Spawned from the discussion (Footy Exploded!)
a question that I feel is worth looking into is the weight of different battery types.
NiCad
NiMH
…
…
What’s NiHM, Chad?
Nickle Metal Hydride (methinks his fingers were too fast for his hand) :bag:
Weight really isn’t a good measure. You need to look at storage capacity to weight ratio.
The order from low to high would be.
- alkalines
- NiCd
- NiMH
- Lithium
sorry Dan, but I think weight IS important in a Footy…will weight when back in Japan…that will be in 2 days:devil2:
Good point (weight vs. Capacity)
I have never actually taken a scale and weighed a NiCad verus an NiMH. Though, I believe it would be minimal impact on performance pertaining to the weight. I am still curious to know.
(going to look for a scale… oh and some batteries) or webpage that lists the weights
The advertisements on NiMH usually say you get double the capacity of a NiCad for the same weight.
For the Footy, how much capacity would you need? You’re using a receiver, and two standard servos. No high-power sailwinch, but the time you spend making it around is a little longer.
The battery is a much bigger percentage of the over-all weight on a footy. If you want to keep sailing longer you can replace the battery. (This goes without saying) So naturally us footy skippers dream of lighter batteries. Of course it isn’t easy to fit things in a footy, take things out but there’s a greater incentive than any other class, I suppose, to find a lighter weight battery. On the other hand, I suppose they sail fine with either battery.
Ok Guys, here’s some actual data:
AA Alkaline 23.25 g
AA NiMH 27.0 g
Scale used is accurate to be within 1g. Sorry, I don’t have Nicad or Li.
Another thing is that the rechargeables put out 1.2 volt, so often an extra one is added. I usually use AA Alks in the boat & sometimes NiMH in the transmitter.
I’m sure in the Footy class, any of them have plenty of capacity, so weight may be the main factor. On bigger boats with sail servos, capacity becomes more important. OTOH, weight down low isn’t always bad, so just use what is most convenient for you.
from what i have read , and saw. most of the guys i sail with are making the switch to the nimh. the expense is the major cost. the nimh does allow more draw to come out of the battery. if , lets say you are using 2300 mah battery.
the nimh will allow you to use all of it. where as the nicad likes to have a little left for reserve. i am using the nicads in my tx. but am slowly buying the 2300 nimh for my IOM. and i can see the improvement. the weigth realy was not an issue. i am still new to this. so when i go into a regatta. i still go out and buy fresh AA alkaline batteries. soon I will not be able to do this. i will have the faith in the nimh
cougar
i am by no meens an expert. this is just an action from observation
- AA NiMH rated @ 2400 mAh (Nexcell)
1st try : 30g ±1g
2nd try : 30g ±1g
-AA NiMH rated @ 2000mAh ([COLOR=SeaGreen]Fujitsu)
1st try : 29g ±1g
2nd try : 28g ±1g
- 4 AA NiCd rated @ 600mAh (packed by Futaba, RX bat. included with TX)
1st try: 88g ±1g
2nd try: 89g ±1g
-Alkaline gen.
1st try: 24g ±1g
2nd try: 24g ±1g
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For all up less weight the lithium non rechargables are 14.5 grams each(Energizer Lithium), alkaline is about 23 grams each and Nickle Metal Hydride are about 30 grams each, all these specs came from the energizer website http://data.energizer.com/DataSheets.aspx, hope this helps guys.
p.s. my first post, will intro myself in the pub.
regards
nick
4 lithium AA cells are $23NZ for 4 (14.5 g each)
4 Alkaline cells are anything from $1.50 to $7 NZ for 4 (25g each)
Lithium is nearly half the weight enabling the weight saved to be placed in the bulb (footy class)
Lithium is approx 4 times more expensive,but the weight saving is so much that a serious racer would design his/her craft around these Lithium cells(at least I would)
Comments anyone?
Technically Lithium has to be the only answer, whether it goes in the bulb, comes off the total displacement or a bit of both.
Let’s get the prices in context (always thinking of the cub scout). NZD 23 is about GBP 8 (or very roughly USD 16). Translate that into what you spend on any other recreational activity and it isn’t a lot of money - 4 pints of beer, petrol for 30 miles and back to see Auntie Bess …
For the very family-minded I checked the admission price to Caernarfon Castle. Family ticket GBP 15.00 - and that’s a government run ancient monument, not a commercial theme park.
What I hadn’t realised is that AA batteries represent a huge range in both price and weight. It is prersumably at least notionally possible for low-tech AAA batteries to be both heavier and cheaper than high-tech AA ones! This does make the Footy rule restriction a bit odd.
A.
Adding AAA size in
Energiser (alkaline) AAA 11.5g each
Lithium AAA 7.6g each
The AAA size 4 pack would bring the lightest possible battery pack weight down to 32g for round figures.
the lightest possible AA pack is around 60g.
One step further,complete radio system for a footy.
JMP( not sure this one is legal for surface models in the states) RX 2 grams
Bluebird servo for rudder 3.5g
I have seen a 16g servo somewhere that has sufficent tourqe for the sail winch with our current rig sizes.
AAA 4 pack lithium batterys 32g
Total system weight 53.5g,most likely closer to 60 once all wires etc are taken into account.
same system with AA lithium cells would be about 85g.
60grams is a fairly cutting edge radio weight al things considered,even with fairly low tech cheap batteries.(AA or AAA)
So let’s do it now!
Most major rule changes are because somebody has twisted the rule and produced a boat that is faster than the rule expected. This means that you can grandfather older boats to whatever extent you like.
The position here is quite different. An external technological change is making it possible to design boats which should be substantialy faster and are little if any more expensive, with the expectatioin that they may actually become cheaper. We cannot grandfather old boats - there is nothing about them that is grandfatherable: they are merely old technology.
Consider also that people are beginning to invest commercial money in Footies. Changing the rule under the feet of the Megacorp GoFaster 12 is not going to be popular, either with Megacorp or their customers.
The number of serious racing Footies in the world is currently very small. Most of them were built by people who like building boats. If the rule should be changed, it should be changed now.
The alternative is to become like Diplodocus.
A.
Personally, I’m in favor of the Footy AA rule, because of the KISS concept. As long as everyone is sailing under the same “penalty” it shouldn’t really matter IMHO. After all, these are not M or 10R boats, so it’s not like we’re trying to break some sort of rc sailboat speed record.
If someone really wants to get carried away with it, perhaps they should consider putting a couple of the batteries in the keel bulb to see if the weight shift benefit would be able to overcome the increased wetted surface & subsequent added drag. The challenge would involve running wires down the fin (easy) and creating a watertight openable battery compartment (not so easy). While we’re at it, get rid of the lead & replace it with depleted uranium…
Bill
ps to Angus: Sorry, I’m not up to speed on my Greek(?) mythology. Who the hell is Diplodocus?
Were it not for the alleged obsolescence of the AA battery, I would agree totally with Bill. Is it real?
A.
Diplodocus was a dinosaur. I think it appeared in the Flintstones!
Well, this is the first I’ve heard of that one! With all the products using them, it’s hard to imagine such a thing happening anytime soon. Where did you hear about this, Angus?
Bill
ps; never watched the Flintstones much…