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Cub Diet Costs

cgoldy

Registered User
Moogerah Queensland Australia
So here are some very very rough numbers


I have put my cub on a diet and am extremely impressed with the results. But it does come at a cost.


These $ numbers are Australian so for all you Americans - $1 US = 70c AUD - Ouch! We pay big time here for your parts. Plus 10% GST and then freight on top then the rip off of many middle men on the way. It doubles our cost.


These are the cost per lb saved in Australian $


Carbon fibre floor boards - 10 lb $120/lb
Earthex battery - 12 lb $58/lb
Magnesium flywheel - 2 lb $540/lb
Dynamo type alternator - 5 lb $160/lb
Whirlwind prop - 20 lb $200/lb
Carbon fibre seat base and backs - 10 lb $30/lb
Carbon fibre doors - 10 lb $60/lb
Remove pod - 22 lb $0/lb
Remove steps - 6 lb $0/lb
Magnesium sump - 6 lb $300/lb
New Javron wings - 84 lb $142/lb (sale of original Smith wings with extend fuel tanks 76 gallons total taken into account)
LED lights - 6 lb $17/lb


No value has been put on the many many hours manufacturing some of these parts.


So far I think I have saved 190lbs - wings still have to be painted and fitted.


These prices take into account the sale of some of the parts I took off. (Still have 84/44 Borer for sale so that is not included - anyone?)


Halve these numbers for equivalent $US


I put more value on each pound the further forward it sits. But I think the flywheel was a bit over the top.


Please don't add it up for me as I don't want to know and I don't want "Her in Doors" to find out- but I am very happy with the results.







 
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What kind of compression are you running? I ask because high compression and super light prop/flywheel combos have been known NOT to play well together.
 
High compression engines have more pronounced impuse cycles and generally require more dampening mass. At 8.5 I wouldn't be concerned, but as you get up around 9.5-10, the harmonics can get unhappy. More than one high comp. experimental engine has sent its prop into the ether, along with the crank flange.

FWIW, when I rebuilt my -12 a few years ago, I also went on a major weight campaign - dollars be damned (well, pretty much). I didn't even TRY to make mathematical sense out of it, I knew better. Hell, I'm still trying to forget how much I spent!
 
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I replaced my traditional master switch when I also changed over to an EarthX battery. The old battery install was mounted under the passenger seat, along with the master. The new setup has the battery and a new mechanical master (Summit Racing) on the inside of the firewall. It was amazing the amount of misc. cabling, fittings, etc. this saved, plus I can now forget to kill the master and not have it drain my battery. A pretty much idiot proof master switch, finally!
 
Why is that? What happens?

O-375 8.5 - 1

I know lots of guys running high compression with light props. No prop separations that I've heard of. Start timing is important as light props can have starter kickback issues. I know about that one up close and personal. :oops:

Does your spendy flywheel use a conventional ring gear?

Lightweight props with moving parts are advised to be dynamically balanced. You may want to look at a Balance master balance ring.
 
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So here are some very very rough numbers


I have put my cub on a diet and am extremely impressed with the results. But it does come at a cost.


These $ numbers are Australian so for all you Americans - $1 US = 70c AUD - Ouch! We pay big time here for your parts. Plus 10% GST and then freight on top then the rip off of many middle men on the way. It doubles our cost.


These are the cost per lb saved in Australian $


Carbon fibre floor boards - 10 lb $120/lb
Earthex battery - 12 lb $58/lb
Titanium flywheel - 2 lb $540/lb
Dynamo type alternator - 5 lb $160/lb
Whirlwind prop - 20 lb $200/lb
Carbon fibre seat base and backs - 10 lb $30/lb
Carbon fibre doors - 10 lb $60/lb
Remove pod - 22 lb $0/lb
Remove steps - 6 lb $0/lb
Titanium sump - 6 lb $300/lb
New Javron wings - 84 lb $142/lb (sale of original Smith wings with extend fuel tanks 76 gallons total taken into account)
LED lights - 6 lb $17/lb


No value has been put on the many many hours manufacturing some of these parts.


So far I think I have saved 190lbs - wings still have to be painted and fitted.


These prices take into account the sale of some of the parts I took off. (Still have 84/44 Borer for sale so that is not included - anyone?)


Halve these numbers for equivalent $US


I put more value on each pound the further forward it sits. But I think the flywheel was a bit over the top.


Please don't add it up for me as I don't want to know and I don't want "Her in Doors" to find out- but I am very happy with the results.









Awsome CGOLDY....Also one overlooked area that you can save some lbs is your battery box. If yours can be removed and you are already using the earthx. Buy their box. weights ounces and is good for over 10 G. Saved almost 5 lbs on my acro mount.
 
I guess it should have had a. ? At the end.
I could loose 10-15# and that would be pretty inexpensive way to cut out some weight.

Not or sure about anyone else. Just me n my bird.
��
Doug
 
190lb is a lot of weight ! Congratulation.

Would like to have some info about : Carbon fibre seat base and backs - 10 lb $30/lb
30$ per pound is in my budjet



Thanks





Titanium flywheel? Where can I get one of those!

I know that you know that he's talking about the magnesium flywheel
 
190lb is a lot of weight ! Congratulation.

Would like to have some info about : Carbon fibre seat base and backs - 10 lb $30/lb
30$ per pound is in my budjet

Thanks

I know that you know that he's talking about the magnesium flywheel

http://www.skydynamics.com/products/engine/featherweight-flywheel

Your right, Magnesium, I better edit my post

Seat backs/bases - I replaced the wood ones with 2 ply and honeycomb core CF I vacuumed bagged down onto a glass table. Also cut down my full width back seat into a single which also gave the passenger access to the under seat storage box either side of the seat. My seats are fancy leather with memory foam so they were very heavy.
 
I'd love to hear about your carbon fiber doors as well. Sounds awesome!

Any pictures of the build process and installed?
 
I'd love to hear about your carbon fiber doors as well. Sounds awesome!

Any pictures of the build process and installed?


Carbon fibre doors and windows

Windows

I cut out of 1" High density foam sheet a 1" wide door frame. Laid it on a sheet of glass and vacuumed baged it with a flange on the outer perimeter to seal the airflow and inner periimiter to fix the window to. Then glued in the window.

Doors,

From the same 1" HD foam I cut out the shape of the door and wrapped it in CF and again vacuumed bagged it to the glass. I wanted a window in it but I was over the whole job by then and just wanted to get on with it. So it is solid, but stiff light and strong. I routed out a chanel on the inside and replicated the door opening mechanism out of CF rods. CF hunting arrows were used as the door latch rods. Then pop riveted a cover over the access hole I had created.

It took weeks!

No photos but I will take some
 
Carbon fibre doors and windows

Windows

I cut out of 1" High density foam sheet a 1" wide door frame. Laid it on a sheet of glass and vacuumed baged it with a flange on the outer perimeter to seal the airflow and inner periimiter to fix the window to. Then glued in the window.

Doors,

From the same 1" HD foam I cut out the shape of the door and wrapped it in CF and again vacuumed bagged it to the glass. I wanted a window in it but I was over the whole job by then and just wanted to get on with it. So it is solid, but stiff light and strong. I routed out a chanel on the inside and replicated the door opening mechanism out of CF rods. CF hunting arrows were used as the door latch rods. Then pop riveted a cover over the access hole I had created.

It took weeks!

No photos but I will take some

Oh, my. That sounds awesome!

Photos please!!!!
 
She flies. Still have new CF lower cowl to make with square airbox. Haven't weighed her yet but will do and post that along with new stall and cruise speed numbers. Busy moving the farm. But she leaps of the ground like you wouldn't believe. I put the pod back on for the ferry flight to new place.DSC_7326-1.jpg
 

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Fantastic!!!

Congratulations. Light weight costs. And I think its an exponential curve.

Very well done.

Bill
 
From all my weights I am seeing a 2.6 lb savings using carbon fiber floorboards over the original plywood.
 
From all my weights I am seeing a 2.6 lb savings using carbon fiber floorboards over the original plywood.


I can't check now. But it included extended baggage. My CF was basic rule of thumb 1/3 steel , 1/2 wood, 2/3 aluminium. Pretty rough figures though. I'm no Bill Rusk!
 
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