KV Ventus 2CX 4.8-meter assembly

[Mark9]

Just took delivery of my new KV 4.8-meter Ventus 2CX today. After going through all I received and a first look at the airframe…WOW! This is a nicely built, good looking model. Well worth the wait to get one and I hope it flies as good as it looks.

So, I know I can’t be the only one to assemble one of these on this side of the big pond, I want to know what you guys did in your assemblies. Also, I will be the first to admit that I don’t know everything and believe the best engineering is built on what worked well in the past. If you have them pictures would be great too.

My surface servos will be MKS HV6100’s all around in frames, except for the elevator. It will be the same servo, just not in a frame. I also plan on a separate battery for the retract. I haven’t looked close enough yet, but I also wonder about the retract servo mount and what type of servo people have used.

Another thing I was surprised about was no hardware, I.E. horns, ETC. Mostly I plan to do what has worked on my TD ships in the past for those controls and wiring connections. Might need to order some G-10 and fabricate my own surface horns though, again any comments or thoughts are appreciated.

[edfmaniac]

Keep the linkages internal if you can. These LDS frames are fairly affordable and look like they have nice horns with them. Says kit includes frames and parts for two servos for under 20 pounds. Your drag profile will thank you. https://www.t9hobbysport.com/mks-ds6...frame-with-lds

[edfmaniac]

If your rudder servo fits inside the tail of the fuse you can build a tray that slides in from the rear and locks in place with one or two screws. I'm using a similar method on my Antares.

[Mark9]

OK, so I received some flak for not posting more pictures of the 2CX. It finally cleared about an hour ago after I finished changing the Mobil 1 in it's hauler. Took it out on my lawn, which shows the results of no watering while I was laid up. No joke this airplane is a quality piece of kit. Very good fit and finish. The joiner system is a work of art and just slides together.

Also, I did some more exploring while it was damp and cloudy today. Sure am glad I waited to order my retract servo...it needs a low profile servo to fit in the mount. OOH, to access it you have to remove the retract and be aware that the door closers either need to be untied or you can just set the retract in the aft end of the cockpit. This is my first glider with a retract, so it was new for me.

Another thought I forgot to take pictures of the underside of the wing. I plan to put dark blue sign vinyl on the center panels and I think I will order some new graphics from Callie. Probably use the font and graphics as stock, just size them to fit between the servo bays. So, let's hear a vote white or silver graphics?

On to the show...

[ARUP]

Very nice! You are 'off the hook', now, since posting pics! I like the silver graphics. They exude 'class' on this bird!

[Mark9]

OK, so it has been a while since I made some progress on the Ventus. Over the last few days I was struggling with the elevator installation. It mounts in the top of the fin with the horn for the elevator being on the bottom of the surface, typical design. Without any instructions this made hooking the system up rather challenging.

After, I can’t remember how many, multiple attempts I came up with what the pictures show below. The biggest hurdle was the pushrod configuration. That was required because of the small confined space for the exit and at full travel aircraft structure. Would not be easy, since I have no access to a dentist’s drill, to increase the available clearances. The mounting plate, BTW, has a pencil mark on it since the piece of ply was a piece of scrap left over from another project. Another note, the picture doesn't show it well but the arc on the pushrod is actually in the vertical plane.

I’m happy with the results. No binding, no surface slop, the little HV6100 is centering well and I can achieve the throw supplied in the information sheet. OHH, also one less channel to program except for dual rates. Still seems like I regularly tackle the most challenging installations of an assembly first.

[Wild Doogie]

I feel your pain on the elevator servo and linkage install!

[Mark9]

While looking closely at something involving my rudder installation last night I found this. It appears to be a micro map of a portion of Czechoslovakia! So, I put it where it belongs. BTW, my rudder installation is nothing special. However, it did require some rather fiddly work in tight confines between the retract support structure and the fuselage wall. BTW, there are quite a few small decals applied around the model, such as tire pressure tags, ETC. Cool!

[ARUP]

Those details are neat!

[Mark9]

Yeah, that is what I thought too when I found it and found the cities on a Google Map of Czechoslovakia. Also, I found recently as well the model is not truly scale.The number has been deregistered in the Swiss Aircraft Registry and was assigned to an IS-28M2 motorglider which was deregistered on 9/3/1981. OOH Well...it's an impressive model to just look at anyway. I hear they fly well too.

[Mark9]

I have been making progress on the fuselage assembly. Down to the small details. Both flight control servos have their structure in place and the battery tray is installed. Today I will install the trimmable nose ballast support. I will be able add or remove up to 5 oz. removing only a winged threaded rod. Waiting on a servo to finally get the retract functioning as designed. Will try to post some information on that later today. When it is fully tested again, after many tests, it will go in, Then a wing wiring loom and permanent nose ballast to finish it. Nothing special in the installations, just the usual plywood structures to support servos and batteries.

[Mark9]

OK, so here’s the start of the updates of what has transpired so far. The kit arrived with no assembly instructions, just CG and throw information. That to some extend for me is not a problem, because I will look at the airframe and decide what I think will work; assembly wise, durability, aero dynamic purposes for what the airplane is designed for, maintenance, ETC. One must assume if you purchase a kit at over $ 2K you know what you are doing.

In one of my earlier posts I presented what I now call my Czechoslovakian brain teaser, the elevator installation. Well the retract assembly proved to be almost to the same level. I found another owner of this aircraft through this site and he warned me of the retract collapsing on landing multiple times on his. When I started to really test the retract assembly with simulated landings it failed and collapsed for me in the shop…not good.

With no servo recommendation and no data on the web, I was shooting in the dark so to speak. One of my sailplane buddies I’ve known for decades who flies TD and aerotow (much longer than me) told me what to look for. The lower carriage is designed to go over center for lock down mode on the lower struts.

As delivered from the manufacturers it would not do that, causing the collapses. So, I set about to rectify that error in manufacturing. The two black marks in the lower strut channels are where I persuaded the channels to allow more travel over center. Those are the actual contact points in the channels of the upper struts. That is where I used the modified chisel, shown in another picture, and a hammer on a wood block. It took about three good firm whacks on each. What I did to the chisel was to blunt and round the contact edge so it bends rather than cuts the metal. One does not have to disassemble the carriage assembly to do this, just remove it from the frame. You can also see the paint wearing off on the upper struts at the contact points.

The chisel was held at a slight angle to add a taper effect back to the pivot and I worked slowly checking by sighting along the struts. The center pin on mine is about .117” in dia. So, when it moves about ½ its diameter past center line one has approximately achieved the 1/16” that my friend recommended as minimum. A slight amount more probably wouldn’t harm a thing, the metal is quite strong.

I have not put it back in the airframe yet with an operational servo, waiting on an appropriate servo. But, I have manually “tested” it. What I did was to lightly push the linkage into locked position attached to the servo, which has inadequate rotation to activate both retracted and extended positions, and with no power on slammed the wheel as hard as I dare on to the floor multiple times. The carriage never budged. I fully believe this has solved the collapsing problem. With this geometry all the servo has to do is not allow the lift pivot pin up past center. Also, any impact loads other than those coming from behind will only force the struts more firmly into the channels, unlikely to happen in an average landing.

More updates to come.

[Mark9]

On with the updates. Attached is a photo of my adjustable nose ballast for the 2CX. Since we usually have the room in our models why not make it easier to trim the plane out when new. Each lead plate weighs about .5 of an ounce. A screw with a wing nut CA’d to it is used as shown to affix the ballast. On the underside of the plywood plate is a blind nut. This allows for simple easy changes to the CG by adding or removing additional plates without tools. I show it with 5 ounces installed, hope I don’t need to make changes any larger than that, but I can. Also, being so close to the longitudinal center it should not too adversely upset the flying characteristics of the airplane.

To install the plate to the fuselage and servo tow release structure I fell back on a technique I used in the 80’s and 90's to install servo trays in TD ships with fiberglass fuselages. I would get as close of a fit as I could dry fitting, align the tray how I wanted it and tack it in place with thin CA. Then using laminating resin on the underside flow the laminating resin on the joint of one side until I saw some beginning to flow out on the other end.

Next before it sets I place the fuselage and tray so they form a 90 degree crotch facing up and level with the world. Then walk away for the night. Do that for the other side the next night and then finish the top sides how I wanted. Now I use vet syringes, available at farm and ranch supply stores to apply the epoxy, instead of just dripping the epoxy where I want it. I never had a tray come loose, even if the fuselage incurred major damage. I’m thinking I may add a layer of fiberglass to the top side like I did with my radio trays, just for insurance.

The USPS says my retract servo should be here today. So, after I install the servo, set up the assembly outside of the airframe and test it again it will get installed in the airframe. That will leave the fixed nose ballast, a fuselage wiring loom (mostly just long extensions) and final pre-maiden CG as the last shop activities.

[Mark9]

Well, I had some more progress this week on the Ventus. I learned something about programmable servos and was rather pleased with a couple of hobby vendors. Also, no pictures since those have been displayed in either this tread or my other one on a retract servo.

First I learned that not all programmable servos are not created equal. I was told that the range of rotation is adjustable on programmable servos. With my luck, with the way this assembly has been going, I found that to not be true. This is my first time in the hobby for forty + years that I have needed a programmable servo, BTW.

Of the 10 adjustable settings one, Stretcher Adjustment, was what I assumed to be the rotation adjustment. Nowhere in Sanwa’s data did I find a definition of what that means, at least in English I could understand. I could not find one that would work after updating the firmware of the programmer and learning all the menus to navigate to program a parameter in the servo. After hours doing all this I gave up and went to bed.

The next day I called Serpent America, the distributor for Sanwa products and talked to a tech support person. When I asked about a rotation adjustment on my model of servo his response was, “I don’t believe that one can do that”. My thoughts were, “great now I have another $80 servo and also a $50 programmer that I can’t use”. I was not amused since I could not find anything saying in English that servo did not have a rotational range adjustment.

So I called AMain Hobbies where I bought the two items. Explained I had opened them, read everything I could, tried to set the servo up and now they were of no use to me. The customer support person quickly sent me a RMA and agreed that he was unaware that some programmable servos could not have that parameter adjusted. Nice service, since most times if you open and function an electronic component it’s yours.

Got off the phone and called Servo City. Then I talked to a tech about the new Hitec D777MG, which is their new low profile programmable servo. The programmer for it is $80 though, but they will extend the rotation for $10 whereas the servo is $75 also. Placed an order asking for the extended rotation and it arrived one day early. Put it in yesterday afternoon and evening and now have a fully functional retract system that won’t collapse. Whew I sure hope that one is done. Checking off till the next update.

[pete914]

Nice work! I've found lots of the scale sailplanes I've built that "just require servo installation" can actually be quite challenging. I have spent days thinking about installs prior to making the first cut. You did really nice work with the elevator install.
I went through similar headaches installing a retract servo on my old Discus 1:3 scale and some of my Top Model sailplanes. I had to get a servo stretcher to get things working properly.
Either way, time invested in this kit is well worth it. I've seen it fly in person and it's a real performer!

[Mark9]

First off thank you Pete for the good comments. In that same vein with some of your thoughts, I have been pondering my wing servo installations, while getting a second hand HLG flyable. I am using MKS HV6100's throughout in external bearing frames. When looking at the servo throws, geometry and wing depth I realized for the flaps I would need to raise the servos. The aileron and spoiler servos do not need to be raised. Their frames mount directly to the wing skin.

My solution was to fabricate some basswood wedges to raise the servos. Next I needed sufficient bonding areas for both the frames and wedges. Quickly I realized the minimum size I desired resulted in installation problems, they were bigger than the bay opening…#*&@! I found if cut them in half that I could insert the forward thicker half first and then insert the aft half.

The first picture shows the wedges cut and ready for installation. In the second shot the servo screws were used to hold the pieces for installation after they were back buttered with slow setting epoxy mixed with cotton flox. And the final picture shows one of the flap servos in the frame installed as the epoxy with cotton flox now is setting. No need to show more of these steps, just wash and repeat…

Next to design and fabricate my surface horns, linkages, complete the wiring and CG it. OOH, I do have some graphics on order with Callie to reproduce the under wing ones after I apply the dark blue sign vinyl. It is for visibility…hate white on the bottom. Is it too early for an adult beverage?

[Mark9]

Over the last few weeks I have made some progress on the Ventus. All of the servo frames are installed and the only gluing I see on the punch list are the wing surface horns. This four servo per panel wing is like assembling two of my TD ships at the same time!

The spoilers are now functional and attached are a couple of shots, close up, of the installation. Again, due to the geometries and how tight everything is I had to come up with another interesting pushrod configuration. I plan on using purple Loctite on the wheel collar grub screws after I get them dialed in and synchronized. Also, the rod has a stepped flat filed on it where the screw is.

How can this airplane be so big, but require radio installation details to be so confined? Makes it fun and challenging though. The whole next week looks poor for flying, so I hope to get more done. Stay tuned…

[Mark9]

OK, so I have reached another milestone in the assembly. All of the wing servos and linkages are ready for final set-up. Since I could not find horns that I was happy with I purchased some .062” G10 plate to fabricate my own. My goal was to use 70-80% of the available travel of my servos and achieve the recommended surface throws in the data supplied by SUSA.

I spent a good deal of time working out the geometry and checking for interferences before beginning fabrication of the surface horns. The first ones I did were the aileron horns. The first picture is the configuration I started with for them. After cutting through the wing skin I found I needed to also cut through the drag spar in the surface to get sufficient bonding area for the horns. Unfortunately I failed to get a picture that is useable of their final configuration and the completed installation. My OCD kicked in again as I didn’t stop till they fit and had been glued in. If anybody wants I can try to get a shot of the final installation, just PM me.

During my installation later of the outboard flap horns I found that I would need to modify my design for each pair. Guess I should have seen that coming since the thickness changes at the hinge line significantly on each surface. Needless to say each pair of surfaces posed similar challenges and new dimensions for the horns. On the right of the second picture is the final configuration for the inboard flap horn. The horn on the left is a horn I fabricated for the outboard flap similar to the aileron horn that ended up being scrap. It would not work to my satisfaction on the outboard flap, again sorry no pre-installation picture of the final detail part.

All of the horns have the hole in the base area, shown in the inboard horn, as a pin and the notch to clear some of the drag spar. These were then installed with cotton flox mixed in with the epoxy and potted in as shown in the third picture. The last two pictures show the outboard flap horn installed and ready for the pushrod. Nothing unusual there, just clevises and 2-56 threaded rods. The slot in the forward wing skin is to allow for full travel. Now on to installing electronics and fabricating a wire loom.

[edfmaniac]

Nice work. I just started on the flap servo installation on the Antares, opting to go with bearing frames and linkages instead of the factory RDS setup so I can get max deflection and use the flaps for airbrakes.