Moving the cg forward

[Dan767]

brown j, not a problem.

[lazyboyflyer]

I think Jim has a good point, your using a 3 bladed prop up front and if you put all the batteries and electrics up front in the dome and then stagger your fuel tank a little forward on the wing tube, you'll have a forward CG for sure. You should consider doing the push-pull set-up, I would. Check the Mark Trent tread before you decide.

[Extra260]

I will not always be using a 3 blade though. What cg should my aimming point be??? I would love to do the push pull for weight but if it means tail heavy I wont. But when I look at murrys plane it makes me think I cant because his tank is all the way in front of the tube and his is 100mm with 2 servos in the back. Remmber that I have greeves if that makes any difference.

[rcdart]

I cant see you getting the CG right with pipes and putting the rudder servos in the tail, but, if you are unsure, build the plane without mounting the rudder servos, then do some CG checks, if you do this, dont forget to place all items needed, eg: extension leads, arms, linkages etc.

[Extra260]

I think I am going to do either 3 5955's in the carbon tray under the tank or 2 8711's. Would this be able to fit under the pipes??

[Dan767]

That works. Look at the pictures in the manual, specifically P44.

I aimed for 95 to 100mm for my cg. The prototype was flown at 120mm. Most IMAC fliers are around the 95 to 100mm.

[Extra260]

The proto was flown at 120??? Thats really tail heavy right?? I ordered 5 5955's today 2 for the elevators and 3 for rudder. I already have 4 for the ailerons. Now the question is wether I should mount them in an swb tray behind the tank or under the pipes under the tank. If I go the under the tank route do I just by an offset arm for the 3rd servo??

[Extra260]

Anyone know how much space there is at that position??? It doesnt give you a good look in the manuel

[Extra260]

Another question I have is how long of extensions do i need the fromeco guys to make for my packs if I mount them up front?

[jack strickland]

Hello All : Dont mean to be a buttinski here, but have any of you fellow IMACers tried a boost tab on the rudder? I just recently did, (the tab is 10% of the approx. 160 sq in. of the rudder, 10in. by 1.750 in the results were quite remarkable. Am using a 150cc engine with a 32x10 Mejdzlik Prop. Have flown these planes for the last 15 years, and have never had one that would knife edge loop with only 270 in. oz. on the rudder, till now, Just a thought. If you are interested, Roger Forgues has a forum on boost tabs. The system really works, and can signifcantly reduce the amount of servo power required.
regards to all.
Jack

[Dan767]

	Quote: Originally Posted by Extra260
	Anyone know how much space there is at that position??? It doesnt give you a good look in the manuel

Here's a picture that may help. I'm on the road and can't get pics of my set up. This is very similar to mine. I've located mine a little more forward than this. The tray comes just as you see it in the picture. Picture is of Darcy Wingo's plane.

[murry]

I don't think you can mount the rudder servos under the pipes, the pull pull wires should hit the pipes. My rudder tray was mounted on the bottom of the fuse and I moved it above the pipes when I changed from cans to greve pipes. I also removed one servo from my swb tray, I think for IMAC in basic or sportsman two is enough.

[3ddd]

i would stay with rcdart's idea.put it all together except for the rudder servos and tray and gear and after the rest is all done you can put them and your batteries in were they are needed for balance.it isn't like the positions won't still be available

[Extra260]

Well I have 3 servos for the rudder and I ended up getting a swb 3 servo offset tray today so I will most likely just mount the rudder servos up front just for redundancy and good measure on the cg. In the manuel it says to mount 4 servos under the greeves. It looks pretty risky though just because the 5955's loose enough power from just heating up I dont think that the pipes would help any. I might mount them down there and make cooling holes under the servo tray but that would be near the seam and I dont no if I want to stress the integrity of it.

[Extra260]

And also I need to know the lengths of battery wires I need fromeco to make