ORIGINAL: cmoulder
Particularly useful in getting epoxy ratios down to the gnat's a..
Nice catch on a superb set of scales, Matt.
Good idea about the epoxy ratios! I hadn't thought of that before because I never had scales that could do it. Figured that estimating the size of the blobs was how everybody does it. Even if the resin and hardener densities are slightly different, it's still going to be very close to perfect in the small amounts we mix.
Concerning the Xoar e-props for the SAP-180 hybrid prop mod, I got two 18x12s in the mail yesterday, as well as a couple of APCs. One of the Xoars weighs 49.7g and the other 45.2g, with the APC 18.1x12 at 124.4g and the 17x12W at 132.1g. Clearly, the modified props (even if they weigh 60g) are going to make a significant difference in rotating mass.
If there isn't anything similar commercially available by the time the weather warms up and I can work out on the deck, I'll have the materials assembled to make them.
Bob,
For epoxy to reach maximum mechanical properties it shouldn't be resin rich or hardener rich. It should be very close to correct stoichiometric ratio. For adhesive types of epoxies, if the viscosities are pretty close, the time honored technique is fine.
For finishing and laminating resins one uses more material and it should be done either by weight or volume depending on mfg recommendation. I will typically use laminating resin for setting things like firewalls, landing gear sockets and practically all other high stress areas because the plastic will wet out the reinforcement better and produce a lighter bond in the long run compared to adhesive types
Some epoxies have the same density for parts A and B so the same ratio for weight and volume methods will give the same results. Aeromarine Epoxy is one such material (JGreer Co). Most do not, so volume and weight require different ratios. A good scale comes in handy since doing it by volume accurately requires syringes which tend to stick
Just completed applying top coat to mine. Once cured, I will polish and wax it to high gloss. BTW, what did the 18x12 cost, delivered? Nice prop eh?
Matt