atrobinson
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I know you have all been waiting with baited breath for my next construction fiasco, and here it is: a completely custom build of the Estes Hi-Flier XL with all high-power rocketry (HPR) parts. After the premature demise of Amethyst Witch Mk I (Hi-Flier XL converted for MPR) and the Amethyst Witch Mk II (same, see https://www.rocketryforum.com/showthread.php?55471), having absolutely nothing to do with the construction of the kit (Mk I went down to a CATO due to improperly constructed RMS motor; Mk II to a snapped 1mm Kevlar shock cord), I decided I should build one from scratch.
To be original, I call it the Hi-Flier HPR. No some of you will be disappointed that I didn't scale the model up. It is longer than the Estes Hi-Flier XL, but is a 38mm body tube and 29mm motor mount rather than BT-60/24mm. But everything is built using HPR-designed components, including the body tubes, motor tube, centering rings, etc.
I wanted the option to fly this rocket with 24mm or 29mm motors all the way up to 29/360 (I200 in Aerotech's line). The original conversion was 24mm only, so I didn't worry too much about fin attachment--reinforcing the fins with CA and attaching them securely seemed sufficient, and the fins survived well--including Mk II's uncontrolled descent through some trees). In the new kit, possibly flying it up to I motors, I wanted a much stronger attachment--so I designed a customer through-the-wall (TTW) fin set in RockSim (see photo 2).
I also wanted the option to convert this to a two-stage, air-start rocket (don't ask why). That didn't work out as I'll explain later, but photos 1 and 3 show how I fit the air start wire guide into the very narrow space between the 29mm motor tube and the 38mm body tube.
Photo 1 - This is the completed MMT with airstart conduit and 2mm Kevlar shock cord attached. The attachment for the shock cord is a 4-40 screw eye that is "closed" with epoxy. This is a potential failure point, but a bigger screw eye wouldn't fit. A better alternative would be a tapped forward closure with a "real" screw eye--but a) as this isn't available for 24mm, and b) as initial launches will be 24mm only, and c) this type of attachment worked well on Mk I, I'll risk it for now.
Photo 3 - Yes, this is out of sequence. Photo 3 shows the airstart conduit. It's a 5/32" ID brass tube (3/16" OD) pounded to a flat 5/32". This allows my 24 gauge two-conductor wire to fit but also fits between the motor tube and the body tube. I cut slots out of the centering rings to accommodate the conduit. These slots were reinforced with CA, and once the tube is in place there is no substantial loss of strength in the MMT assembly.
This effort of putting the conduit in place was for naught, by the way: I installed an AeroPack 29mm retainer and lo and behold the outer ring does not fit inside a 38mm body tube--so the 1" offset between the end of the body tube and the aft centering ring for a staging coupler became a 1/2" offset with no room for a staging coupler (even when the other ring of the retainer isn't attached, a 38mm coupler will not fit between the inner ring and the inside of the body tube.
Of course there are other stage coupling methods of which I may avail myself, and there is (barely) enough room between the retainer inner ring and the body tube to thread an airstart wire through the conduit (will have to friction-fit the motor in that case.
Photo 2 - These are the custom fins. They are designed in RockSim to be pretty much an exact match to the stock balsa fins, but they are made of basswood and have TTW tabs as shown (the Estes stock fin is at the left).
I cut these out from the bassword stock using a scroll saw, which is definitely sub-optimal for this sort of thing. But using small clamps and another piece of straight stock, I was able to get the cuts straight, and was able to sand everything down to fairly constant dimensions. There are a few mistakes, but those can be solved with epoxy clay ;-)
I rounded the edges using a Dremel router table and a Dremel 1/4" radius bit. That worked very well.
Photo 4 - It's good to show my failures as well as my successes (well, so far everything I have posted either hasn't flown or has failed). But these fin slots are an abortion. I tried two methods using an Estes BT-60 body tube for practice: using a Dremel router table (about $30) and a Dremel drill press/workstation (about $80).
The Dremel 1/8" slotting bit works great.
The router is tough because you can't see where you are in the cut--but I did get to the point where my slots were quite straight, and I could extend them slightly by hand if I didn't make them long enough. The router table has a fence that makes straight cuts fairly easy.
The drill press method is easier from the perspective that you can see your work, but there is no fence--and I wasn't able to easily construct a guide or jig with materials I had on hand. I never succeeded in getting very straight edges on my slots with the drill press.
Of course I used the drill press method to cut the slots in these heavy duty body tubes. They are UGLY. But again, I did nothing that can't be covered up with epoxy clay or epoxy + microballoons.
In the next set of photos you'll be amazed by the completed (but not finished) lower body, avionics bay (designed for Raven 3), and upper body.
To be original, I call it the Hi-Flier HPR. No some of you will be disappointed that I didn't scale the model up. It is longer than the Estes Hi-Flier XL, but is a 38mm body tube and 29mm motor mount rather than BT-60/24mm. But everything is built using HPR-designed components, including the body tubes, motor tube, centering rings, etc.
I wanted the option to fly this rocket with 24mm or 29mm motors all the way up to 29/360 (I200 in Aerotech's line). The original conversion was 24mm only, so I didn't worry too much about fin attachment--reinforcing the fins with CA and attaching them securely seemed sufficient, and the fins survived well--including Mk II's uncontrolled descent through some trees). In the new kit, possibly flying it up to I motors, I wanted a much stronger attachment--so I designed a customer through-the-wall (TTW) fin set in RockSim (see photo 2).
I also wanted the option to convert this to a two-stage, air-start rocket (don't ask why). That didn't work out as I'll explain later, but photos 1 and 3 show how I fit the air start wire guide into the very narrow space between the 29mm motor tube and the 38mm body tube.
Photo 1 - This is the completed MMT with airstart conduit and 2mm Kevlar shock cord attached. The attachment for the shock cord is a 4-40 screw eye that is "closed" with epoxy. This is a potential failure point, but a bigger screw eye wouldn't fit. A better alternative would be a tapped forward closure with a "real" screw eye--but a) as this isn't available for 24mm, and b) as initial launches will be 24mm only, and c) this type of attachment worked well on Mk I, I'll risk it for now.
Photo 3 - Yes, this is out of sequence. Photo 3 shows the airstart conduit. It's a 5/32" ID brass tube (3/16" OD) pounded to a flat 5/32". This allows my 24 gauge two-conductor wire to fit but also fits between the motor tube and the body tube. I cut slots out of the centering rings to accommodate the conduit. These slots were reinforced with CA, and once the tube is in place there is no substantial loss of strength in the MMT assembly.
This effort of putting the conduit in place was for naught, by the way: I installed an AeroPack 29mm retainer and lo and behold the outer ring does not fit inside a 38mm body tube--so the 1" offset between the end of the body tube and the aft centering ring for a staging coupler became a 1/2" offset with no room for a staging coupler (even when the other ring of the retainer isn't attached, a 38mm coupler will not fit between the inner ring and the inside of the body tube.
Of course there are other stage coupling methods of which I may avail myself, and there is (barely) enough room between the retainer inner ring and the body tube to thread an airstart wire through the conduit (will have to friction-fit the motor in that case.
Photo 2 - These are the custom fins. They are designed in RockSim to be pretty much an exact match to the stock balsa fins, but they are made of basswood and have TTW tabs as shown (the Estes stock fin is at the left).
I cut these out from the bassword stock using a scroll saw, which is definitely sub-optimal for this sort of thing. But using small clamps and another piece of straight stock, I was able to get the cuts straight, and was able to sand everything down to fairly constant dimensions. There are a few mistakes, but those can be solved with epoxy clay ;-)
I rounded the edges using a Dremel router table and a Dremel 1/4" radius bit. That worked very well.
Photo 4 - It's good to show my failures as well as my successes (well, so far everything I have posted either hasn't flown or has failed). But these fin slots are an abortion. I tried two methods using an Estes BT-60 body tube for practice: using a Dremel router table (about $30) and a Dremel drill press/workstation (about $80).
The Dremel 1/8" slotting bit works great.
The router is tough because you can't see where you are in the cut--but I did get to the point where my slots were quite straight, and I could extend them slightly by hand if I didn't make them long enough. The router table has a fence that makes straight cuts fairly easy.
The drill press method is easier from the perspective that you can see your work, but there is no fence--and I wasn't able to easily construct a guide or jig with materials I had on hand. I never succeeded in getting very straight edges on my slots with the drill press.
Of course I used the drill press method to cut the slots in these heavy duty body tubes. They are UGLY. But again, I did nothing that can't be covered up with epoxy clay or epoxy + microballoons.
In the next set of photos you'll be amazed by the completed (but not finished) lower body, avionics bay (designed for Raven 3), and upper body.
