Semroc SLS Brighton: A clone build

[kuririn]

Think Big Bertha or Ranger on steroids.


I never purchased the Semroc kit while it was in production. I thought it was overpriced.
But then I saw that it had three interchangeable motor mounts: 4X18mm, 3X24mm, and a 29mm motor mount.
So now it seems reasonable.
This build will be done between painting and decaling my previous builds, which will be prioritized.
So don't expect a speed build.
Purchased the parts from erockets many moons ago, but the decals were out. No biggie, will home print.
Parts:

Laser cut TTW plywood fins.
BTH-80 slotted body tubes
BNC80 Bertha style balsa nose cone.
A ton of centering rings couplers, motor tubes, etc.
24" nylon chute and small parts from my parts stash.
Instructions downloaded from the old Semroc website.
TBC.

 

[GlenP]

a Texas Ranger, perhaps?

Heck, just call it the Chuck Norris.

 

[NOLA_BAR]

Think Big Bertha or Ranger on steroids.
View attachment 420566

I never purchased the Semroc kit while it was in production. I thought it was overpriced.
But then I saw that it had three interchangeable motor mounts: 4X18mm, 3X24mm, and a 29mm motor mount.
So now it seems reasonable.
This build will be done between painting and decaling my previous builds, which will be prioritized.
So don't expect a speed build.
Purchased the parts from erockets many moons ago, but the decals were out. No biggie, will home print.
Parts:
View attachment 420567
Laser cut TTW plywood fins.
BTH-80 slotted body tubes
BNC80 Bertha style balsa nose cone.
A ton of centering rings couplers, motor tubes, etc.
24" nylon chute and small parts from my parts stash.
Instructions downloaded from the old Semroc website.
TBC.

That’s a lot of material! I guess that is why it was a bit pricey as a kit. ERockets has pretty much moved away from the Semroc SLS line of kits and parts.

 

[BABAR]

call it “RMDU”
Rapid Motor Disposal Unit

 

[Buzzard]

I build a SEMROC SLS Brighton years ago and have flown it twice. The first time was with a cluster of three D12-5 motors. The motor mount ejected as the engine hook did not stand up to the ejection charges. Fortunately, someone saw where it fell. I decided to glue to motor mount in instead of leaving it interchangeable. I love the kit and have a spare one.
Interestingly, Carl McLawhorn asked Vern Estes about calling it the SLS Ranger. Vern had preferred that he not do so. Hence it became the Brighton.

Chas

 

[kuririn]

Thanks for the insights, Charles. An SLS Ranger with upscaled decals would have been cool. Maybe I'll do mine that way.

Have to run down to Lowe's this morning and get some non-clogging spray paint cans, running out of some colors. So in lieu of painting and primering my other builds, last night I assembled the "mother" mount.


Instructions say to tack on the fin strips with CA. Then sand the strip edges to match the contour of the main tube. Heed these instructions, this alignment is critical. First dry fitting after sanding one of the fin strips was just a hair offline. Had to break it off and reglue. Once all strips are in alignment then fillet the strips and glue the mother mount into the main tube.


Also assembled the baffle

TBC

 

[kuririn]

Hmmm.....
Wheels are turning.
How about a Boosted Brighton, with interchangeable motor mounts in the booster?

call it “RMDU”
Rapid Motor Disposal Unit

How about a three stage clustered model?
4X18/4X18/4X18mm

 

[kuririn]

Scratch that, too heavy.
How about 3X24/3X24/4X18?

 

[neil_w]

Instructions say to tack on the fin strips with CA. Then sand the strip edges to match the contour of the main tube. Heed these instructions, this alignment is critical. First dry fitting after sanding one of the fin strips was just a hair offline. Had to break it off and reglue. Once all strips are in alignment then fillet the strips and glue the mother mount into the main tube.

I can't tell what's going on there. What exactly are the "fin strips"? Are they glued inside or out? What is their function? It looks to me like the mother mount would just glue into the tube, and then the fins would glue TTW normally. Obviously something else going on there.

 

[kuririn]

Better yet. 3X29/3X24/4X18mm.
I need to start a GoFundMe page.

 

[kuririn]

I can't tell what's going on there. What exactly are the "fin strips"? Are they glued inside or out? What is their function?

Here's a better shot. I haven't glued it in yet cuz I needed to run fillets first.


They line up with the slots in the body tube, and the fin tangs go into both.
Also act as centering rings so no aft centering ring is needed.

 

[neil_w]

Got it. I thought the fin strips were somehow separate from the mother mount. All makes sense now.

 

[sandeja1]

Yea! I am working on a clone of this one myself! Will be following your build as well. I wasn't able to get the slotted tube when I started obtaining parts for mine so I will have to cut the slots myself.

I had heard of the motor retention issue mentioned above and found a possible "solution" at: https://roborocketry.blogspot.com/2009/05/enhanced-motor-retention-for-semroc.html This is what I think I am going to try.

 

[kuririn]

Yea! I am working on a clone of this one myself! Will be following your build as well. I wasn't able to get the slotted tube when I started obtaining parts for mine so I will have to cut the slots myself.

I had heard of the motor retention issue mentioned above and found a possible "solution" at: https://roborocketry.blogspot.com/2009/05/enhanced-motor-retention-for-semroc.html This is what I think I am going to try.

Thanks for the link!
Funny, Blackbeltrocketeer's blog shows the Brighton with one retention hook for the mounts, but my instructions show two. I think two will solve the motor mount blowout issue.

 

[kuririn]

By the way, those of you that have built the later SLS kits with interchangeable mounts will notice that they use a twist lock method of retention rather than dual engine hooks. And plywood centering rings. They seem more robust.
Speaking of plywood, does anyone have an original Brighton kit? Are the centering rings made of plywood? The centering ring set I received from erockets is made of fiber. Instructions mention plywood centering rings. Just wondering.

 

[NOLA_BAR]

I built the SLS Laser-X. The rings were plywood but ejection charges would shatter the forward ring. The plywood was kinda squishy. I just got a second kit so I’ll probably just make it a permanent 29mm.

It does look like the Brighton did have plywood rings.
https://archive.rocketreviews.com/reviews/all/sem_brighton.shtml

 

[kuririn]

It does look like the Brighton did have plywood rings.

Hmmm... I wonder if they switched to fiber in later production runs?
Well, I'm committed now, come hell or high water.

 

[NOLA_BAR]

Hmmm... I wonder if they switched to fiber in later production runs?
Well, I'm committed now, come hell or high water.

It looks like the rings are mounted to couplers, so they should be fine. Maybe add a third retaining hook?

 

[Blast it Tom!]

Very interesting kit & build. I like the interchangeable mount, neat idea if it doesn't become an "RMDS"! But I'm sure Kuririn can handle that. It brings back memories of the last rocket of my childhood, a self-designed 3 "D" clustered beauty - I believe BT-80 from ESTES fits the 3 "D" tubes quite well, from my nearly -50 year old recollections. Had a forward payload bay and a similar nosecone, 4 "double triangle" fins with the CP at the end of the body tube (it was designed on real paper first using CG/CP "moments and centroids" long before personal computers, spreadsheets or OpenRocket, etc.). Sadly, it never got painted or flew, due to upheaval in the home. I never did find out what happened to it.

Back to your regularly scheduled thread. This one may just go on the "must build" list.

 

[BABAR]

Hmmm.....
Wheels are turning.
How about a Boosted Brighton, with interchangeable motor mounts in the booster?

How about a three stage clustered model?
4X18/4X18/4X18mm

I did a Three-Two-One. Three stages
First booster 3x18 mm (one with a nose cone and short delay motor with recovery chute, other two were C6-0)
Second booster 2x 18mm. (Again one nose cone and short delay motor with recovery chute, other was a C6-0)
Sustainer was anA8-3 with a streamer,

Worked well, especially if goal was to use up a bunch of motors in a single launch.

 

[kuririn]

Glued mother mount into the airframe.
Glued and aligned fins into slots.


Assembled the three mounts.



Note: Slight mod for the 29mm mount - installed a screw on retainer and lengthened the motor tube. Stock build doesn't have any motor retention for 29mm, instead you are supposed to do a tape wrap for the motor at the TOP of the motor tube then slide the mount into the airframe. I'd rather not have to do a wrap for each 29mm launch.

Here's a look at how each mount goes into the airframe:

TBC

 

[sandeja1]

What did you do for centering rings for the 3 x 24mm mount?

 

[kuririn]

Here's a look from the other end. One centering ring for this mount comes in the set. Three bt-50 or ST-9 tubes fit snugly inside a BT-70. In fact there are some 3 clustered models that have you glue the motor tubes directly to the airframe. I ran fillets down the back end.
Make sure you keep the skinny outside ring attached on the 3X24 centering ring while assembling. If you cut it off early you will have three crescent shaped pieces to deal with. Much easier to glue as one piece, then cut off the ring after it's done.


PS Keep the triangular piece, you can use it to close the gap between the motor tubes.

 

[kuririn]

I should also mention that the instructions do not include gluing thrust rings ahead of the engine hooks for the 18 and 24 mm tubes. But I will do so just as a good practice.

 

[kuririn]

Last night, glued launch lugs and applied 1st round of fillets.


Instead of tying a knot anchored under the hole in the baffle ring I tied the end of the kevlar leader to one of the baffle tubes and embedded it in glue. Then glued the baffle into the airframe.


Dry fit. Couldn't resist (heh).


TBC

 

[Blast it Tom!]

That really reminds me of the one I mentioned above! It's a big'un! (For LPR, at least...) Beautiful work.

 

[GlenP]

I should also mention that the instructions do not include gluing thrust rings ahead of the engine hooks for the 18 and 24 mm tubes. But I will do so just as a good practice.

Yeah, the engine tube can get stretched out where the motor hook goes through, I like to glue/wrap a cardstock band around the outside of the motor tube just behind the hook slot for a little reinforcement of the ejection charge loads in the other direction. Dr. Zooch kits tend to have this reinforcement band in the instructions.

 

[kuririn]

Applied third and final round of fillets.
Assembled 24" PS II nylon chute and PS II elastic shock cord to long kevlar leader.


Shot of each motor mount in situ


And assembly is done.

Since I have a nearly full can of Magenta paint the scheme will be the same as the pic at the top of this thread.
Update pic after I fill/primer/paint/decal this.
Hopefully in my lifetime.

 

[kuririn]

I just noticed something.


Virtually identical to the SBB.
Slightly longer airframe, and longer pointier nose.

 

[Scott_650]

I just noticed something.

Virtually identical to the SBB.
Slightly longer airframe, and longer pointier nose.

I think the SLS Brighton nose cone is the same shape as the original Ranger/BB cone - circa 1965-6ish. The BB switched to the more rounded cone a few years later. Personally I’ve never cared for the rounder style, the original pointier cone looks better to me. Someday I’ll have to have a Ranger-style cone for my SBB. This is a great build thread - thanks for posting it!