Originally Posted by rdgood

Ok I'm psyched now...

Your going to love it! Fly's as good as it looks!
I'm at 26 flights on mine, zero issues and it continues to amaze me every flight.

they make it assemble with 4 screws like other bipes I'm sold. not counting tail

I'm thinking of going with the MKS777A servos...
I have a Smartfly EQ with turbo reg and integrated optic ignition cut off...


I can push 6.5 volts at servos regulated at the 777A's should put me well over 400 oz/in of torque...


Thanks,
Ronster

Svan,
Have you looked at your firewall??
Previous thread was saying that he was getting stress cracks in the firewall area...


He was talking about reinforcing it...
I really don't see a need to...
the Tri stock looks very healthy...


Ronster

Originally Posted by rdgood

Svan,
Have you looked at your firewall??
Previous thread was saying that he was getting stress cracks in the firewall area...


He was talking about reinforcing it...
I really don't see a need to...
the Tri stock looks very healthy...


Ronster

I have a couple of times. No issues so far. (26 flights)It wouldn’t hurt anything to add some reinforcement but if you go over the glue joints I think it will be fine. It may be that a few have gotten out with ether poor quality wood or inadequate glue joints. The structure itself looks up to the task. Like all my planes, I will continue to inspect the airframe periodically.

Originally Posted by rdgood

Svan,
Have you looked at your firewall??
Previous thread was saying that he was getting stress cracks in the firewall area...


He was talking about reinforcing it...
I really don't see a need to...
the Tri stock looks very healthy...


Ronster

So, based upon my experience, I would add tri-stock between the first former and the engine box, and look at the bottom of the firewall. It's effectively only held in with 1/8" ply. I added about a 4" long piece of 1/4" ply with tri-stock to the sides to re-enforce that.

In my case, mine was a vibration machine from day one. I checked the prop pretty quickly and found that despite my best efforts, it wasn't perfect and fixed that. That didn't seem to change much, but maybe the damage had already been done. After that, I seemed to be chasing a progressively worse problem with vibration. First, separation from the former (fixed that), then the bottom of the firewall, leading to the firewall splitting, and finally, I saw damage to all the 1/8" heavily cut out ply structure leading back into the fuselage. I ended up having to double the firewall and add bass wood sheeting to all that cutout structure. So, despite my individual problem, remember the airframe was designed for a DA-100. I would advise you to re-enforce around the first former and the bottom of the firewall like I said above. After that, deal with any excessive vibration immediately.

The other problem I've had? Blind nuts! This thing has a ton of blind nuts. Hit them all with thick CA. Pay close attention to assembling the struts. Make sure not to cross thread into the blind nuts, and especially don't push and pop out a blind nut. You'll really regret it!

Look at the wing tabs. If you cross thread or pop out any of those 8 blind nuts at the field, for the life of the plane, trust me. You'll be screwed sitting there with a pair of needle nose pliers for 45 minutes desperately trying to get that screw out. When you assemble, be very careful not to cross thread and make sure you never push into that blind nut. Don't over tighten those either. If you start to crush that plywood, the blind nut might come lose. I had that happen, and by the time I got that frick'en bolt out !@%!!!!, that tab was toast, and I had a bear of a time digging it out and replacing it. So, beware of the blind nuts!

Speaking of that, get a box for your assembly bolts and washers. There's a lot of them. Fill it with only the screws and washers you need for assembly. For the 10 or 15 minutes it takes to assemble, don't let anyone distract you, and make sure all the bolts are gone when you're finished. We lost a big bi-plane at our field because he got distracted and didn't bolt on one of the wings. I almost did it myself one day. Be diligent and pay close attention when you assemble!

Beyond that, get you a 6" aluminum spinner and enjoy the hell out of this plane!

Here's a couple of pictures. The firewall is held in with 1/8" ply with at best a layer of that heavily cut out ply. In the first picture, I think I added tri-stock to the front and back of the first former. In the second picture, the whole bottom of the firewall/tri-stock separated and eventually split the firewall.

not good but most times is caused by a loose or over torqued engine mount bolts

Originally Posted by airboss/oc

not good but most times is caused by a loose or over torqued engine mount bolts

So you think firewall cracked first and that caused all the vibration and subsequent damage?

Look like the right hand bottom stand off was overtighen to a point it show compression and crack.. or a hard landing did that ?
Out of balance prop and spinner will do a lots af damage if not taken care off. Hard on electronics also.
That airframe construction is very similar to the Beast and have a proven record of durability.

It's light weight guys. At best, it was designed for the DA-100. On my Extreme Flight Extra, the engine box for the 120cc engine is solid 1/4" ply all around and 12" back. It's got tri-stock front and back on the firewall as well as all around the first former. The structure is distributed into the fuselage with 10" vertical solid 1/8" plywood well into the fuselage. That not to mention the heavy duty formers that attach to the wings and outer fuselage. There's no comparison to this Viking, and I don't think you'll find anything substantially different on the other 35% airframes. The Viking is light, but at what cost?

We can speculate on why mine failed. I certainly have. Bottom line though, I speculate that whatever the cause on my individual plane, it would have held up a lot better with a stronger engine box. Adding a little tri-stock, some extra ply underneath, and even re-enforcing the structure into the fuselage with some solid ply or basswood is cheap and easy insurance. That's my advice, take it or leave it!

Dlduece,


I don't mind an ounce or 2 of prevention. After looking at the firewall thoroughly - it is a bit under engineered IMHO.


Have you had any more cracks develop since you reinforced the structure???


Thx,
Ronster

Keep in mind this airframe was designed by Quique when he had qqac as the Python. A scale version of my full scale design. Back then, there was no DA 120. It was designed for the DA85 and DA 100. Then Quique went to work for horizon and brought me and my full scale designs along with him. The airplane got the Beast scheme on it and began the run of beasts at horizon from UMX to 100cc. The full scale python was rebranded into the Viking and got a new tail I designed for it. So, horizon updated the shapes and scheme to market it as Viking. Recall Quique flew his 44% DA200 Viking at the sun n fun airshow with team horizon a few months before he left the company. Yes a few changes were made but basically, it is the same airframe as the python from 12 or 14 years ago. Quique designs airplanes to be light and fly light. Not overbuilt to take hard landings and such. I still have an original qqac python although I don’t fly it any longer. A bit of a trophy from the past.

Wouldn't be hard to laminate another layer of whatever thickness ply you want onto that firewall. Or better yet some thin G10 or carbon like you see on some newer designs. I love the G10 laminated firewall on my 79" 3DHS Slick, it doesn't compress at all so after 3 years I've never had to tighten my engine mounting bolts.

Something to consider, an ounce of prevention for those that have this otherwise awesome airframe!

Originally Posted by rdgood

Dlduece,


I don't mind an ounce or 2 of prevention. After looking at the firewall thoroughly - it is a bit under engineered IMHO.


Have you had any more cracks develop since you reinforced the structure???

No, but I haven't flown it that much. The vibration is much improved though, although still more than my monoplanes. So, time will tell. I accept that my experience may be unique. A little tri-stock and the extra ply on the bottom can't hurt. Fly it, and then get after any excessive vibration if it ever shows up. Don't worry about it too much unless you need to!