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SST 1/2A engine

Old 08-31-2010, 01:13 PM
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richardgerardi
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Default SST 1/2A engine

I found an SST in my basement that I buitl 20+ years ago and trying to finish. i got a .061 Norvel this weekend that some one did not want and I am planning on using it on this plane. Is that a good choice. New to 1/2 A stuff.
Old 08-31-2010, 02:16 PM
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combatpigg
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Default RE: SST 1/2A engine

The Hobby Shack SST I built 20 years ago needed a .09-.15 to perform well. A friend took it from me.... IIRC he added a few inches to each wing panel and stuck a Cox .09-.15 on it.

I originally tried it with a TD .049 and it was a dog. Barely air worthy.
Old 08-31-2010, 02:19 PM
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fizzwater2
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Default RE: SST 1/2A engine

But, CP, was that with 20 year ago radio equipment also? I'm sure it could be built lighter today.

I remember when 1/2A pylon racers were light if they were under 22 ounces... that would be absurd today!

Old 08-31-2010, 02:24 PM
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Default RE: SST 1/2A engine

I think back them it had 2 Futaba S133s [similar to HS81s], a 270 NICAD and some kind of smaller than standard RX.
I think the plane had way too much heavy wood designed into it....and it had a dense molded foam wing with sheeting to boot.
Old 08-31-2010, 03:14 PM
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richardgerardi
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Default RE: SST 1/2A engine

So the 061 Norvel is not going to do the trick? I am mounting micro servos, micro rx, and 600mh battery. too heavy still?
Old 08-31-2010, 04:05 PM
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Default RE: SST 1/2A engine

Never having flown an SST, I would bow to CP's experience and think it might be marginal.
Old 08-31-2010, 04:31 PM
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Default RE: SST 1/2A engine

You won't need a 600 mAh battery and can save some weight if you look at something in the NiMH 350 to 400 mAh range - should come in around 1 oz. The SST fuselage is a little boxy, but about the only place you can put it on a diet is in wood selection (not really an option if you're using the kit wood) and hollowing out the blocks in the nose area.

The wing is the killer. The foam used during that era is dense and the wing is partially sheeted to boot. You could go with a fully built-up wing - not a big step up from sheeting the foam core. If that's not appealing, you might consider hogging out the foam in the rib bays, either with a hot wire or cutting out large circles using a tin can with one end sharpened.

What are your plans for covering?

With some care in weight savings, the NORVEL should give you a sporty plane, but without unlimited vertical. I have a Honker (similar in size to the SST) with a NORVEL .061 C/L engine that's a decent flyer. It's R/E, but does loops, rolls, immelmans and split-S's without a problem.

I've attached a pic of a SST that was posted by the late Lynn Sipes several years ago.

andrew
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Old 08-31-2010, 06:13 PM
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airraptor
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Default RE: SST 1/2A engine

this is a great battery choice very smal and light weight.

http://www3.towerhobbies.com/cgi-bin...?&I=LXYXA6&P=0
Old 08-31-2010, 07:22 PM
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fritzke
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Default RE: SST 1/2A engine

Shoot for 16 oz, all ready to go. The SST is just like my old Hornet (RCM plan) and at 1 pound
and a hot TeeDee it flew nice. Every ounce matters. Since yours is built, not much you can do.
If it's over 12 ounces without engine or radio, I think the Norvel will have it's work cut out for it!
My SST kit contents weigh 11.6 oz, and just the two fuselage sides weigh 1.75 ounces. I'd replace those
first off. Save an ounce right there.
Dave
Old 08-31-2010, 10:59 PM
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Default RE: SST 1/2A engine

At any rate and just about any weight that modern onboard equipment will get you, it can't hurt to try the .061. I'm just going by ancient recollection of the way mine turned out...but I've got no idea what it weighed.
Back then I didn't have a .074 to bail me out of some 1/2A projects that got too big.
Old 09-01-2010, 07:03 AM
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richardgerardi
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Default RE: SST 1/2A engine

It is covered in monokote and it is already finished. I will look at smaller baterry packs and try it out this weekend. I will let you know how it went. Thanks for the info.
Old 09-01-2010, 07:48 AM
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Default RE: SST 1/2A engine

How much does it weight now?

The LiFe battery, linked to above, will need a voltage regulator too, so the practical weight gain is very low. You will also need a special, and expensive, charger for it.
There are plenty of NiMh choices at [link=http://www.radicalrc.com/category/Receiver-Packs-NiMH-NiCd-19]radicalrc[/link] for instance.
Old 09-01-2010, 12:58 PM
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Default RE: SST 1/2A engine


ORIGINAL: Mr Cox

How much does it weight now?

The LiFe battery, linked to above, will need a voltage regulator too, so the practical weight gain is very low. You will also need a special, and expensive, charger for it.
There are plenty of NiMh choices at [link=http://www.radicalrc.com/category/Receiver-Packs-NiMH-NiCd-19]radicalrc[/link] for instance.

Why does it need a regulator??? here is a quote directly from tower:
This is the Hobbico LiFe 6.6V 200mAh 1C Receiver Battery Pack
with Universal Connector.

FEATURES: LiFe (lithium iron phosphate LiFePO4) offers a lightweight, high
energy density battery with more power than NiCd and NiMH receiver
batteries provide
Ideal for receivers used in 1/10 and 1/12 scale racing where a 1S
LiPo is used as a power pack
May also be used for small gliders and other lightweight aircraft
Nominal voltage rating of only 6.6V typically does not require a
regulator to power receiver and servos

INCLUDES: Hobbico LiFe 6.6V 200mAh 1C Receiver Battery Pack with Universal
Connector

REQUIRES: Charger such as the Great Planes Triton EQ (GPMM3155) Triton EQ
(GPMM3156) or the Duratrax Onyx 230 (DTXP4230)
(only use chargers that specifically say they are compatible with
LiFe cells)

SPECS: Capacity: 200mAh
Number of Cells in Series: 2
Rated Voltage: 6.6V
Continuous Discharge Rate: 1C (0.2amps)
Maximum Recommended Charge Rate: 1C (0.2amps)
Connector: Universal
Dimensions: 1.2 x 0.90 x 0.47" (30 x 23 x 12mm)
Weight: 0.53oz (15g)
a fully charged NiMh 5 cell pack is 6.9-7.1 volts this one fully charged is 7.2 volts so i wouldnt think it would hurt anything. i have two of the 1100 packs in my revolover and everything works just fine with out regulator.
Old 09-01-2010, 01:31 PM
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Mr Cox
 
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Default RE: SST 1/2A engine

Most receivers and servos are only rated up to 6V, and I don't know what safety margin they have on that. A NiMh battery drops fairly quickly once they are off the charger and I wouldn't expect more than about 6.5V from a 5cell pack when it is in use, but I do not run these myself. The higher voltage will draw more current so in theory one should use a higher mAh rating also.

From radicalrc you can get a 160mAh (17.8g) 4.8V pack for $11, so I don't really see the purpose or need of going to LiFe batteries. If you already have the charger and like LiFe batteries for some reason, that's fine for you of course, but I just don't think it is a good general recommendation.
Old 09-01-2010, 04:41 PM
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Default RE: SST 1/2A engine

COX lol i would think that with higher voltage the current would be less but the reguired "power" to move the servo would stay the same.

With the JR 2.4 stuff i will never ever run a 4 cell pack. when most reciever/servo companys put 4.8-6 volt range they mean a 4-5 cell nicad/NiMh pack, now with that they may not recomend the life stuff. i will call them now to find out if ok.
Old 09-01-2010, 05:45 PM
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Default RE: SST 1/2A engine

Actually Mr Cox is correct, the current is higher with higher voltages, Why?

Ohms Law I(current) = E(voltage) over(dividedby) R(resistance)

The resistance parth from the battery through the servo will remain constant ,so with riseing voltage the current flow will increase.
Stewart
Old 09-01-2010, 08:05 PM
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Default RE: SST 1/2A engine

ORIGINAL: airraptor

COX lol i would think that with higher voltage the current would be less but the reguired ''power'' to move the servo would stay the same.
That behaviour may be true for AC synchronous motors, but not for DC brushed motors. Increase voltage, rpm rises, current rises. Power rises due to increased rpm, more work is done per second.
Old 09-02-2010, 07:34 AM
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Default RE: SST 1/2A engine

Yup I agree with Stewart and Mike.

While many of the battery manufacturers will advertise that a higher voltage is acceptable, some of the smaller servos are neither designed nor rated for 6+ volts. Most receivers generally will function with 6+ volts.

andrew
Old 09-02-2010, 10:56 AM
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Default RE: SST 1/2A engine


ORIGINAL: combatpigg

I originally tried it with a TD .049 and it was a dog. Barely air worthy.
For whatever reason, a lot of the 1/2A designs from that era were built like tanks. I think another mod that might help is thinning the airfoil a little. The original was about 15%. Going with a 12 to 13% foil might reduce the drag coefficient a bit.
Old 09-02-2010, 01:32 PM
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Default RE: SST 1/2A engine

lol i must have been sick that day or thinking about watt hours.
Old 09-02-2010, 04:49 PM
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Default RE: SST 1/2A engine


ORIGINAL: Andrew

For whatever reason, a lot of the 1/2A designs from that era were built like tanks. I think another mod that might help is thinning the airfoil a little. The original was about 15%. Going with a 12 to 13% foil might reduce the drag coefficient a bit.
I'm pretty sure it was this plane that inspired me to start scratch building instead of building from kits. After seeing what was in the box for $19.99 [or was it $29,99?] it didn't seem to be as good a deal as mail ordering a big pile of wood.

It would be a fun kit to revisit....to do the little things we do now-a-days to keep the weight down. It's a nice looking model.
Old 09-03-2010, 02:25 PM
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Default RE: SST 1/2A engine

If I may - after receiving some 9g servos and a servo tester recently, I hooked my multimeter up to one of these servos. Whilst holding the servo arm stationary, I gave it full signal. Nearly flipped over backwards - that tiny servo was drawing 0.5 A under a locked rotor test. Should you wish to use smallish batteries, please double check your moving surfaces.
Old 09-03-2010, 02:50 PM
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Default RE: SST 1/2A engine

Been there, throttle servo jammed, planted one...
Old 09-03-2010, 04:22 PM
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Default RE: SST 1/2A engine

ORIGINAL: LouisB

<snip>.....Nearly flipped over backwards - that tiny servo was drawing 0.5 A under a locked rotor test. Should you wish to use smallish batteries, please double check your moving surfaces.
The current draw for the sub-micro/micro/mini servo family is surprisingly high. Check the no-load operating current for Hitec servos on the [link=http://www.servocity.com/html/hitec_servos.html]ServoCity[/link] site. The smaller the servo, the higher the draw. The HS-56HB (sub-micro) and HS-65HB (micro) both pull 400ma @ 4.8v; the HS-325HB (standard) is listed at 160ma @ 4.8v.

andrew
Old 09-04-2010, 11:56 AM
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Default RE: SST 1/2A engine

Andrew... help me out here.. all I see at the Servo-City site is the 'ounce-inch' of the torque from the servo. Where is the sheet with the current draw?

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