Ch 25 Finishing

While waiting for other things I’ve started the ‘finishing’ process. While I have the wings on its a good time to blend the strakes profile to the wings as a sort of side job.

While the plans say to get 36 grit paper to sand in prep for filling. and so to the blending, well that is seriously rough.  I’ve gone for a type of scotch brite material in a disk that I can use in a drill attachment. Yes it rotates quite slowly.

The idea is that I may do less damage to the top ply while still getting it 100% dull.

It is tedious work, especially on the underside of the strake. I’m going for that rather than flipping the plane inverted. I just crouch underneath with my adapted screwdriver sander.

The strakes are about 70% done after several days sanding. There is still more to do but its a good start.

I’ve been a bit stuck on how to do this step. The method in the previous log entry really didn’t work out for me. I tried a few other things and then put the job off for a while -grin-. I made more templates including one out of aluminium so I could get some marks but dragging it over the curve doesn’t work for me.

Long story short, I’m using my steel templates, the long permagrit block and using a marker pen to find the high spots as you see in pic two. See the dirty marks just forward of the template? I have to be careful to position the template so it matches a line at the leading edge and hooking on the trailing edge. I also have to keep remarking the template edge so I get a bit of ink on the filler surface. After a lot of false starts it seems this method is going to work.

I’m staying a bit shy of the LE so I don’t loose the line and I’ll flip it over and do the bottom before returning to the top the complete this area once the rest of the profile is done. Pic 3 shows I had to add a little more filler in a few divets and low points… which invalidates a lot of work already done. Yeah I’ve done this a few times. I remain committed to do my best work here.

I’ll probably get a good, but not perfect profile sorted out then get the plane off site to mount the wings and canard to the fuselage. Of course with the canard profiling pretty good I should get the incidence correct. Then a post cure of the canard before the final near ‘perfect’ profiling and epoxy wipe stages. Yeah….this will be fun to look back on hahahah.

More filler

Using marks for high spots

More filler

I kept filling and sanding and refilling the top side until it was pretty good. Next up was working on the bottom. Pretty much the same endless task of sanding and filling, sanding and more filling.

I won’t bore you with endless pics that look the same. I started doing the tips top and bottom too. I spent a lot more than 30 hours doing all this and I seemed to have it about right. Within .1 of a degree. Then I mounted the canard back on the fuselage and got different numbers.

The plan is to just continue on, finish fixing the canard attachment points, the tabs and so on and then have a final go with the level and more sanding. I think I have enough material (filler) on the canard top to get pretty close now without adding more.

So on to the tabs.

Bottom profile

More fill

Tip treatment

was doing this in March 2015. Time to get it right. I have set the canard on the fuselage exactly as it was when the wings were lined up using markings I had saved. I’ve moved to using West Systems 105 resin, 205 fast hardener and West 410 filler. While not structural this is proven for faring work and sands really well.

I’ve made another profile template from the plans but this time in aluminium which leaves marks on the filler giving a sanding guide. The profile has a little ledge too which fits the digital level nicely. Previously I tried to use the minimum filler and kept going down to the glass before I got the profile right. All that work is gone with more filler on top now.

I need to not only have a perfect profile but I will get to 0.1 of a degree or better which is a kind of creative thing even though its precision work. There are many hours to go yet but I can see a result possible.

Then of course I have to turn the canard over and do the underside! Ahhh there are a couple of weeks left of on this job for sure. There isn’t a lot to put in the log. I seem to get close and then find I need more filler which means almost starting again. I need to get the canard straight horizontally too of course as I sand. Finally NO waviness over the profile will make a big positive difference to flying qualities. Wish me luck!

Back on the fuselage

Getting closer

More fill and sand

Off we go on the bottom skin. The initial profile was pretty close but could be better in the cove.

The second pic has the usual filler mess and I found that the bottom has very small ups and downs over its length so its looking like another lot of filler and just as much fun as the top profile if not more. One reason it takes so long is I’m going for the minimum fill. This means if I get almost to the glass in one area I’m up for another lot of filler as this becomes my no go low point.

It also looks like I’ll have a slightly thicker canard than the templates suggest. I’m not sure how this would effect things. Its really just a function of the cores and glass and this is where I find myself. I’m not too concerned as long as the shape is spot on and I get the surface with the minimum possible waviness.

This is not the most fun part of the build but great to get it happening early as it becomes one less task at the end. Yeah I keep finding other things to do rather than sanding….

Close to start

Pile on the filler

Not so close now

This took many days. I though I had the profile pretty good to the LE but then on checking along the canard…. Oh well there was a bit of a dip just at the end. Not much but maybe half a millimeter. Yeah why settle when I can get it straight?

So another lot of 410 filler and another few days and as you see in pic three, not too bad. Certainly good enough to set the incidence and go to post cure later. This took another week although I’m just allotting the usual 10 hours in the log…I just don’t want to know.

Of course this is only one side…. so time to flip it over.

Looking good

NQR so add a little

Good again

So begins the profiling of the canard, the most important of the build. I’ve spent days trying to work out how to do this. I’m still not 100% sure but doing it anyway.

I’m already close to the correct curve in bare glass and have a base line drawn on the leading edge that I’ll work the template from matched with the TE position. The idea is to make several stations at the correct height by dropping the template into wet feather fill (I’m using West 410) and establish a top contour in strips and then use this as a high point to work between. It’s covered in the West literature so not a new method yet rarely done by canard people.

I made 8 piles or stations as best I could yet it didn’t cure the next day! Turns out my scales had a drop of glue on them bridging the weigh plate and the base that caused an incorrect reading so while the numbers were right the amount of hardener I put in was not. Hmmm another day or two gone getting all that work scraped off and down to a pristine undamaged surface to try again. Naturally I just did half the canard this time…just in case.

It worked out OK but this method seems pretty rough as I have so little to fill and the paste filler doesn’t give a very clean line. Good enough to get a feel for where we are and I can see how to use the minimum amount i.e down to the glass for the lowest point and work from there. I spent an hour or two sanding with my long permagrit stick then mixed another batch to make lines on the second half of the canard. I did a bit of a fill on the TE too with the mix I had prepared.

More sanding tomorrow and I’ll have the beginnings of a base line to add the filler in between. This is gonna take a while and I have some skills to learn and various methods to try with a cure cycle each time.

Template markings

Template high points

Multi places

Seems a little early for finishing yet I have an idea that I’ll get a more acurate canard and correct incidence if its contour is correct. The open EZ project has templates and on it is a ruler so you can check that the copies from the pdf are the right size. I had one printed a while ago and these matched pretty closely to the Eureka CNC templates. However the Eureka ones are not 100% and I’m calling the Roncz plans good… which also match the open EZ plans. My next copies however were 0.1″ out which is a lot and that took a couple of days and many hours at a print shop to get sorted.

I bought some 1mm or about 0.040″ sheet aluminium, 5mt the paper templates to the metal and cut them pretty close to the line on my band saw. Oh, and the switch broke on that so it was a few more hours getting a new switch. I then spent a couple more afternoons cutting these two sets of templates with the fine work to the line on an upside down dremel sanding drum and a lot of patience. Then a bit of hand sanding and I had two templates made separately but very very close to each other.

Why two sets ?…back to the TE of the canard needing a tweak with the heat gun due to the counterweight straps causing a loss of range. This means that the last 3/8″ or so of the TE in places is out of profile and goes up… so I needed a template with a notch in it as well as a perfect one. You can see the second one at the front in pic three has the slight cutout.

The pics also show that I have a nice radiused spar cap as planned and I think I won’t need too much filler. I’ll be using 410 BTW and an ‘interesting’ profile method that I will detail. Oh yeah and I’ve been lightly sanding and using scotch brite to get the shine off the glass. Bit more to do yet.

Templates on metal ready for trimming

Trial fit

More trial checking