My Glasair III Construction Diary - Page 13
By
Roger Halstead

Just getting started on page 13

As I mention near the end of page 12, I'll probably move a good portion of the latter part of page 12 to here once the images are installed as that page is getting quite large and only about half the images are in place.

I'm currently building up the end ribs to match the shear web plus a little fill on the outboard end of the shear web to prevent the elevator shell from resting directly on the hinge. There is very little space to "play with" due to the tight clearance between the elevator shells and the trailing edges of the horizontal stab.  This is another one of those places where, were if I were doing it again, I'd do it different.  In the manual they have you use a tapered support for trailing edge of the upper horizontal stabilizer shell (remember they are jigged upside down), then bond in the shear web using a mill fiber mix and weights to hold it down and straight.  That is fine as far as it goes, but I think they need some dimensions to shoot for.  I'd set up outside dimensions for the shells at the shear web. This would require using a few small spacers during the bonding process, but over all would, or should, reduce the work of fitting the elevators substantially. It would also give a fixed and predictable thickness between the shear-web and the shell which in the end would make for a Horizontal stabilizer of a given and predictable thickness across the area of the shear-web. I do think the ends of the stabilizer and elevators should be about 1/16" *thicker" than following the manual produces and I'd move the outboard rib and hinges in between a quarter and half inch.  Of course I'd shoot for set dimensions of the elevator at its shear web as well.

Another note as to the elevator end ribs.  The manuals make no note of it, but the use of shims, or spacers to center the ribs on the shear web with an even spacing between the rib and shells would also make things both easier and neater. (The ribs are some what smaller than the shear web where they come together.)  That space is designed in to allow for the mill fiber mix used to bond the shells, but the space can vary considerably with the amount of weight used when bonding the shear web and the end ribs.  A few small spacers would take care of that variable.

While doing the fill on the elevators I'm letting the temperature drop to 62 F after I quit work at 3:00 AM and not raising it back up to 70 until 6:00 PM that evening.  This lets me work with relatively cool resin and surface temps in the afternoon. At 62 F,  I can figure on 25 to 30 minutes to Gel time which is about 10 minutes longer than what I get at 70 F.

2 Hours 17 January 2006

Building up end rib and adding thickness to shear web near end for added clearance for the end hinge.

2 Hours 18 January 2006

Block sanding shear web and end rib for both elevators.  Ordered new hinges and a gallon of resin with promoter and catalyst.

2 Hours 27 January 2006

This is an accumulation of a few minutes here and a few minutes there:  Sanding on the leading edges of the elevator shells to gain the proper clearance between them and the trailing edge of the horizontal stabilizer and building up portions of the same leading edges so they have a constant clearance throughout their range of travel.  This is leading to a lot of "sand and fill, sand and fill, sand and fill".

Man, but I sure am getting behind on this diary. Today is the 10th of October and the previous entry was done on January 28 for the 27th.  So, I start here and then will have to do a bit of "back filling".  I did take most of the summer off from building as there were just too many other projects that required my attention. However I've been working on the elevators for several weeks now. There will probably be about two pages of entries between now and the previous 2 hours on January 27th.  Lots of images to put up as well.

2 hours 8 October, 2006.

I prep sanded and acetone washed each elevator shell trailing edge. I added a 3/4 inch wide single layer lay-up to the inside trailing edge of each elevator shell to give me a trailing edge thickness of about 1/8inch to 5/32nds inch.

Sooo...

5 Hours 10 October 2006.

I finished prep sanding and acetone washed both shells for the left side elevator, set the shell containing the ribs and shear-web on the bottom frame, mixed up 130 grams of mill fiber and resin along with a shot of Cabosil and put a bead on the shear web, ribs, end rib, trailing edges and two inches of the curved portion of the shells. I had to mix an extra 30 grams to finish the trailing edge.  I then set the top shell in place, put the top fixture in place and clamped it with five clamps to hold everything in place until the resin cured.

When the mix reached the green state I trimmed the trailing edge  as well as the excess mix at the forward edge between the shear-web and top shell. Then I put the whole works back in the fixture.

8 Hours October 21, 2006 All nighter

Block sanded the trailing edge of the left elevator. Created a set of 6 elevator contour templates to aid in building up the leading edges of the elevators to the proper contour.  The left elevator is about ready to have the proper contour built up on the leading edges and the reinforcement lay-ups.  

9 Hours October 22, 2006 Another all nighter

I'm still getting farther behind on this diary, but I'm going to try and do a bit of filling in.  I've spent quite a bit of time fitting the left elevator to the stab now that it's closed.  Although the shells were fitted  prior to closing that operation did change the dimensions a small amount. This resulted in the bottom elevator shell binding at the end of its nose down travel.  The manual suggests using emery cloth sheets between the elevator and the trailing edge of the horizontal stab but this is a very tedious operation.  I have done enough of that to make the tight spots show up.  I then slid a sheet of carbon paper into the slot and moved it from one end of the elevator to the other while moving the elevator to the point of binding the carbon paper in place.  This thoroughly marked the tight fitting spots on the trailing edge of the horizontal stab.  I then marked a 1/16th strip down the bottom side of the horizontal stabilizer trailing edge, removed the elevators from both sides and then block sanded the edge. I test fit the elevators again and the one on the left now moves through the proper range nicely.   I also did some more fitting of the right side shells which are now about ready to bond/close.  I have the rough cutouts for elevator hinge access done for both sides, but they are undersize.  I picked up some 1/8" bits for my small router and have started building a small fixture that can be clamped to the elevator shells to make the final hinge access cutouts. I've decided to make the cutouts reach 2 inches to the "bolt side" of the hinges and the openings will be 3 1/2 inches wide.  I have yet to determine the depth.

Again there are lots more photos to put up.

Oct 24...Clean up day.  Built support for large air-conditioner and brought air-conditioner inside for the winter.  Cleaned floor across the front of the shop and under the door.  Can barely move today.

12 Hours November 7, 2006

Not a good day.  I "retrenched" on the width of the elevator hinge access point cut out sizes based on the users group recommendations.  The goal "now" if for the opening to be about 2 inches overall in width. This means doing a bit of fill on a few of the rough openings.  This is not difficult, just time consuming.  It basically involves sanding/grinding away some of the inside of the forward edges of the elevator shells adjacent to the present openings then filling with fresh cloth and resin lay-ups "feathered" into the existing edges.  I chose to use about a one inch overlap.  After the prep sanding and Acetone wash, I went the area with fresh resin. I then fitted the cloth into place with a lot of stippling. It came out well enough I decided to add a mill fiber/Cabosil/resin mix to fill in the front side flush with the shell surface.  This should work fine as there will be a single layer of BID over most of the mix from the leading edge back and about a 5/8" wide strip on top of that from the leading edge back.  At any rate I stopped after doing the fill in the openings. I put some low heat on the work as I wanted to continue on as soon as I managed to get some sleep. UNFORTUNATELY after about 12 hours at roughly 90 F the fill was still like rubber and removing the peel ply also removed the lay-ups which had only partially cured.

8 Hours November 8, 2006

<sigh> I removed all of the lay-ups and fill from the 7th, scraped and cleaned the surfaces and then gave it a thorough Acetone wash.  The Acetone easily removed the sticky resin. So now the elevator shell is back to the state where it was when I started the previous day's lay-ups and fill.  HOWEVER after having had a poor cure on all that work I decided it was time to make some "hockey pucks". In other words make up some test mixes of resin and catalyst.  This batch of resin had always been a bit slow to cure but it always reached a full cure and with a little heat would be ready to sand in a couple of hours.

15 Grams of resin into each of two clear plastic film canisters.0.15 grams of catalyst in one and 0.20 grams in the other. The temperature with all the equipment running out here was up to 74F.  Jell times were about 15 minutes which is pretty close. The surface remaining "sticky" is normal, but full cure "usually" happens with in 4 hours or so. However if you plan on sanding it 90 to 100 F will give a surface ready to sand within a couple hours.  This surface was a little more tacky than usual and this batch of resin had been behaving that way, but again a little heat was giving full cure prior to the "failed batch".    As I usually use the minimum promoter (CoNap) and no accelerator I had room to add about 2 CC without exceeding the maximum stated amount.  I decided to promote a new batch as well from resin dated Feb 2006. I used nearly 5 CC on that as it can get pretty chilly out here at times.  5 CC is listed as maximum. Again I made up two test batches (one with the previous resin and one with the newly opened and promoted can) with new catalyst and the same conditions as the previous tests. Jell times were within a minute of the previous tests and almost identical between the two batches of resin.  After 4 hours cure time the surfaces were solid and only slightly tacky.  The older resin is OK, it should have had enough promoter in it as it had given a full cure previously although it tended to be a tad more tacky after cure. Heat 90-100F for a couple of hours would produce a good, hard, surface that could easily be sanded.  I could find no reason for the partial slow, partial, cure but as I have lots of catalyst (MEKP) that I'd pitch the old stuff and go with the new bottle.

NOTE I have taken to keeping CoNap  in a half pint sealed fruit jars. Even after a year it shows no sign of thickening. These jars used the two piece top with a gasket molded into the lid. Prior to this even kept in the original two layer sealed plastic the stuff would get very thick within a year.

After being satisfied with the resin/catalyst mix I redid the lay-ups on the right side elevator shell. In 12 hours it is hard cured but not ready to sand. OTOH it is ready for the next lay-ups and fill.