Barnaby

Hi, I've recently completed a electric version of Wolfgang Matt's Atlas, it was a winter build project that a number of us at my local club decided to do, so far three have been maidened and one is hopefully not too far away. It flies very well, and it was satisfying having built it myself, although a little frustrating at times, but I think a lot of that was down to having only put together a couple of ARTFs and building from plans is quite different.

I'm looking ahead and would like to build another classic pattern plane and it makes sense to jump ahead in style. I'd like to keep with the 6S electric set up, so the Saphir rather than the Rubin would seem to be a good next choice, and I'm now hunting around trying to collate as much info as possible.

If anyone has had experience building and or flying this plane I'd love to hear your thoughts on it.

I'm assuming the wings will have been foam cored? And I'm curious to know how the angled tips were have been done initially I thought they would have been glued on, but the plan shows a projected tip aerofoil so I'm now assuming it was all one piece but the tips will have been a secondary shaping process.

I think the Saphir II with the YS120AC would have swung a 14x13 prop at a max RPM of 9,000, please correct me if I'm wrong, but I don't know what the earlier Saphir with the Webra 61LS would have swung or at what RPM, it would be nice to know so that I can try and get an equivalent electric motor set up.

All the best, Barnaby

flywilly

My Feedback: (121)

Hi Barnaby,
I had a Model Tech Saphir which was an ARC. It was straight, but a little heavy. Mine was powered with an OS 61RF-ABC Pumper with the Shadel/Nelson modified piston sleeve assembly which provided power close to the OS Hanno Special. I flew mine with a 12.5x11 (around 9500 rpm), but probably should have tried a 13x9 (APC). The airplane flew well, but needed a bit more power or a bit less weight. I was going to put a YS 91AC in it, but a fellow club member made me an offer I couldn't refuse. I saw Wolfgang fly the Saphir at the '89 F3A World Championships (in Tidewater, VA.). He had retrofitted his models with the YS 120 (the original version) and they had very impressive vertical capability and it was probably the fastest model in the finals. His models were custom built in Japan and were immaculate. I did not know that plans for the Saphir were available, where did you get them as I would like to have a copy. I have the plans for the Diamante designed by W. Matt which is larger than the Rubin. I reduced the plans to a 60 sized model and am having the parts laser cut. This is a nice way to get the size model that you want and have a short kit made for it.
I'm not an electric 'guy', but there are many who can provide assistance if you want advice.
Good luck,
Will

doxilia

My Feedback: (3)

Barnaby,

based on your Matt Atlas comments, I assume you're located in the UK. Please correct me if I'm wrong.

Like flywilly, I too have a MT Saphir I ARC except mine is unbuilt. I've given engines and e-power a thought and am likely going to use an electric 2x4s (8s) setup with electric retracts. I'm planning on a 2KW setup (29.6V @ ~65A) on a 14-15" prop. A Kv of somewhere in the 450 range should serve well. A Rimfire 80 or 120 or a Scorpion 4025-440 for example. None of these motors are "approved" for 8s but on a smaller prop at low current, they should be fine.

We're planning on turning these same Scorpions on an electric Super Chipmunk 120 but on 6s on larger 16x10" props.

David

Barnaby

Hi Will,

Thanks for the information, it's great to hear from someone who has flown one. It certainly sounds like it would be worth trying to lighten it where possible and crucial to sort out an appropriately powerful electric setup.

Late last night I read that with the Webra 61LS Wolfgang Matt used an 11x10.5 prop at the 1987 championships and his plane was fast! I'm guessing a long stroke 61 will have a different performance to your OS 61RF-ABC Pumper.
The plans I found are on this site: http://www.hippocketaeronautics.com/hpa_plans/search.php?search_keywords=%22Pattern+-+F3A+-+Wolgang+Matt+-+Saphir%22

Good luck with the 60 sized Diamante, that sounds like a fun project.

Hi David, Yes I am based in the UK, I suspect you've seen Mike's Atlas build thread on RC groups? Here's a pic of our two Atlas's together, mine is the blue one:



I plan to use electric retracts too, and having been impressed with the HK SK3 range of motors for the money, I had intended to use one of them, but they seem to be on back order everywhere. I did manage to get one of the last 500KV motors in the UK warehouse, but hope they come back in stock so there is more options. I'l have a look at the motors your thinking of using tonight, but ideally I'd run a 6S set up as I'd then have three planes that use the same batteries.

Are the wings in your MT kit already skinned? I'd be interested to know if they are foam cored and if so, are the angled tips a separate piece that is glued on, or it they have been cut out of the same blank as the main wing?

Best wishes, Barnaby

SuperNash

Hello Barnaby

I built one of the Dave Smith kits in the early 90s, fitted an OS RF-P (which is a longstroke) with OS pipe for power. 12x10 APC at around 11k, I think. As an aside - brilliant motor, started first flick every time, just grabbing the spinner and flicking it backwards against compression, superbly reliable.

It's a great design, really very nice to fly indeed. Not so great kit. Heart of oak balsa lead to an all up weight of around 9lb which was just too much for the 2 strokes. I see no reason it couldn't be built to 8lb with better materials and construction. The DSM kit simplified the Matt design a little - vertical fuse sides, open pipe area. It was typical DSM - thick balsa box fuse with veneer foam decks, foam wings + tail.

I don't know that the Saphir 2 was any bigger than the Saphir 1, I think it was just modified to accept the 1.20 four strokes that were coming in at that time. The 1.20s had a bit more usable power and could pull 9lb around no problem.

The Saphir wingtips didn't stick around on any further designs and they add complexity without any obvious benefit. They were done as separate bits of veneered foam, so you have 3 wing joins to make. And the same with the tail.

Would I build one again? I'm not sure. I'd probably build a Joker instead. Or a Saphir fuse and Joker wings. The Saphir is basically a Joker with awkward wingtips and a 3" longer fuse anyway. IIRC the wing/tail area is near identical and the family resemblance on the fuse is plain to see.


You can find footage of Matt flying the Saphir at the 87 worlds on youtube.

https://www.youtube.com/watch?v=1BmjeUtIH3k

SuperNash

Scaled Saphir & Joker.

Saphir is a bit deeper to cover more of the pipe, plus a bit more nose/tail moment.

MTK

I built and campaigned the Joker in the mid to late 80s. The kit was by MK. Wish I had bought a few more for the future but who knew. It flew well on a stretched pipe and 60 and a 12-11. The small 15cc gas engine from OS with an ESComposites carbon pipe would make the ideal set up. A 14-10 to 15-10 prop would be the choice. Ground clearance would need to be thought through.

Later, when the Saphir came out, I wanted one of them but never got one. The tips were a good idea for today's schedules, not the schedules back then. We had practically no snaps in any schedule if I recall. They enhance the wing's ability to snap and spin. I suppose we flew spins back then so that was one reason for them.

SuperNash

Were the European schedules different?

Wouldn't a slight CG change, or marginally thinner tip section, achieve the same end with less construction complexity? Either way, the tips looked cool, which I always thought was 90% of the reason behind them.

Barnaby

Thanks SuperNash,

The Joker was one of the models that I considered, but the only plan I've seen is the Joker25 and had read that it's a little more involved than just scaling the plans up if you want the 60 size. The plans I have for the Saphir include a projected wing tip aerofoil cross section as though the angled back wing tips weren't there. What I don't know is, was this intended to offer an easier wing option, or is this a hint to suggest a way to cut the wing. i.e. cut the foam without the angled wing tip, then in a second process created the tip angle.

Hi MTK, A club mate said the same thing regarding the wing tip design, but it was dropped after by the time the Rubin was being designed. Thanks for the info on the props and engines.

Barnaby

SuperNash

"Simple wing variant" was how I understood the drawing... which seems to about make a "Saphir fuse and Joker wings".


BTW, have you seen

http://www.andy-green.co.uk/saphir/

You can see how the DSM kit simplified the fuse build. No underside foam decking, just some thick-ish balsa carved to shape. Front + rear decks on top (the core fuse had a nice straight edge so you could build it inverted straight on the board). Block fill in around the fin/tail area. The pipe tunnel in the kit was just two bits of 3/4" block cut to wing outline and glued on, again just carved to follow the fuse shape. I'm pretty sure DSM reduced the nose depth as well. To something suspiciously close to their Joker kit sizes...

MTK

F3A schedules were the same. Lower classes were different.

A CG change is not advised to make the plane do snaps and spins. The better solution is better wing design that enables these maneuvers. CG movements could adversely affect too much of the flight envelope. It could be made to helps snaps and spins but chances are knife edge flight would be compromised.

the tips looked Kool. "Marginally thinner" is relative. Short answer, that's what a wing needs. A couple different ways to get there. One simple way is to thin down the tip in terms of percent but keeping the chord unchanged. The tendency here would be a faster wing which is not necessarily what we want.
the better way is to reduce chord at the tip. Don't have that luxury with classics if we want to preserve the original planform unfortunately. All of my designs though sport this approach and have since the 90s when I figured it out. There are several key benefits in addition to simpler snap and spin entry and most importantly, recovery.

dhal22

Nice reading here from some experienced pattern guys. Thanks

doxilia

My Feedback: (3)

Beautiful builds! Yes, I did follow Mike's build on RCG. If you would like to continue a build thread and dialogue, I would strongly encourage you to switch venues. That forum just works, this one..., what can I say, no longer does...

There is no reason not to use electric retracts (trike or otherwise) on e-powered models. The nose gear presents a problem often on glow classics but here, that issue isn't present. I understand the e-tracts sold (and temporarily discontinued) for the Curare ARF on the Schweighofer site are/were pretty good. I think they are updating them to even better units. When they will be available, I don't know. Maybe they already are.

There are so many motor choices available these days its a little overwhelming. However, the main thing to look for is a motor capable of ~2000W power input and I would go for a Kv on the order of 600-650 for a 6s setup on a conventional gear model where you can turn a 13-14" prop. The main concern in a larger pattern classic to my mind running on 6s is that you end up pulling a lot of Amps (~85-90) on a 6s setup. Folks who have built larger classics (e.g., Conquest IV, EU-1A) have seen/experienced these limitations and have steered their builds toward 8s (or even 10s) setups. I think 8s is the optimal "120 equivalent" cell count as it allows you to get up to 2 KW quickly while keep the current in check at ~65-70A. Naturally, planning for the high cell count to keep the model weight in check is needed but this is of course true for any electric model.

Like Will said, the ARC was/is a little heavy but given you're starting from plans, you can get much of that weight down. 1/8" sides, lightened 1/32" doublers, 1/32" wing/stab/deck skins on foam cores, CF laminated balsa formers/plates and so forth. We re-designed an MK 120 size scale pattern classic (a Super Chipmunk) originally designed for the YS 120AC (or OS) engine for e-power and our target AUW was 9 lbs which I think we'll achieve with the much lighter re-design. A 4 lbs ready to finish airframe would be the max target weight. Given the narrow fuse design of the Saphir, I think this should be quite doable. I'm thinking you can even hit 8 lbs with diligence.

Yes, the ARC comes with pre-skinned (balsa) cores. I intend to thoroughly sand them down as I think 2 mm balsa is used. The angled "tips" are added after being skinned seperately (so the core is a two-part joined affair) and glued on. The tips consist of a small foam core and a balsa tip. My S1 comes with three glass pieces (the S2 came with two I think) - one for the wing bottom and one for the header area. There is a separate glass cowl for the engine which my kit is lacking but I may just make one from balsa using 1/8" lite ply formers at the front (ring) and back (for attachment to the model) if using e-power. The pan that covers the header area provides a nice space for the ESC but a scratch build would be different.

I hope this helps,

David

drac1

My Feedback: (4)

The Saphir 2 was bigger. Approximately 120mm bigger wingspan and around 250mm longer.

drac1

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My first pattern plane was a Model Tech Saphir kit - OS Hanno Special 2 ringed engine. Final prop I used was a 13.5 x 10.5 Bolly Clubman. It flew extremely well and had great vertical performance with this set up.

flywilly

My Feedback: (121)

Hi Drac1,
You are the first person that I know of who has run the ringed version of the Hanno. It sounds like you were very happy with that engine. I am quite interested in the performance and longevity of the ringed version (I have one NIB). Interestingly, the ringed version lacks the 'notches' at the top of the exhaust ports found in all the 'ABC' versions of the Hanno. My research has indicated that the notches in a ringed engine probably would have caused problems with the ring. I wonder if the notches are providing any benefit to the performance of the Hanno? Back in the mid '80s, Henry Nelson produced a replacement piston sleeve set for the OS 61RF ABC-P which significantly improved the performance of the engine, actually it was pretty close to the stock Hanno in performance without any 'notches' in the exhaust port.
How much nitro were you running to spin the 13.5x10.5? That's a lot of prop for a .60!
Thanks,
Will

drac1

My Feedback: (4)

Hi will,

Yes, it was a great engine. There weren't many ringed versions compared to ABC and they are hard to find now. I sold my original Saphir and it was crashed, but the guy still has the engine and red pipe. I have tried to buy it back, but he isn't willing to sell. Yet anyway. I know of another Saphir with a ringed Hanno in it, but he is also unwilling to sell at this stage, even though I am fairly certain he will not get to the level of flying it. I will keep trying though.

I have a standard 61 RFP that has the Nelson liner and piston, but haven't run it.

I ran 30% nitro in the Hanno. Do you want to sell your ringed Hanno?

SuperNash

That's a big stretch, and puts it around the size of Matt's next one, Rubin.

Was there a corresponding chord increase or just extra wingspan?

Quote:

1/8" sides, lightened 1/32" doublers, 1/32" wing/stab/deck skins on foam cores

Only thing I'd point out is that the fuse sides are not very deep over the wing's max chord point and I would guess the upper decking is structurally significant here. Maybe go a bit thicker on the upper decking skins?

Quote:

I'm thinking you can even hit 8 lbs with diligence

Quite.

doxilia

My Feedback: (3)

No need. The 1/32 skins on the foam cores give them all the stiffness required particularly once the decks are bonded to the flat top sides. For additional strength one can x-grain the flat top with 1/16 first to which the decks are bonded.

The sides receive 3/16 balsa doublers inside of the 1/32 in the saddle area between formers and a lite ply former in the middle (where convenient) to support the saddle and a lite ply (or CF lam balsa) radio tray. Once all squared off, the saddle is very stiff.

David

Barnaby

Hi David,

Thanks for the detailed info and suggestions on where and how to save some weight. It was interesting to hear how the wing tips are just butt jointed, I would have thought the wing skins would have overlapped the join in the foam for strength, but if I've understood correctly the tips are skinned separately and the wing and tip are just glued together.

I think I'll have to use one of the online motor calculators to see what power setup would be best, but I have a sneaking suspicion you're right with your 8S setup, which might push this into the realm of being too expensive at the moment, a HV ESC and a new load of batteries starts to add up.

I believe the Curare JetCraft retracts will be back along with another batch of Schweighofer's ARF Curare, I didn't know they were being improved though, it will be interesting to see what they do. I missed the boat on the Jet Craft retracts for my Atlas and instead went down the cheapest route possible with a set of Hobby King's finest at £10 for a pair! So far so good, but time will tell.

When a build gets underway I'll see about putting something on RCG, but that's a long way off, I did start a wordpress blog for the Atlas build, but it's a little out of date now!


Hi drac1,

The plans I have seem to be for both the 2 stroke and 4 stroke Saphir, whether that's version I and version II, or just Version I adapted to take a 4 stroke I don't know, but the lenght and wingspan are the same. Also on Wolfgang Matt's website both the Saphir and Saphir II-4T have the same specs, Wingspan: 1780mm and Length: 1600mm. Is it possible you're talking about the Rubin?

Thanks for everyones help,
Barnaby

drac1

My Feedback: (4)

I have both versions and they are definitely both Saphirs. The 60 size isn't my original, but it is a Model Tech kit like mine was. I bought the 120 size partially built, but not sure who made the kit.

I'm away at work until next Tuesday, but when I get home I'll drag everything out and see what's what.

drac1

My Feedback: (4)

Actually thinking about it now, I reckon the prop was a 13.5 x 8.5. That was nearly 20 years ago, so the memory takes a bit to get going sometimes.

SuperNash

Ok, cool, so the extra material gets closer to the saddle that way. I guess the radio tray is glued in and becomes structural as well.

PS Kudos for the multiple classics redesigns BTW. I can see lots of work gone into refining the structures down in weight.

drac1

My Feedback: (4)

Here is the 60 size and 120 size Sahirs. The finished one is the 60. The 120 wing is not from the kit, but one I picked up after the fuse was destroyed in a domestic dispute.

Here are the specs as measured. A bit different to my roughly taken measurements before, but the 120 is definitely bigger.


60 size
Length 1555
Wing span 1775
Stab span 730
Wing chord 395


120 size
Length 1650
Wing span 1880
Stab span 760
Wing chord 435

Barnaby

Hi Drac1,

Thank you so much for taking the time to measure your two Saphirs and for taking the photos, that's really helpful.