Yak13

My Feedback: (17)

We definitely want to give the jet guys a rough time. I am planning on 200+ mph, with more visibility and endurance than a jet. Regarding the test site, we have a beautiful runway away from any kind of civilization.

jeffk464

Why not build it for DA50CC type engines. DA50cc and the chinese copies are all over the market and actually pretty darn affordable these days. I think a 200mph plane running on an affordable gasser would be pretty awsome, but everyone at my field would probably hate me.

Yak13

My Feedback: (17)

I have a couple of DA50s, but they are a high-torque, low RPM engine. The G62 can go up to 11K rpm, especially with the pipe. One more option is the Zenoah GT80 twin, but the pipe setup would be more complicated and heavy.

jeffk464

Ya, I would stick with single cylinder. Can the higher torque lower rpm engine be propped different to get the speed up, sounds like you might need the G62 to get the speed you want.

Yak13

My Feedback: (17)

Hi fellas
The two first fuselages are here!! These are of the small model. I also got a good deal on a new Rossi 90 DF, which will power prototype #1. #2 will be pulled by a Weston 50V.

Just finished cutting the wings. It turns out the design is "engine-oriented", so the specs were modified a bit for the Rossi:

550 sq in
60 in wingspan
8.5% wing profile
Looks really nice!!

Any suggestions on the Rossi will be appreciated, as I have only owned one Rossi 46, no pipe. The 90 looks awesome. It should deliver.

Two fuses of the big model due in a couple of weeks. The G62 and the pipe are here, ready and willing. Will discuss prop later.

Please comment!!!

I-Love-Jets

Well a ROSSI .90 DF engine is a very different animal compared to the West 50V1 being just a higher-timed WEBRA .50 FISE. Talking 5 HP versus 2.5 HP output... [sm=omg_smile.gif]

Because the speed prop size is essential especially in combination with a ducted fan engine, here are suggestions for a low drag 10 cc to 20 cc speed airframe mainly based on the long speed history of glow powered German speed planes often being considerably faster than 200 mph:
[ul][*] widest part of the fuselage should be 60 to 70 mm in case of 10 to 20 cc FIRE or RIRE speed or DF engines[*] nice smooth fillets at the intersections of fuse and wing and fuse and tail feathers[*] no swept-back wing geometry, instead trapezoid shaped wing[*] wing root length of about 28 cm[*] upright engine mounting position[*] fully enclosed engine and tuned pipe[*] no landing gear[*] bladder tank volume of about 300 cc[*] R/C in-flight mixture control (e.g. Perry VP-IMC-05 http://www.perrypumps.com/prod03.htm )[*] in case of a venturi speed carb usage of a fuel shut-off device[*] fully hidden linkages[*] MACS tuned pipe #1190 for engines from 13 to 20 cc[*] depending on the prop size used for the ROSSI .90 DF: tuned pipe length of about 29 cm between glow plug and middle of the pipe belly[*] MCCoy MC-9 plug[*] fuel: nitro content max 5% for the 15 cc ROSSI DF engine; generally recommended oil content of 22 to 25 %
[/ul]

More in detail to read here: http://www.rcuniverse.com/forum/fb.asp?m=8751461



These requirements will enable the application of a prop diameter small enough allowing a 10 cc to 20 cc high-timed speed engine to run at its intended rpm/torque peak, meaning above 20.000 rpm. So you should look at a maximum prop diameter of 9� in case of the ROSSI .90 ducted fan engine to avoid transonic prop tip speeds. A prop pitch of at least 10� is desirable (the amount of prop pitch efficiently usable is directly connected to the aerodynamic quality of your airframe – the cleaner the more prop pitch [8D] ).

RocketRob for instance makes strong 9x10 carbon fiber props. For safety reasons the continuous strand carbon fiber propeller technology (tempered) is mandatory in combination with these 10 to 20 cc high-timed engines made by OPS, OS, PICCO, ROSSI, NOVAROSSI, BVM/Nelson, K&B, ANGSTREM etc.

As for breaking-in ABC high performance engines, you must run them WOT right from the very first fire-up!
Reason: They have to reach operating temperature a soon as possible. If the piston is very tight at TDC (which is good because that stands for long lasting good piston/sleeve fit) just take a heat gun and warm up the cylinder head appropriately before the first start. These engines have to run on the rich side ever meaning a big white smoke trail at full throttle is a must, see pics below. The in-flight R/C-mixture control is very useful to maintain that “smoke� setting during flight...

Yak13

My Feedback: (17)

Thanks for the help. Definitely the Rossi is the official one. The West will be used because its the only other fast engine I have. Still, the West version should be a very fun plane. I might even make a smaller wing for it, maybe in the range of 350/400 sq in. If I can get my hands on one of the bay's OPS 67s then we can keep the current wings.

Most of the stuff you mention we have covered. At 60" this bird should be more visible than our Magnums, which tend to get "lost".

Thanks again for the tips on the Rossi, they definitely help.

Now lets not forget that the REAL intention is to make the larger, G62 powered airframe very fast. I will start with a Zinger 16x16 prop, reducing diameter and increasing pitch until we get a static 9,500 RPM. What is your opinion on that setup? The airframe is exactly the same as the other one (larger, of course).

Saludos

I-Love-Jets

Well assuming
[ul][*] your highly modified ZG62 will reach 11K rpm unloaded “on pipe� during diving and[*] you're going to install a narrow swan-neck shaped exhaust header http://www.merker-modellbau.de/kruemmer.htm like MERKER #02455 and [*] a fully cowled MACS #1197 tuned pipe
[/ul]
then a prop size of about 14x18� (two-bladed) would be worth a try. Find a propeller that doesn't need much shortening of the diameter because in most cases prop efficiency is badly harmed due to shortening (the choice of prop outer section airfoil(s) and their pitch distribution are most important for any speed prop). Maybe contact www.supercoolprops.com for a custom speed prop design...

P.S. For the ZG62 tuners: http://www.rcuniverse.com/forum/fb.asp?m=8992127

P.P.S Mr. Fuchs also is a highly recommended maker of giant scale racing props http://www.cfk-fuchs.de/html/propeller.html . You may ask him for a suitable "oversquared" speed prop fitting the rpm/torque regime of a highly modified ZG62.

Yak13

My Feedback: (17)

ILJ, One question:
If I use the Macs 1190 pipe I will not be able to achieve the 29-30 cm. The pipe is too long. Maybe a 1160?
I have one of the guys mounting the Rossi today, Ill try to take some pics.

Thanks

I-Love-Jets

Do you mean that there's not enough space available for installing the #1190 tuned pipe in the fuse, especially the back reflector cone and the stinger part?

The MACS pipe #1160 sadly features not enough internal pipe volume for a .90 DF engine even if set much longer than 29 cm (by adding mucho header length). The #1160 would already lead to engine overheating on a .13 cc speed engine. [sm=frown.gif]

Normally when drawing a purpose speed plane folks take the engine plus header plus pipe (adjusted at the correct pipe length) and design the plane “skin-tight� around these most important components. However due to lack of space in many cases custom solutions are necessary, e.g. for the tank compartment, the aluminium engine mount, the header/pipe heat shield etc

Yak13

My Feedback: (17)

I have a Macs 1290 right here, but it is too long, so it would have to be cut to be able to have 30 cm length including the header (to the belly of the pipe). I think this is the best shot for initial flights, while I get the 1190.

I-Love-Jets

As far as know MACS #1290 muffled tuned pipe features the identical twin-cone geometry like the #1190. So just cut-off the entire muffler section of your #1290 to obtain a MACS #1190 tuned pipe.

Meantime I've calculated a “fat + high volume� version of a non-muffled high performance full length tuned pipe.






The geometry of this fat pipe is mainly based on the 5+2 ports ROSSI .90 sleeve timings (see below), port areas etc but it will work nicely with any 15 to 20 cc speed engine.




The internal volume of this fat pipe has been increased by about 15% versus MACS #1190. Therefore we can reduce the pipe length distinctly without the risk of engine overheating - meaning in case of a 15 cc DF engine approx. 25 cm tuned pipe length between glow plug and center of the belly section.

This custom fat pipe will serve as an effective alternative not only to MACS #1190 but also to OPS #5270 (see below) for example – just in case a shorter pipe length is required.


BTW, the best pressure fitting location to achieve high and even tank pressure is at the beginning of the high point belly part.

Yak13

My Feedback: (17)

ILJ, thanks again!
Can you suggest a method for making this pipe? I have a very competent team that can do it if we give them a head start.

Ed

lfinney

My Feedback: (44)

you may also want to try the marine versions of the mac's pipes, they have more volume and a twin taper front cone, the 1385&1395, these work well with the higher rpm range boats see as well as responding well tot the higher volume of gas produced by higher nitro content, they are the preferred pipe for my speed usage, they have a much sharper spike when coming on, so dont be suprised that the throttle isnt so linear ....[8D]

I-Love-Jets

A simple and inexpensive way to make a tuned pipe is a combination of
[ul][*] trimming bar stock aluminium on a lathe (lead-in pipe part + stinger) creating a wall thickness of 1 mm and of[*] applying 1 mm thick aluminium sheet material for the two cones as well as for the center belly part.
[/ul]

The type of aluminium recommended is 6061-T6 for instance.

By using the following trigonometric correlations you can draw the required templates for cutting the 1 mm thick aluminium sheet for the cones. Please leave addidtional 5 mm sheet on each long side ("m") and bend it to 90 degrees – this excess material will be spent for MIG or WIG welding each cone together.


Before joining all sections by welding [lead-in pipe - diffusor cone - high point (belly) - reflector cone - stinger pipe] it is wise to create a solid base (welded) for the pressure fitting.

P.S Please don't shorten the length of the stinger of the custom made “fat� pipe. The given geometry is essential for maximum engine output.

Yak13

My Feedback: (17)

Im uploading some photos

Yak13

My Feedback: (17)

Ok, some pics

Yak13

My Feedback: (17)

Fuse with both wings planked. A high-tech micro video camera will be housed in the right wing.

dhal22

nice! more please.

Yak13

My Feedback: (17)

This is the wing tip

dhal22

well, i asked i suppose.

Yak13

My Feedback: (17)

Jeje. Sorry Dhal, The intended quote was "This is the 8.5% profile at the tip".

dhal22

no problem, keep us posted on your build.

RocketRob

My Feedback: (1)

Yak,
You can speak with Dave at Mac's products and he can weld an extension and mouth to his pipe to fit your Rossi to the appropriate length.
I was at his shop yesterday and it is exactly what he is doing for me on my OS powered Sunshine ME163 after I was having trouble cracking headers.

combatpigg

My Feedback: (3)

Yak, everything looks tremendous! Are you doing this project with alot of prior experience?