Certify Level 1

hi this is John this video is on building your first high power rocket typically for level 1 certification I'm going to show you building a kit and I'm going to show you a very typical high powered kit this one is the lock for kit by lock precision lock is one of the oldest manufacturers of kits makes very nice rockets and also the materials using this kit will be ones that are familiar to you from model and mid power rocketry it's got paper tubes plywood fins apply the centering rings all easy to work with and familiar materials so let's open the package and take a look at what we got just like a model rocket kit you'll have your nose cone your airframe a motor mount tube and various parts as well as instructions one different thing to notice right off the bat that's typical of high-power kits is the tube is slotted this is because the fins are mounted not only to the surface but also go through the outside body tube and our epoxy to the motor mount tube inside now let's talk a little bit about kit selection what I have here is three sizes of motor mount - this is the motor mount tube that came with the kit it's 38 millimeter in diameter for comparison of the 29 millimeter and a 54 millimeter all three of these sizes are plausible when you choose your level one kit I've chosen this lot for partly because its simplicity longevity but also partly because I think 38 millimeter makes a good size there's a wide range of motors available in 38 millimeter in H&I impulse some other attributes that make this a good choice is its simplicity and its moderate tops this is what it's called a three fin the nose cone kit because it's basically just simple you've got your airframe one-piece nose cone three fins pre slotted pretty much everything ready to go there are a few parts we're going to switch out but basically we can build this stock and have a great flying rocket without too much complexity okay the first thing you should do when you open your kit is identify all the parts find the instructions and read through the instructions to make sure you understand how the kits going together this is fairly typical for a traditional high-power rocketry kit we have a shock cord in this case it's elastic we have a nylon parachute plywood centering rings plywood fins launch lugs now we could build this rocket totally fine with the pieces that came but there are a few substitutions and additions that are common and that I recommend the first and in my opinion most important is to replace the elastic elastic belongs in underwear not in rockets I like to use nylon strap other people prefer Kevlar but choose a bridle that's a little more durable than elastic the rule of thumb is that your bridle should be four to six times as long as the rocket since this is a single deployment I chose four times as long and I've chosen a relatively small 7/16 wide nylon strap the other thing is you need to protect the recovery system the bridle and the parachute from the motor ejection gases you can do that with whiting or you can use a parachute protective I like these no mix sheet parachute protectors as a way to insulate your recovery system from the ejection charges I'll show you more about that when we pack the rocket the next thing to consider is motor attention high power rockets don't use motor hooks instead you have to provide some mechanism for holding the motor into the rocket now high-power motors have a lip on the back so under thrust that lip will push tight against the aft end of the motor tube and it won't go in so you don't need a motor block ever ejection charge from the motor provides force this way but of course the force is actually in both directions and could push the motor out afterwards so in order to lock the motor into the rocket we like to use some mechanism of motor attention that could be tape or it could be a natural motor retainer here I have two commercial motor retainers that are commonly used this first one is the Aero pack retainer with the screw on cap the second one is the giant leap slimline with a snap ring both of these mount to the outside of the motor mount tube you can slide the motor through and then the motor is held in place either by the exterior screw on ring or the interior snap ring another thing you want to consider during construction is whether you want to use launch lugs or rail buttons lock has provided this kit with two different size launch lives this is probably four quarter of three sixteenths this is probably four half or seven sixteenths but in any case the launch lug requires you to launch from a launch rod which is suboptimal for several reasons if your club has rails you probably want to build your kit to use those rails are different than launch lugs instead of the rocket having a lug that slides over the launch rod the rocket has two buttons or possibly more that slide into the side of the slot of the launch rail if your club has rails I suggest you set up your rocket with rail buttons instead of launch lugs another good practice with the recovery system is to attach the bridle solidly to the forward centering ring to do that I like to mount an eyebolt or a u-bolt for heavier rockets you probably want to you bolt or a forged eye bolt for this light rocket a regular eye bolt is fine so we'll mount the eye bolt to the centering ring and then we'll use a quick link to attach the bridle this quick link means that we can replace the bridle if we need to it's easiest to mount the eye bolt to the centering ring before you bond it to the motor mount tube and as of course with any connection that you're not going to have access to later use thread Locker so it doesn't back out another little trick mount the eye bolt across the centering ring this will make it easier when you're reaching inside the airframe to hook in the quick link lock precision supplies plywood fins these look like eighth inch thick and they're perfectly good for rocket this size one thing that the instructions recommend is to round the edges which is probably a good idea for cosmetic reasons if nothing else now there are various ways we can finish the edge of the fin we can route it over as suggested in the instructions or we could even send a bevel there's a method for creating perfect thin bevels on my website but let's keep it simple and send a round over the easiest way to do that is to use a sanding block so that we have a nice even round over along the pole length and we don't get ridges or other artifacts of sanding aprox or with a shorter uneven stroke so if you go slowly and carefully you can get quite a nice job of a round over edge on the fin just with sandpaper now the lock instructions are good at mentioning this but I want to reiterate it's important to sand off this smooth glassine surface of the cardboard tubes now this is the motor mount to we're going to have the app centering ring the retainer mounted at the end then the thin tabs then this part with nothing and then the forward centering ring here so I want to at least scuff up the aerial that indium will be bonded to so the back section and the front I'll do that by lightly by thoroughly standing with 150 grit sandpaper again I don't need to take down the tube I just want to remove any glossy surface and make sure that the epoxy is not blocked from wicking into the fibers of the carpet of the cardboard so now we'll lay out the positions of the centering rings the kid instructions to jets mounting the centering rings and eight from the end of both tubes that's pretty reasonable except that we need to leave space for the motor retainer now the way the motor retainer works is it will bond to the end of this and then the motor will slide in and then the cap will screw so we want to make sure that we have enough space behind the app centering ring so that the motor retainer can attach so we can measure it or we can just mark it by placing things the way they will go now we want to make sure that the centering ring outside comes no close to the end of the tube than that so we have the maximal area for bonding did motivate Ainur as far as the forward centering ring 1/8 inch is fine we just need enough that we can get an epoxy filling so now I've slipped the forward centering ring onto the motor mount tube and lined it up at right angles it's on there reasonably tight but just to make sure it can't I like to put a few drops of CA this way it'll be held in place the way I've set it up while we're mixing and spreading epoxy now 1 another thing that I'm going to do a little differently than the kit instructions is not to bond the op centering ring quite yet we mark where it will go based on our motor retainer but I don't want to actually install it yet the reason I like to leave it off is because access to the inside of the airframe allows me to put some backing for the rail button and also it allows me to run Phillips on both sides of the route edge of the fin where it touches the motor mount tube now it's always a good idea to layout the components and see how it's all going to fit together and make sure you have planned everything properly I've slipped the app center ring ring on but not bonded it I have placed the thin the way it will go through the slot you can see the forward end of the center ring is at the slot the thin tab is going to be obviously forward of the slot which kind of shows how everything will arrange for this to work the motor retainer is going to stick out from the aft end of the rocket a little bit that's fine no big deal one thing I like to do is place a mark where the forward centering ring will hit on the outside of the airframe this helps me to plan the location of the forward rail button here's our mark and it's easy to extend it all the way around the tube by taking a longer piece of paper wrapping it tightly around making sure the ends but and then running a pencil now whether you plan to use the launch lugs or rail buttons we need to measure a center point between two of the fins we measure the center point evenly and then extend it using a piece of angle iron this is the HPR analogy of the door frame method that is mentioned in the SS case now we have a line evenly spaced between two to the fins and another line up where the forward centering is going to be now I'm going to use rail buttons but if you wanted to use a launch lug you would probably located somewhere in this area I'm going to place one rail button in the app just forward of the rear centering ring and one in the middle area just forward of the front centering ring the rail buttons mount with a number eight screw so certainly for cardboard and in my opinion for all air frame types you need to mount into something more solid than just the air frame itself so what I like to do is back it with a tee nut through a small chunk of plywood for example this case these number 80 nuts are mounted through small pieces of quarter-inch plywood that all epoxy from the inside of the airframe that allows me to screw the rail button into the air frame as it was designed and also to take it out and replace it if it gets worn down again it's always helpful to lay out things to envision how they will fit together before you mix any epoxy that way you minimize the chance of painting yourself into a corner as it were we've marked where the aft end of the forward centering rim will be quarter inch forward of that is the forward end hatching indicates where the center room will be located I have left at least a quarter inch of space before the little block which will be epoxy forward to the forward centering ring and there is the center hole where I will drill for the rail button screw and similarly for the after L button we know where the forward end of the app Center room will go based on the end of the slots for the through the wall pin mounts so we know where the apt centering ring will occupy then space quarter inch forward to get plenty of clearance and mark the area for the aft rail button plate where that will go and then there's the hole that we drill for the rail buttons group when drilling holes in airframe tube you'll get much better results if you have some sort of backing here I've used a scrap piece of coupler inside and clamped it so that when I drill through I won't splinter the inside of the tube going slowly I can drill a nice clean hole now drilling paper - or cutting it for that matter will often give you kind of a soft and slightly frayed edge so you can deal with that by wicking some CA into the cut or drilled edges this will harden up and provide a firm surface once the CA Drive you can read rill the hole clearing out any fibers and making sure the hole is nice and clean now before we go bonding anything we also want to scuff up the exterior surface of the tube so that we can get a good epoxy bond while less than the motor mount tube the body tube still has a slick surface and we want to rough that up a bit with 150 grit sandpaper so the area around the slots is critical because we're going to have a filling but we need not just the slot but also the area forward of the tab again we don't want to kill the tube but we do want to rough it up so the epoxy gives a good solid bond okay and we start with the epoxy epoxy is the subject all to itself and I've put together a video with a lot of basic techniques so I won't concentrate too much on actually oxy preparation here our first epoxy joint following the instructions is to bond the forward centering ring to the motor mount tube so a generous epoxy fill it along the joint between the centering ring and the motor mount tube and we let that clear and once we have a solid bond the forward centering ring and epoxy is fully cured we're ready to continue following the instructions and install the motor mount tube into the air frame now I like to before mixing any poxy get everything set up the way I want it to be so I've slid the motor tube in make sure that it stays exactly the way I've measured it so we have room for the motor retainer this app centering ring is still loose but it's in place so that I make sure when I bond the tube in it stays centered in the body this isn't to longer reach but it still helps to use a stick to get the epoxy all along the joint once we have the epoxy spread nicely we can make a Philip with our finger we just want to be very careful to keep the inside of the tube clean as we go so that the nose come will still slide smoothly once the forward centering ring is securely bonded and fully cured we can use the thin slots to push the absent room most of the way out not all the way out because we do want to keep the motor metal tube centered but enough that we can pull it out when we need to then we want to take our fins and test fit them to make sure that they work well in the slot they should be a tight fit and we should they should go all the way down to the motor mount tube now the instructions suggest tube arm the AB centering ring in first and then apply the fins by putting a little bit of epoxy on the route to get to the motor mount tube you actually will make a stronger joint if you can put a proper fill from the inside so what I like to do is just tack the fins in place all the way around take off the off centering ring apply the fills from the inside anyway place your fill through the slot make sure the tab engages with the motor mount tube and then just pack it into place with CA again this is just a temporary bond to hold things together until we can get in there with epoxy now once we have everything lined up and the op centering ring off we can apply Phillips to the root of the thin tab along the motor mount tubes these fins aren't too deep but it's still easier if you use a stick you can do the Philips two at a time for a three thin rocket in three sections it's best to let them get at least to the leather stage before you rotate to the next fins in my case I'll let them fully cure so then get all the internal Philips one at a time this is a good thing to do during the week because you can do one felt in the morning and then another one in the evening when you come home from work the other thing is get the backing for the rail button while the aft end is open and of course as you're going be careful to keep the motor mount tube and the inside of the airframe clean because we're still going to need to put the app centering ring on and you don't want any epoxy lumps getting in the way and now once we've gone all the way around doing the interior Philips we can put on the off centering ring I like to run epoxy around the motor math tube on the inside the body tube on the ends of the fence this way everything will be bonded together in a nice solid unit then we just slide the app centering ring in flush with the back of the fence once all the internal bonds are done for the app centering ring I like to seal the grain of the wood and the inside of the tube with a little thin epoxy soot from the motor burning will collect on the back of the rock and it's easy to wipe up if you have a smooth surface obviously unpick and epoxy in this way doesn't really add strength but our goal here is to seal the wood grain and provide a smooth hard surface so we can clean it up and then an epoxy fill it but just on the outside between the ring and the body tube we want to leave the inside clean for the motor retainer now we can install the motor retainer we bond this on to the outside of the motor mount tube using jb weld for its superior heat resistance and now to complete the construction our last little bit of epoxy work is the external Phillips these provide strength as well as creating a nice rounded transition between the fins and the airframe to at this point the basic construction of our rocket is complete we built it pretty much following the directions with a few additions such as the use of rail buttons and the addition of a motor retainer plus we've done internal Philips for extra strength unless you're one of those people who like to fly the Rockets naked the next step is to finish it which is a topic all on its own which is why I put together a video to help you out once the rocket is finished you can do the final preparations per plot so the airframe construction is complete now and we're ready to start preparing the rocket for flight firstly this consists of rigging the recovery system again I replaced the elastic with a nylon strap it's also longer which makes for a little bit safer recovery I divide the nylon strap three quarters or two thirds with the shorter length to the nose cone the off center point to the parachute and the long leg to the airframe for the main recovery this quick link attaches the I bolt and the forward centering ring the bridle runs through the parachute protector here so we protect the parachute from exhaust gases I've used quick links here and here because it's easier if you can carry things separately and when you're recovering the rocket you can unclip it but I didn't use a quick link at the nose cone because I feel that the plastic loop is a little weak and I didn't want a metal attachment point so the bridle directly connects to the nose you can make loops by knotting or sewing them take a look at my bridle sewing page to see how I made these loops once your rocket is finished it's important to get a final weight the kit will come with an estimate of the weight in the case of this get 28 ounces which is a little under two pounds however painting can add weight plus we replace the bridle and added some metal pieces that weren't in the kit so let's weigh our rocket can see what we came out to see I came to 2.2 pounds which is significantly heavier than what the kit estimated the reason this initial weight is important is because we may want to increase the size of the parachutes particularly if you like me fly in the West where there aren't any trees and the ground is hard once you finalize your parachute size pack the rocket is so ready to fly but without a motor and balance it to get a CG position this is important for running an accurate simulation when you choose the motor you want to carefully choose your motor so that you have a reasonably gentle ride for your level one search but still have no issues with stability on the flight once you've done the simulations involved with choosing your motor it's a good idea to mark the center of pressure which the simulators will give you on the rocket itself for a three fit nose cone rocket like this it's going to be nicely far aft and you won't have any stability issues the conventional center of pressure mark is a circle with a dot and there you have it relatively straightforward build techniques for your certification rocket have a great flight and welcome to high-power

Channel: John Coker

Views: 142,152

Keywords: rocketry, level 1 cert, hpr certification, hpr kit building, high-power rockets

Id: Xtr3758PvzA

Length: 27min 55sec (1675 seconds)

Published: Sat Mar 08 2014