SBR Fusion 4" build weight?

[mach0_001]

For those who have built the SBR Fusion 4", how much did the finished rocket weigh? Would it be difficult to keep the weight under 1500g ready to fly with a G75 or similar motor? I'm shopping for my first HPR kit and would like something that I could test fly a few times at the local (non waivered) club range before the certification flight.

Does anyone have an openrocket or rocksim file for the Fusion 4"?

This rocket uses a different style AV bay than any of the other rockets that I am looking at. Instead of heavy 1/4-20 all-thread, the halves of the AV bay are held together by plastic rivets. It seems like a clever design, and saves a lot of weight. Has anyone ever have trouble with the AV bay getting ripped apart during deployment? I really like the design, but I'm wondering why more rockets do not use this style of AV bay.


Thank you!

 

[MarsLander]

Send a message to Scott at SBR, he will send you the file…

 

[mach0_001]

The Fusion 3" is really what I want, but the Fusion 4" comes with a complete kit, and is currently the only thing in stock at the SBR store. I messaged them on FB to ask about the openrocket model and whether the 3" kit will come back in stock.

 

[mikec]

I haven't built this kit or ever seen one, but FWIW I took a quick peek at the Youtube assembly videos and this kit appears to have the same sort of coupler arrangement that some have complained about with the larger 5.5" kit. It seems to have a very small length of coupler that gets riveted and this is a potential failure point. Having a caliber of length for a coupler-tube joint is best practice.

Not having an avbay at all would make it much more likely you'd stay under the 1500 gram limit. There are other 4" kits that would be more likely to be this light.

 

[ShadowSpire48]

I haven't built this kit or ever seen one, but FWIW I took a quick peek at the Youtube assembly videos and this kit appears to have the same sort of coupler arrangement that some have complained about with the larger 5.5" kit. It seems to have a very small length of coupler that gets riveted and this is a potential failure point. Having a caliber of length for a coupler-tube joint is best practice.

Not having an avbay at all would make it much more likely you'd stay under the 1500 gram limit. There are other 4" kits that would be more likely to be this light.

I believe there are a few videos on Youtube regarding the 5.5" one folding under power because of the coupler being too short. I was always told a coupler length on each side should be the body diameter so a 4" rocket should have a coupler length of 8" (4" on each side) but I think once you get past 4" tubing, it should be longer for safety.

 

[Jim P.]

I have built and flown the SBR 4" Fusion using the stock coupler-based altimeter bay. By stock, I mean I followed all of the steps in Scott Binder's various build videos, including epoxying the inside of the couplers and CAing the rivet and toothpick holes. Mine weighs a little under 5 lbs when ready to fly without the motor. I hope that helps.

 

[K'Tesh]

Send a message to Scott at SBR, he will send you the file…

I'm glad to hear he's sharing that. I had fun making it. I promised however, not to share it w/o his permission.

 

[K'Tesh]

Hey! I contacted Scott and he OK'd me sharing the files I made for him...


This file has been updated to the latest version of OR, eliminating the air fin for the decal, and adding the proper rail buttons.

 

[mach0_001]

Thanks Everyone. I did message Scott and he said that the Fusion 3" kit will be back in stock soon. I think that may be a better fit for what I am looking for.