What's the best way to add weight at the nose to achieve CoG

[Bob Moore]

Hi all

 

I finally fitted the SC40 engine to the Wot 4 I just rebuilt and recovered, but find it's quite tail heavy.  I usually add a couple of little strips of lead at the front of the engine firewall, but this needs 3 or 4 ozs.  I can't really think of anyway to make the back end lighter apart from fitting snakes instead of the push rods things that are original. And I don't think it will make a lot of difference anyway. I guess a more powerful engine would do it, but I find the 40 is sufficient  for me. (And it will cost!)

 

At 5 3/4 pounds it seemed quite heavy, but it's almost identical in weight to my ARTF Wot 4 with a 40.

 

What is the best and most secure way to add a lump of lead please?

 

Here it is.  It didn't come out quite as well as I'd hoped, but looks ok from a distance!  The wing is all red underside so should be easier to 'read' in the sky than the ARTF colour scheme which is identical both surfaces? The yellow was too transparent, so I can see any imperfections through it. And the top surface of the wing had been laquered or something so when I ironed on the film (solarfilm I think?) it bubbled a bit.

 

Overall I'm quite please with it though. I had to repair the fusi and make a new tail fin and re fit the tail.

 

Bright enough to find if it gets lost in the bushes!

 

 

 

Edited By Bob Moore on 28/10/2010 10:42:23

[leccyflyer]

You can use self adhesive tyre weights, fixed to the firewall, or screwed with self tappers to the engine mount itself. The further forward you can get it, the less you need.

[Bob Moore]

Thanks . Tyre weights?   A good idea.

[JayCee]

 Hi Bob

 

I think 'Great Planes' do weighted prop nuts, can't get any further forward than that

 

JC

[Bob Moore]

That makes good sense, as the further forward the better. I hate adding weight!

I guess if you could mould it well enough you could fit weight into the spinner (nose cone)?

Balance would be important of course to avoid vibration.

[Vecchio Austriaco]

I normally use a flat piece of lead - folded if there is not enough space - and screw it to the firewall using self cutting screws. (I don't trust adhesive stuff in an area where the temperature could be high and where fuel could be present)

[ken anderson.]

hello bob-up here in the backwood's of northumberland..we use various method's as mentioned...also wot you can do - is use offcut's of lead flashing...the type you see on roof's etc....thin strip's- i use-cut to size and slid alongside/on top/underneath the fuel tank...the one's outside on the firewall etc..can sometime's come loose with the fuel.....

 

watch you dont get caught on the  roof's when you are up getting some...   ..

 

 ken anderson   ne...1.

[Myron Beaumont]

No wonder not many people go to church in the NE .What with all the rain pouring in etc

[leccyflyer]

Posted by Vecchio Austriaco on 28/10/2010 12:04:35:

I normally use a flat piece of lead - folded if there is not enough space - and screw it to the firewall using self cutting screws. (I don't trust adhesive stuff in an area where the temperature could be high and where fuel could be present)

 Like on the rim of a tyre for instance?

 

Seriously, I'd suggest using self-tappers to fix tyre weights to the firewall or engine mount as well. I've previously used the heavyweight dome nuts on the propeller but have been concerned about that affecting the balance of the shaft and premature wear and tear.

[Marko]

Hi Bob have you tried putting the rx batt under the fuel Tank and changing the spinner to a Ali one ? also props differ in weight aswell maybe a asp but some time adding lead can't be helped hope this helps cheers ............... mark

[Myron Beaumont]

Bob

I suppose you could line a plastic spinner with Bacofoil or somesuch & pour molten lead into it  (& even incorporate the propnut ?) -Then run the engine and turn it down as if on a lathe .A bit dodgy though

[Ernie]

Hi Guys, I have an old friend in Scotland, who does use lead in the spinner. He mixes lead shott with epoxy,, and pours it in.

I wouldn't even consider it, but it does seem to work fine for him.

 

ernie

[Vecchio Austriaco]

Hi Leccyflyer,

 

Until today I magange to refuel my car without spills - and I use diesel and not glow fuel. So the fuel spills are not present on my tires.   By the way - these weights  - are they made from lead or another metal?

 

About weight on the "nose" - The engine should not have to many problems - think about the difference in weight of some spinners - there is quite a lot of difference between an aluminium spinner and a plastic one.

 

 

[Bob Moore]

I just moved the rx battery from immediately behind the fuel tank, to on top of it and as far as possible forward (in a piece of foam.)

 

That has reduced the amount of lead I need (I do use sheet flashing already.)

 

It appeared to need 5 or 6 ozs when I first tested. Seems such a shame to add the much weight to a model? But I guess relative to its weight of 5 3/4 lbs it's not that bad?

 

I'm just melting some lead on the gas cooker as we speak (using a tin lid as a mould) with the intention of bolting it under the engine mount.

 

I like the lead shot in the nose cone idea I must say. Might try that. As it's close to the centre of rotation it might be ok. If not I guess it would vibrate like crazy and even mess up bearings?

[Myron Beaumont]

Vecchio

I think the wheel balance weights are made from the same stuff as fishing weights as lead is dangerous of course (H & S again -mind you, it did bring down the Roman empire & if that's not off thread ,I don't know what is !) Sorry .

I like Ernies Scottish friends idea of lead shot & epoxy in the spinner .Bit dodgy if you hit someone -Insurance looms its head again ? I could go on but I won't BUT then there's the question of --------------------- ad infinitum etc etc

[Richard Wood]

Hi Bob,

Have you tried putting a wee bit of packing or stand-offs between

the engine mount & firewall to get the weight of the motor a tad

further fwd?

I notice you're not using a cowl on your Wottie so there's a bit of scope

here for experimentation.

It might reduce the amount of church roof you need to use.

 

 

 

[Bob Moore]

Hi Richard,

 

the thought did cross my mind, though I've now screwed my newly melted and moulded bit of lead on the firewall.  If and when I break the engine mount (it'll happen some time )  I'll give that a try. Obviously better all round than adding unnecessary weight.

[Stephen Grigg]

I like what youve done to the Wot 4 .,I bought one last year as a winter hack flew well but did a sharp right turn every time it took off which was frustrating.Might get it out and try new U/C this winter.If it works it may turn Yellow

[001]

Can you reduce weight at the rear end? Cut holes in the fin, rudder, tailplane and elevator withou weakening them. Save 5 grams at the back, avoid adding 20 or more at the front.

I do not like the idea of adding weight in the spinner at all.

If you must add weight at the front, in the past I have cast U shaped lead weights with 4 holes in to match the (longer) engine mounting bolts and fixed it with big washers under the nuts. The U shape is to clear the crankcase. Picture available if required..

[ken anderson.]

putting lead in the spinner was something i overheard someone talking about year's ago when i was having a prob with space in a model(i had only been RC modelling over a year)...yabba i thought and i put some in the plastic spinner.......the vibration when i started the motor was something else....and it wrecked the RX...lesson learnt the hard way...... ...

 

 Green as Grass(years ago) ken anderson   ne....1.        

[Bob Moore]

Thanks Stephen, I was pleased with the colour scheme. As I said, the underside of the wing is all red, so will be easy to spot.  The yellow side looked a bit bland till I added the stripes and Hitec sticker.  The u/c is rather ugly, I might invest in something more attractive (if I can find something?)

 

I get the idea of the U shaped weight. Good idea and allows you to get the weight as far forward as possible. Can't really think of a way to shed weight at the back end.  Because the whole tail was a bit damaged I had to disassemble it and double up on a couple of bits of balsa. I doubt it added anything significant though. A couple of snakes might be slightly lighter,  to replace the push pull rods that are original.

 

On my ARTF Wot, which has the engine mounted sideways I bolted lead under the engine mount. It also counterbalances the exhaust on the other side a bit.

 

This is the weight on my 'new' old Wotty.

 

 

 

Edited By Bob Moore on 28/10/2010 18:08:09

Edited By Bob Moore on 28/10/2010 18:11:40

[Ernie]

Hi Guys, Anything that spins, should be balanced.

 

ernie

[Phil Claridge]

if you put lead under the mounting use longer bolts and bolt the  engine up first then fit the lead with extra bolts and washers. if possible use washers and nylock nuts

[Bob Moore]

if you put lead under the mounting use longer bolts and bolt the  engine up first then fit the lead with extra bolts and washers. if possible use washers and nylock nuts

 

 

I must say I second that. When I had occasion to remove the cowl off my artf wotty, I found that because of vibration (not excessive) the mounting holes on the lead had increased to the point where it was falling off.

[Martin Harris - Moderator]

Use the biggest washers possible  or ideally a steel plate to spread the clamping force. Phil's advice is very sound - the lead WILL compress and fret with any vibrationand any plain nut will loosen. Nylocs are best but you could get away with properly applied locknuts.