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Estes Ascender - Av Bay Addition

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GregGleason

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I am in the process of adding an av bay to my Estes Ascender.

Ascender.on.Stand.jpg

It's a great flyer, but I want to try to stretch it's legs a little with higher thrust motors. I'm only comfortable with a motor no larger than an AT F40 in it's stock configuration, but a G64 with a dual deploy option sounds like fun.

Greg
 

GregGleason

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The first thing I did was order some airframe tubing and couplers from Estes. Response time and condition of the order was good (typical of my experience with Estes).

The coupler length is 4" (101.6 mm), so there is not a lot of room for the MAWD and the 9 V battery. It will be cozy, but I think it will work.

I did some CAD work to get the arrangement where I wanted it.

Rhino.Ascender.Design.F.B.View.jpg

Rhino.Ascender.Shade.Persp.View.jpg

Greg
 

dhkaiser

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I will follow this thread with interest as I just lost a Ascender on a G125. Blew a fin off. For now I am sticking with F motors for the PSII kits.
 

GregGleason

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I will follow this thread with interest as I just lost a Ascender on a G125. Blew a fin off. For now I am sticking with F motors for the PSII kits.
Ugh. That's a tough loss. These birds can take moderate speed but I would want to keep the average thrust at or below 100 N. Above that could be a bit dicey.

Greg
 

GregGleason

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I wanted the caps to be self-orienting with the sled, so the sled has tabs that will only fit one way with the grooves in the caps.

Here is the sled after milling.

Sled.After.Milling.jpg

Greg
 

GregGleason

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I designed the end caps similar to how I designed the caps for Wild Child Av Bay 2.0 (link). The only significant difference being that there are holes for 2 all threads for the Ascender rather than the Wild Child's one.

Cap.B.Top.jpg

Cap.B.Bottom.jpg

Here is the finished product after milling:

Cap.B.Top.Milled.jpg

Cap.B.Bottom.Milled.jpg

Greg
 

GregGleason

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Once the end caps were milled, they were test fit into the caps.

Cap.B.Sled.Union.jpg

Greg
 

GregGleason

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One of the things I had to figure out is how to orient the sled with respect to the coupler. The system that I used on the Wild Child worked, but it wasn't that robust. I came up with standalone dowels with the base of each epoxied to the coupler. It's a simpler system, so I just had to make sure I had the appropriate amount of space. The base is made from the same plywood as the end caps (1/2" birch plywood).

Here is a test fit of the system before joining it to the coupler. The all thread tubes have already been epoxied to the sled.

Sled.with.Indexing.Pins.Before.Gluing.jpg

Greg
 

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One of the top two hardest things to figure out is how to mount recovery hardware to the av bay. I liked the solution that I came up with the Wild Child, but it didn't lend itself to this solution. I wanted the loads to be going though the all threads and not the end caps. The solution that I came up with is the cap bar (that's the only name I could think of calling it) that would mount onto the all threads and would have slots for Kelvar line to loop it through, and in which a quick could then be connected.

This was the preliminary design:

Cap.Bar.Preliminary.Design.jpg

I then further refined the design to make sure it could be properly milled.

Cap.Bar.Detail.Design.jpg

Then I milled it from 3/16" (4.76 mm) aluminum bar stock.

Cap.Bars.after.Milling.jpg

They are small, strong, and very light weight. I think they came out pretty well.

Greg
 

GregGleason

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The aluminum washers that I had on-hand from McMaster-Carr had an outside diameter that was too large to use in the av bay. So I milled 8 (4 for the av bay and 4 spares) so accommodate the tight space.

Lower left is the stock washer, lower right is the custom washer, and above is an aluminum 1/4-20 nut.

Washers.Stock.and.Custom.jpg

Greg
 

GregGleason

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After calculating how long I needed the all thread, they were cut and cleaned up. The lengths may not match, but they are close enough.

Then it was time for a test fit. I gathered all of the parts and this is the result.

Av.Bay.Test.Fit.B.Side.jpg

Av.Bay.Test.Fit.B.Side.Closeup.jpg

Av.Bay.Test.Fit.T.Side.Closeup.jpg

Av.Bay.Test.Fit.Plan.jpg

Things went together without a hitch, in that there was no binding or forcing necessary to bring it all together. So far, I am pleased with the results.

I did discover that I wont need tools to torque down the nuts, as I would run the risk of putting a kink in the tube (I didn't fiberglass it). But I began to wonder if the nuts could back out under vibration. After doing some research and some thinking, I remembered a comment from years on TRF where someone put plastic stretch wrap (like what you put over food bowls to keep the contents fresh) on the stud. It acts like a nylon-insert nut, just a bit cheaper. But maybe I'm overthinking things and that there is not enough cyclic vibration to really make bad things happen. Maybe someone could chime in on their thoughts on the subject.

Greg
 

GregGleason

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I tackled the switch band today. Technically it is not a switch band for this av bay, because the switch is not there. Of all the things I could make work for this av bay, making this happen was a "bridge too far". So it is a port band, since that's the function it will serve; that and serve as an airframe stop for the lower and upper airframes. The switch port (the switch guide is the brass-colored object with a hole in it) is going to go through the upper airframe, where the main chute will reside. It's a bit unconventional, but I can't think of a good reason why it should not work. But I haven't come up with a port or hatch configuration for it yet, so I still need to think through that. But I digress.

I was going to make the port band have a length of 1/8", but that seemed a little unreasonable from a construction standpoint. So I used the TLAR method to determine what it should be and the "as built" length is 0.545" (13.8mm).

Rhino.Av.Bay.Port.Band.jpg

Greg
 

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Yesterday, I mounted the charge tubes, base, and plugs to the end caps. The "B" side is longer to accommodate the larger volume of that airframe. BTW, I do like shiny brass.

Charge.Tubes.Mounted.jpg

Here the switch band (aka, port band) has been epoxied to the coupler. The switch band isn't perfect in that there are gaps, but it looks like it is less than a mm so maybe my OCD tendencies can live with it.

Switch.Band.Mounted.on.Av.Bay.Coupler.jpg

On the bottom of the cap you can see a number of holes. The major holes in the 3 o'clock and 9 o'clock position are for the all threads. The holes in the center and 8 o'clock position are for indexing pins for milling to keep the part in proper orientation. The hole in the 2 o'clock position is the e-match port. The hole in the 10 o'clock position is for orientation pin inside the av bay coupler.

Greg
 

GregGleason

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I added the Kevlar loops to the cap bars. I cut the Kevlar lines to 10" lengths and put masking tape at the ends as an anti-fray. I put Ashley Stopper Knots at the end (using the handy Grog Knot app) to keep the loops in place. The loops will be where I attach the quick links.

Cap.Bars.with.Kevlar.Loops.jpg

Greg
 

K'Tesh

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Looks good!
 

Salvage-1

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Loving this build. I am kitbashing a Ventris plus a PSII booster into a decent two stage and realised I needed an AV bay. I used two of the couplers and a piece of body tube. Now I have to come up with the lids and internals.

Yours is looking real nice and I am getting envy!!

Ugh. That's a tough loss. These birds can take moderate speed but I would want to keep the average thrust at or below 100 N. Above that could be a bit dicey.

Greg
I have to throw in something here. I have flown the cr@p out of an Estes PSII Nike Smoke with 2oz of extra nose weight and a CTi H410Vmax ! The only reason it isnt still flying is that it got stuck way up in a tree. I am going to replace it with an exact copy and continue the abuse. (this time with a Jolly Logic Chute Release)
My trick with those two part plastic fins is gorilla glue!
Rough up the insides real good with sandpaper and give them a mist of water, then use the gorilla glue. Clamp the fins tight as the glue will expand. I drilled a couple of holes in the fin tabs to allow the glue a place to escape.
When you bond the fins to the body, rough up all the plastic slot areas and fin tabs and use the same gorilla glue approach.
Sets like concrete!!
 

GregGleason

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Loving this build. I am kitbashing a Ventris plus a PSII booster into a decent two stage and realised I needed an AV bay. I used two of the couplers and a piece of body tube. Now I have to come up with the lids and internals.

Yours is looking real nice and I am getting envy!!
Thanks. It's been a lot of hard thinking for me to get it this far, as this is only my 3rd av bay configuration. I probably wouldn't be such a challenge if the airframe was 2.60" or larger where I had a lot more volume to play with. One of the challenges was that I wanted something that could work in the field, which means simplifying everything you can to minimize the possibility of mental errors (which can happen when you are baked by the Texas sun).

I have to throw in something here. I have flown the cr@p out of an Estes PSII Nike Smoke with 2oz of extra nose weight and a CTi H410Vmax ! The only reason it isnt still flying is that it got stuck way up in a tree. I am going to replace it with an exact copy and continue the abuse. (this time with a Jolly Logic Chute Release)
My trick with those two part plastic fins is gorilla glue!
Rough up the insides real good with sandpaper and give them a mist of water, then use the gorilla glue. Clamp the fins tight as the glue will expand. I drilled a couple of holes in the fin tabs to allow the glue a place to escape.
When you bond the fins to the body, rough up all the plastic slot areas and fin tabs and use the same gorilla glue approach.
Sets like concrete!!
That's a good data point. Perhaps the Gorilla Glue has properties that increase the flexural stiffness that can allow higher velocities before fin flutter occurs.

Greg
 

Salvage-1

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That's a good data point. Perhaps the Gorilla Glue has properties that increase the flexural stiffness that can allow higher velocities before fin flutter occurs.

Greg
It expands and sets almost like a honeycomb structure. The spritz of water gives it a primary kick and helps slick the internals to let the expanding glue slide around. Or at least thats what I am hoping. When it sets.... wow...

I love these PSII kits. Excellent choice low cost!
 
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GregGleason

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I couldn't stand the switch band not being square, so I fixed it to my satisfaction. The result is a much cleaner joint between the shoulders of the airframes. One of the problems that I had with the av bay coupler is how quickly it picked up moisture. To remedy that problem and make it a bit more moisture resistant, I mixed laminating epoxy with microballoons and brushed it on the coupler and then wiped off the excess. After about an hour of cure time, I dry brushed microballoons onto the tacky area. Once the epoxy is cured I plan to sand it with fine grit sandpaper to smooth it up.

Av.Bay.after.Switch.Band.Squared.Up.jpg

Greg
 

GregGleason

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I did a test fit with the new arrangement. So far it seems to be coming together ok. But I think it needs to have an indexing key on the airframes to help with alignment of the holes for the sheer pins and retaining screws. I have some ideas on how to do that, but I haven't seen anything that makes me "Wow, that's it!".

Here is the stock configuration ...

Ascender.Stock.Arrangement.jpg

... and the closeup of the site.

Ascender.Stock.Arrangement.Av.Bay.Site.jpg

Here is the dual deployment configuration ...

Ascender.Dual.Deploy.Arrangement.jpg

... and the closeup of the av bay in place.

Ascender.Dual.Deploy.Arrangement.Av.Bay.Site.jpg

I think I am seeing some light at the end of the tunnel.

Greg
 

dhkaiser

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Greg, you do beautiful work, very nice. How does adding all this affect the stability? A friend and I added a TRS system to the existing payload bay and the stability went over 3.
 

GregGleason

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Greg, you do beautiful work, very nice. How does adding all this affect the stability? A friend and I added a TRS system to the existing payload bay and the stability went over 3.
Thanks.

I don't know yet. Obvious the CG is going to be a bit further away then the CG, but I don't know if that is going to be a flight issue. The stock configuration with an AT F40 weighed in at a little less than 600 grams. I don't know what the all in DD-configuration weight will be, but probably another 200 grams or so.

I do hope to figure it out relatively quickly, as I would like to launch it in the new configuration this Saturday.

Greg
 

GregGleason

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It was time to bite the bullet and figure out the airframe keys. I did something similar to the Wild Child, but wanted to extend it a bit with a little more precision. I decided to go with 1/4" discs to fit into recesses of the av bay. I considered wood, but I didn't thing they would hold up well over time, so I went with aluminum for the disc material.

I had to figure out out to orient the airframe with respect to the av bay. Since the Ascender has 3 fins and in two of the in between were dedicated to lugs and and rail screws, the natural thing was to pick the vacant 1/3rd as the key area. I had to figure out what the exact in-between part of the fins, so the best I could come up with is to lay the airframe horizontal on some "V" blocks put a level between the fins and then center the bubble. Once I had it figured out, I could set up the airframe to receive the pockets.

Av.Bay.Fore.Key.Hole.jpg

Av.Bay.Aft.Key.Hole.jpg

I mixed up some Aeropoxy adhesive (not the laminating epoxy) and filled the pockets and set the aluminum discs in place. I then placed some clear packing take to help keep things in place while curing.

Av.Bay.Keys.in.Place.jpg

This was a painful step, but I'm glad this part is now behind me. But the result is a solid and positive orientation to help things work in the field.

Now it's on to completing the sled and switch.

Greg
 

KenECoyote

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WOW! :jaw:

When I first saw "Ascender" in the topic, I figured it was some "cross your fingers" first attempt at an AV bay using craft sticks and masking tape, but I was really blown away with the detail, planning and incredible workmanship. My hat's off to you for that beautiful work!

BTW - Funnier yet, I just won an Ascender off Ebay last night. :)
 

GregGleason

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WOW! :jaw:

When I first saw "Ascender" in the topic, I figured it was some "cross your fingers" first attempt at an AV bay using craft sticks and masking tape, but I was really blown away with the detail, planning and incredible workmanship. My hat's off to you for that beautiful work!

BTW - Funnier yet, I just won an Ascender off Ebay last night. :)
Thanks for those kind words. I am not an av bay expert by any stretch, so I have to think through every step. I know when I assembled my first one, it took about an hour to put things together and it was put together "with hope". That's not the way I want to fly and as a result the flight was only a partial success (main didn't deploy). I felt bad about the experience and didn't want to fly that way again. The upshot is that it gave me some very important lessons: If you are going to fly DD rockets then you must do your homework and mitigate all of the risks that you can think of AND make assembly in the field as easy as possible.

I had hoped to fly today but it is still not flight ready. I'm not happy with the 9V battery and how it is secured. I am thinking about scrapping what's in place now, but there are no useful off-the-shelf options available that I know of. I would consider Li-Po's, but that is not in the budget *. So I'm left scratching my head a bit.

On the bright side, I am much closer and the airframe is all but done regarding the holes needed for the 2-56 screws and ports. I do need to think of a way to improve the assembly of those little screws in the field. Either that or have a boat load available for all the ones you drop. Hmmm ... I think I have an idea already on that.

Greg



* The Li-Po battery and charger I'm guessing is out of my price range, but I haven't priced things in quite a while and I don't even know what is compatible with PerfectFlite's MAWD. Electronics are not my strong suit, so if anyone has suggestions then I am very open to them.
 

KenECoyote

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Lots of research and ground tests can help prevent issues when going DD. :)

Regarding how to secure your battery, if using a 9V, it can be as simple as drilling a pair of holes vertically and one pair horizontally on the sides of the 9V (make sure to have the battery connector on when you do this) and then use zip ties to secure - I use removable zip ties (has a little tab that releases the zip.

I like these 9V Lipos I got on Amazon for my DD setups and they're only $23 for 4 along with a charger...600mah no less! I liked them so much that I just ordered another 4 batteries a few days ago.
 
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GregGleason

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Well after a bit of thinking I decided to go in a different direction. Instead of the big ol' 9V battery, I am going for the 6 x silver oxide button batteries (i.e., the SR44, or the Energizer 357/303). These batteries when placed in series will have 9V and have a capacity 150 mAh AND will work with Perfectflite's MAWD.

There are two main reasons for the shift in batteries. 1) The smaller batteries allowed the switch band on the coupler to have the switch port and solves a couple of problems, and 2) the batteries are smaller and lighter, which lends itself to a smaller housing because of the reduced mass. The 6 batteries will have a mass of about 13.8 grams, as opposed to 45.6 grams of the standard 9V battery (mass is 3.3 times greater).

There are two configurations of the battery arrangments that I considered. One is a simple "all in line" and the other is a "split bay".

Config 1:

Battery.Configuration.1.jpg

Config 2:

Battery.Configuration.2.jpg

The "all in line" is the one I chose, mostly because it is the most simple and that is one of my goals in the field. The one drawback is that I need to manage the battery holder size with respect to the switch.

Now on to figure out how the batteries can be housed.

Greg
 

GregGleason

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Well, the inline design was not going to work. There wasn't enough room to use that configuration so I am going with the alternate.

Here is what the design looks like so far.

The blue area are off-the-shelf "N" battery holders trimmed to hold 3 batteries.

Battery.Pack.Detail.Design.1.jpg

Adding a 1/2" plywood collar.

Battery.Pack.Detail.Design.2.jpg

Adding a 1/4" plywood cap.

Battery.Pack.Detail.Design.3.jpg

Greg
 

GregGleason

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As it turned out, I had to rebuild my sled because the battery compartment on the old one could not be adapted for the new power assembly.

So I milled a new sled and epoxied the guide tube on.

Here is a test fit with the MAWD. As you can see there isn't much room, but the MAWD is now "old school" but still is a good altimeter and data logger. As an aside, I finally have the exact hole locations figured out for the MAWD mounting hardware (for along time, what I had was a little off).

New.Sled.MAWD.Side.jpg

And here is the other side, where the power assembly will be attached. The four small holes are reference locations where the power assembly will go. You can see where I put a little light fiberglass on the sled. I thought about putting some FG on the other side, but I think this is strong enough as it stands.

New.Sled.Power.Side.jpg

Greg
 
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