HSD 105mm F-16 EDF Jet

[Aros]

Wow, I must have been really nose heavy! Further evidence I need a CG stand. So it looks like I will need to get those 6000's a good inch or two aft of where I had them. I will need to re-route the strap too as it's already at the LE of the batteries. Thanks Lcacing for the info!

[Lcacing]

Aros I rechecked the CG with the HRB 6000, almost same weight as admirlas, placed as you have your 6000’ and the best CG I was a able to get was around 160mm. One thing that I didn’t consider was the extra weight that was added with the paint job. I would think most of the weight was added aft of the CG so compering battery placement is irrelevant, yours would be further forward even if using same batteries.

[Lcacing]

Aros , I am so sorry, they weigh in at 834-840 g, not 634-640 g. The website is correct. That's what I get for not proof reading before hitting "Post". Never was much good with typing when it comes to numbers! My apologies! My only point was that the 2 Admirals may weigh in at 30 g each (totaling 60 g) more than the 2 RT 5500's so you may still be a little more nose heavy at the same location than what Pilot Ryan had in his shakedown.

Pilot Ryan was flying his at 160mm, way to nose heavy but also had a cortex gyro so it compensated for a bad CG. I think he also had the elevator/ throttle mix on.
I figured the weight of the Admiral 6000 was a typo, no way a battery that size could be that lite and still provide anyway near advertised Mah or “C“ rating.

[Aros]

Oh wow, that's really far back Lcacing ! I need to get a CG stand soon so I can really make sure my CG reading is accurate. Thanks for the photos! Hugh Wiedman no worries! Whew, I'm just glad we weren't way off on the weight spec, lol...Maybe I was really nose heavy after all on the maiden. That certainly would explain the extra long takeoff roll and having to give it a ton of up trim.

[Lcacing]

Here are the weights off the batteries, I don’t use the HRB 5000’ in the F16 simply because I prefer longer flights, I can essentially use the other 3 in the same position and the plane still feels locked in. I haven’t felt the need to go further back than 175mm (gear down) because as PaulZ mentioned, you end up having to add elevator mix to compensate for a tail heavy plane during landing.
From what you described it sounds like you have some gremlins running around. Lol. You mention your batteries are at the leading edge of the black foam, check out where mine are.

[Hugh Wiedman]

Hugh Wiedman I was hoping you would chime in you Battery Virtuoso! Now hold on, you are telling me the Admiral 6000's you have weigh between 634-640g and we list them at 844g? If that's the case I need to update those specs pronto! That's a major discrepancy in weight. I do appreciate your offer for trade but I will respectfully pass.



Lcacing I am fairly sure (Fairly because the Finger Method is not ideal to find the true CG on a model this size and weight but it's ballpark) I was somewhere around 170mm for the maiden. Give or take several mm's lol. A part of me feels like it will be more stable at a nose-heavy CG like 165-170 (which I have found success at before)...Yet I have many folks like you basically saying 175 or even further aft is the way to go. All I know is this bird has been quite the enigma for me. Some flights it feels totally locked in and other times it's like fighting a bucking bronco in the skies. Something has to give, lol. Expo, rates, CG, throws...Gyro?! I guess I love a good mystery.

Aros , I am so sorry, they weigh in at 834-840 g, not 634-640 g. The website is correct. That's what I get for not proof reading before hitting "Post". Never was much good with typing when it comes to numbers! My apologies! My only point was that the 2 Admirals may weigh in at 30 g each (totaling 60 g) more than the 2 RT 5500's so you may still be a little more nose heavy at the same location than what Pilot Ryan had in his shakedown.

[Aros]

Hugh Wiedman I was hoping you would chime in you Battery Virtuoso! Now hold on, you are telling me the Admiral 6000's you have weigh between 634-640g and we list them at 844g? If that's the case I need to update those specs pronto! That's a major discrepancy in weight. I do appreciate your offer for trade but I will respectfully pass.



Lcacing I am fairly sure (Fairly because the Finger Method is not ideal to find the true CG on a model this size and weight but it's ballpark) I was somewhere around 170mm for the maiden. Give or take several mm's lol. A part of me feels like it will be more stable at a nose-heavy CG like 165-170 (which I have found success at before)...Yet I have many folks like you basically saying 175 or even further aft is the way to go. All I know is this bird has been quite the enigma for me. Some flights it feels totally locked in and other times it's like fighting a bucking bronco in the skies. Something has to give, lol. Expo, rates, CG, throws...Gyro?! I guess I love a good mystery.

[Lcacing]

Aros good to hear you had a “successful” maiden. For sure the RT 5500 70c and even the 45c weigh less than their advertised numbers. I have a set of each and also use HRB 6000’. I’ll check the weights tomorrow but in reality unless you use some some light weight batteries. The stock CG can not be achieved without removing foam. I’m confident that with the Admiral 6000 your CG is too far forward if you didn’t remove foam.

I now have at least 60 flights on my F-16, no gyro or elevator compensation mixes added. CG is set at 175mm gear down, I did have to remove foam to move the batteries back to achieve CG.

https://youtu.be/ECIpwDBl7yI

[Hugh Wiedman]

Okay I found out the specs for both batteries.


Roaring Top 5500 70C specs:

53 x 43 x 157mm (Height x Width x Length) 825g weight

Admiral 6000 50C specs:

45 x 53 x 160mm (Height x Width x Length) 844g weight

So the Admirals are 19 grams heavier. So maybe they need to be further aft than I even had it? I need to invest in a CG stand. The finger method isn't very effective for something this big and heavy.

Aros I know this may be splitting hairs, but I have a fairly accurate digital food scale I use to weigh batteries with (it's sole purpose, since there isn't a scale big enough for my appetite) and of the 12 Admiral 6000's I have, they weigh between 634-640 g. Of the 8 RT 5500 70C's the weight is 795-805 g (although I know their website lists the weight at 825 g). So you may be looking at an even bigger difference, some 30 g. Since you're talking about 2 batteries, that's almost 60 g heavier which is a little over 2 ounces. You may want to weigh your batteries just in case, but it seems the published weight of the Admiral is close to what I've found as actual and the RT is actually less than what they publish, so it does seem like a prudent idea to at least get a more accurate CG meter than your fingers, no offense intended.

I use the Great Planes CG meter (relatively inexpensive $30) but not sure if your HSD is at it's size limit. The heaviest and largest I've done is the SU-30 at 65" length, 45" wingspan and something like 125 pounds in weight! Since the F-16 is 71" in length and 49" wingspan, I'm fairly confident that the GP meter will handle it. Actually, FORGET this, I just looked EVERYWHERE and it seems to be discontinued and is unavailable everywhere I looked, sorry. On second thought, since the're so rare now, I'll trade you mine for your HSD F-16 straight up and I'll pay the shipping (of the meter, you get the shipping of the jet). Then you won't have to worry about the CG anymore. Just trying to help a brother out any way I can.

[Aros]

I hear that! Thanks man, just whenever you get a chance, much appreciated!

[PaulZ]

Great info PaulZ , thank you! So where is your CG at specifically? Also, would you mind taking a shot of your battery placement? I am running two Admiral 6000s and they are near the LE of the black foam. I couldn't move them much further aft if I wanted to. Also, are you running on Spektrum? If so I would love your SPM file. I am always searching for that "Sweet Spot" with this girl.

I'll take some pictures and send you in a couple days. Sorry, that pesky work is getting in the way!

[Aros]

Wow, a whole new world for me! I will check it out, thanks again!

[wolpertinger]

Xicoy uses 3 scales to measure the planes weight just as in real scale. The basic one uses wireless to connect to a phone or iPad to give the operational screens. Just need a measuring tape for measurement of wheel distance and CG position to gear. Pretty easy to use, but cost about 200. Just did the new HSD L39 and was spot on...

[Aros]

Awesome gents, thanks for the info!

How does that Xicoy basic unit work exactly?

[wolpertinger]

Okay I found out the specs for both batteries.


Roaring Top 5500 70C specs:

53 x 43 x 157mm (Height x Width x Length) 825g weight

Admiral 6000 50C specs:

45 x 53 x 160mm (Height x Width x Length) 844g weight

So the Admirals are 19 grams heavier. So maybe they need to be further aft than I even had it? I need to invest in a CG stand. The finger method isn't very effective for something this big and heavy.

Aros, best thing I found is the xicoy basic unit. Using scales give you a better information and is great for tricycle type gear...

[T-CAT]

Okay I found out the specs for both batteries.


Roaring Top 5500 70C specs:

53 x 43 x 157mm (Height x Width x Length) 825g weight

Admiral 6000 50C specs:

45 x 53 x 160mm (Height x Width x Length) 844g weight

So the Admirals are 19 grams heavier. So maybe they need to be further aft than I even had it? I need to invest in a CG stand. The finger method isn't very effective for something this big and heavy.

Although rather expensive options, if someone is looking for these types of CG stands/meters, they can come in handy.

Pacific Jets CG stand:

https://pacificrcjets.com/products/prcj-advanced-cg-stand

Xicoy CG Meter(s):

https://www.jetsmuntusa.com/collections/xicoy-c-g-throw-meter

[Aros]

Okay I found out the specs for both batteries.


Roaring Top 5500 70C specs:

53 x 43 x 157mm (Height x Width x Length) 825g weight

Admiral 6000 50C specs:

45 x 53 x 160mm (Height x Width x Length) 844g weight

So the Admirals are 19 grams heavier. So maybe they need to be further aft than I even had it? I need to invest in a CG stand. The finger method isn't very effective for something this big and heavy.

[Aros]

Thanks Bogietrim , it was a classic Pucker Flight the whole way...

It felt tail heavy to me in the air but nose heavy on takeoff hence having to max out the back pressure to rotate before she ran out of room. Just squirrelly. I was looking at Pilot Ryan's HSD F-16 Shakedown video and he has his RT 5500's at the very front edge of the black foam. Even though I am using Admiral 6000's, I think the batteries are similar in size and weight so I may push the batteries forward to that same black foam edge. I can always increase the takeoff space if I need to. The parking lot is huge.

Well better luck to us both!!

[Bogietrim]

Aros good job staying with her to get her back. Your landing was much better than mine! LOL! Hoping to get mine back out this weekend for another go.

[Aros]

Here’s where my battery placement was for the maiden.



This is what I ended up with for elev trim...




































Proof she survived...