Forza 2.5

[Doc J]

Hmm, the term shotgun loading makes me envision an over-under breech loader, and I certainly don't want to see the nose of my glider in that configuration.

It doesn't seem like Jonty's rudder pushrod would get in the way of ballast slugs, and a top load configuraiton would make the fuse even that much stronger (moving any destructive forces to another part of the airframe).

Just picked up some System Three T-88 yesterday at a local hardwood shop and have a pound of milled glass fibers to mix it with, so once that tube gets installed it isn't going to be moving. Perhaps I'll just install it and leave the dremel work until later. Thanks for the reference links.

Hey JJ,

In racing here is perhaps one small advantage in the fuse-based ballast system and that is the much lower moment of inertia that it has compared to ballast spead across the inner parts of the wing span. It takes a lot more force, and hence drag to move the wing ballasted model into and out of a roll, than it does the fuselage ballast model.

How much? Not sure but it could be significant.

Thats the beauty of using smaller span models for racing, lower MOI. They roll in and out of turns faster.

Just rambling thoughts.

Cheers,

Doc

 

[JJ Colorado]

Agree. Ballast the wings if you plan to pull heavy G's and want smooth stable flight for DS'ing, but for most glider flying a lower MOI is better. More responsive.

While I may occasionally race the Forza, its primary mission is fun, fast, flying in a wide variety of conditions. My primary concern at this point is that I may enjoy flying it so much that I'll be afraid to race it. Worse things could happen.

 

[Hill Hobbit]

Hi JJ, I confirmed (at 1.30 this am) that a ballast slug will drop in between my rudder pushrod and the fuz side, so you’re good to go with your plan. I also made my own servo tray from 3mm G10, chamfered along the sides to give good glueing area and nice fillets, rather than the ply tray supplied.
Even with wing ballast, this model is very responsive in roll, and on high rates is ‘Wow’.

 

[Red]

Hey JJ,

In racing here is perhaps one small advantage in the fuse-based ballast system and that is the much lower moment of inertia that it has compared to ballast spead across the inner parts of the wing span. It takes a lot more force, and hence drag to move the wing ballasted model into and out of a roll, than it does the fuselage ballast model.

How much? Not sure but it could be significant.

Thats the beauty of using smaller span models for racing, lower MOI. They roll in and out of turns faster.

Just rambling thoughts.

Cheers,

Doc

Back in my ISR days I raced a span loaded Acaia 2 . It increased the MOI significantly in roll, making for a very smooth flying plane. I found it easier to fly fast laps, it was more predictable in big bumpy air as the the longitudinal MOI wasn't effected so it still pinged the turns. The fuselage ballast cavity wasn't large enough to get to max weight, so I added tubes between the main and outer panels. I loved the way it flew. I have span loaded other planes too, mainly DS and it can be a favorable alternative. For something like F where roll rate is a bit more desirable it may not be the way to go but overall I was very pleased with the results.

Red

 

[JJ Colorado]

First major build decision. Two servos in the tail. Had planned for the rudder up front, but even though the tail hatch is small and I'll need to glue a servo in, having the rudder servo in the tail will make a cleaner and crisper setup.

Doc, if you ever make an update, might I suggest widening the tail servo hatch to make a 2 tail servo option easier.

Having both servos in the tail will also facilitate a top load ballast tube while reducing any issues with pushrod flex or interference.

 

[Doc J]

Back in my ISR days I raced a span loaded Acaia 2 . It increased the MOI significantly in roll, making for a very smooth flying plane. I found it easier to fly fast laps, it was more predictable in big bumpy air as the the longitudinal MOI wasn't effected so it still pinged the turns. The fuselage ballast cavity wasn't large enough to get to max weight, so I added tubes between the main and outer panels. I loved the way it flew. I have span loaded other planes too, mainly DS and it can be a favorable alternative. For something like F where roll rate is a bit more desirable it may not be the way to go but overall I was very pleased with the results.

Red

I think it depends on the way you fly, and I find it hard to get very excited in F3f - but then I used to fly the real thing!
Maybe in MOM (AKA "The real thing") it depends on your excitement jitter level (!)

For landing, I definitely like the span-loaded option.

I once landed a fully fuse loaded MOM racer in the safest place, eye-high elephant grass, so maybe I was not really concentrating too much on energy management. So what the heck was that loud crack? Some kind person had dumped an unwanted table in the vegetation...when I got to it, the very front of my model, along with the battery and all the ballast slugs were neatly stacked on the ground beside it while the model looked like it has just been placed on top. Improved table manners needed? Ho hum.

I suppose in a way its nice to have both options, especially as you can use one, or the other, OR both.

Cheers,

Doc.

 

[Hill Hobbit]

Hi JJ, how’s it going with your Forza?

 

[JJ Colorado]

Slowly. Three builds going on in parallel. But after some frustration with the tail elevator servo arm rubbing the servo cover hatch I came upon a flash of innovation. I decided to Up-Cycle my yogurt container (Skyr actually). It is a translucent flexible plastic so I copied the size of the glass or CF hatch and made one of flexible plastic. Now I can heat it and make a little bump for the control horn, or I can mark where the horn rubs agains the plastic cover then transfer that to the yellow CF hatch so that my clearance slot is cut in the exact location and nothing more. As I have Skyr several times a week I've found a source of see through servo hatch covers that can be taped or glued in place permanently or simply used to reduce the guess work of servo arm positioning.

 

[Doc J]

Slowly. Three builds going on in parallel. But after some frustration with the tail elevator servo arm rubbing the servo cover hatch I came upon a flash of innovation. I decided to Up-Cycle my yogurt container (Skyr actually). It is a translucent flexible plastic so I copied the size of the glass or CF hatch and made one of flexible plastic. Now I can heat it and make a little bump for the control horn, or I can mark where the horn rubs agains the plastic cover then transfer that to the yellow CF hatch so that my clearance slot is cut in the exact location and nothing more. As I have Skyr several times a week I've found a source of see through servo hatch covers that can be taped or glued in place permanently or simply used to reduce the guess work of servo arm positioning.

Great work around from JJ.

With the advent of the more powerful mini servos recently, the new Forza can now have rear mounted servos, whereas in the the orginal design that method was not really an option. As I design all my models to be a bit 'minimalist' the room at the back is a bit tight.

Following JJ's design idea I will probably make a special "bumpy" hatch for back there to help with the problem.

Cheers,

J.

 

[Hill Hobbit]

IMHO, there’s no need whatsoever for a blistered servo cover. With an 8mm elevator servo using a very short horn
redrilled/tapped for a 2mm threaded rod bent at 90 degrees (no clevis or ball joint) the flat cover works perfectly. I cut a clear cover from Frsky rx packaging so I could keep an eye on things.
Cheers
Jonty

 

[Doc J]

IMHO, there’s no need whatsoever for a blistered servo cover. With an 8mm elevator servo using a very short horn
redrilled/tapped for a 2mm threaded rod bent at 90 degrees (no clevis or ball joint) the flat cover works perfectly. I cut a clear cover from Frsky rx packaging so I could keep an eye on things.
Cheers
Jonty

Woo...any pics Jonty?

Chers,

Doc.

 

[Hill Hobbit]

In the middle of something right now. Pic in a while…

 

[Hill Hobbit]

With my servo horn and linkage as described earlier, I have 1mm clearance (if not more) between the cover and the servo horn. The other pic is of total down elevator throw in landing mode (full down elevator compensation plus around 2mm+ full down elevator). Easy peasy.
Cheers
Jonty

 

[Hill Hobbit]

I must do a better job of taping the cover on methinks…

 

[JJ Colorado]

Looks good! I'm using a HS08 which is a littler larger but still supposedly 8mm wide and it seems the arm is just slightly rubbing the hatch cover. Maybe if I use an A08 it might squeeze in a little more. I like the supposedly stronger gear set of the HS08 for the elevator, but the A08 might make for a cleaner installation. Ballast tube installed with T88 and just about ready to install the elevator servo but haven't epoxied the servo in yet. Decisions, decisions.

Once I'm happy with the servo covers I'll remove the tape, put a tiny bead of E6000 or similar adhesive on the recess area then glue the covers in place. They can be removed and the glue typically an be rubbed off to install the hatch over again. But the clear tape works fine too and you can't even notice it except in close up pictures.

 

[JJ Colorado]

Made some progress on the Forza today. Ballast tube in, rudder servo and linkage set, elevator servo epoxied in (but may add a little more bracing). Not crazy about servos in the tail. Things are in and working but 8mm up and 10mm down max and no way to adjust that or put in a slightly longer arm. Should work but little ability to tweak or change anything if needed. HS08s on Rudder and Elevator. Ballast will normally be slid back with epp foam in the insertion slot, but left slid forward in the photo for clarity. Eight slugs will fit weighing 13oz or 370 grams. Need to find a source for wing ballast.

 

[Doc J]

Made some progress on the Forza today. Ballast tube in, rudder servo and linkage set, elevator servo epoxied in (but may add a little more bracing). Not crazy about servos in the tail. Things are in and working but 8mm up and 10mm down max and no way to adjust that or put in a slightly longer arm. Should work but little ability to tweak or change anything if needed. HS08s on Rudder and Elevator. Ballast will normally be slid back with epp foam in the insertion slot, but left slid forward in the photo for clarity. Eight slugs will fit weighing 13oz or 370 grams. Need to find a source for wing ballast.

You dont need any more elevator, JJ - it works very well as you will find out.

Cheers,

Doc.

 

[Hill Hobbit]

I have on high rate 6mm up/down, mid rate just under 5mm up/down, low rate 3.5mm up/down. I also use more expo in the down direction. I usually fly with snap flap switched in all the time, and use snap both up and down, the up flap and aileron at about 1.5mm, coming in at about 1/3 of down elevator stick. Down flap/aileron of around 3mm comes in at about 1/4 of up elevator stick. Up/down snap throws are using different curves for smooth responses.
As Doc said, 8mm up and 10 down is much more than needed, so it’s a shame you’ve stuck the elevator servo in, as you could have used a pushrod pickup point closer to the servo axis and a shorter arm.
Nothing to worry about though!

 

[JJ Colorado]

Thank you for the comments and your throws. That makes me a lot more comfortable with my setup. The instruction manual states 8mm up and down and makes it seem like you might need an additional 5mm down for full flaps on landing. Instructions Normal: Ele +8 -8, Landing: Normal flight movements plus -5 Ele. That made me think I needed a range of +8 and -13mm for the elevator. From the above posts it seems like the range of 6-8mm up and down should be sufficient. Jonty, since you fly with a fairly aft CG so I would expect your throws to be a bit smaller, but as I expect to be in the 95-100 CoG range, the throws I have should be good.

I don't think I could actually get my control horn in any further. As it is I had to whittle a bit of the area that grips the splines back to nearly nothing.

Happy with the ballast tube as it is securely in place by T-88 epoxy mixed with glass fibers, and the top load for the ballast slugs works fine. No cutting of the fuse as required with the bottom load configuration, so between the ballast tube and the G10 servo platform the nose section should be particularly strong.

 

[Hill Hobbit]

95 will be very nose heavy indeed. 98 is a start point, but even then I think you’ll need up trim for level flight, so it’ll zoom up at speed and need lots of down for inverted. I started at 100, very nice with no elevator trim required, elevator throws as I posted, but went to 102 a while back. Thermals even better now!