Build Thread - Seraphim - Level 3 Certification Scratch Build

The Rocketry Forum

Help Support The Rocketry Forum:

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
My level 3 certification rocket is a 14' tall, 6" diameter, 75mm motor mount scratch build dubbed the "Seraphim."

I have the blue tubes and centering rings in and have begun processing the tubes by sealing them with sanding sealer, and beginning to build up the motor mount and avionics bay. Like with my prototype in another build thread, the holes in the centering rings are for threaded rod reinforcement.

I do not have the fins and nose yet so there is only so far I can go for now. I am hoping to order the fins and nose by late July.

20210703_144636.jpg


20210703_145046.jpg
 

Theory

Well-Known Member
Joined
Nov 30, 2018
Messages
1,003
Reaction score
772
good deal! 14' will make for an impressive bird.

can you school me on blue tube and sanding sealer? i have seen people on here using it and know that the manufacturer recommends it, but what does it actually do? cant see it adding any strength, and if anything would likely prohibit epoxy from "wicking" into the air-frame fibers.

i have never used blue tube, however i do find it intreguing. save for the tube spirals... higher strength than cardboard, however, not as heavy as fiberglass.
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
can you school me on blue tube and sanding sealer? i have seen people on here using it and know that the manufacturer recommends it, but what does it actually do? cant see it adding any strength, and if anything would likely prohibit epoxy from "wicking" into the air-frame fibers.
Blue tube's biggest weakness is its bad tendency to absorb water, which causes it to warp. Sealing all the tubes with an oil-based sanding sealer mitigates that problem.

I also asked Dave Ebersole (proprietor of Always Ready Rocketry and supplier of blue tube) about whether sealing it before assembling would inhibit epoxy bonding, and he said it didn't matter as long as you sand your mating surfaces, which we should all be doing anyway.

The spiral groove is a downside, but blue tube doesn't shatter on a hard landing like phenolic and doesn't need to be glassed to go Mach. It also costs about the same as phenolic and won't break the bank like fiberglass can. I really have grown to like it.
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
Looking forward to this awesome build - Flying at MDRA?
Yes. The goal is to fly a shakedown flight on a 75mm full K late this year, a full-up dress rehearsal on an L early next year, and the certification flight on an M1297W at Red Glare 2022, all at MDRA's Higgs Farm, though there is a chance the shakedown flight could take place at the Central Sod Farm in October. It depends on how the build and getting my hands on the motors works out.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 10, 2015
Messages
520
Reaction score
308
Location
Denver, Colorado, USA
My level 3 certification rocket is a 14' tall, 6" diameter, 75mm motor mount scratch build dubbed the "Seraphim."

I have the blue tubes and centering rings in and have begun processing the tubes by sealing them with sanding sealer, and beginning to build up the motor mount and avionics bay. Like with my prototype in another build thread, the holes in the centering rings are for threaded rod reinforcement.

I do not have the fins and nose yet so there is only so far I can go for now. I am hoping to order the fins and nose by late July.

View attachment 471334

View attachment 471335
Are those, uh, "centering rings"?
 

Theory

Well-Known Member
Joined
Nov 30, 2018
Messages
1,003
Reaction score
772
Worth the wait. PML cut the fins for my last project and did an excellent job.

no reason to rush quality work
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
Worth the wait. PML cut the fins for my last project and did an excellent job.

no reason to rush quality work
Agreed, I've had PML make fins for two past projects, and when those two rockets were wrecked, those fins were among the parts in good enough shape to be reused in two new projects.
 

RobertH3

No need to buy stands after a launch day!
TRF Supporter
Joined
Apr 18, 2020
Messages
245
Reaction score
271
Location
Central Indiana
Sounds and looks cool - you can do a cluster version after you get level 3 and call it "Nephilim!"

Cheers / Robert
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
Another update... just placed an order with Ted at @Onebadhawk for the harnesses, drogue parachute, nomex blankets, and recovery attachment hardware. I'm going to need a few more odds and ends still, but I think the only major purchase left is going to be the main parachute, which is going to wait until the rest of the rocket is built and I have the final weight that's going under it to ensure I pick the right size.

Edit: Okay, I also need to get the motor reloads. I already have the 75/5120 case at least.
 

Frederocket

Well-Known Member
TRF Supporter
Joined
Jul 31, 2011
Messages
473
Reaction score
103
Location
Maryland
Blue tube's biggest weakness is its bad tendency to absorb water, which causes it to warp. Sealing all the tubes with an oil-based sanding sealer mitigates that problem.

I also asked Dave Ebersole (proprietor of Always Ready Rocketry and supplier of blue tube) about whether sealing it before assembling would inhibit epoxy bonding, and he said it didn't matter as long as you sand your mating surfaces, which we should all be doing anyway.

The spiral groove is a downside, but blue tube doesn't shatter on a hard landing like phenolic and doesn't need to be glassed to go Mach. It also costs about the same as phenolic and won't break the bank like fiberglass can. I really have grown to like it.
The problem with oil based sealer is the extended cure time after application. Normally, it takes 30 plus days for oil based paint/sealer to fully cure. If the sealer is not fully cured, epoxy will not adequately mechanically bond to the sealed tube. I suggest, before starting construction assembly, you do a glue strength test with scrap wood or better yet, use scrap blue tube and wood that has been sealed with the oil based sealer you used. Regardless, you will need to remove the sealer at the adhesion point for each glue joint, (centering ring to tube, fin to tube and tube to tube), to insure a good epoxy mechanical bond. You have Dave's and my email. Please let us know how you proceed.
 
Last edited:

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
I just got a shipping notice with a tracking number from PML for the nose and fins much earlier than expected!

After the scramble to complete the Phoenix though, I'm probably still going to take a break from HPR building for a little while after this week, and resume this build in early September.
 

Theory

Well-Known Member
Joined
Nov 30, 2018
Messages
1,003
Reaction score
772
I hear ya on the break.

good idea to step away from even our favorite activities for a while
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
I just ordered the Aerotech 75mm RAS to use for the K1000T and L1256SW shakedown flights from our good friends at Wildman Rocketry. I'll be getting back underway on this build this weekend with the goal of motor mount installation by Labor Day.
 

Antares JS

Professional Amateur
Joined
Mar 5, 2020
Messages
1,373
Reaction score
1,797
Location
Eastern Shore, VA
Due to various personal circumstances, my start was delayed, but this morning, I have measured and marked out the locations of all the parts on the motor mount and epoxied the middle centering ring.

20210919_115328.jpg


20210919_122525.jpg
 
Top