Fixing lead inside engine cowl

[Frank Skilbeck]

Just finishing off an old Sid King Privateer, it's come out tail heavy (probably due to engine being some 600 grams lighter than what the original flew on). So I'm going to need 400-500 grams of lead right up front. The cowl is a fairly substantial fibre glass (polyester probably), so plan is to fibre glass a couple of sheets of lead right up front.

But I'm open to any better suggestions, thanks.

[Martin Harris - Moderator]

I don't know the model (nothing found on a quick Google either) but my general preference is to fit lead to the engine mounting rather than the cowl - assuming it's removable, there's a lot of additional load on the fixings and of course, the ability to fly without it can sometimes be an advantage when setting up or diagnosing any engine problems.

[Denis Watkins]

Agree with Martin onto the engine mounting.

The last 2 times I decided to spend money on the problem and have bolted a single weight between the bearers

Behind the motor

Pre drilled right through the weight

from eBay 1g 5g 10g 50g 100g 200g 500g Silver Calibration Weight For Weigh Scale

100 gram weight bolted on little Tiger Moth in the loft

 

 

 

Edited By Denis Watkins on 22/07/2020 14:37:53

[Jon H]

On my little Hurricane i made a horse shoe of lead that wrapped around the front of the engine. I then drilled the lead and hammered captive nuts into it. I could then support it on some steel plates screwed to the engine mount.

On my much bigger sea fury i have a laser V upright and installed a normal 40 size nylon engine mount under the engine. The lead then sits on the nylon mount with screws/nylocs to hold it all together.

[Martin Harris - Moderator]

I also aim to keep the weight as low as possible, which usually improves ground handling/take-offs by lowering the C of G.

[Frank Skilbeck]

Thanks all for the suggestions, there's plenty of room to add the weight on the engine bulkhead, but then I'd be looking at more like 1kg . I like the idea or a horseshoe mount from the engine mount and will investigate this further.

Yes this is an old model, the plan says 1994, and it was originally powered by a Zenoah 38cc, I'm using a NGH 38cc fourstroke which is approx 600 grams lighter. Picture below of the model.

[Martin McIntosh]

I have tried casting lead into the spinner which can work if it is a substantial one but I cannot recommend that route. The horse shoe method works for me but not on a full grp cowl.

I would be interested to find out how you get on with that motor. On the face of it and the mag. test report they look great but the one I bought was 2000 revs down on a small prop. due to the cams breaking up after less than two tanks of fuel on a test bench.

[Richard Acland]

My Tony Nijhuis Spitfire was pretty tail heavy. The only answer was to bolt a load of lead to the firewall. It brought the CofG to the right position and it still came in under the design weight. It flies beautifully.

[Mike T]

I always wanted a Privateer! It was recommended to me as a good first petrol model!

The last time I need substantial weight up front was in a Flair Yak55. I removed the lead gooped into the front of the cowl and built a box, bolted to the bulkhead, which filled the ample space left opposite the cylinder head.

The box projected right to the front of the cowl and carried a 5 cell Sub C NiMH pack, the throttle servo and much less lead than I took out. All that and moving the rx and rudder/elevator servos forward brought me to balance with a weight saving of nearly a pound.

[Jon Laughton]

Get and fit a larger / heavier engine? Then the added weight has a value in terms of more power (you don’t have to use it)

[leccyflyer]

Been messing with lead up front in a couple of models recently. The Magnatilla has two big chunks of lead secured with two hefty self tappers from underneath on the aluminium cowl, The Zero has a bunch of smaller tyre weights sitting in lashings of hot glue inserted under the lip of the bottom front half of the fibreglass cowl.

[Frank Skilbeck]

Here's a photo without the cowl, will probably look at the option of mounting lead above the engine by using longer engine bolts. Thanks for all the suggestions.

[Frank Skilbeck]

Just to close out, here's what I've done to add some weight up front

Final balance to check and then trim the bolts so the cowl fits. Maiden flight next week sometime.

BTW engine ran very nicely, but the exhaust gas is much hotter than a glow fourstroke.

Edited By Frank Skilbeck on 24/07/2020 21:18:54