WOT 4 CG and adding nose weight

[Bob Burton]

I have just "built" a WOT 4 foam-e 2+, if you can call adding stickers, screwing on the U/C and slotting in the tail and fin building. The recommended CG is 70mm back from the leading edge at the root but as built it is 80mm back.

So it looks like I will need to add weight to the nose to put it right, but what is the best way to do it ? The 2200 mAh 3S Lipo is as far forward as it can be and there is no room to move the receiver or ESC further forward. From experimenting with weights it looks like I am going to need to add about 3oz of weight up front but what is the best way to do it ?

I had high hopes of stick on weights but those available from the local car tyre fitters are steel not lead and are puny. Has anyone got any experience of the WOT 4 foam-e ? Will it be OK with the CG at 80mm and/or what is the best way to add nose weight ?

[CARPERFECT]

Just fly it. it will be fine. Hundreds have been built and they a fine.

[Bob Cotsford]

I don't think I've ever checked the balance on mine when changing between battery brands or after various repairs. A couple of clicks of trim covers any 2200 3S I've tried that will fit in the bay. It really is tolerant of the CofG position.

[Braddock, VC]

Review in this month's rcmw says ripmax concede there is a misprint and the c of g should be 80 mm back from leading edge, came about as a result of testing showing the model was even better flying than when balanced on the original c of g which was 60 mm back iirc.

So I'll have to change the c of g on my mk1 mk2 foam-e.

[Bob Burton]

Thanks for that. I will read the review next time I am in the library (aka W.H. Smiths)

[Mark a]

I bought one of these Mk2 + wotty's at Weston this year. My old foamie Wot 4 flew straight out of the box the new one did not. I found mine very nose heavy even with the battery pushed as far back as possible.

[Bob Burton]

Ripmax Customer Services don't answer the 'phone and no reply to email yet, but reading the review in RCMW I see that the mistake has been acknowledged on the WOT4 Mk2+ page on the Ripmax site, which says

"Notice: The manual states the 'Center of Gravity' should be 70mm, it should say 80mm back from the leading edge. A standard Wot4 Foam-E Mk2+ should balance with no extra weight." so it looks like I am good to go.

[FlyinBrian]

In My experience ( Mk 1 ) the recommended CG is too far forward, I have about an ounce of lead in the rectangular hole under the fin secured with a piece of selotape.

Edited By FlyinBrian on 23/07/2015 12:36:05

[Bob Burton]

I have just had the first flights with the CG at 80mm from the leading edge and it is certainly safe with it there. Once I am more familiar with the handling I may sneak it back a bit to liven up the handling. As it is I am quite pleased with it and as I haven't flown a model like this for years I was happy to pootle about, add a bit of trim and execute couple of far from perfect but non damaging landings.

[michael mannings 1]

Poor customer service at Ripmax.. The above thread about the c of g is dated July 2015.. I have just purchased a Mak 2 foamie and guess what, the instructions still say 70mm, two years on.. Or is it I bought very ol stock!!

[Andy48]

Just finished building an electric Wot 4 mk 2 balsa version. Put a Turnigy SK3 3548 840 motor in it with a 3300 4S battery and an 11x7. This gives over 2kg static thrust, yet keeps the maximum current below 50amps. The battery bay is fitted as suggested, and I've used standard servos. First thing I found was that with the CofG at 82mm, it needed about 250gm of lead in the nose to get the balance exactly right, which makes it a heavy plane for the size, especially as the electric version contains a seriously heavy engine mount.

Took it out for its maiden flight this morning with light winds, and it flew like a dog, it was difficult to control at any speed and needed constant elevator and aileron input just to keep it out of a bin bag. It didn't improve with different throttle settings either. More by luck than any skill I managed to land without damage. First impression is that it is severely tail heavy still, and the CofG therefore must be wrong.

Any ideas?

[Denis Watkins]

From the current manual

The Centre of Gravity (C/G or Balance Point) should be 82mm (3-1/4" back from the leading edge of the wing at the
root. This should be measured with the fuel tank empty. Support the completed model under the wing either side of the
fuselage at this point and add weight or adjust the position of the radio battery in as necessary to achieve a slightly nose
down attitude.

Edited By Denis Watkins on 28/09/2017 15:59:37

[Andy48]

I think if you read my post, the Cof G is exactly 82mm.

[brokenenglish]

Bob, before you start adding weight, check that there is none already added.

The last W4 foamie I had (fairly recently, the current model) came with a big metal weight in the slot under the fin, as delivered. So have a look there before you start adding at the nose.

[John Muir]

I doubt that it's tail heavy to be honest. My old Wot 4 Classic (essentially the same plane, aerodynamically speaking at least) flies really well with the CG at 106mm back. Also a rearward CG wouldn't affect the aileron response. I'd be tempted to simply cut the control movements down and add plenty expo, or check for something loose or out of kilter although I'm betting you've already done that.