Alpha 2.8 TJIRC (AKA, TJIRC Great Wall 2.8m)

[Konrad]

This will be a discussion of the TJIRC Alpha 2.8 as sold by Aloft Hobbies.

What drove me to look at the TJIRC Alpha 2.8 was that I damaged my two RCRCM Stregas' in the first race of the NCSS F3F season. I hate to say it but it looks like I'll be behind the power curve trying to keep some kind of F3F ship ready for racing.

I went into Aloft Hobbies to get a next level up F3F ship. As is typical with Wayne at Aloft Hobbies I came out with a different ship than I was planing to buy. This is a good thing as I went in wanting to get an $1500 Rotmilan. This is a nice older well proven F3F ship. After my talk with Wayne it was decided that I really shouldn't destroy such a nice classic ship as the Rotmilan (Ok, he was out of stock). Wayne actually down sold me a TJIRC Great Wall 2.8m carbon lay up glider. While a bit smaller than the RCRCM Stregas' I'm flying, the TJIRC Great Wall will actually be a huge step up. At $850 dollars it is one of the best valued gliders out there in the 2.7 to 3 meter F3F class of carbon ship!

Add to the great NIB value I got an even larger price break as the TJIRC Great wall 2.8 I got had some shipping damage to the wing tip. To be honest my ships all look this beat up after the first test flight!

I'm of the opinion that TJIRC is a huge step up from what we get with RCRCM products. Basically they are what an RCRCM product might look like if manufactured properly (for the price point). That is to say TJIRC planes are a great value!

Wayne tells me that the TJIRC Great Wall is the exact same model as the one he is marketing as the TJIRC Alpha 2.8. So from here on out I'll be calling this a TJIRC Alpha 2.8.

Wow, this is a Strega killer! While being a bit smaller at 2.8m it's design and construction are much better than the RCRCM Strega.
The first thing I noticed is that the cloth lay ups in the wing are biased at 45°. This costs a bit more as there is more waste at the end of the cloth bolts. But this makes for a wing that is much better at resisting torsional loads.

The second thing I saw was that the shear webs are place in what looks like a carbon sock. This will help with the bonding between the two heavy carbon caps and stabilize the shear web's grain. This is a nod to a real spar! I also notice that there are oversized and properly placed carbon stiffeners to spread the wing servo loads.

While Wayne did say the Great Wall and the Alpha 2.8 are the same I did noticed that this Great Wall has a set of 11.9mm round ballast tubes in the wings. Most Alpha 2.8s that I've seen have a rectangular ballast tube. I like the round tube as I think it might be easier to find tungsten ballast rod. But I think most folks are actually using rectangular brass as ballast. The only downside I see is the 11.9 is too small for a 12mm rod!

The wings of the TJIRC Alpha 2.8 are a bit thinner at 19mm, than those on the RCRCM Strega which are 19.5mm thick. The only odd thing I notice is the convex wing TE and the wider tips than those of the Strega. I don't know what these style features will do to the roll rate and stall of the wing.

Now what caught my attention was the fuselage. It is so much better than the RCRCM Strega's. First it has a longer tail boom (I love long boom gliders)! The servo tray is a bottom feeder with slip on nose cone. This adds a lot of crash resistance as there are now a lot more fibers on the top of the nose holding the nose in place on most landing (read my hard landings). I also like that the slip on nose cone part line is slated forward a bit. This again was done to align the structure with the landing loads. It looks like the fuse has a full carbon layup aft of the wing leading edge!

This brings me to one of the few concerns I have. The nose appears to have a lot of carbon strips as nose stiffeners. I fear these may block most 2.4 gHz signals. I'd have liked to see some heavy kevlar rather that carbon in the nose.

Now what baffles me Is how am I to actuate the V-tail flippers? I see that TJIRC has supplied me with 1.7mm wire control horns and two full length 5 mm carbon push rods. But I fail to see how I'm going to get these control horns past the fuselage sides into the fuselage center bulb. Right now I'm thinking I'll have to cut the fuselage side from the control horn axis all the way to the fuse top opening. while that would work I don't like the idea. (I guess it really is no worse than the aft tail cone we got with the Strega). If anybody knows how this was to be done please let me know. I'm thinking that the V-tails are thick enough that I might place a set of KST X0-8 in the stabs and set up the V-Tail as a fly by wire and do away with the 5mm carbon push rods.

 

[Konrad]

Starting to cut glass! It looks like this Alpha 2.8 will be a fly by wire set up, in that the servos will be in the stabs. I think I can get an effective control arm length of 6mm maybe even 7mm and with a servo arm of 4mm to 5mm I should be able to keep all the linkage in the stab or at least in the turbulent boundary layer. (This was based on using an IDS style actuator. I’ve abandoned that configuration in favor of using the tail bulb to house the linkage).

 

[Konrad]

After having slept on the idea and seeing that I don't have a 1.6mm x 0.35mm tap and die I'm starting to have second thought on the rear mounted servo. My idea is to make a custom IDS.
While I like to experiment on low cost items this Alpha 2.8 was mainly purchased to get a ship ready for the next F3F. So for expediency do I go with the supplied hardware?

On the subject of IDS you might have noticed in the 3 wing photo that the Alpha 2.8 doesn't have any control horns or hoods installed for the ailerons and flaps. This is a big plus in setting up radio. Other than landings I do more damage removing these factory installed features, than any other action. While the Alpha 2.8 does come with control horns and nice router cut plywood servo trays (30mm x 35mm x 10mm), I will be using IDS.

Now a bit on quality. Please remember that this is an early model. Every production run I see from TJIRC appears to have improvements made in quality.
My Great Wall has a paint finish that is a bit on the semi gloss side. I think this was done on purpose as it is easy to see the cloth weave in the epoxy. I don't think TJIRC uses a light weigh cloth (0.7 oz/yard glass) to limit this cloth bleed through. The paint on my Great Wall is impervious to IPA and Acetone which leads to think that it is a catalyzed paint. The fuselage part line is a bit proud but there appears to be a lot more fiber across the part line that what we see in the RCRCM product. The only issue I see is that it looks like TJIRC is using the same fiberglass supplier as RCRCM in that what I see of the fiberglass has those horse hair in the weave.

 

[Wayne]

Your Great Wall was a sample we brought in to see if we wanted to sell them. We shared with them a number of items we wanted to see changed on this and the 2 meter glider and then gave them the Alpha paint scheme and name. Otherwise the same. With this Said, I know TJI takes feedback from all of their dealers and many of their customers to help improve the planes. I suspect the change in wing ballast is one of those, we did not request it, but someone probably did.

We have been getting good reports back with these planes, it is sure hard to argue for the price of them.

 

[Konrad]

... I don't think TJIRC uses a light weigh cloth (0.7 oz/yard glass) to limit this cloth bleed through. ...

I think I need to make a retraction as it does look like TJIRC does use a layer of light glass to try to control heavy weave bleed through.

Here I'm getting ready to sand the nose to remove about 40mm of carbon to make sure it is 2.4 gHz safe. As I cut through the paint I saw the fine weave of light cloth that was used against the molds to control the bleed through of the heavier structural glass. Looking at the wings up close I see that these also have this light weight cloth. I'm pleasantly surprised at just how heavy the carbon cloth is on the wings.

Wayne can you share with us what changes you may have asked for in your Alpha 2.8 branding. Looking at my Great Wall I assume it mainly is cosmetic. I'm impressed at just how much better these are than the RCRCM product. TJIRC and RCRCM look to be in the same price range (class).

How are folks setting up the V-Tails? Are they using the supplied hardware.

All the best,

Konrad

P.S.
Don't know what happened but the heavy weave photo is about 15% too large. But I think most of you will get the idea as to just how much different the inner cloth is from the outer cloth (finish cloth)

 

[Konrad]

Oops! When changing the livery it is often best to remove and dark colors that might show through the lighter top coat So with a rigid sanding block I sanded away the black ideographs. Only to now have a reverse image of the characters. This is because the wings are painted in the mold. I'm hoping that since the white wing is on top of the black carbon that it might color balance. I know, I know I'm hoping against hope!

On a more important issue I want to provide a good environment for the 2.4gHz antennas. Unfortunately I found carbon tow in the nose of the fuselage. I will have to remove a band of carbon that is about 50mm wide. I'll have to use a lot of Kevlar to bring back the strength.

With a slip on nose and carbon wings it is rather difficult to place the antennas properly for good RF reception.

 

[purview]

Very interesting to see what you did with a brand new kit. Does here anybody know what these characters on the right wing mean (ideographs)?

Konrad, is the joiner in good quality for this price segment? Weight?

Many Regards
Chris

 

[Konrad]

What do you do with a new kit? This is just part of my build process. I try to address problems I see before they materialize. (My builds are rarely kit reviews, I show what I'm doing to make the kit fit my needs).

The wing joiner is a carbon copy of the Strega. In fact they are interchangeable.

From an engineering perspective this is looking a lot better than my two Stregas. My white and red Strega has a much better finish, less weave bleed through and a higher gloss finish. Note TJIRC has been getting much better with the paint in later production runs.

The wings look to be of a second tier design when looked at against our Redshifts. I do like the Alpha 2.8 fuselage as it has a longer tail boom than the Redshift and is a bottom feeder.

 

[Konrad]

Konrad, is the joiner in good quality for this price segment? Weight?

Many Regards
Chris

Good question.

I was in error when I said the Alpha joiner would fit the Strega. While all three ships have the same cross section joiner, they vary in length. The Alph 2.8 has the largest and heaviest joiner at 44cm long and 150 gram.

Note the Alpha does not have a sine wave spar of the Redshift. It is looking like TJIRC is getting some of this stiffness back with a longer but heaver joiner.

 

[purview]

I have the same issue with my China products. I can change them but not all fit in all. The match is that I have one other brand too, so I keep joiners at spare..

Yes, I see the alpha is another type of joiner box.

 

[Nigel]

You could also mount the antennas externally. Not really much of an aerodynamic footprint, and definitely much easier than all the sanding you're doing.

 

[Ryanenc89]

Konrad I’m out of town for work but when I get back I’ll take some pics of my 2.8 carbon alpha. I’ve got a newer version and the wing ballast is set up more like the Magnus. The wings are super stiff! Haven’t built it yet but I assume you need to notch both side of the tail to install the V tail linkage. I’ve got everything but the mini q by tjirc. The 2.8 blows all the others out of the water. The layup, edges, cuts, paint is pretty darn good for the $. Like you’ve mention I think the production is getting better from tjirc as time goes. Time will tell.

 

[Konrad]

I have the same issue with my China products. I can change them but not all fit in all. The match is that I have one other brand too, so I keep joiners at spare..

Yes, I see the alpha is another type of joiner box.

Chris, are you expecting the joiners to be built to standards sizes, like fasteners? I look at the joiner as a component the designer makes to fit the application. Cross section, weight, length and dihedral are all unique to each design (aircraft). With in a OEM or designer I might see some commonality but I wouldn't expect interchangeable joiners between aircraft designs.

 

[Konrad]

You could also mount the antennas externally. Not really much of an aerodynamic footprint, and definitely much easier than all the sanding you're doing.

Now you tell me!

But I have to ask how? As the nose cone slips on and off off I assume that the furthest forward I could place the antenna exit is just aft of the nose cone part line. This then places the antenna in the shadow of the carbon wings. One could put an antenna above the wing and the other below to mitigate some of this. But I find landing on an antenna a good way to shorten ones flying day.

The other possibility is to place the antennas aft of the wing. But how to thread the antennas way back there with no hatch?

And the last would be to use a secondary redundant RX (MX+) in the tail cone and splay the antennas 90° from there.

But yes, sanding the 70mm band is a pain. I'm open to better ideas.

 

[Konrad]

Konrad I’m out of town for work but when I get back I’ll take some pics of my 2.8 carbon alpha. I’ve got a newer version and the wing ballast is set up more like the Magnus. The wings are super stiff! Haven’t built it yet but I assume you need to notch both side of the tail to install the V tail linkage. I’ve got everything but the mini q by tjirc. The 2.8 blows all the others out of the water. The layup, edges, cuts, paint is pretty darn good for the $. Like you’ve mention I think the production is getting better from tjirc as time goes. Time will tell.

Yes, cutting through the side wall is a time honored way to get the control horns inside the fuselage. I just think that there are tail cones that do this much more elegantly.

I too have most of the TJIRC products that Aloft Hobbies imports into the states.

And I too have noticed how much better they are than the same type/class of model manufactured by RCRCM. After my experiance with RCRCM's glass offering (Strega, and Sunbird) they are on my do not purchase list! Well, the glass lay ups that is. Now with the RCRCM carbon lay up I'd have to think real hard, and look to see if there actually was any value in the product. (Or put another way, how much were they paying me to take the model)!

 

[Konrad]

Last night I did my Kevlar lay up in the nose to support the nose for the removal of carbon in a 70mm RF band. You can see where I trimmed the Kevlar to the nose while the epoxy was still green. You really don't want to sand Kevlar as it just makes a fuzzy mess! You can see where I didn't saturate the fibers enough and have the start of that fuzz ball. I'll have to saturate the fuzz with CA and try to trim to size.

I've removed all the carbon in a 70mm band. I'll now have to build up the void left by the removal of the carbon with some glass cording. I'll follow this with an S glass bandage over the reworked area. This and the use of a full nose servo tray should result in a solid nose, that can withstand my landings.

 

[purview]

Chris, are you expecting the joiners to be built to standards sizes, like fasteners? I look at the joiner as a component the designer makes to fit the application. Cross section, weight, length and dihedral are all unique to each design (aircraft). With in a OEM or designer I might see some commonality but I wouldn't expect interchangeable joiners between aircraft designs.

No, not all. Thickness of the aerofoil is the limit. Although I use the same joiners from Stormbird and Redshift from AEROIC and the Link from RCRCM

 

[purview]

Sorry, James. It can't complain. ?

 

[Konrad]

Ok back to square one.

That is I think I've corrected a potential problem with the 2.4 gHz. Time to start the repair of the shipping damage and general build.

I think you can see how I laid up the repair after removing the carbon. I hope the inner Kevlar will give me the needed toughness. And the S-glass cloth and roving will add the lost stiffness from the removal of the carbon.

 

[Konrad]

I'm looking to learn how other may have added a ballast tube.

The Alpha2.8 is a nice enough ship as it is worth the effort to add a ballast tube to the center line of the fuselage. While all the fast F3F racers are using wing mounted ballast, this is done because the fuselage cross section is too small to place the ballast tube on the fuselage center line. Since the Alpha2.8 has a very nice sport width fuselage it actually is preferred to have the ballast on the fuselage center line. (Less inertia to over come rolling the airplane into and out of the turn, less control drag).

While I want to set up this Alpha 2.8 with the fuselage servos in the rear (fly by wire). I want to leave open the option for nose mounted servos should I find that I have problems with the rear mounted servos. It is looking like using a 22mm o.d./ 20mm i.d. tube will allow enough clearance for 4mm carbon push rods running down the side. 19mm lead slugs may not have enough mass for the slopes around here so I'll be using Tungsten crankshaft counter weight. Yes, the Alpha 2.8 is that nice a ship as to warrant the cost of tungsten.