Estes Impulse down scale. Calling this one "Half Impulse"

The Rocketry Forum

Help Support The Rocketry Forum:

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


Well-Known Member
TRF Supporter
Jul 16, 2019
Reaction score
Chicago Burbs.
With the Laser upscale completed I decided that I wanted to go in the other direction. I recently built a Quest Magnum Payloader that was designed with a cluster mount but I decided at the last minute not to use it and instead install a single 24mm mount. This decision left me with an assembled, unused 18mm, two motor cluster mount looking for a home. After kicking around various ideas I finally decided how I wanted to use it.

Some of you might be familiar with the old Estes Pro Series Impulse from the 90's. It was a 2.5" kit with a twin 24mm cluster. I always like the clean simple lines so I figured I'd do something different and do a down scale.

Using my unbuilt Impulse templates and measurements, I settled on doing a BT60 build. What you see below is the parts that will be used for this project.

- 18mm Cluster mount left over from the Magnum build. I have added additional centering rings to bring this up to BT60 size.
- BT60 nose cone. This came from Apogee a few years back but I can't recall the exact part number. When scaled it's within .25" of the actual Estes Nose Cone.
- 6' of 300# Kevlar for the Shock Cord.
- BT60 Body Tube cut to 16.25" Exact upscale should have been 16.17 but this is close enough.
- Balsa fins papered then sealed with T-88 Epoxy. For reference, the fins on the stock full scale Impulse as the exact same shape as the Red Flare / Maxi Alpha III with one exception. The Impulse adds a 1/8" hard wood strip around each edge for strength.


Starting with the motor mount. Here you can see that I added a plywood BT60 upper ring to the Quest mount to make it fit the larger tube. I used an off the shelf BT50/60 centering ring then opened up the holes for the cluster for ejection. The Kevlar has a knot in one end that will be inserted into a hole in the upper ring and pulled through.


With the Kevlar pulled through the upper ring, it was glued in place and a short piece of heat shrink was applied to the lower section to help with heat protection.


The motor mount was then inserted into the tube. Care was taken to ensure that the motor mount lined up perfectly with the fin slot. The idea is that two of the fins with the longer tabs will sit in the valley between the motor tubes. This was glued in with TBII and allowed to cure.


Next it was time to attach the first fin. The fin tab needed to be sanded a bit to get a perfect fin. Once adjusted the fin was attached with T-88 epoxy.


Working on fins over the next couple of days.
Last edited:
Did the external fillets Weds night and gave them a full day to cure. After that It was time for primer and filler. I shot on two coats of SEM high build and let that cure.

I was still seeing some spirals and a few uneven areas in the fillets so the entire rocket was coated in a very thin coat of DAP brand wood filler. This stuff sands so easily that I don't mine coating the entire rocket it in. I'm going to let this dry then sand with 400 grit.

Paint was ordered but I haven't received a tracking number on it just yet so no telling when it will arrive. I will be doing a base coat of white primer before paint.

The paint for this one finally showed up Saturday morning so I was able to get everything painted and get some vinyl cut and applied. Since my last post I shot the Impulse with one coat of SEM white primer. The main body was then painted with two coats of Krylon Hot Pink. This was the closest I could find to the catalog color. The pink was left to dry for a couple of days before I masked off the fins, a stripe on the main body and the nose cone and shot them with a couple of coats of Krylon Foil Red. Finally, the detail on the fins was applied with Tamiya acrylic black.

I like the paint job on that particular Impulse. Or should I say on that specific Impulse! :cool:
Cool, I've definitely never seen a downscale of this one!
Do you freehand the masking tape on the nose or is there a technique for getting that curve symmetrical?