Modified SIG Twister

Very clean build Ron. Are you going to box the TE? It'll make it strong and difficult to twist.

Lieven

Twisted Sister?   













Edited by Rusty... Revived the video

What a ridiculous decade....my daughter thinks it's cool that I grew up in the 80's. I should show her this video.

Cribbs74 wrote:What a ridiculous decade....my daughter thinks it's cool that I grew up in the 80's. I should show her this video.

Ya, but I do like the song and band though

Both my Sons are into Atari, Sega and Nintendo from the 80s-90s, they say the games are more fun from back then

Sorry for the hijack, I seen the name of your thread and Twisted Sister popped in my head... proceed kind sir

No worries

Ron, I'm not sure if your aware of this particular wing having half ribs. This is one modification I would truly do. Installing 1/2 ribs from the spars to the leading edge in between the stock ribs helps this plane immensely. The rib spacing is too far apart allowing the covering to really sag in between. You could easily stand the wing up on end and get a pattern and then stack cut a few of them. Another thing is to install vertical grain 1/16th in between the ribs on the back of the spars from top to bottom for a few bays from the center of fuse outwards towards both tips. Ken

Ken,

I'll probably do the 1/2 ribs as you suggest. I am having a little trouble picturing the other modification you suggested.


Ron

Ken Cook wrote:... Another thing is to install vertical grain 1/16th in between the ribs on the back of the spars from top to bottom for a few bays from the center of fuse outwards towards both tips. Ken

Cribbs74 wrote:Ken,

I'll probably do the 1/2 ribs as you suggest. I am having a little trouble picturing the other modification you suggested.

Ron

Like shear webs I think. To stiffen the wing as it extends out from the root.

Ah! I get it, pretty cool. Thanks Rusty!

Ron

I put the nose ribs on my Fancherized Twister, and I think it helps maintain the airfoil. Besides, it looks cool.

Those shear webs are better installed so they exactly fit the spar spacing, and are centered on the underside of the spar. The reason is the same as why I beams are used in structures instead of C beams. The C configuration puts a twist on the spar under load, where the I configuration does not.

Now, how much of a practical difference is this?

Good question. I decide my answer when I build. I have built both I and C configurations with excellent results, but I still crash a lot.

Phil

Thanks Phil,

So what you are saying is they should be in between the spars and not the outside?

Ron

The I beam is definitely stronger than the C. But if the C will do an adequate job of stiffening, perhaps it would just let go and cause less destruction in a crash? Wondering out loud.
Rusty

Ron, I personally see no  advantage to placing the shear webbing within the spar area. The bottom line is that you should have them and  place them at least to the middle of the wing approx 4 bays out towards the tip.  True a I beam is strong, but the shear webs and glue stop the spars from flexing and in the event of terra firma, the webs being placed on the outside can be sacrificial saving the spars as they will just crack or  pop off. They're stong enough as is and that's all that you need which is far more than what the original kit offers. Flex the wing over your knee prior to installing these and then do it afterwards. You will note the strength advantage.  Lieven mentioned this above by doing this to the trailing edge as well. Depending on wood selection, I like to do this to every bay of the trailing edge by gluing the pieces from top to bottom of the trailing edge sheets. I've done this where you made the pieces go within the opening but it's very time consuming and not necessary. Many of us have avoided this step by just swapping out the stock spars and leading edge material on the Twister for spruce. Ken

One advantage of placing the shear webbing between the spars, as I see it, is that you do not rely on the glue to do all the job...

Plus, as mentioned before, the I beam will bend symmetrically. On the other hand, one could possibly get the C-beam to twist the wing in the right direction (to give washout) under load...   

Ken Cook wrote:Many of us have avoided this step by just swapping out the stock spars and leading edge material on the Twister for spruce. Ken

The leading and trailing edges of my Twister were so twisted I replaced them with basswood.

Jim

JPvelo wrote:

Ken Cook wrote:Many of us have avoided this step by just swapping out the stock spars and leading edge material on the Twister for spruce. Ken

The leading and trailing edges of my Twister were so twisted I replaced them with basswood.

Jim

Probably not a bad idea. Mine were terrible as well. I should have replaced the wood. Oh well, not turning back now.

Here is a little update.

I installed the beam mounts and created a fin/rudder more to my liking. I will work on the shear webs and half ribs next. The .40FP is rubber banded to the nose. Looks like I will have to cut more area between the mounts to slide the engine back.

This thing feels heavy already. I am not happy about that. I'll weigh it and see.

Ron

Is that an MGA sitting there Ron?  

Ron,
I added three inches to the tail of my twister and left the nose the same length. I came out tail heavy and am using a 2oz prop hub to balance properly. Before moving the engine back I would consider cutting new ply doublers that will accomadate a filler behind the engine. You will want to replace the kit supplied ply anyway, at least on the outboard side.

Jim

Jim,

I added 2" to the rear and cut off one from the front. Not sure where that puts me. I guess in reality that is 1" extra in the back end.

I'll keep that in mind Jim. You used the the FP correct?

roddie wrote:Is that an MGA sitting there Ron?  

Yes sir, 1958 fresh