GSN GIVE-A-WAY Hangar 9 35% Extra 300X Assembly

[Snoopy1]

Last night I squeezed the airplane back into my workshop and got it on the bench. I pulled the cowl off to make sure everything survived maiden day, and other than one Teflon coupler leaking just a bit it all looks great.

I need to add some down thrust so I spent some time figuring out just how I wanted to do it. I decided to take one of the plastic spacers that came with Blazing Star mount and sand it into an angled shim. I'm going to put it between the mount and the firewall, so that way the engine is still bolted to a nice flat piece of aluminum. Today at work I sanded the spacer and it turned out pretty good. I'm not sure how much down it will give me, but I'll try and check it tonight.


Stock Spacer

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Sanded Shim.

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I also have a nasty surge when flying level and steady half throttle. It's not a burble, but a surge like your moving the throttle that I need to deal with. It could be several things, starting with tuning. Other causes could be air flow/air pressure at the carb, or header length, and a few more things. It's more than likely tuning, but there is a big hole in the cowl right in front of the carb so it gets a lot of air blown right on it. The common fix for the air pressure problem is to put a fitting in the diaphragm plate and run a hole into the fuselage. Another fix I've seen is to add a flat plate in front of the diaphragm plate to keep the air from blowing right on it. My DA120 has the red aluminum diaphragm cover with the holes in the top and bottom which is supposed to help stop that problem. But as you can see, this carb gets a pretty big air blast.

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Now I could close the hole in the cowl, but I don't want to for several reasons. It's how I set the choke, It's how I see the needles to adjust them, and it's a straight through flow for air to cool the cans. Now I know a lot of people say they should be closed to help the air flow for cooling the engine from the front of the cowl and the baffles, and they could be right, but I like to get more air flowing over the cans since they are directly under the fuel tank and the batteries. I am planning on adding more exit vents, since I think I don't have enough.

Tonight I'm going to make an aluminum plate that bolts on over the original diaphragm cover with some small standoffs. It will block the direct air blast from the holes in the diaphragm cover and hang low enough to keep it off of the choke blade and throat as well. Will this help the surge, maybe, if it's an air pressure thing, but chances are it's tuning. But since I like to make little things out of aluminum, and it 's free, and it wont hurt anything I'm going to build one.


Here is one that Richo from DA Australia posted a picture of.

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Nice shim that is not easy to do and get flat on both sides. My question is now when you install the shim the spinner is going to be off. I have done this and then end up getting very frustrated trying to get the cowl centred again if you know how to do this an easy way please let me know. Because I have left engine alone just because it so difficult to correct the cowl . Thanks

 

[Jetpainter]

Nice shim that is not easy to do and get flat on both sides. My question is now when you install the shim the spinner is going to be off. I have done this and then end up getting very frustrated trying to get the cowl centred again if you know how to do this an easy way please let me know. Because I have left engine alone just because it so difficult to correct the cowl . Thanks

Well luckily this is a 300X and not a 33oSC. The 300X doesn't really have a spinner ring on the cowl, so if it's off a tad there really isn't anything to match it to, so hopefully it will look okay. Time will tell.

There is quite a difference in the two cowls.

 

[Snoopy1]

Well luckily this is a 300X and not a 33oSC. The 300X doesn't really have a spinner ring on the cowl, so if it's off a tad there really isn't anything to match it to, so hopefully it will look okay. Time will tell.

There is quite a difference in the two cowls.

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Yes I see what you mean that does make it a lot easier if it just a miner amount you will never see it. Thanks.

 

[Jetpainter]

Tonight I installed my thrust shim. It worked out great and took it from zero to one degree down thrust. Time will tell if that's the right amount.

I also made my plate to block the air from blowing directly on the carb. The aluminum I used is overkill, but it's all I had here.

 

[Luchnia]

Tonight I installed my thrust shim. It worked out great and took it from zero to one degree down thrust. Time will tell if that's the right amount.

I also made my plate to block the air from blowing directly on the carb. The aluminum I used is overkill, but it's all I had here.

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I am curious if that thrust plate will work for the mid range surge. I have done that on some smaller planes and it worked. I have one DA 120 that has a mid-range surge, but DA never advised to put a plate on it and I just never got around to it. I am thinking now that I should at least go that route first. The surge is not bad, but enough that it is annoying.

 

[Snoopy1]

Tonight I installed my thrust shim. It worked out great and took it from zero to one degree down thrust. Time will tell if that's the right amount.

I also made my plate to block the air from blowing directly on the carb. The aluminum I used is overkill, but it's all I had here.

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Looks good to me that will do the trick for you. How about a little polish job on the plate, knowing your trade you will most likely have 10 different ways to shine it up in about a minute. Or at least paint it yellow or red.

 

[Jetpainter]

Looks good to me that will do the trick for you. How about a little polish job on the plate, knowing your trade you will most likely have 10 different ways to shine it up in about a minute. Or at least paint it yellow or red.

I was going to give it an engine turned finish like I do most of the time, but I somehow managed to misplace my wire wheel end brush I use to do it with in my drill press. I looked for it when I made my canister mount and couldn't find it. If it were in a spot that you could see it without kneeling on the ground I might have made an effort, but I'm getting very lazy, and crabby, in my old age.

 

[Jetpainter]

Another issue I have to deal with is some transportation damage. Monday night when I set the airplane up on my bench I found damage on the right wheel pant. Evidently my "Hillbilly Hauler" mount, was hitting the pant and I never noticed. Today at work I modified the mounts so they don't come anywhere near the wheel pants now.

You can see in the pictures it was very close before I changed it.
I left the stock 3 1/2" wheels on. I never run one that small. Now I'm paying for my decision to leave them on.

 

[Snoopy1]

I was going to give it an engine turned finish like I do most of the time, but I somehow managed to misplace my wire wheel end brush I use to do it with in my drill press. I looked for it when I made my canister mount and couldn't find it. If it were in a spot that you could see it without kneeling on the ground I might have made an effort, but I'm getting very lazy, and crabby, in my old age.

How true I know exactly what you mean. I have to admit that often when building I am standing in front of the plane and will say that is good enough while before I would fuss and make beautiful with no gain, I guess I am also getting old and lazy.

 

[Jetpainter]

A few nights ago I glassed my wheel pants back together. I wasn't planning on doing much more than touching it up with a brush, but today I took it to work and did a really quick spot repair.

I featheredged it, smeared some Dolphin Glaze on it with my finger, sanded that, primed it with a spray can, sanded and spot painted. I just happened to have some red enamel from painting a sign that matched great!