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Old Dec 23, 2009, 04:23 PM
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What do you think about the J2M Raiden

Since I have gotten into the F3P thing this fall I have built a number of Fancy Foam models as well as a plans built Index and Morback. I am looking for another build and was pleased to see the Construction Article on the J2M Raiden designed by John Glezellis in the January issue of Model Aviation.

I've seen John fly at a local Huckfest so I am sure he knows more than a little about designing a decent plane.

I was wondering if anyone was planning on building this plane, or what folks think about it.

Unfortunately the AMA Plans service seems a little archaic as purchasing plans is done by mail and they say to allow 3 to 6 weeks for delivery. I'd much prefer paying by PayPal and downloading plans to take to my local printer. I guess I can scale up the little tiny plan fairly quickly if I decide to build it.

Just wanted to start a discussion on this plane.
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Old Dec 24, 2009, 01:12 PM
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I just called MA plan services and ordered with CC. They said it would only take 3 or 4 days for delivery. I agree though, tiled PDFs with Paypal and everybody wins including the creators of these marvelous airplanes
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Old Dec 24, 2009, 02:22 PM
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Not to ruffle any feathers, but the plans are right there on page 27. In the time that it takes to get the full-size plans delivered, you could scale up the reduced ones.

Tom
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Old Dec 24, 2009, 04:05 PM
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Hi Tom,

I'm actually on my way out the door, but saw your post.

I'll post some information on this airplane either late tonight or early tomorrow morning- my thoughts on the flight performance, equipment, etc.

I built several of these models, each with different equipment (servos and motor combinations). Also, I'll talk briefly about some of the design changes that I did from my first J2M to the final version...

Best Regards,
John
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Old Dec 24, 2009, 04:30 PM
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Originally Posted by Trisquire View Post
Not to ruffle any feathers, but the plans are right there on page 27. In the time that it takes to get the full-size plans delivered, you could scale up the reduced ones.

Tom
Yeah, that's what I did. Didn't realize they would ship in a few days since it said 3 to 6 weeks!
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Old Dec 24, 2009, 08:05 PM
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Originally Posted by John Glezellis View Post
Hi Tom,

I'm actually on my way out the door, but saw your post.

I'll post some information on this airplane either late tonight or early tomorrow morning- my thoughts on the flight performance, equipment, etc.

I built several of these models, each with different equipment (servos and motor combinations). Also, I'll talk briefly about some of the design changes that I did from my first J2M to the final version...

Best Regards,
John
Hi John,

I guess it would be easier to work off of the full-scale plans. Also, some of the fine print is hard to decipher on the reduced picture. Its a good looking plane.

I enjoy your contributions to MA. I'm looking forward to your thoughts on the J2M Raiden.

Regards,
Tom
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Old Dec 25, 2009, 12:17 AM
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Here's a pic of mine scaled to 65% from plans in the rag,
I plan on using the ar6400 and as2000L servos with a 1S 240ma batt and 2gram BL motor AUW projected about 50 grams

WS is 24 inches

Roger aka GIFLYRC
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Old Dec 25, 2009, 06:41 AM
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Originally Posted by John Glezellis View Post
Hi Tom,

I'm actually on my way out the door, but saw your post.

I'll post some information on this airplane either late tonight or early tomorrow morning- my thoughts on the flight performance, equipment, etc.

I built several of these models, each with different equipment (servos and motor combinations). Also, I'll talk briefly about some of the design changes that I did from my first J2M to the final version...

Best Regards,
John
Thanks John. It would be very interesting to know more about the design changes.

I am pretty new to these planes, but after doing a couple kits and a couple scratch builds, I decided to do scratch out a Spitfire and am currently doing a F4F-Wildcat. I have been a "slave to scale" and have pretty much built these warbird flat plate foamies true to scale, except that I have enlarged the rudders and of course made the ailerons take up a larger proportion of the wing and the elevators a larger proportion of the tail and made the wings slightly shorter than scale. I have compared them to my Fancy Foam Yak and my Index and find that building to scale gives very similar proportions to the Yak. With the Spitfire of course I put the wing in the center of the fuselage which is not a scale feature. What attracted me to the Wildcat is that is is one of very few planes were the wing is actually located pretty close to the centerline of the fuselage. The tailfeathers are a little higher and so I raised them a little as per the Raiden. The Wildcat is just cut out and of course hasn't flown, but the Spit flies very nicely, pretty much like the FF Yak, and looks cool with the elliptical wing.

Anyhow, to get to the point, you (as a very talented pilot) found that deviations from scale made the plane fly better and it will be very interesting to hear about these changes. For example, the wingtips are cut back kind of like the Osiris. I am very curious what effect this has. I'd also like to know a little more about what the side force generators do. Lots of these planes have them but I don't understand what they "do". Finally, I notice that your wing drag plates do not have holes in them like most of the ones I see, and would like to understand that better.

I was looking for something to scratch out and really appreciate your making this available. I am torn as to whether to finish my Wildcat or start cutting out the Raiden from the plans I scaled up. Its like too many Christmas presents and I don't know what to play with. It makes an old dubber feel like a kid again. Merry Christmas everyone!
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Old Dec 26, 2009, 12:49 PM
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Roger- The little J2M looks great!! Curious to see how it flies! Keep us posted on pictures!

U2Builder- Glad to see you’re doing a few scale type aerobats- they are definitely different and unique. Send a few pics of your Spitfire! Regarding your questions, I’ll divide them up:

SFG’s- Side Force Generators increase the side area of your model. You can add SFG’s if you feel that you need more rudder authority. I urge you to try your model with and without them to see how the model behaves, and how it differs. The benefit with foamies is that you can make drastic design changes in a matter of minutes!

Leading edge design and wing platform: On my original J2M, I kept a wing taper and outline that was very similar to the real model. Resulting, the roll rate was not what I wanted out of a 3D foamy. To keep more wing area at the root of the wing, I cut back the leading edge after the SFG to decrease the wing tip area (which resulted in a roll rate increase, and a better snapping model).

Airbrakes- I’ve tried a few different airbrake designs, and airbrakes do change the feel of the model. If airbrakes are too large, they can decrease the roll rate of the model. The J2M’s airbrakes are fairly small and ideal for both indoor and outdoor applications.

As for the evolution of the J2M……

I wanted to make a larger F3P model so that builders could use equipment that they currently have. For equipment, the article was based on one of my models, which had a Park 300. This was for outdoor flying and indoor sport flying. My latest model has a Hacker A10 9L, and uses both 2-cell 350 mAh and 3-cell 250 mAh packs from Thunder Power to keep the weight down. For servos, I started off with the JR 185’s, and then went to the 188 (the digital version of the 185) for better centering. While I have also tried various 4.7g servos, I prefer the speed and torque of the 188.

If building this model for competition, mill-away as much material as you can to keep it light. Weight is critical in how the model will fly.

My first J2M had a larger fuselage in terms of height and the wing outline as it was discussed earlier. Cutting back the fuselage height and changing the wing taper made the model more linear in feel for rolling maneuvers and increased the roll rate.

All the Best,
John
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Old Dec 29, 2009, 07:31 PM
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John, I have another question. I noticed that, unlike most designs, you raised the horizontal tail above the wing line. You mentioned in the article that you did this, but I would love to know the reason for this change from the "usual" design. Thanks!
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Old Dec 29, 2009, 09:18 PM
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John,
How is the size/area of the drag brakes determined?

Is it a % of the aileron area and if so, what is the formula?

Thank's,
Roger aka GIFLYRC
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Old Jan 01, 2010, 05:06 PM
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Hey how cool is RCgroups....we can read about a new/cool plane in Model Aviation then converse directly w/ the designer via this forum!

I really like the J2M paintjob in MA...esp the "weathering". Looks like it was done with just some grey airbrushing over a bit of aluminum screening?
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Old Jan 02, 2010, 08:40 AM
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Originally Posted by u2builder View Post
John, I have another question. I noticed that, unlike most designs, you raised the horizontal tail above the wing line. You mentioned in the article that you did this, but I would love to know the reason for this change from the "usual" design. Thanks!
I can't speak for John, but the model is loosely based upon a full scale aircraft. The real Raiden's wing is below the thrust line, and its stab is above it.

Tom
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Old Jan 02, 2010, 11:29 AM
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Originally Posted by u2builder View Post
John, I have another question. I noticed that, unlike most designs, you raised the horizontal tail above the wing line. You mentioned in the article that you did this, but I would love to know the reason for this change from the "usual" design. Thanks!
The location of the horizontal stabilizer can vary from model to model. While it is lighter and easier to have the horizontal stabilizer mount on the horizontal cruciform, adding the horizontal stabilizer above the thrustline added two benefits for this "larger" model.

Structurally, the stab has four foam supports that tie it in to the fuselage (two supports are glued to the fuselage sides between the stab location and the horizontal cruciform, and two supports are glued on the outer edge of the horizontal cruciform and the stabilizer. Having a few 3mm depron supports, the center of the stabilizer becomes extremely rigid. Then, once the carbon bracing is added, the tail section is very strong.

In an aerodynamic sense, I found that this location worked very well for minimal rudder to elevator mixing values and when using various size battery packs. Of course, changing the height location of the battery does play a huge role when it comes time to properly trim your model for knife edge flight.

Regards,
John
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Old Jan 02, 2010, 11:34 AM
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Originally Posted by GIFLYRC View Post
John,
How is the size/area of the drag brakes determined?

Is it a % of the aileron area and if so, what is the formula?

Thank's,
Roger aka GIFLYRC
Over the years, I've tried many different types of airbrakes and different sizes. All in all, larger airbrakes tend to slow the roll rate down on an airplane. Also, location matters as moving the airbrake towards the root or the tip can change the flight characteristics and "feel" of the model.

Also, just because one airbrake style and size works on one type of an airplane, it doesn't mean it will work on all. I recommend starting with a larger airbrake, flying the model, and changing the size of it until you are satisfied with the roll rate of the model and the speed on down lines. Also, keep in mind that it is best to try different locations on the aileron too. Use a "T-Pin" to pin the brakes in place on the aileron. Try different locations until you are satisfied, and then CA them in place.

Regards,
John
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