Re: Sig Akromaster build.

JPvelo Fri Mar 07, 2014 5:13 pm

Well, frustrating day. I'll start with the positive. I adjusted and increased control throws. Insides and outsides are now the same size and a little tighter. I may increase throws still more as the plane slows some at full throw but but isn't stalling yet. I'm at about 22* up and down right now.

As for the fuel system I'm having problems. I shortened the clunk and uni line to free it from the corner of the tank. I launched with the same needle setting as last time and was way lean, slowing and dying in loops. I richened to a very wet two cycle that leaned way out in less than a quarter lap in the air, but it pulled strong through loops without slowing when it pulled fuel. Fuel draw is an issue on out sides and inverted. I think my tubing is too stiff for the short length required for the two ounce tank. I will replace with surgical tubing before I go out again. If that doesn't work I will take along a one ounce metal wedge tank that I have and see how that works.

On the plus side I took the little satan out today to teach my son inverted flight. I forgot what a blast that plane is even with a relatively mild reedie. My son flew inverted surprisingly well for his first time, I attribute that to a high level of hand eye coordination that comes from video games.

Jim

**Cribbs74** Fri Mar 07, 2014 6:02 pm

Jim,

Have you pressure tested the tank? What you describe sound like an air leak. Do it under water and look for bubbles. 1 is too many.

Tell your son congrats! Most of us trash planes trying to learn that for the first time.

Ron

JPvelo Fri Mar 07, 2014 6:19 pm

Thanks Ron, I will try that first. My son thrashed the plane, that's why I took the satan. He just did very well before the thrashing!

Jim

Ken Cook Fri Mar 07, 2014 6:24 pm

Jim, could you provide a close up of your tank. One thing I found viable with plastic clunk tanks. Sullivan makes a larger heavier clunk http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXBWL1&P=8 which works far superior. It has considerable weight over a standard clunk and it's tapered. The standard clunk typically has a slight radius but I file a hard angle on the clunk to allow it to fit into the corner of the radius. It can be difficult plumbing a 2 oz. tank due to exactly what you've mentioned. Ken

JPvelo Fri Mar 07, 2014 9:36 pm

Ken, I like the look of that big clunk. If the surgical tubing doesn't work I will order one. I will post a photo of my tank/fuel line setup but it won't be until Monday evening.

Jim

**Cribbs74** Fri Mar 07, 2014 9:42 pm

Jim,

I didn't realize you were running a plastic clunk tank. An air leak may still be an issue but not likely.

Wouldn't hurt to check I suppose. It could very well be a clunk issue as Ken mentioned.

Ron

**RknRusty** Fri Mar 07, 2014 9:50 pm

The surgical tube may be too limp and let it fall to the front when you are diving. I use medium fuel tube and it works fine, hitting all four rear corners pretty quickly. I had to shorten the uniflow tube slightly to keep it out of its way. I do not use the sintered brass clunks, but mine is similar to Ken's picture, only somewhat more blunt tipped. There's almost no fuel left after a flight.
Rusty

JPvelo Fri Mar 07, 2014 10:52 pm

Rusty,

It's a 2oz tank so the fuel/uni lines are only about 1 1/4 inch long. I think surgical might be the only thing flexible enough.

Jim

**RknRusty** Sat Mar 08, 2014 1:08 am

JPvelo wrote:Rusty,

It's a 2oz tank so the fuel/uni lines are only about 1 1/4 inch long. I think surgical might be the only thing flexible enough.

Jim

Yes, sorry I forgot that, I was thinking on terms of a bigger tank.

Ken Cook Sat Mar 08, 2014 5:50 am

I've also plumbed these tanks with hard plumbing and had no fuel feed issues. This would be difficult to do with a 2oz. but maybe worth a try is to make it a uniflow clunk. I can provide a pic of a setup I utilize. If it doesn't work, you can always disconnect it. Ken

JPvelo Sun Apr 27, 2014 8:26 pm

Well, I reinstalled the muffler and added weight to the back for balance. It's now plumbed uniflow with exhaust pressure, works like a charm. Good solid run no matter the planes orientation and completely drains the tank.

Jim

**944_Jim** Mon Jul 12, 2021 4:42 pm

I'm moving up from 1/2A...time to do some thorough reading between here and SH. It appears that I'll build it stock fuselage, but wider WS on the first one. All parts will be traced so I can build (and crash) often. This looks like a fast build!

First iteration will get my lightest .15 engine...most likely a Medallion, unless a Norvel Big Mig .15 somehow is lighter.

I do have a .09 Medallion, but there is an 80% sized Akro on the board here. Off to go do some reading and studying.

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Ken Cook Mon Jul 12, 2021 4:59 pm

A very important thing to do with the Akromaster is to not build the elevator as designed. Slice at least a 1/4"-3/8" off of the leading edge of the elevator and glue bass all the way across the full width. That cheesy little stick Sig offers is just their way of crashing the plane so you can buy another.

Ken Cook Mon Jul 12, 2021 5:32 pm

Another tid bit of info. When mounting the Medallion .15 or TD on a profile model use caution in regards to fire. These tend to backfire a bit especially if over primed when on their side any residual fuel can quickly and aggressively ignite.

Ken Cook Mon Jul 12, 2021 5:32 pm

Another tid bit of info. When mounting the Medallion .15 or TD on a profile model use caution in regards to fire. These tend to backfire a bit especially if over primed when on their side any residual fuel can quickly and aggressively ignite. Other than being loud, it would make a good combination on this plane. The Fox slant plug .15X also shares the same bolt pattern.

getback Tue Jul 13, 2021 7:02 am

Jim is that kit die cut or print/dye on balsa to cut it out yourself ? I have the kit and mine is dye print and after seeing that i just sealed the kit back up ( very disappointed ) I could do it but will take a lot longer !! Good advice Ken thanks !

**944_Jim** Tue Jul 13, 2021 8:40 am

Ken,

I really don't know yet. I **think** I saw die-cut, and mildly disappointed-not shocked it wasn't lasercut. The box was shrinkwrapped, so this picture is just after I cut the plastic. I wanted to smell the balsa!

Looking at the plans, this think is like a few british plans on OZ...except I don't have to source/cut wood. That last piece is why I bought it new from Eugene Hobby Shop (Oregon) last Thursday evening. While USPS got it here quickly, I can commend the hobby shop on getting the hole shot because they had it to USPS Friday (with an estimated delivery of mid-week).

I'll use a rib or two to calibrate my rib-marking jig. If all is well, this wing gets done in two-three hours. I may be able to make this a night time priority and have it done in a week. Huh...

**944_Jim** Tue Jul 13, 2021 11:49 am

Yup.Die-cut.

getback Tue Jul 13, 2021 5:37 pm

You dog you got Lucky ! Very Happy

COOL

Ken Cook Wed Jul 14, 2021 4:30 pm

Inked is far superior to a die cut kit and with a Akromaster, there's nothing to it. You have probably 10 ribs tops and you stack them and sand them all at once making them perfect to each other opposed to die smashing.

getback Wed Jul 14, 2021 4:47 pm

OK Do you cut on inside of the line or the outside ?

Ken Cook Wed Jul 14, 2021 6:08 pm

I would cut the ribs 1/8" outside the lines. Tack glue the whole stack together and sand to the line

Ken Cook Wed Jul 14, 2021 6:10 pm

I would cut the ribs 1/8" outside the lines. Tack glue the whole stack together and sand to the line. My sanding tool is a 1/2" thick piece of Corian cut so that a 4" wide sanding belt fits on it perfectly and tight. I use 36 grit on that and it cuts very quickly.

andrew Wed Jul 14, 2021 6:13 pm

getback wrote:OK Do you cut on inside of the line or the outside ?

For me, I tend to cut just outside the line, then final sand to shape -- this applies to all parts. I also do the same as Ken with ribs. Cutting slightly fat gives me some sanding leeway and lets me remove those invariable nicks and flat spots. Just make sure your top and bottom rib are the correct shape since they will determine the sanding pattern.

The attached picture has a rib stack and the original pattern I used to rough cut the blanks. I print the rib pattern from either Airfoil Tools or Profili, glue the pattern to a piece of Formica laminate, then cut and sand to shape. The formica is hard and I can use an Xacto or razor blade to zip around it. I have several sanding bars from the old Great Planes site that I use for finish sanding.

a--

**944_Jim** Thu Jul 15, 2021 6:20 am

I started checking out the kit contents. Would you believe laser cut plywood and tail group, and die-cut ribsheet? My R1 (center) rib sheet was "off target" at cutting time, so R1 is missing a section from being at the wrong place at the wrong time. I may shoot SIG an email/picture...I may just scab some scrap on the rib and fix it.

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