doxilia

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Matt,

Thanks for the insightful post on the Nova 28 RE. I had researched it around the same time as the MVVS and decided against posting about it because I found the price tag unacceptable. At a cost higher than the 61 RE, it joins the ranks of the elite with the Jett 30.

My vision for these 20 size classics is that they be affordable. The MVVS fits the bill nicely and is probably the least expensive of the group followed by the discontinued OS 25 and the OPS 29. The latter, while discontinued, can actually still be purchased new however the shipping cost does add to the price tag. Shipping in Europe is quite reasonable though (as recently confirmed with OPS 61 RE's). I believe the MVVS would also come directly from Europe but is less expensive. The Enya 32 is also an interesting option but dealership in NA seems to be scarce. If available, I don't think the carb would be an issue; they do make carbs for the SE version.

Last but not least, a RE design configuration does not preclude the use of SE engines like the OS 32/35's or even the ST 34 with an appropriate wrap around header. I built a Prettner Mystic 30 with an inverted 32 SX, Hatori 300 and a wrap around header which I still have to obtain. I believe I may have located one though.

Whatever my thoughts may be, it is good to know that there are about 1/2 dozen RE engine options for models such as the Skymaster, Aurora (our concept), Magic and Arrow. Jeff's Skymaster, along with another Curare and the recently posted original (from MK kits) BA and Aurora, will be a nice addition to this thread.

David

Huang

My Feedback: (27)

Indeed! Those RovaRossis are way too expensive!! I forgot Jett had the .30 FIRE, but also way out price range for a 25-sized classic. The MVVS or OS32SX with S-header would be a great choice.

This size is perfect for electric conversion with 4S 2650mah size lipos for the electric willing, much cheaper and a lot less work.

AllTheGoodNamesAreTaken

My Feedback: (180)

The OPS and NovaRossi would choke on a long pipe set-up. The Jett would probably fine as it makes it's power at 17-18K. On my Skymaster 20 with the OS 25VF DF, I had to trim the header to it's horizontal minimum and take all of the front end off the pipe, just to get 20K on an 8x5. The standard VF is a better choice with it's lower RPM powerband. The MVVS and Jett are the only choices in my mind but what about the header? It would make the most sense to design it for *cough* electric power and SE Glow engines. Integrating an easily removable hatch to access batteries would be an added bonus. Personally I would prefer the Jett if you could get appropriate headers.

Roguedog

FWIW,

I did some experimentingwith my OS25 VFDF's and it turns out the major difference is in the Crankshaft rotor timing as compared to the 25 VF.

I also found out that a 25 FSR or 25 SF crankshaft fits as a replacement as they are the same stroke and bore. Have to run it to see if it will work though. Will post here as soon as i know if it works.

Bryan

Huang

My Feedback: (27)

+1 on what Jeff said...

doxilia

My Feedback: (3)

Jeff, this makes sense. I'm not intimate with the OPS specs but I can see that it would be a bigger brother to the Italian Rossi, Supertigre, OPS and Picco .15 heritage. After your testing and tuning of the VF DF, I wondered if a 2.5 cc pipe might have been better suited and would have brought the engine on tune better. Kato shows an equivalent Hatori 200 series pipe which is quite small and narrow.

This is a very good point and back when, I could see a number of people preferring the electric route. With several designs this is rather straight forward - the Curare & Magic are easily convertible and even the Skymaster could have an open tank bay, however, access would still require removal of the glass deck. For this reason, I always saw the SM as the RE piped cool model that it is. As for the other two true RE designs, the Arrow and Aurora, the former is also to my mind a RE candidate and I wouldn't envision it otherwise. As for the Aurora, this is the one design which could really be SE, RE or electric. It's predecessor, the Cosmos, strikes me as being nicely setup design wise to use a side mounted engine with muffled exhaust or a "re-entrant" pipe recessed under the wing. The two smaller Blue Angel and Mattlas designs are both well suited for SE or electric with the canopy position in the Japanese designs being a potential limiting factor in the conversion to electric.

So to summarize:

SE designs
Blue Angel
Mattlas
Magic
Curare
Cosmos

RE designs
Skymaster
Arrow
Aurora

Electric candidates
Blue Angel
Mattlas
Curare
Magic
Aurora

While the Skymaster, Arrow and Cosmos could be converted, they strike me as better suited to glow power.

As far as headers go, if a custom setup is needed as with the specialized SM S-header, I think that these could be made for either RE or SE engines without any disadvantage to either. Fortunately, I think that the standard MVVS & Macs RE headers could be made to work with the 28 in either the Arrow or the Aurora.

For builders who choose to go with a RE Jett, having an application specific header made by Dubb shouldn't significantly increase the price tag to the prized engine.

David

bushpilot-RCU

My Feedback: (3)

Hi david I have a Aurora 25 nib as well as a Pilot Shooting Star 20 , let me know if you would like to make patterns of them.

doxilia

My Feedback: (3)

I've been a little slow in my follow up on this thread.

Thanks to all for your input on the engines available for the MK 20 size. Between Jeff's recent Skymaster 20 build and Jason's Curare 20 and Yoshioka Ursa Major 20 builds we have a few more 20 size classics to add to the books.

After a little research I have been able to source a pair of nice new MVVS 28's. While these engines are still in production and available from European sources (mvvs.nl and mvvs.cz) I opted to seek them out from individuals. The first of the two I picked up has a red head and was configured for CL and didn't come with an RC carb. The second I bought from a nice fellow in the Czech Republic (home of MVVS) and has a silver head and came with the standard current MVVS carb. The older RC carb on the red head I pulled from an MVVS 40 I have. All MVVS carbs used on 25's to 48's are the same in inner and outer bore so they fit any and all of these engines. The issue with the older carbs is they apparently have a poor transition caused by a very modal high speed needle. Replacement of the high needle with the new "sleeved" needle solves the problem and the engines apparently perform very well. Naturally, current production MVVS 28's bought from the distributors come with the proper new carb. It's worth noting that current engine head and thrust washer anodization is apparently blue as shown in the manufacturers picture I posted a few posts up.

The MVVS's are very nicely made. The 28's and 40's more so than the 60's but this also depends on manufacture date (the older engines were not quite as well made as the current engines). They are solid yet light and comparable to Webra 25-36's in weight. They are shorter in height than Webra's but a fair bit longer in the crank with the full thickness of the thrust washer over extending the Webra's. I have configured all the MVVS engines I have recently bought (a 40 and a 60 as well) into RE mode as that is what I find interesting about these engines. RE classic designs usually accommodate longer engines without too much trouble so I don't anticipate any issues in being able to use the 28's on the MK 20 classics where desired. They can be mounted inverted (e.g., Skymaster, Magic, Aurora) or upright (e.g., Arrow, Citation) and could even be used in a side mounted engine setup with a pipe down the side of the fuse. Naturally, the engines can be used in their factory SE configuration as well using either a Macs pipe setup, MVVS' own mousse type performance boost mufflers or simply an MVVS muffler. The SE configuration would be suitable for the Mattlas, Curare, Blue Angel and Cosmos. Personally I find the elegance and beauty in these engines when used in RE configuration with a longer concealed Macs pipe setup using a 9x5, 9x6 prop. Performance on a pipe should be in the 700W ball park - more than ample to expedite these little classics straight up.

While neither MK nor Yoshioka ever came out with a 20 size Arrow or Citation, respectively, I plan to design both of these with the MVVS RE 28 specifically in mind. Of the three easily obtainable "30 class" RE engines (MVVS 28, NovaRossi 28 and Jett 30), the MVVS is the least expensive and therefore, the most attractive IMO for these little classics. Naturally, nothing would preclude one from using either a NR 28 or a Jett 30 in these two designs with little, if any modification. I plan to design the models using 5/16" horizontal ply "bearer" engine mounts that integrate into the fuse design and build producing the required down/side thrust. Actually, to be frank, the models are already designed but for 40 class engines so the job is to scale the design down and simplify somewhat and "re-select" materials and wood thicknesses for a 20 size build. The two will be scaled to specs similar to the Skymaster and Magic which are not the very small Mattlas and Blue Angel but aren't the larger Cosmos or Aurora either. Because the Arrow and Citation have such different wing planforms, they will likely have quite different spans which track the 40 size version counterparts.

Production of my first MK CAD efforts in the form of a Super Chipmunk 120 will soon be underway so the 20 size classics should not be too far away after that. I may well start with the RE "non existent" Arrow and Citation which might help to inject a little excitement back into this project.

Below are a few snaps I took of the MVVS 28's. Interestingly, the fuse top Macs header you see on the red head is for an OS 25 VF. The difference in screw spacing between the OS and MVVS is ever so slight so it actually fits. That said, Macs has serial production MVVS RE and SE headers for the 28's, 40's and 60's. The 28 takes the "MVVS 20" 3370/71/72 series of RE headers. The Arrow will likely require a fuse top 3372 header (as shown on the red head) while the Citation will probably require a 0 degree 3370 header (straight back).

David

doxilia

My Feedback: (3)

Bushpilot,

Thanks for the offer. Could you post or send me some pictures of the Pilot Shooting Star? We're set for the Aurora (much design work has been done on it) but the OK Model designs are certainly in my "wanting to develop" book.

David

AllTheGoodNamesAreTaken

My Feedback: (180)

How about a Mystic 30 or a Supra Fly 25?

engineMagnet

Nice project! Good luck and hope to hear about developments.,,

Cheers,
/Rui

GuilhermeMZE

Subscribed.
Congratulations on project.

Guilherme

mchandrayan

Subscribed to the thread.

Air_Boss

This is a great thead! Just found it and read it through completely. I found it while searching for Blue Angel 20 size templates.
doxilia: Your Blue Angel 30 project is awesome! I used to fly a 60 size Blue Angel, and altough it was a little rough, it was an original MK kit build, and easily the best flying airplane I have ever owned, and probably will ever own. I sold it in 2014 with most of my glow powered planes because I was emigrating and couldn't take any large planes with me. I have been missing it ever since, so I am planning on building a smaller one. You are right that the bigger BA has more elegant lines than the BA 20, so the 30 size project of yours would fit the bill perfectly. How far are the plans comming along? I've included a picture of my old Blue Angel. Like I said, not the most beatiful one, but I was used when I bought it, and never restored. Just flew the heck out of it