould that I made back then in the '80's and a few propellers (7x5 Good Year), they are in good condition.
I am contemplating moulding some blades for a Free Flight competition power model to suit a re-worked Rossi .61 FIRE. The prop shall be (approximately) 11"x4" diameter, and it has to be a folder.
So is the glass core still advised nowadays?
I apologise that this is not exactly a C/L speed question, but not many people are moulding their own props nowadays so this is about manufacturing and safe techniques.
Regards * M2Z *
Danny
The glass core add's toughness, this is useful if the prop is going to get landing forces applied to it such as combat and maybe lower level team racing events.
For events where you are only interested in performance then go with a 100% carbon layup.
If you are making a folding prop then it is essential that long fibres come from the blade and wrap around the pin and go back into the blade, this ties the blade to the pin, it will burst open at the hub if you don't do this.
I read on another forum you asking about material supplies in Australia, I know nothing of suppliers in Australia but they are there for sure, my advise would be to drop Bruce De Chastel a line (he makes and sells RC pylon racers in quantity) and ask where to buy materials or maybe he will supply you the materials, tell Bruce that I said to contact him about this. Bruce has made more carbon props that most people could only dream about.
In my experience the epoxy is not super critical so long as it can survive crankshaft temps. so look for a Tg figure over 100 deg C, most important is to do a post cure. A great high performance epoxy that has not been post cured will get out performed by an average epoxy that has been fully post cured on 9 out of 10 occasions.
Your questions whilst not directly relating to CL speed are very valid to discuss in this forum.
Regards
Barrie
Danny
Iornbark Composites sell good resin, ask for the MGS285 resin with the 285 hardener, you will not go far wrong with that resin.
I tend to buy carbon UD tape about 200mm wide (100 grams sq metre) and slice 20mm wide strips out of it, I then fold these strips over into 10mm wide once wet out with resin.
Works good for me.
B.
G'day Barrie et al.
Another local (Oz) pointed me to the same supplier with positive results.
I am just awaiting an email from their sales rep.
UD tape, well that's a new twist for the props. I was contemplating using tow as easier to wrap around the pin.
One thing that I could not locate was any info about 'high modulus' carbon fibre, such as IMX or IM3 as used in my (very expensive) top shelf fishing rod blanks.
I once met a rod maker (Gary Loomis) during a visit to Australia many years ago and the advantages of the high modulus fibres were well explained and a fly rod made from such materials is a delight to use. Lol, I would love to get my hands on some of that material.
* M2Z *
Danny
There is a tangible difference when using HM carbon, the props can be noticeably stiffer.
Nowhere near as easy to obtain though.
You would still be able to wrap back around the pin with the UD tape material folded over as I describe.
B.
Danny
Iornbark Composites sell good resin, ask for the MGS285 resin with the 285 hardener, you will not go far wrong with that resin.
Just to follow up, I contacted Dick at Ironbark and ordered some 50k tow, Hexion MGS L285 resin and hardener and mould wax. Unfortunately could not locate any light carbon twill in the 80-120 gsm range (lightest is 200 gsm) but as your per article, nice to add but not vital.
I plan to use my existing 7" x 5" Goodyear prop mould to practise with the materials before cloning an APC prop blade (after bench tests of a few sizes on my Rossi .61 FIRE)
As you already know, the first propeller is going to be the most expensive 😕
