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Saito 62 for Wot 4

Started by Unichap, February 02, 2019, 20:00:20 pm

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Unichap

Am building a Chris Foss Wot 4 and hoping to use a Saito 62.
Any suggestions as to where to put the firewall?
1/2 inch / 1 inch back?

Thanks

PDR

I'd definitely put the firewall at the front - it would be too far from the engine if you installed it at the back.

HTH,

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

Charlie C

In the meantime  ::)

Set the firewall such that the propdriver is a couple of mm in front ofvthe hole in the cowl   :af :af

Charlie C
Global Moderator

The Saint. (Owen)

Make sure that the firewall is behind the engine.  :''
Electrickery is the work of the devil.
Proper aeroplanes are powered by engines.

British Victory

February 03, 2019, 08:52:43 am #4 Last Edit: February 03, 2019, 09:21:06 am by British Victory
I have one in one of my wot4s, I don't bother with the cowl and went my own way, setting the firewall 6mm back for firewall security, then fitting a spacer to bring the engine out a little bit. To get the c of g in the right place the battery, which is a 2 cell 1100 mAh LiFe, is astern of the servos.
There is a law of diminishing returns when taking the firewall back further, tied up with the tank position which, in the case of a larger 2 stroke, can intrude significantly into the "load space" for want of a better word and for interference with the carb etc in the case of a larger 4 stroke.
[attach=3]
I also attach a pic showing the 6 ounce slec tank installation, a12 ounce tank for a 61 isn't overlarge and sits back another inch or so.




[attach=2]

there's only one f in RCMF,
               John

British Victory

February 03, 2019, 08:56:25 am #5 Last Edit: February 03, 2019, 09:19:05 am by British Victory
Forgot to mention, it hasn't flown yet as my other wottie (mk2 kit built) with an irvine 39 and a throttle pipe is still operational after 31 years, though not with the original engine or wings.
there's only one f in RCMF,
               John

Unichap


itsme

I am curious to see how this flies, as it is way overpowered. I used to have a kit build Acrowot with Irvine 46 and tuned pipe that would go vertical out of sight if you let it. Adding the extra weight may reduce performance. Bit like the long forgotten MGC car, the MGB with a bigger engine which was actually slower than the B...

PDR

Huh? When the Wottie was first kitted (both as a Mk1 plan-pack and the Mk2 full kit) the default engine choice was a 60 2-stroke on a big prop (graupner 12.5-6 paddleblade or similar). I can't see that a .60 4-stroke would be in any way inappropriate myself...

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

itsme

Quote from: PDR on February 04, 2019, 10:48:15 am
Huh? When the Wottie was first kitted (both as a Mk1 plan-pack and the Mk2 full kit) the default engine choice was a 60 2-stroke on a big prop (graupner 12.5-6 paddleblade or similar). I can't see that a .60 4-stroke would be in any way inappropriate myself...

PDR
From Chris Foss- "With a .30 two stroke or a .40 four stroke, it is docile and forgiving yet fully aerobatic and is an ideal follow on from a primary trainer for an early solo pilot." a .60 was for extreme aerobatics. I took my B with a .46 powered Wot 4.

British Victory

I've flown wot 4s with many different engines, from 36 irvine up to a 72 irvine via Irvine 39, tt 42GP, YS 45, MDS 48, OS 46FX, 52 surpass, 61 fsr, 61 magnum 4 stroke and Saito 82a and now a saito 62.
One of my wotties, the one now fitted with the saito 62, previously had the irvine 72 which I changed for the irvine 36 with a TT 42 silencer.
I changed out the servos for 4 corona 339s, the fuel tank downsized to 6 and then 4 ounces and the fibreglass u/c for the wire variety, the weight dropped by more than a pound and a bit, subjectively I felt it performed better with the 36.
I've since rebuilt the fuselage and it has hitec servos now and a 6 ounce tank and is about 6 ounces heavier than when the 36 adorned the front. but balances without ballast and I've yet to maiden it, I'm looking forward to see how it performs; I suspect I'll be disappointed with it compared to the 36 2 stroke.
My other wot4, a kit built mk2 from the 80s had an OS 61 fsr abc in which I've changed out for an Irvine 39 with a westonuk throttle pipe. Because it has an epoxy fuselage it is significantly heavier than the balsa ply one and, naturally, has a smaller wing area. It would hover and pull out of the hover with the OS, it'll still hover, just, but pulling out of it is less urgent with the 39.
I have an apc 11.5x4 wide blade prop on it and, tbh, it does all that I want out of a wottie, but I don't think there's such a thing as an overpowered wot 4.
FWIW, just for the experience, I flew my kit built acrowot with an OS 91 Fx. The landing speed tended to be higher than with the previous saito 82a fitted.......I wouldn't do it again, I've an OS 61 fx earmarked for it.
there's only one f in RCMF,
               John

itsme

Yes. I was wondering if there was some sort of law of diminishing returns with it, ie once past a certain point there is nothing to be gained.

British Victory

Forgot to mention the first couple I had had an HB 50, bloody noisy thing, and an os 61 fs, the one with the camshaft on the front, I still have the spinner cut out for a 3 bladed 12.5x6 graupner somewhere. Memory isn't as good as it used to be.
I remember the first one vividly now, I'd taken it to the flying field for its maiden and run the engine up and was having some difficulty getting the carb in tune when one of the clubmates asked if I wanted to sell it and made me an offer I couldn't refuse, so I never even got to fly it. I bought another one almost immediately from harry brooks(?), who didn't have them in stock so he phoned chris foss up and he brought a few down at £32.50 each I think.
Didn't get the 61 fs until a few years later as I changed jobs and moved down here from essex.
Since then, including those two, I've built 11 and have a mk3 fibreglass kit sitting ready to build, if the two I have (and the third I'm making from patterns from the kit) don't last another season.
Once they get much over 4 pounds they seem, like you say, to have diminishing returns as you up the power.
The one I'm building from patterns (and a patched up wing from a broken one) is destined to have a fairly new OS 40 Surpass so it will be film covered with really soft wood in the tail reinforced by ca'ed in 6mmx0.8mm carbon strip and just a 4 ounce tank, u/c will be 4mm wire torsion bar type with HK foam wheels.
there's only one f in RCMF,
               John