Estes Door Knob Build-Log with Modifications,,,,,and,,,Night Launch LEDs!!!!

[Paul Howard]

This is my first "Dipping my Toes" into "Mid" Power rocketry, I've done Low Power for decades.

First I'm making an Ejection Baffle and basing it sorta from Apogee Ejection Baffle kit and using the kit to scratch build my own baffle since the original takes up way too much space and the 1/4" plywood is overkill by a large margin. I used the Apogee plywood parts for templates and cut my own baffle pieces from Lite-Ply and used my cutting jug to cut a much shorter length of coupler tubing from the tube that came with the Apogee kit. I also use a stout small Eyelet Screw (for a Kevlar shock cord) anchor to lighten things and theres added depth of material of both Lite-Ply and "real" plywood for the screw to thread into quite securely (much better than the kit directions to use just the 1/4" rubber elastic and the classic "Estes 3-fold paper anchor to the inside of the tube".

The "nose-side" where the Eyelet Screw Anchor is, is a little flexy in one axis, so a 1.25" wide Lite-Ply doubler was added, then a LitePly 1.25" x 1.25" "tripler" was added, then 2 small 1/8" thick "real" plywood squares were added for best anchoring of the screw and then filed down into a "pyramid" to reduce weight and bulk inside the baffle.

I came up with the 3 layers of the baffle to best knock out any flame and have big enough holes/gaps for plenty of pressure/gases to flow through and so that any charred junk or ejection caps from composite motors have an easier route out with some shaking.

All pieces were pre-glued, dried, sanded and then glued and filleted. The exceptions were use of a Hot Iron to Heat-Bond the pre-glued and dried (yes, it REALLY works WELL) Lite-Ply baffles and tubing into place, then followup with glue fillets. All glue has so far been Yellow Alphatic Resin Wood Glue other than the JB Quick for the "Blast Side".

I like Ejection Baffles just to reduce the chances of wildfire and parachute burns, but since I shelled out the $ for a Jolly Logic Chute release, I want to better protect that investment from possible CATO's as another reason to put in a baffle. Also, I want a better anchor for the shock cord Kevlar to attach to.

JB Kwik was thinned with Denatured Alcohol for better spreading and penetration to (a) add blast protection to the "blast side" and (b) attach the tin-can lid cutout "blast shield" on the "blast side" where the most ejection charge will likely hit.

The Tin-Can "Blast Shield" has tiny holes punched with a finish nail (and finish hammer) so that the JB Quick can squish through and act like "epoxy rivets" to help hold it on. Also, the tin was scoured with rough emery cloth to roughen it then cleaned with denatured alcohol prior to glue-up.

This has been awesome! - I've probably already more than doubled the required effort, ha, ha.

The pictures are a little out of order but you'll get the idea.

More to come, stay tuned.................

 

[Paul Howard]

More pictures of the same thing as above.

 

[Azamiryou]

I've found that if a baffle is too short, it restricts the ejection charge too much causing unreliable ejection (and unreliable motor retention).

I don't know what the minimum length is, but that one looks shorter than I'd be comfortable with...

 

[Paul Howard]

I've found that if a baffle is too short, it restricts the ejection charge too much causing unreliable ejection (and unreliable motor retention).

I don't know what the minimum length is, but that one looks shorter than I'd be comfortable with...

Actually, I've been using shortened baffles for several years on a bunch of LPR's and had pretty good luck so far - this one is less compact and far more "open" in it's gaps than anything I've built yet for LPR's.

The only problems of non-ejection I've had were from Estes D12's that had less than normal amounts of ejection charge and they made up for it with thicker clay cap on top. I have verified "that" happens from taking a LOT of D12's into where I work and X-Ray'ing them. I've "cured" that problem by scoring an "X" into the clay until I see Black Powder then stop and put masking tape over the cap. I have posts on this on the Low Power Forum.

I've also been told that a Lot of composite motors have not-enough Ejection Charge in them and I have been advised to pull the caps, empty the Black Powder, weight it and add more if needed then re-cap the motor. I have the amounts of Black Powder weights written down with my motor stash but don't remember them off the top of my head. There are also guide lines for how much to add (or not) depending on body tube lengths and diameters.

Good to know your experiences though and I'll keep that in mind.

Thanks-Paul

 

[terryg]

Reconsider using the small diameter unwelded eyebolt to attach the recovery system to. It takes surprisingly little force to open them up. If the delay is very early or very late the forces that occur can easily do this. You can get small stainless steel eyebolts that will take much more shock force.

 

[Paul Howard]

Reconsider using the small diameter unwelded eyebolt to attach the recovery system to. It takes surprisingly little force to open them up. If the delay is very early or very late the forces that occur can easily do this. You can get small stainless steel eyebolts that will take much more shock force.

I probably could have bought a smaller Eyebolt with washer and nut - I think that's a good idea and I'll keep that in mind for the next baffle I make.

Since this baffle is already assembled, getting a washer and nut on the "inside" side is pretty much not an option.

The EyeScrew I'm using is pretty strong, I tested it by tugged on it with needle nose pliers to see what it "opening resistance" was like, and in short, the rocket will tear apart before this screw opens. It has substantial threads so I may advance it a little further possibly and glue it in. I do know about EyeScrews opening under strain so that was on my mind when I picked the one I had in my stash (I have a pretty substantial "Middle Age Man/Old Man" stash of screws, nuts, nails, bolts,and other odds-n-ends waiting to get used up).

Since this is the Estes Door Knob, it's not as heavy as other many other MPR's and I plan on keeping the "Fuselage" lighter with using the balsa fins (I'll add hardwood leading and trailing edges, sand an airfoil in which reduces weight somewhat and probably put white tissue paper over them with shellac since that will show off the nice streaky "character" balsa. The main weight that will be added will be in the nose since I'm adding an Apogee Electronic Bay (but lightening it as much as possible)_so that I can add LED's for night launches. All that said, this kit does need some beefing up (like the 2 feet of 1/4" elastic shock cord attached with the "Estes 3 Fold" paper and glue anchor).

Thanks for the input, it's all good info for if I make more bigger & heavier rockets.

 

[Back_at_it]

Nice build. I like the work on the baffle. I'm generally not a fan of those baffles as they normally only have two plates and don't effectively stop burning embers from passing through. With the addition of the third plate, you should be good to go.

The diameter of the screw eye does make me pause as I have had more than my fair share of them open up. I'd consider going with something a little bit larger. If it's too late for that, just ensure that you have a very long shock cord and you might consider adding a length of elastic up toward the nose cone to soften the pull on the screw eye.

As for the length of the baffle. Don't sweat it. I've built them as short as 1.5 inches and used them in my Fat boy with a 24mm mount. While mine are three plate half moon designs, I've never had a failure due to a baffle. I have had a number of them fail due to failed motor ejections.

 

[Paul Howard]

Nice build. I like the work on the baffle. I'm generally not a fan of those baffles as they normally only have two plates and don't effectively stop burning embers from passing through. With the addition of the third plate, you should be good to go.

The diameter of the screw eye does make me pause as I have had more than my fair share of them open up. I'd consider going with something a little bit larger. If it's too late for that, just ensure that you have a very long shock cord and you might consider adding a length of elastic up toward the nose cone to soften the pull on the screw eye.

As for the length of the baffle. Don't sweat it. I'm built them as short as 1.5 inches and used them in my Fat boy with a 24mm mount. While mine are three plate half moon designs, I've never has a failure due to a baffle. I have had a number of them fail due to failed motor ejections.

Good to know!

Even though the Door Knob has some "roominess", it's not a "lot" and my goal is (a) stop embers, (b) protect my JL Chute Release from CATO's (c) don't take up too much space with the baffle (d) try to avoid too much added weight since I want to stick with the balsa fins and not bang the shock cord as much.

As far as shock cords, I agree 100% and that's part of the plan: "Really long" and with "plenty of elastic", that's been my M.O. for quite a while - If I don't have enough "heavier-duty" elastic in my stash, it's an easy trip to Jo-Ann's Fabric to get heavy enough elastic ribbon fabric. The 2ft of 1/4" rubber supplied with the kit is not impressing me.

I've already pull-teste the Eyescrew with needle nose pliers, and it's quite sturdy, I did end up putting it in deeper and glued it in (and it goes through the Lite-Ply and all the way into the 3/8" layers of "real plywood" on the inside) so considering my end-weight goal of the whole "fuselage" staying as light as I can manage + long shock cord + long elastic = I should be OK.

Thanks for the input!

 

[Paul Howard]

Here's some hardwood edges for durability. Obviously I'm drawing in my model airplane-building past. These will be sanded and slightly airfoiled with a conventional subsonic airfoil (not the scale super-sonic airfoil). I'll have to use some self-restraint here and not-do my usual sharp trailing edges since this rocket is a bit heavier and will land with more force than my LPR's and it's not going to win any altitude contest anyway.

 

[Paul Howard]

Question for those who have built an Estes Door Knob: I fully understand how to follow the instructions for the fin and motor mount assembly - The Question is,,,,,,,,,,,,,,Am I the only one who is scratching my head about Why one of the centering rings is slotted to go through the forward part of where the Fin mounts to the motor-tube and leaving a small bit of wood ahead of it that really can't take much force, and the odd (to me) placement of the Green ring that will go under the forward section of the fin???

It's almost as if the whole fin and motor mount were designed to resist force pushing out the tail end of the rocket rather than emphasizing resisting force going upward with the thrust of the motor?!?!?!?! Does anyone else see that???

I do realize that as the instructions and the design call for, it should be just fine, it seems a little off to me since I've scratch-built enough rockets with Through-The-Wall fins-to-motormount and maximizing connections of fins to body-tube, and fins to motor-mount to handle the thrust going, well, upward and not pushing out the tail. Also, I'm making a (maybe 2) Lite-Ply Centering Ring(s) to either add to, or replace cardboard centering rings for more strength.

Thanks - Paul

 

[Paul Howard]

NERD ALERT!!!!!!

I'm going with a "Lifting Airfoil" on each fin to induce slight spin since that has worked well for me in the past in terms of flight characteristics and it also reduces some aft weight. I guess I could have done this on just 2 opposing fins and saved some work and time for myself. Whatever.

This is the initial angular "bevel" portion of sanding which will soon be followed with rounding of the airfoil, then rounding of the leading and trailing edges. I used the tried-n-true method of drawing multiple lines in pencil (or pen) with a ruler and carefully sanding to the lines, then examining and re-drawing the lines and re-sanding, re-examining, etc, until I get the shape I want and keep them as consistent as possible. I also raised each fin as I sanded it by putting it on top of another longer wood sanding block so I have more room to work and can keep track of the angle I sanding. This is a skill common to anyone who builds RC and FreeFlight Glider wings that start from balsa sheet planks (that may get hollowed and filled with ribs) which is where I got this habit (and it's a good habit).

Here's where I'll use some self-restraint and NOT taper the trailing edges to a sharp edge since I want this bigger heavier rocket to have more crush/ding-resistant trailing edges.

If you know your airfoil talk, the leading edges will get a little "Phillips Entry" by sanding a small curve on the "flat side", then rounded. The outer edges or Tips will stay pretty squared-off but with very slight rounding. Yeah, I know, this rocket's not bound for any altitude competition, but old habits die hard from aircraft and I just love airfoils (NACA, Benedict, Selig, and the Selig-Donovan, Selig-Golanathaparnum collaboration airfoils - all from "Extremely Low Reynold's Number RC and FreeFlight Glider Airfoils").

 

[Paul Howard]

Airfoils Finished! Next I'll wrap these in Sig brand White Tissue Paper and either White Glue or a water based tissue-glue/past made for model aircraft. Once the adhesive dries it will dry clear to show off the cool streaky balsa and hardwood edges.

Stay tuned!

 

[Paul Howard]

Silkspan-Wrapping the Fins. I chose White since it will still show the streaky balsa nicely and the hardwood edges with a clear finish. Once I got done trimming and sanding off the excess Silkspan, I had to look closely to tell, it's almost unseeable in the photos.

As usual the pictures are a little out of order but you'll get the idea.

I like Sig Brand Tissue and Silkspan because it has a "grain" or "stronger-axis" which I like to line up with axis I'm most concerned about. In this case, I want the "grain" of the Tissue oriented Perpendicular to the "grain" of the Balsa to prevent splitting, and because there's a roughly 45 deg angle to the leading edge of each fin relative to the axis of the rocket, the "grain" of the Silkspan is running approx 45 degree across the fin from root to tip, so, therefore, it's also providing some break-resistance still to mid fin from bad landing snaps.

Also, I'm a big believer in running Tissue, Silkspan, Paper, or Fiberglass or whatever (even cotton or nylon fabric and yellow glue or whatever adhesive) from tip to base of where a "Through-The-Body/Wall" fin will attach to the motor tube.

I first sprayed the Silkspan with water to dampen it then did one side at a time and folded the Silkspan over the leading edges and used Elmer's White Glue thinned with water to make it brush on easier then brushed more glue "on and through" the silkspan once it was applied. I think you can also spray with Denatured Alcohol and thin the Elmer's with it as well and I'll try that next time I have more ventilation - the advantage is not loading the balsa with sooooo much water in the process as I did here.

By wetting the Silkspan (or Tissue, or paper) it will slightly stretch and dry tighter. If applying with Shellac, it's better to use the Denatured Alcohol to spray the tissue or Silkspan than water - just ventilate well.

I hung the fins to dry, and if you look closely, you'll see a tiny piece of Waxed Paper between the Wood Clothes-Pin and the drying Silkspan/Fin. Then once dry, I trimmed the Silkspan close to the fin then put them directly on top of the electric radiator to dry all the water out. It's important to have both sides evenly heated to avoid possible unequal shrinkage and warping or curling of fins.

 

[Paul Howard]

It's starting to look like,,,,,,,,,,,,,A Rocket!

Since I added the Silkspan, the fins are a little thicker so I used and emery-board to widen the gap in each fin-slot. Since each fin is slightly different, I labelled each fin and slot "A, B, C & D" to keep each fin with it's own slot. This will come in really handy later with the motor mount.

Once I got the Slots widened, I went through the base mounting surfaces to look for gaps and sand things more even. I marked the contact side with thin sharpee marker so I could keep track of where I sanded off wood and how much un-sanded wood remained as a method to keep track of wood removal. This is something I use when making Wood Bows and sanding airfoils into balsa (see prior airfoil stuff). I held the rocket up to the light as a gap-checker.

 

[Paul Howard]

"I Did the Motor Mount My Way,,,,,,,,,,,"

As usual the pictures loaded somewhat out of order.

After a lot of test fitting, the Estes Paper Motor Mount Centering Rings were rather loose and sloppy in terms of contact of outer edges to the inside of the body tube. After trying to add shimming paper to each individual ring, I got tired of it and glued 2 of 3 paper centering rings together for a thicker edge to actually be able to achieve adding paper shimming (with yellow glue). I kept thinking "Sheesh If scratch built this, I could do this better". I've scratch cut my own TTW slots & Lite-Ply Centering Rings plenty of times and whatnot with great results and it was WAY easier than dealing with the slotted ring that's only there for alignment. I filled the slots in the fins that fit over the slotted ring for better structural integrity. Since I scratch build RC Gliders with built-up frame wings, tail surfaces and fuselages so this is pretty basic for me. So, here it is.

You'll see a Lite-Ply Centering ring Ring at the end of the body-tube, Note the pencil marking, that's to note where it needs final touch-up sanding to get a nice fit that isn't too tight but not loose and sloppy either, and that will make the glue-up & installation Way easier. I also pre-glued and sanded the outer edges of the rings and inside the tube with a thin layer of yellow glue, let it dry, sanded it and tested for having enough "slip" before the actual glue-up.

I put vent holes in the aft 2 of 3 rings between all fins since this thing's going to get hot, go high, go fast, and there's a lot of internal air-volume between rings that I would rather vent out that pressure than wear out the cardboard tube.

I also added copy-paper wraps around the top and bottom of the body tube since that's where I often used to end up with dings in the rockets as a kid and I got tired of it, so that's been a good cure.

 

[Paul Howard]

Here's my special long dowel to get glue on top of the top centering rings, by sanding in the bevel on the dowel, it leaves a better fillet of glue connecting the Centering Ring and Wall of the Tube. I dripped one drop at time of yellow glue with careful aim, then used the dowel rotating around the tube to make the fillet all smooth and even.

"What's up with the goofy wraping of Kevlar around the Eye-Screw on top of the Ejection Baffle" you may ask - This arrangement does several things, it disperses the load better so that the Kevlar won't fray from one loop around the metal screw, and, this is a Quite Strong Eyelet Screw, but it also will prevent (or greatly reduce the chances of) a weaker Eyelet-screw from being pulled open, again by dispersing the pull-load (but this screw is strong enough after pull-testing that I'm not worried about "that"). I sealed the knot with yellow glue and the end tip of the Kevlar "base" is also sealed with yellow glue.

I added CA to the Insides of the Launch Lugs, the Top end of the Body Tube and the Motor Tube. If I though ahead, I would done this with the Motor Tube prior to glueing it into the body tube, but it was still easy. I just used a dowel with a tough and rough Paper towel taped onto the dowel, drizzled a bunch of CA in the end and swooshed/swabbed it around with the dowel-n-papertowel tool like cleaning a gun barrel.

I'm "staining" the fins with decorative swooshes of Neon Yellow, Orange, Blue & Fuscia by smearing the Acrylic Paint with a clean sock-rag. This will add some color splashes and still show off the cool looking streaky balsa and hardwood edges.

The Nose will have the E-Bay installed for LED lights, but it's sorta heavy overkill 1/4" Real Plywood so I'll likely use some of it to use as a template and replace as much as I can with Lite-Ply.

Stay Tuned and Thanks for Watching.

 

[Paul Howard]

Fins pre-painted, launch lugs glued on, ejection baffle glued in, LED sets that will go into the nose for night launches and prepping (roughing the surface with the rat-tail file) the Motor Retainer prior to putting on with epoxy (Probably JB Kwik).

And there you have it for now.

 

[Paul Howard]

Here's the latest:

For the Motor Retainer - I thinned some JB Kwik Epoxy with Denatured Alcohol to make fill gaps and just smear around a LOT nicer. If you notice the BLACK THIN COFFEE STIR STRAW, that was used as a PIPETTE to draw Denatured Alcohol out of the can and drop it into the mixing cup with the JB Kwik which is much more controllable for dinky amounts of Denatured Alcohol with small amounts of epoxy.

I'll say it again, JB Kwik lives up to it's name and sets up fast in about 5 minutes so definitely have everything present you need and Know what you're going to do or it might run-away on you. I really like it, especially thinned. Also, any epoxy can be greatly strengthened by adding short fibers 1mm-5mm of anything (fiberglass, carbon fiber, cotton, hemp, dog-hair, nylon, etc) and thinning helps that process. I do that a LOT with JB Weld and JB Kwikk on other bigger and higher load projects where I want added strength and shatter/crack resistance. And yes, the (clean after a dog-bath and dried) Dog-Hair really works and has become a favorite added material.

I used the Fin-Alignment guide in the plans which was actually really nice to have, I would have been fine without, but since it was there, it was really nice to use. Coming from a balsa-frame aircraft building background with plans that are built-over, I really like that.

I Glue-filleted the fins with Yellow Glue and suspended the whole works over the electric radiator in the workroom, horizonally at first on the Black & Decker Workmate bench until dry enough to hang vertically so all fins plus any not-fully dry glue inside gets more chance to dry with the heat, "That" is another reason I like to put vent-holes in my aft centering rings in addition to all the pressure change during flight reasons.

For finishing the fins, I'm going with (Casey) Birchwood Gun-Stock Tru-Oil finish. Normally my first pick would be Clear Shellac, but I got talked into buying the "Amber" Shellac (which really is sorta peat-bog brackish-water brown in tone) and I used some already on another project of nice streaky different color-toned cedar and the "Amber" just dampened the contrast in the wood and hid some of the streakiness and color-tone variations. It still looks nice, but the "Amber" does hide "character" in wood more than I like. So, next time, I'll buy "Clear" Shellac. So, on the "character" topic, I looked at various clear finishes I had already and since the Tru-Oil needs to get used up, this was a good opportunity. I'm now 3 thin coats into it and will likely use 4 or 5 which is usually how many coats I apply to the Wood bows I make (it's my favorite finish for wood bows in terms of water-resistance and durability when out bow-hunting and looks great on bows).

Shellac is nice on rocket fins, thinned (with Denatured Alcohol) for balsa gliders, and arrows because it's light, dries fast and cleans from hands and brushes really well with Denatured Alcohol.

Sorry for the somewhat out-of-order pictures, again.

 

[Paul Howard]

I started building the EBay mount for my LED's that I got from Apogee - I am really impressed with the quality of the 1/4" Plywood, the laser-cutting and the fitting of the parts for this 3" Diameter Nose Cone EBay Kit made and sold by Apogee. There is some sanding/filing/rasping required to get it to fit into the nose cone which is to be expected and I'd rather have that than too loose and having to add layers of paper shimming (not the end of the world though, I've done that plenty of times with motor mounts over the years).

I'll be cutting out as much wood as possible from the "sled" portion to reduce weight since for my purposes it's a bit of overkill and more weight than I want but for most people and uses it's probably great, or I may use the supplied "sled" as a template to make another from 1/8" Lite-Ply with 2 "faces" of 1/16" Real Plywood at the base where the shock cord connection will go. I haven't decided yet.

I used a spent D12-3 friction fitted to a Hazel Stick with masking tape, then used a 24mm-29mm Estes Adapter with the D12-3, then locked all of that into to the motor mount with the threaded Motor Retainer and masked up my fins getting ready to spray-paint the fuselage.

And, Surprise!!!!!!a special bonus picture of an Oregon Dunes Garter Snake, the subspecies that can eat the poisonous Rough Skinned Newts, and in turn those snakes carry that toxin and become toxic to everything else.

More to come! Stay tuned.