Seatback top done (sort of)

[TMann]

A lot of what I've seen as far as the main funtionality of the micro, is to act as a filler (much like a sanding sealer in woodworking.) If you take a couple scraps of the thin bulkhead material (like where you cut out leg holes) and coat one piece with the micro and just squegee off the excess. Then on the other, coat it with epoxy like you were doing a layup. let it set a few seconds and it's almost dry so add more epoxy and is sucks it up again. That will make for a heavy part.

SUBNOTE: and I'm not going to quote the exact CP it's in ......... Burt recommends using micro on all foams prior to applying glass.

[Lynn Erickson]

Originally Posted by Erick

I thought this might be a good place to ask a question about micro. How much should I be applying to the surface of the lay-up? Should it be scraped completely off the part then apply the glass or left thicker? Is it supposed to completely fill the pores of the low density foam?

Chapter 7

Micro should be used as dry as practical. it is used to fill the foam pores and small voids under the glass layup. it is lighter than straight resin that would fill the pores if the micro was not used. it weights about the same as the foam so it can be used to improve the foam shape to allow the glass to lay smooth over the surface. if the foam shape is good then you only put on enough to fill the pores

[Jason Heath]

Originally Posted by TMann

Hmmm..... were you sanding in one hour?

Nope, I was doing it the conventional way. see post

Originally Posted by TMann

The point here is that there are a lot of 1-2 hour opportunities to work on your plane during the week that will help you stay on track on your project as a whole so use the full spectum of opportunities that MGS offers with the compatability that the hardener (both slow and fast) has to offer.

Agreed, good point! use the full spectrum of opportunities that MGS has to offer, my question/point was only that you made it sounds like 3-plus hours to layup the seatback and that doesnt sound like a wise use of time.

[John Slade]

Is it supposed to completely fill the pores of the low density foam?

Yes, but that's all. Scrape off all you can before adding the glass.

[chasingmars]

Originally Posted by Steve parkins

don't scare the fish
the + or - 2 is for 100% we like 100 % but need to stay near the top of that graft, but....the epoxy is stable at less then 30%.
some epoxy will hold to 100/100 before it becomes unstable
the epoxy is only 20% of the overall , so a little off will be fine.
plus, at the start, you cant hurt anything (in my planes)
much later, you'll do harder layers that WILL count IMHO

No, +/- 2 (i.e. 38 to 42 parts hardener to 100 parts resin) is the published acceptable range by MGS. Physical properties start to degrade as soon as you move off design point, but are ok (according to MGS) within this range.

The epoxy may appear to cure outside the +/- 2 but I won't use a batch that I'm not sure I've mixed to that tolerance on an airplane.

I'm not sure I followed the last half of your post, but if you're saying that mix ratios of 100:30 or 100:100 are ok for MGS, that's just unsafe, and while it may only be 20% of the mass of the plane (or of whatever, it's about 40% of the laminate in gentle vac bagging, about 50% in good hand layup, by weight), it's vital it be mixed right!

Or were you just yanking my engineer chain?

[Steve parkins]

no, not yankin, lol
just saying if you a little off you wont fall out of the sky !
or redo a 100 dollar part
just live and learn and enjoy the build
but for yous engine types..........redo every thing ! test then redo !
more testing, more redo's....est.

mean wile us noobs will fly over your house and look down at your lawn dart......

[TMann]

Originally Posted by Jason Heath

......you made it sounds like 3-plus hours to layup the seatback and that doesnt sound like a wise use of time.

Nope...... I was working on other parts at the same time (and worked dinner in there as well.)

Sounds like your burning right along. What chapter are you on now?

[chasingmars]

Originally Posted by Steve parkins

but for yous engine types..........redo every thing ! test then redo !
more testing, more redo's....est.

It's sad but it's true... I have a new simple way of figuring out how long a step will take. I double the published estimate.

[Jason Heath]

Originally Posted by TMann

Sounds like your burning right along. What chapter are you on now?

I wouldnt call it burning right along, but I'm working on chapters 9 & 10

[TMann]

Originally Posted by TMann

.... so use the full spectum of opportunities that MGS offers with the compatability that the hardener (both slow and fast) has to offer.

Wow ...... had exactly the situation I spoke of happen to me today.
I go to do my tape layups on F22 and ..... what??? That doesn't look right!
Cr@p..... I floxed the bulkhead in backwards with the doubler facing out.
Maybe it won't make a difference ........ yeah, right!
Crank up the Fein Multimaster ......... maybe I can cut it off clean.
No chance. Well just cut it off and get on with a proper fix!

2:40 PM - the new bulkhead is cutout to the proper shape. Doubler as well.
Mark it as "INSIDE" in case some moron tries to put it in the wrong way.
2:58 PM - Both sides are micro'd with MGS fast. Hmmmmm ......... got some extra micro so I micro the foam pieces together for the floor of the fuse.
4:30 PM - Hardshell is sanded both sides.
5:15 PM - F22 is glassed 1 side with MGS Fast. Doubler is in place and in the Vacuum bag it goes.
6:40 PM - F22 comes out of the bag. I did my 9 plies for the back side of F22 as a isolated layup between peel ply. Put my batting layer on top and put the whole works as a sandwich between poly and 2 boards. The vacuum bag will put a ton of pressure on the part. Into the bag it goes.
8:30 PM - Flip side is glassed with MGS Fast. The 9 ply panels were cut to 5" x 16" and set into the layup. Into the vacuum bag it goes.
It's a done deal.

So I lost a little time on chapter 6 today but come tomorrow, I'll be right back at it doing my tape layups on F22. A small bump but it's done right.