Semroc Micron Build 3

Good evening everyone. Boy, was I pleased to see that my blog has thus far received over a dozen views! Then I realized they were me, viewing my posts repeatedly to catch errors. But I’m certain some slip through anyhow lol.

Today I continued to fill and sand balsa. I put a second coat of the thinned CWF on the fin I coated and sanded yesterday, and thus far today have put the CWF on the nose cone and the other three fins. 

I sanded the fin I filled yesterday. For one coat it felt pretty smooth IMHO. I coated this fin and sanded it a second time for this shot:

I think it feels almost to ready to paint with primer. I do still need to sand off some residual CWF that collected along the fin’s root edge while it was hanging down drying. Also note the new dimple in the side of the fin. I skewered it with its music wire holder while reinserting the wire to recoat it. A second fin was later inadvertently so treated.

Then I filled and sanded the nose cone. Here are before and after shots with before sanding obviously on the left:

I’ve coated it with CWF for a second time and it’s drying again right now. 

Meanwhile at the beginning of today’s session (or first shift, it depends on what my dear wife Bridgid has planned tonight lol) I also coated the remaining three fins with CWF and let them dry. I like the Apogee guy’s music wire technique. Here’s what the three fins looked like right after coating:

As you can see I again put it on quite heavily. Remember last night I made passing mention of how I thought the excess CWF would sand off just fine? Well, it actually did, at least on the first fin and the nose cone. Anyhow the three remaining fins are now drying as well. I’m giving them an hour before sanding them down. I’ll post a photo of one after it’s dried & been sanded, filled and sanded one more time. Then these should be ready to paint along with the nose cone.

Somewhere along in here I found time to try and fill the body tube spirals with the CWF. I decided to use another tip from Apogee and use the back of a #11 blade in a #1 handle to fill in the spirals - more on this later. I found out after I started that there are indeed spirals in the plural, extending parallel down the body tube. I’m sure there’s some painfully obvious mathematical reason why there must be more than one spiral, but I for one was mildly surprised to see this.

Oh wait I forgot - I marked the fin attachment lines next. I used my good old Estes tube marking guide (#302227) to make the necessary little marks around the base of the body tube. Then I extended the lines up the tube a ways, I just eyeballed the length, and I’m hoping like hell I drew them long enough. After all, I could have gone totally old school and cut out the fin marking guide, destroying the instructions, and then wrapping the guide around the tube to mark it. Or I could have gone high tech and photocopied the guide out of the instructions, cut that out, and used it to mark the tube precisely. But hey - I’m Not-So-Good and proud of it, damn it! In the photo on the right below, I’m using an Estes Ultimate Tube Marking Guide (#002228) to rest the body tube on my lap while I extend the fin lines with a pencil. My trusty kitty-cat Cry Baby watches me like a hawk, looking for the slightest tremor, in which case - she’ll pounce!

As seen above, these little marks would be extended into equally spaced lines along the tube upon which to mount the fins. I read one fin mounting technique that suggested scuffing the body tube with a little #0 steel wool along these lines to help the glue on the fins adhere to the body tube. But I took care of that later, when I sanded off the CWF I filled the spiral with. 

Here’s a photograph of the body tube before any sort of preparation. Can you see the spirals?

Yeah, me too. So for the first time I tried the aforementioned method of teasing the thinned CWF into the relatively shallow body tube spirals. It involves dipping the blade of your knife into the CWF and then drawing the back of the blade along the spiral, depositing CWF along the way. As a corollary to what I mentioned above, you have to do this twice, since there’s two spirals! But it turned out to be fairly easy. In the video, the Apogee guy outlined the spirals with a mechanical pencil before starting to fill them. I didn’t bother with this, as I predicted (correctly, as it turned out) that this was going to be a mighty tedious process.

I’ve been concerned all throughout this process that I had thinned the CWF too much but as it turns out it seemed to be thinned to just about the right consistency to deal with both filing the all the balsa and the body tube spirals as well so I was pretty pleased about my lucky guess, though I have no way to precisely repeat the dilution I now have. I wish I had mixed up a lot more of the stuff lol.

So I started filling in the spiral:

As you can see, I my technique has lots of room for improvement! But overall I was surprised how simple it was to fill the spirals this way. I was griping about how tedious the whole thing was the whole time I was doing it of course. But it was soon all done and here’s how the tube looked while drying:

Next I let the tube dry for an hour, then sanded the tube gently with a nice flexible sanding sponge I have. I have no idea what grit it is but it worked great for this purpose. Here’s the finished product:

It appears that the spirals have filled in pretty well, to my eye. But I’m really uncertain because if I run my fingernail gently up and down the tube I still sense slight indentations. I’m hoping a heavy coat of primer will fix this. Maybe the CWF was a bit too thin for this application, however, because it appears excess water has leached into the tube from the filler in spots. So I’d prefer to avoid repeating trying fill the spiral with CWF if I can.

All righty, I have to go sand off the last coats of CWF now. I probably won’t blog photographs after sanding them, at least tonight but I’m posting pics of them tomorrow if not tonight.