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Sig four*40 kit

Old 04-07-2007, 01:01 PM
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mmh
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Default Sig four*40 kit

Hi , I am new to this hobby and building my first kit. I ran into a problem and would appriciate some help on clearfying the following
I am trying to figure out the exact placement for the engine mounts on the firewall. The kit came with 2 glass filed mounts and the diagram said to mark the center line and the thrust line on the firewall but it does say if the mount needs to to alligned with the thrust line. I have an OS 40LA engine. Does the thrust line have to rn through the center of the engine? does the center of the mount have to be alligned with the thrust line?
Your help in this matter will be appriciated
Thanks
Old 04-07-2007, 02:00 PM
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Default RE: Sig four*40 kit

Yes. Those line must line up in the center of the engine. CLamp the engine to the mounts or use Thin CA to hold it on and place that engine right in the center of those lines.
Old 04-07-2007, 02:42 PM
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horace315
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Default RE: Sig four*40 kit

the kit i built had alignment marks on the mount itself and said to align the cross marks with that line,unless you are goint to mount the engine diagonally use those marks.
Old 04-07-2007, 04:00 PM
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mmh
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Default RE: Sig four*40 kit

there are 2 lines on the mount which one shall i use and do i align it with the thrust line ?
thanks for helping
Old 04-07-2007, 05:08 PM
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Default RE: Sig four*40 kit

Yes, use both those lines. Those lines are there to help get the engine and the mounts in the correct position. The 4* already has thrust built into the airframe so you do not have to figuer that out for yourself. You will actually make a cross with the lines and you put the engine right in the middle of the lines. Let me just say though that the plane is such a forgiving plane you can be off a bit and it will still fly nice.
Old 04-07-2007, 05:26 PM
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Default RE: Sig four*40 kit

I`m to the point of covering mine, hope this pic helps.
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Old 04-07-2007, 06:12 PM
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Campgems
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Default RE: Sig four*40 kit

Guys, an added heads up. I busted my 4* 60 in half on a hard landing. Going over old forums, it seems that that is a problem with the 4* series. Do your self a favor and re-enforce the buklhead at the end of the wing saddle and lay in some 1/4" sq bass wood or poplar along the joing between the sides and the bottom of hte fuselage in at least the first bay behind the wing. I am using 3/4" bass wood cut to tri stock and framing in that bulkhead, fore and aft.

The landing gear mount is another issue. Laminate in a 1/8" birch ply on top of the existing mount and overlap it over the bottom sheeting at least an inch or so. The langing gear mount ripped out on the same landing and the wheels raised hell with the bottom of the wings.

I'm about back together now, just a couple more glue sessions and I'll be ready to recover.

Other than this problem, the 4* is a great flying airplane. Just watch that you keep up some speed on landing, it floats so that it is tempting to try to land to slow. It don't work that way.[&o]

Don
Old 04-07-2007, 09:29 PM
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mmh
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Default RE: Sig four*40 kit

Thanks again guys , guess i will go and read the manual one more time to see if i can make some sense of it. Thanks for all the information.
Old 04-08-2007, 11:52 AM
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mmh
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Default RE: Sig four*40 kit

Hi
I took a couple of pic to clarify my confusion, you will note that in one picture i have placed the mount with the thrust line right inbetween the two lines on the mount and in the second the thrust line is alligned with one of the lines on the mount. Are either one of these the correct position or am I totally off the track.
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Old 04-08-2007, 12:01 PM
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Default RE: Sig four*40 kit

My friend you are doing great. The first picture on the left looks just right.
Old 04-08-2007, 12:12 PM
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Default RE: Sig four*40 kit

The thrust line is where the prop shaft will be. That's the center of it.
Old 04-09-2007, 01:53 AM
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Campgems
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Default RE: Sig four*40 kit

Ditto the one on the left. In all engines that I know of, the bottom of the mounting lugs is dead on center to the crank shaft. So, placing the top of the moter mound on the thrust line is correct. Just like shown on the left photo.

Don
Old 04-09-2007, 10:02 AM
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mmh
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Default RE: Sig four*40 kit

Thanks again for all your help. The mount and engine are now in , placed it just like in the pic to the left that I had posted.......hope it will fly.....although still a long ways to go before its ready, I hear sanding and covering are pretty tough to do when its your first time. The weather here still sucks and too cold to go to the field so I have some time to complete
Old 04-23-2007, 08:56 AM
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Default RE: Sig four*40 kit

I`m just setting up my CG on the 4 star. I have a Saito 56 mounted and had to put the battery in the fuse behind the wing. Is this normal ? Calls for a Saito 50 in the plans.
Old 04-23-2007, 09:11 AM
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Default RE: Sig four*40 kit

Insane,
There really isn't a "normal" place to put the battery in a plane. Since it's used a tool to help balance the plane where it is placed will vary from plane to plane. I've had planes that had the batter directly behind the firewall, and I've had planes that had the battery installed at the end of the fuselage in the tail. Just as long as you secure the battery pack so that it can't move while in flight you'll be fine wherever you put the pack at. Just remember, no matter where you move the pack to it's still better than adding "dead" weight to a plane to balance it.

Hope this helps

Ken
Old 04-23-2007, 09:45 AM
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Default RE: Sig four*40 kit

Thanks Ken. I thought it would be closer than that , as the plane was built very close to the plans.
It shows the CG point on the lower spar , which means setting the CG with the plane right side up . It sets on the CG machine better upside down . Will this throw off the CG. I checked it up right and it seemed close ?
I`m shooting for a maiden tomorrow , if I get all my honey do list done today.
Old 04-23-2007, 04:05 PM
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Default RE: Sig four*40 kit

No Prob Robbie.
Old 04-23-2007, 07:51 PM
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Default RE: Sig four*40 kit


ORIGINAL: Insanemoondoggie

Thanks Ken. I thought it would be closer than that , as the plane was built very close to the plans.
It shows the CG point on the lower spar , which means setting the CG with the plane right side up . It sets on the CG machine better upside down . Will this throw off the CG. I checked it up right and it seemed close ?
I`m shooting for a maiden tomorrow , if I get all my honey do list done today.
It is much easier to balance upside down because most of the mass will be hanging below the wing that way. If it balances on the top main spar, you'll be just fine. On my last 4*, I added a balsa stick accross the width of the fuse behind the wing. The battery was zip tied to it. Doing it that way made the plane blance right without adding lead.
Old 04-23-2007, 08:29 PM
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Default RE: Sig four*40 kit

We are on the same wave link Chuck. Thats what I ended up doing. Thanks for the info.
Old 04-25-2007, 10:10 PM
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Default RE: Sig four*40 kit

Maiden the 4* yesterday. Crosswinds 10 to 20 and changing directions like crazy. I was so nervous about flying my first low wing , I flew the heck out of my LT40 first , doing 2 hours of touch n go`s to get use to the wind.

Well time had come. Taxed out two the run way , rolled into the throttle and she was airborne. Flew a couple of circuits in the pattern to get her trimmed. 2 clicks up and good to go.

I fell in love with 4 strokes yesterday. The power at lower rpm`s is just what I`ve been hoping for. No more flying at the speed of sound , just to get some hp & torque . Instant on and go. The Saito 56 , pulls it straight up tell you tell it different.

I flew 8 , 15 min. flights of. inside , outside loops , inverted , split s , stall turns , ect. Wow! I can not stop grinning, it is so much easier to fly than a trainer. But I believe flying the covering off the LT40 , prepared me for the 4 Star . I was getting bored , but not no more , I`m so darn hooked.

Bipes next. lol Skybolt and GP Ultimate should be ready in the next month or so. And the GP Ultra Sport 40 comes out in June. I`m set. lol
Old 04-25-2007, 10:32 PM
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Default RE: Sig four*40 kit

Insane,

I know what you mean. I have about 10 flights on my scratch built Stitchen. It's a low wing trainer. It only has a 44" wingspan and a HB25 for power. But it sure is a lot more fun to fly than my trainer. Got a couple of decent patterns inverted tonight in about a 10 mph wind. She seems to come in a little hot, but hey it's good practice. Next time out will be touch and goes till it's second nature to put her on the ground. Glad to hear your gettin plenty of flight time. I got 3 flights in tonight myself. Sure is nice living 1 mile from the field. The other nice thing about the smaller plane is that I can put the wing on in the basement and put it in the jeep ready for gas and go.

See ya,
Del
Old 04-25-2007, 10:48 PM
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Default RE: Sig four*40 kit

Hi Del. Been wondering were you been .

Good to hear your getting some fly time. And your ahead of me , scratch builts are tough. Labor of Luv. Way to go.

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