Love kits with pre-slotted body tubes and through the wall fins….

[artgsc]

All my favorite rocket builds have been kits that come with pre-slotted body tubes and through the wall fin construction. My first build of this type was an Estes Argent and I thought “hey this is great!” My question is why don’t smaller rocket kits ever use through the wall fins? I realize they aren’t “necessary” in many applications but I still would prefer if given the choice. For example Apogee just announced their new MPR “Quick Draw’” kit but without a pre-slotted body tube and through the wall fins I am just not interested….

 

[Hobie1dog]

most of them feel that there is no need for them, especially with low power kits, and it also cost them more, so they lose profit.

 

[kuririn]

My question is why don’t smaller rocket kits ever use through the wall fins? I realize they aren’t “necessary” in many applications but I still would prefer if given the choice. For example Apogee just announced their new MPR “Quick Draw’” kit but without a pre-slotted body tube and through the wall fins I am just not interested….

There are a few that do have slotted tubes for TTW fins, but definitely just a handful.
For the Quick Draw TTW fins are a no go due to the interchangeable motor mounts.
Edit: You could make TTW fins with interchangeable mounts like Semroc did but it would make the building process much harder due to tighter tolerances and the fin roots would not be secured to the motor tubes so no advantage there.

 

[artgsc]

Good point about the Apogee "Quick Draw" and its interchangeable motor mounts. I should have realized that!

 

[lakeroadster]

All my favorite rocket builds have been kits that come with pre-slotted body tubes and through the wall fin construction. My first build of this type was an Estes Argent and I thought “hey this is great!” My question is why don’t smaller rocket kits ever use through the wall fins? I realize they aren’t “necessary” in many applications but I still would prefer if given the choice. For example Apogee just announced their new MPR “Quick Draw’” kit but without a pre-slotted body tube and through the wall fins I am just not interested….

You could always modify the std kit and convert it to TTW. I'm a big fan of through the wall and home made balsa / basswood plywood fins... regardless of the rockets size. Stronger Be Betta.

 

[Scott_650]

You could always modify the std kit and convert it to TTW. I'm a big fan of through the wall and home made balsa / basswood plywood fins... regardless of the rockets size. Stronger Be Betta.

And you don’t necessarily need to make new fins - most kits are “over-finned” (except for some scale and near scale kits - like models of the Patriot missile) so trimming the root edge to provide a TTW tab can be done with the fins in the kit. You might not have enough material to allow gluing to the motor tube but typically there’s plenty to do TTW construction. Cutting fin slots is a fairly straightforward skill to learn, print out some cutting guides from https://www.payloadbay.com/page-Tools.html and practice on scrap tubes.

As always, when you do mods to standard kits, a sim file and/or swing test is a good idea.

 

[John Brohm]

When I built my clone of the Estes #0817 AERO-HI I opted for TTW fins, as it permitted me to finish the components separately.

 

[lakeroadster]

And you don’t necessarily need to make new fins - most kits are “over-finned” (except for some scale and near scale kits - like models of the Patriot missile) so trimming the root edge to provide a TTW tab can be done with the fins in the kit. You might not have enough material to allow gluing to the motor tube but typically there’s plenty to do TTW construction. Cutting fin slots is a fairly straightforward skill to learn, print out some cutting guides from https://www.payloadbay.com/page-Tools.html and practice on scrap tubes.

As always, when you do mods to standard kits, a sim file and/or swing test is a good idea.

But if your going to the trouble of making it TTW.. it seems like going to plywood is the logical thing to do.

A short piece of aluminum angle is what I use to cut the TTW slots... it's a @neil_w technique... easy peazy.

 

[OC-Patrick]

When I built my clone of the Estes #0817 AERO-HI I opted for TTW fins, as it permitted me to finish the components separately.

John - outstanding work on the fin flanges and rivet details! how did you do that?

 

[John Brohm]

With some Styrene strip and some faux bolt heads. Staying with the thread topic, going with body tube slots and TTW fins set up the situation for that detail.

 

[tjkopena]

My question is why don’t smaller rocket kits ever use through the wall fins?

Not gonna get much smaller than this...

 

[Scott_650]

Not gonna get much smaller than this...

View attachment 556915

One consumer’s opinion: one of the nicest kits I’ve built - I built two - just because it’s small doesn’t take anything away from how well thought out it is and how high quality the parts are. And the TTW fin slots make attaching the fins possible (for me) without a magnifying device. Plus it flies straight and true to a surprising and satisfying apogee. I’ve even had the streamers deploy on the majority of flights.

 

[Chris541]

All my favorite rocket builds have been kits that come with pre-slotted body tubes and through the wall fin construction. My first build of this type was an Estes Argent and I thought “hey this is great!” My question is why don’t smaller rocket kits ever use through the wall fins? I realize they aren’t “necessary” in many applications but I still would prefer if given the choice. For example Apogee just announced their new MPR “Quick Draw’” kit but without a pre-slotted body tube and through the wall fins I am just not interested….

LOC Precision has 4 or 5 smaller 1" diameter rockets that all use ttw fin construction

 

[Chris541]

LOC Precision has 4 or 5 smaller 1" diameter rockets that all use ttw fin construction

Not to mention the goblin and other estes kit that have ttw fins and many upgrade kits that have this option

 

[BEC]

The Estes Goblin in its original form or the more recent re-release (and the Semroc clone of same) do not have TTW fins. That is one model, flown as designed, that sure needs 'em....

 

[Chris541]

The Estes Goblin in its original form or the more recent re-release (and the Semroc clone of same) do not have TTW fins. That is one model, flown as designed, that sure needs 'em....

But the ttw fin kits ,even for the goblin, are easily bought.

 

[Scott_650]

Not to mention the goblin…that have ttw fins

No TTW fins on the Goblin - it’s almost a rite of passage for membership in Team Goblin to reattach a popped fin at the launch site with CA so you can fly again that day…can’t let Team DRM win you know - danged oversized fancy parachute…

 

[BigMacDaddy]

I like to use TTW fins even if I need to slot my own body tube. It makes it easier to get the fins straight.

As I think about this I am also doing lots of rockets with relatively large wings / fins, angled wings, boat tails that are notched for fins, etc... so this might be why I got in the habit of slotting body tubes.

I also started designing internal supports for some models with large fins / wings (e.g., notched centering rings that fin tabs fit inside of) to give extra stability to fins without the need to glue tabs to motor tube. They work really well and give amazing rigidity to fins.

I think the first kit I did the internal fin tab support centering ring was on was the Bomarc but have also done it on the A-10 and the R1 Rheintochter.

 

[Gramparocket]

All my favorite rocket builds have been kits that come with pre-slotted body tubes and through the wall fin construction. My first build of this type was an Estes Argent and I thought “hey this is great!” My question is why don’t smaller rocket kits ever use through the wall fins? I realize they aren’t “necessary” in many applications but I still would prefer if given the choice. For example Apogee just announced their new MPR “Quick Draw’” kit but without a pre-slotted body tube and through the wall fins I am just not interested….

That is because Quick Draw has an interchangeable motor mounts. It come with a 29mmt and a cluster of 3 24mmt

 

[Gramparocket]

Oops sorry I didn't read though the post

 

[Paul Howard]

"Discount Rocketry US" makes most if not All of their rocket kits with through-the-wall fins. I've built 2 and have one still in the package waiting to be built - they're good kits. Unfortunately, the availability seems to come and go with whatever their priority is since I think rockets are not their "day jobs". Anyhow, you might want to check out their website.

 

[user 35280]

But the ttw fin kits ,even for the goblin, are easily bought.

https://www.launchlabrocketry.com/shop/p/vanderburngoblinupgradekit

 

[Grog6]

BMS sells the tubes with slots, and the ttw plywood fins, laser cut. Nice stuff!

 

[Alan15578]

Slots compromise the integrity of the tube.

 

[pdooley]

BMS sells the tubes with slots, and the ttw plywood fins, laser cut. Nice stuff!

how do they know where the slots should be? if the slots are cut long to accommodate various fin positions that would compromise tube strength, or at best make for more work closing them up.

 

[teepot]

The BMS 3" School Rocket uses TTW and had Plywood fins. I do TTW on everything unless it's a MD. I use my Dremel with a cut off wheel to cut fin slots. It is very quick and easy. Slots for 4 fins in 2 minutes or less.

 

[lakeroadster]

how do they know where the slots should be? if the slots are cut long to accommodate various fin positions that would compromise tube strength, or at best make for more work closing them up.

The slots are located for specific kits, or end user specified.

Attaching the fins to the inner tube and the outer tube makes the fin can final assembly so much stronger that any loss in the outer tube strength, due to slotting the outer tube, is negligible.

 

[pdooley]

no doubt thru wall is stronger. but how do you deal with broken fins?

 

[lakeroadster]

no doubt thru wall is stronger. but how do you deal with broken fins?

Chances are if the fin is busted, the rest of the rocket is damaged beyond repair.

A TTW plywood finned rocket fin can is a strong design...

 

[bad_idea]

no doubt thru wall is stronger. but how do you deal with broken fins?

Depends where they are broken. If broken internally, you can go through the tube wall to replace it and patch the tube up later. (There are probably other ways too.) If externally, you can epoxy the fin back together then fiberglass both sides of it.