Rich's GLR Nuclear Sledgehammer...continuation of original build thread

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

rharshberger

Well-Known Member
Joined
Oct 13, 2014
Messages
12,707
Reaction score
4,707
Location
Pasco, WA
The original build thread is here:
https://www.rocketryforum.com/threads/wasnt-planning-l3-but.106203/



So finally after nearly 6 months...SO IT BEGINS!

Edit: This thread was originally started by SteeleyEyed and he originally started this build, in fact he is the designer of the rocket for GLR. He has since exited the hobby (for a number of reasons, none bad). I inherited the kit from him last June (2018) with the commitment I would finish it. My plan is to fly it at SodBlaster 2 Labor Day weekend 2019.

Only the two main wings are shown bare, I received the kit with the fins (all of them) already to this stage. The lines on the one fin is for me to get accurate measurements for my OR file. Each fin will get one layer of 5.7oz Carbon Fibre Twill on each side and then per the builders instruction book (and it is a book, about the thickness of a Sport Rocketry mag) the fins will get tip to tip FG. If the carbon turns out nice enough looking I will incorporate that look into the final appearance.

glrnuclearsledgehammer1-jpg.370022



All carbon skins cut slightly oversized.

glrnuclearsledgehammer2-jpg.370023



Skins applied and the fins in the bag, all 5 of them, I use about the cheapest breather cloth you can get...felt from JoAnn's fabrics, there is so far no substitute for good perforated release film that I have found. As soon as the sample swatch hits the leather stage I will de-bag and trim the excess probably about 6-8 hours sample swatch is visible in lower left corner. Though its overkill I am running the pump at full vacuum, usually 18-20" Hg is fine for layups, but my bleeder isn't quite working like I like it too, and this is a new setup for me. Eventually I will build the addon resevoir and cycling switch to allow the pump to run as needed. Most of the bagging materials are from ACP Sales, the CF is from Soller Composites,and the resin is US Composites 635 3:1. As I am getting better with the US Composites resin, my next order will probably be the 4:1 to quicken the build process.

glrnuclearsledgehammer3-jpg.370024
 
First side of fins done, it took between 5-6 hours for the resin to set to the point it was no longer tacky and at the leather stage. The reason for pulling from the bag before full cure is to trim the excess while its easy to do with a sharp razor knife. Not sure until after the fins are lightly sanded if imperfections are epoxy wrinkles or something else, fairly happy with the results though, will do the rest in the morning.

GLRNuclearSledgehammer4.jpg
 
That fin geometry looks like tip-tip will be interesting. Running around with cutouts for the wings and all.
 
That fin geometry looks like tip-tip will be interesting. Running around with cutouts for the wings and all.

Yes,yes it will.... I will probably do the 3 tail fins first then add the wings to simplify the process a little (maybe).

Side two of the fins are in the bag, in 5 hours I should be able to de-bag and trim the excess.

Advice to anyone ordering release film, make sure it is shipped rolled not folded, part of the issues I have been having with cosmetic look is the release film was folded and it likes to maintain the fold even after having been rolled onto a dowel for over a year, its only very minor and sanding generally is enough to knock off the epoxy ridges formed but its still a pain.

20181206_144047.jpg GLRNuclearSledgehammer5.jpg
 
Nice! Can't weight to see it fly. We should launch the original then your big one in succession at the next Sod Blaster.
 
Side two out of the bag and trimmed. Waiting for epoxy to finish curing before lightly sanding to remove epoxy ridges.

GLRNuclearSledgehammer6.jpg

Motor mount assembly, this how I received the motor mount and the reason it would be a pain to make a 98mm motor mount. The 6" airframe section is designed to be the ISC for the 2 stage version of this rocket. Removal of the boattail allows the booster to be added. Lines are for the fins and fin pockets.

GLRNuclearSledgehammer8.jpg

GLRNuclearSledgehammer7.jpg
Fin pockets added, rear CR will be removeable until after I get the assembly into the airframe and can confirm a solid joint between the airframe and the forward CR (double CR), that way if I need to I can pour additional epoxy on to the rear of the CR to fillet it a bit more. Fin pockets are just attached using BSI 15 minute epoxy and are made of balsa. Fins will be attached using US Composites 150 Structural adhesive with a bit of milled fiber mixed in, I still have to figure the CC's of epoxy needed to fill the gap between the fin and each fin pocket, then its just a simple matter of injecting the right amount into the pocket and inserting the fin, a small amount of epoxy should squeeze out along the fin to outer airframe. The wing fin roots will be too large to make use of fin pockets (easily anyways), instead they will be done normally using internal fillets and US Comp 150 with much more milled FG added in.

GLRNuclearSledgehammer9.jpg
 
Side two out of the bag and trimmed. Waiting for epoxy to finish curing before lightly sanding to remove epoxy ridges.

View attachment 370104

Motor mount assembly, this how I received the motor mount and the reason it would be a pain to make a 98mm motor mount. The 6" airframe section is designed to be the ISC for the 2 stage version of this rocket. Removal of the boattail allows the booster to be added. Lines are for the fins and fin pockets.

View attachment 370106

View attachment 370105
Fin pockets added, rear CR will be removeable until after I get the assembly into the airframe and can confirm a solid joint between the airframe and the forward CR (double CR), that way if I need to I can pour additional epoxy on to the rear of the CR to fillet it a bit more. Fin pockets are just attached using BSI 15 minute epoxy and are made of balsa. Fins will be attached using US Composites 150 Structural adhesive with a bit of milled fiber mixed in, I still have to figure the CC's of epoxy needed to fill the gap between the fin and each fin pocket, then its just a simple matter of injecting the right amount into the pocket and inserting the fin, a small amount of epoxy should squeeze out along the fin to outer airframe. The wing fin roots will be too large to make use of fin pockets (easily anyways), instead they will be done normally using internal fillets and US Comp 150 with much more milled FG added in.

View attachment 370107

Nice lay up, but if I may ask, why did you not do the"thru the wall tabs"?
 
The fins will be getting tip to tip layups on top of the carbon, the tabs are already pretty stiff, actually the fins without the carbon are pretty stiff. So I didn't feel it was necessary to do the tabs. The fins are a phenolic honeycomb material and really don't need the carbon at all. The carbon is mostly for appearance, even though it does add some stiffness with a single layer. Once the fins arecattached to the airframe they get two more layers of FG tip to tip, and the tabs will not been seen.
 
Will the glass lay up also cover the fillets?

Yes, fillets are done before tip to tip. Based on a step back and look at the design review the section containing all the long tabs will be getting foamed after the external fillets are done. I have never used foam on a build before as I try and avoid the extra weight at the wrong end of the rocket, but 2.5" fin tabs make for a huge fin pocket and with the complexity of the number of fillets and 5 fins in the tube foaming will probably be easier.
Here's a great video by TFish on how to TT a rocket;

To the rest of the TRF crew....what density of foam is typically used for foaming fin cans, is 2 pound density enough for this build (shouldn't excess 10 G's acceleration max, though sims say 6 G's)?

I have used 2 part foam in forever, and have little practical experience with it (haven't used any in so many years I can't remember what I used it on before). I have to get the foam anyways because I want to foam the nose cone bay into the rocket.
 
Last edited:
Did about an hour and a half's work on the rocket this evening.

First up was making a drilling template for the narrow centering ring that goes between the 6" and 7.5" airfames, the 6" is the ISC coupler if I desire to make the rocket 2 stage at some point, so I decided the boattail would bolt on to the rear of the rocket via 6 screws counter sunk in the boattail. Thankfully a couple of years ago on a whim I picked up a couple of piloted 3/8" diameter counter-boring bits, one with a #6 and one with a #8 pilot bit. The template was made old school with drafting tools..remember those compass, rulers, 30-60 triangle, took me back to high school and college drafting (my freshman year of HS we actually had familiarization classes in AutoCad (not version 1, version 0). The gap between the CR ring and the boattail ID for the 6" airframe section was filled with a very long strip of poster board to keep it centered. Then after everything was setup it was off to the shop/garage and six 23gauge pins were used to hold the two parts together during the machining operations, I love the pinner for prototyping stuff as it makes needle sized holes that a really unobtrusive and separating the two parts will be really easy.
GLRNuclearSledgehammer10.jpg

Counter-bores drilled for #6 screws (one is actually shown in the lower right hole), a 1/8" washer fits the hole perfectly (didn't have any #6 on hand to check), the counter-bore, the counter-boring bits leave a dome bottom on the counter-bores so a 3/8" Forstner bit was used to flatten the bottom. The effect kind of reminds me of the ISC bolts on the Nike-Ajax and some Nike Sounding rockets and nosecones.
GLRNuclearSledgehammer11.jpg
Different view of above picture with slightly better light.
GLRNuclearSledgehammer13.jpg
Bottom view of 6 holes, the boattail is drilled for lightening purposes, and yes the boattail is part of the original kit, these kits were amazingly complete, afaik everything but electronics and chutes was included except for some construction supplies.
GLRNuclearSledgehammer14.jpg

Picture showing small amount of fin pocket, top of the pocket is about .375" and bottom tapers to about .312" ( 3/8 and 5/16").

GLRNuclearSledgehammer19.jpg

View of bottom of rocket on risers to allow the ISC coupler to flush with rear of airframe.
GLRNuclearSledgehammer16.jpg

Making the fincan look more massive than it really is....

GLRNuclearSledgehammer17.jpg
 
To the rest of the TRF crew....what density of foam is typically used for foaming fin cans, is 2 pound density enough for this build (shouldn't excess 10 G's acceleration max, though sims say 6 G's)?

I have used a crap ton of foam over the years for NC's and fin cans. My exposure has been with PML 6lb. only. The stuff Wildman sells and has also used a crap ton of. It really does the job. We use it as an adhesive as well as filling spaces.

Remember this never try to wipe up any excess before total cure, then it will easily scrape/sand off where you don't want it.
 
To the rest of the TRF crew....what density of foam is typically used for foaming fin cans, is 2 pound density enough for this build (shouldn't excess 10 G's acceleration max, though sims say 6 G's)?

I have used a crap ton of foam over the years for NC's and fin cans. My exposure has been with PML 6lb. only. The stuff Wildman sells and has also used a crap ton of. It really does the job. We use it as an adhesive as well as filling spaces.

Remember this never try to wipe up any excess before total cure, then it will easily scrape/sand off where you don't want it.

Thanks CJ, I have only dealt with the stuff once and it was lots of years ago, as for messing with it, I plan on pouring in 5 to 6 lifts.
 
Went back to the boattail this morning and decided to instead of 6 fasteners to increase it to 12 fasteners (only 6 of which are actually functional). I like the look better now.


Before:
GLRNuclearSledgehammer13.jpg

After:
GLRNuclearSledgehammer20.jpg GLRNuclearSledgehammer21.jpg GLRNuclearSledgehammer22.jpg

Backside showing rivet nuts used for threaded inserts, they are a light press fit and will be locked in place with a dab of epoxy.
GLRNuclearSledgehammer23.jpg
 
Back at it again this morning.

First things first its a trip to Payload Bay ( https://www.payloadbay.com/page-Tools.html ) to create 2 fin guides one a 3 fin and one a 4 fin (only two of the 4 fins will actually be cut out). Then attach patters together and apply to 1/4" foam board (30x40" iirc) with Aleene's Repositionable Spray Adhesive (its what my wife had :)). Then cut to match. I really like these fin guides when working with TTW fins, as long as I do my part and the fin roots are parallel to the axis of the tube then the fin sides are almost perfectly perpendicular to the airframe.
GLRNuclearSledgehammer24.jpg

Mixed up 40grams of US Composites 150 Structural Epoxy, added Milled FG to slightly thicken, then poured the fin pocket a little more than half full. With the rest of the epoxy I added some more milled FG and cabosil to thickent to peanut butter consistency. The fin tab edges were thoroughly coated to fill the honeycomb holes on the edges. The fin was inserted into the slot, then removed and the tabs recoated with even more epoxy (aka double dipped) and the fin pocket had a little more added to it. Fin was re-inserted this time getting a bit of squeeze out from the fin pocket. As I was sitting there looking at how much epoxy I still had left I realized I could go ahead and make a small 1/4" radius fillet on the fin. Later the fins will get beefy fillets prior to tip to tip glassing them. I cranked the heat up in the shop to about 80F for this part of the project. The US Composites 150 got pretty warm in the plastic Dixie cup (small ones) but not even close to cooking off. Should be about 2-3 hours before insertion of 2nd fin, I want to allow the thinner epoxy in the fin pocket to set before rotating. Should have all three tail fins on by this late this evening and possibly the wings too. Once all fins and wings are on and filleted it will be timer for foaming the fin can.Very little of the 40grams mixed was left over maybe 3-5 grams.

GLRNuclearSledgehammer26.jpg

And yes I did go back and fill that airbubble in the fin fillet :)
GLRNuclearSledgehammer25.jpg
 
Second Fin on and first fillet (no pictures this time of the fin) but I did take pics of the first fins internal tab forward of the fin pocket.

The double dipping technique gave a nice 1/4" thick fillet on the root edge. I am temped to put a another centering ring (I already have it) on top of the forward edges of the tabs (tail fins) and notch the wing tab to fit over it then double dip the wing tabs and do some internal fillets and totally ditch the foam.
What say ye experienced TRF'ers to me just doing internal fillets plus the additional CR instead of foam? This thing does get two layers of tip to tip as well.
GLRNuclearSledgehammer27.jpg GLRNuclearSledgehammer28.jpg
 
Whatever makes YOU comfortable!
That maybe Derek but some backup is nice occasionally. I have no reason to believe the build would be compromised by ditching the foam and adding the additional CR should also stiffen the tabs and assist with thrust transfer to airframe ( the rear CR with bottatil bolted in place should act as a thrust plate as well, this rocket is pretty much low performance for its size anyways). There is just something about additional weight at the wrong end of the rocket I dont like. [emoji3]
 
New CR is in place, this is a slight internal design change to do away with foam filling the fincan portion of the rocket (saving weight). My desire is to be able to fly this rocket on any 75mm L motor with sufficent thrust (to be determined once I know final construction weight) so far OR's estimated weight plus past experience are looking good that an L motor with more than 1150s newton of max thrust will get it safely off the pad with a 12' rail.


Centering ring prior to insertion in airframe, notches on edge are to allow epoxy to be forced in deeper (ring was also painted ID and OD with thin epoxy and allowed to soak in for a few minutes. Edges of ring facing rear are beveled slightly to deal with harden epoxy from the previous fins attached, this little change required corrective actions to make it work. The three holes are if I decide later on that I need to go back and add foam for any reason (not likely) than by cutting out the forward CR which is lots easier than the lower one, I can pour it into the lower section of the fin can.
GLRNuclearSledgehammer29.jpg

Top view of ring installed.

GLRNuclearSledgehammer30.jpg

Mixed 72 grams of US Composites 150 Structural Epoxy with milled FG and cabosil/fumed silica to a consistency of peanut butter and applied it pretty thick to the outside of the motor tube and the inside of the airframe, and some thick mounds on the forward edges of the 3 fin tabs. Fitting the CR took about an hour during the week to make sure it would seat properly against the tabs, it sort of did as the tabs are slightly tapered top to bottom, so the ring is right up against the tabs at the OD and about 1/8" shy on the motor tube side, hence the thick mounds of epoxy as a gap filler. As the view through the wing slot shows the backside of the CR self filleted pretty well (only one tab visible here) on all three tabs and the mmt and as best I can tell the OD as well. The edges of the CR were measured at the wing slots and it has a slight cant of about 1/16" or less from one side to the other which I can live with as everything is well filleted and tight. I was able to use a "craft" stick aka popsical stick to dress up where the tab and tube fillets weren't full formed (there was epoxy in the bevels though). Due to the additional CR it will be necessary to cut an additional slot in the wing tabs.

GLRNuclearSledgehammer31.jpg
 
Started tip to tip on the tail fins today.

Prepped and ready:

GLRNuclearSledgehammer32.jpg

First section, back of rocket, one layer each 10oz FG and 3oz FG and peel ply, US Composites 635 3:1 resin.
GLRNuclearSledgehammer33.jpg

3 hours later after peel ply removed, the big air bubble was totally my fault, as I placed a bag of weight on the fin then decided it wasn't a good idea and when removed it pulled a bubbe in the peel ply. FG plys are fine just going to take a bit of effort to fix.
GLRNuclearSledgehammer34.jpg

Second section prepared and covered this time no stupid moves.
GLRNuclearSledgehammer35.jpg
 
All three fins tip to tip complete and sanded to remove overlap with airframe. Definitely going to be painting this one due to the air bubble in the one fin, but I had planned on that anyways. For the most part all three "bays" look like the picture below. Next up is attaching the wings which will get traditional internal and external fillets at all junctures between airframe and wings.


20190107_201029.jpeg
 
Got the wings on this evening and the first external fillets (small ones using left over epoxy) on. The nomex honeycomb root edges were pre-filled with epoxy to make sure they were fully adhered, then the tab root edges were "double-dipped" to get plenty of epoxy on the initial bonding. As I used the last of my Cab-o-sil and milled FG for the batch of epoxy it will be next week before I can do the full external fillets and the inner fillets. Some people will ask why I didn't use my usual fin pockets, and the answer is that on a gap between airframes this large the pocket would be a pain to make in such a way as to keep the epoxy usage from being excessive/wasteful. The fin pockets work best when there is very limited space to use tools in to create internal fillets, in this air frame they would be two inches deep and would need to be chamfered top and bottom to create the self fillet effect and yet keep epoxy usage within reason. Due to the large gap between motor mount and airframe it will be easier, quicker and use less epoxy to do traditional fillets. Normal fin pockets take me less than 30 minutes to make and fin installation is very quick, fin pockets for this large of gap would take at a minimum an hour to make (probably two hours) and be a pain to align properly, as the forward CR is not pre-installed.

New order of Cab-o-Sil and 1/32" milled FG ordered from Fiberglass Supply today, so I am expecting it early next week and the final fillets and tip to tip of the wings can be done. Tomorrow I will cut the pattern for the tip to tip fabrics.



Fins on and external small radius fillets.
GLRNuclearSledgehammer36.jpg

Next two pictures demonstrate the variance in squeeze out from the double dip technique, top one is most squeeze out and lower is smallest amount. Both have a bead the full length of the tab root edge (at least the visible part, there is about 6" of tab behind the lower centering ring).
GLRNuclearSledgehammer37.jpg

GLRNuclearSledgehammer38.jpg
 
Last edited:
Back
Top