IMAC Pattern - Cadence w/ DA 35

[Alky6]

This build has me really intrigued to the methods and materials used in construction. Looking forward to your continued progress Paul.

Thanks Kelly. I am enjoying it. Definitely seems out of the norm for RC planes. A bit worried about the weight, but we’ll see. Might be a couple of these to be made up as I learn. Was easy building a race boat - never had to worry as much about a little bit of extra glue when you were saving 70 pounds over a standard wooden version. And when the all up weight with engine, fuel, and driver soaking wet was about 450 pounds that did a lot for acceleration! Boy, I miss those days of getting peeled off the steering wheel accelerating out of a turn. Sigh.

 

[dhal22]

My brother used to drag boat race. Not top fuel but something fast with a nasty blown 454. Crazy hobby.

 

[Alky6]

Indeed! The drag guys were “crazy.” They would say the same about us circle guys running around on a shingle. Hahaha!

 

[TonyHallo]

Likewise, really interesting build. What is your recipe for epoxy mashed potatoes?

 

[Alky6]

Epoxy mashed potatoes = Epoxy (west systems, Tap Plastics’ marine epoxy, hysol 9412/9430) and Cabosil. If it has a structural component (like the hole filling for the engine motor mounts, I will add a bit of milled glass fibers (but that stuff adds weight quickly). I rarely use microballoons as it takes a ton more to make mashed potatoes consistency, but if you need to do fairing, you can’t beat micro balloons. West systems is convenient with their pump system (1 pump each resin/hardener, tap plastics has measured pumps available but you have to count as the volumes are the same (can get wasteful if you only need a small amount). If you really want to measure up the perfect amount, hysol is the ticket. It is done by weight. I use a triple beam gram scale and measure out the amount of resin needed, throw it on the scale, do the calc and add the hardener. The hardener is in liquid form so I usually just pour it the cap to help measure out small amounts. Stuff works great and has a long pot life - 45min to an hour.

On the firewall holes I used west systems as I was a bit lazy and didn’t want to drag out the triple beam, nor wait 24 hours for set.

 

[Bartman]

For what it's worth, West epoxy can be measured in very small amounts with a cheap digital scale like this

https://www.amazon.com/AMIR-Back-Lit-Function-Stainless-Batteries/dp/B01HCKQG7G?ref_=fsclp_pl_dp_4

I used to only use the pumps and throw a lot of it away but now I mix as little as 10g (5 parts resin to 1 part hardener) of the resin and it turns out perfectly. If anyone wants to learn how to do this I can make a short video.

The West system of epoxies includes a line of fillers. I use the 404 High Density Filler by first mixing the epoxy, then painting it onto the parts to bond (because the epoxy soaks in better without the filler), then I mix in the filler and use the paste over where I've already brushed on the straight epoxy. The reason being because the straight epoxy will run out of joints that aren't perfect while the filler stays in the joint better and the 404 filler is considered structural. The other fillers aren't.

Here's the whole lineup of fillers
https://www.westsystem.com/the-105-system/fillers/

Even with the fast cure hardener it is still at least a few hours to cure in a warm workshop but the stuff is sooooooo much stronger than hardware store 5 minute epoxy that it's worth it most of the time.

Nice build you've got going there @Alky6 ! You're keeping me motivated to get my 26cc pattern plane started!

 

[Alky6]

For what it's worth, West epoxy can be measured in very small amounts with a cheap digital scale like this

https://www.amazon.com/AMIR-Back-Lit-Function-Stainless-Batteries/dp/B01HCKQG7G?ref_=fsclp_pl_dp_4

I used to only use the pumps and throw a lot of it away but now I mix as little as 10g (5 parts resin to 1 part hardener) of the resin and it turns out perfectly. If anyone wants to learn how to do this I can make a short video.

The West system of epoxies includes a line of fillers. I use the 404 High Density Filler by first mixing the epoxy, then painting it onto the parts to bond (because the epoxy soaks in better without the filler), then I mix in the filler and use the paste over where I've already brushed on the straight epoxy. The reason being because the straight epoxy will run out of joints that aren't perfect while the filler stays in the joint better and the 404 filler is considered structural. The other fillers aren't.

Here's the whole lineup of fillers
https://www.westsystem.com/the-105-system/fillers/

Even with the fast cure hardener it is still at least a few hours to cure in a warm workshop but the stuff is sooooooo much stronger than hardware store 5 minute epoxy that it's worth it most of the time.

Nice build you've got going there @Alky6 ! You're keeping me motivated to get my 26cc pattern plane started!

Thanks for the info. Is the density the same for resin and hardener (probably close enough)? Although, West system seems to have a pretty "large" mixing ratio in that if it is not spot on, it still goes off.

 

[TonyHallo]

Is Cabosil and West System 406 Colloidal Silica similar?

 

[Alky6]

I don’t really have any hands-on experience with the fillers from West System. However, in reading through the ingredients and msds sheets the 406 appears to be a synthetic cabosil which is a fired silica. In honesty, I don’t know a ton about them, just know what I have used, mostly from Tap Plastics as it was close to me and reasonably priced - My choices there were cabosil and microballoons.

 

[Bartman]

Thanks for the info. Is the density the same for resin and hardener (probably close enough)? Although, West system seems to have a pretty "large" mixing ratio in that if it is not spot on, it still goes off.

the parts weigh out as if they are equal density. you just zero the scale and add the resin, then zero the scale again and add one fifth the resin's weight in grams then stir. I think West tech service told me once you can be off by about 5% and it's ok after I screwed up a big batch and was trying to not have to redo it.