Upscale Hi-Flier Question

[doug_kosty]

I have always loved the look of the Estes Hi-Flier, and since my last one was run over by a car(!), I've decided to do an upscale version. Based on my available components, this will be a 2.6X upscale and should fly acceptably on D,E, and F motors. ( I guess that this straddles the area between LPR and MPR? )

I have also decided to work at NOT overbuilding - I've been making glue bombs, and want to try and be a little more careful and minimize things where possible.

To that end I am considering the fins. These will protrude from the body by 3.5 inches, and I am wondering if papered balsa will be durable enough? I will likely surface mount them, and my only concession to overbuilding will probably be small epoxy fillets - I am getting pretty good at that and like the appearance.


Any comments regarding the fin material selection?

 

[cjl]

Balsa will probably work, but I'd be tempted to use thin ply instead. There's definitely no need for anything like fiberglass or composites (though fiberglassed balsa would also work, and if done right, can come out quite light).

How large will a 2.6x upscale be? That's around 2", right?

 

[doug_kosty]

The body tube will be ~ 1.8 inches in diameter and 23 inches long. That is not including the nosecone.

I am putting in a 24mm engine mount and plan on mostly RMS24/40 motors.

 

[MattieShoes]

I think papered balsa would be plenty strong. I don't know how much strength "epoxy rivets" actually add, but they're a simple low-weight trick for body mounted fins... :confused2:

 

[TheAviator]

You really don't even need to paper the balsa. None of the 24/40 motors really have enough oomph to reach the speed of balsa in this size rocket. For comparison, I have flown a Stormcaster on an E30 with no problems whatsoever, and it is in just about the same size range. It even has the larger span swept fins similar to the Hi-Flier.

 

[shreadvector]

Anyone else experience unstable flights with a C motor in a standard Hi-Flyer on every flight?

In other words, anyone else confirm the fundamental design flaw and instability of this mass produced kit?

We no longer allow them to be flown on C motors at our club launches after witnessing unstable flights and then carefully observing many more models (for proper construction) and flights (to see behavior with A, B and C motors).

And, yes, we've told each and every modeler to contact Estes to report the problem. Several have come back to us and told us that they were told by Customer Serivce that they've "never heard of any problems with the Hi-Flyer".

 

[tbzep]

You really don't even need to paper the balsa. None of the 24/40 motors really have enough oomph to reach the speed of balsa in this size rocket. For comparison, I have flown a Stormcaster on an E30 with no problems whatsoever, and it is in just about the same size range. It even has the larger span swept fins similar to the Hi-Flier.

That's also similar in size to the Big Bertha. I've chad staged them with D12's and seen E15's and E30's in them also. If those big fins hanging out in the breeze can handle it, an ST-18 based Hi-Flier with papered balsa fins can too.

 

[cjl]

24mm?

Balsa's fine - you don't even need to paper it. I was thinking 29mm for some reason.

 

[Queeg500]

Anyone else experience unstable flights with a C motor in a standard Hi-Flyer on every flight?

In other words, anyone else confirm the fundamental design flaw and instability of this mass produced kit?

Yes! I was instantly attracted to the flechette profile of the Hi-Flyer but after two "what the hell was that?" flights I became a fan of the Sizzler which was right next to the Hi-Flyer on the Hobby-Lobby shelf. You should upscale the Siz instead.

 

[cjl]

Just because the standard one is unstable doesn't mean an upscale will be. Since the upscale will not be minimum diameter, I'd guess that its motor will shift the CG less than the one in the standard size hi-flyer will, and it will probably be stable. It's worth swing testing or simulating to make sure, but there's no reason why it shouldn't be a fairly easy design to make stable.

Oh, and although I've never personally owned a Hi-Flyer, I can confirm that I've seen several flights of questionable stability. I have seen fully stable C flights, but I've also seen ones in which the rocket was definitely unstable. I think it's related to how far in the engine block is placed - if it isn't in far enough, the stability is severely compromised (an easy mistake to make, and one which I have made on my own minimum diameter models once or twice). If you just add a bit of clay to the nose, it should fix it though, regardless of the engine block location, and it won't significantly affect performance. For an upscale, I'd actually prefer the Hi-Flyer to a Sizzler - the Sizzler's swept back, pointed fins will cause much bigger problems with snapping fin tips at landing, and will also be worse structurally during flight (which will only be an issue if the rocket is really pushed hard).

 

[powderburner]

Balsa's fine - you don't even need to paper it.

Every bit as important as fin material or adhesive is: get a good fit between the fin root and the local BT.

Also, scuff-sand the BT under the fins to remove that layer of plastic seal material on the outside surface of the cardboard.

As far as adhesive, plain old white or yellow glues will work fine. Glue rivets along the fin root are OK but if they are too much hassle (such as glue protruding inside the BT and interfering with loading the motor) you can skip them. Fillets don't need to be the biggest ones you have ever seen: you can also reinforce fin roots with strips of paper or mesh material glued into the corners (in fact, this technique was used on the first model rocket ever built!) Bare balsa will work fine, but if you are losing sleep over this, using paper-laminated-balsa (or basswood) won't hurt much (yeah it's heavier, but it won't kill you).

 

[dave carver]

I recently purchased 2 tube assortments from SEMROC and ordered a BT70 cone, coupler, and BT70 to 29 mm motor mount to be flown on the E and F loads for the AeroTech 29 40-120. The fins are 3" square fins from 1/8 balsa with a 2x2" 1/16th piece laminated to both sides. I'm in the process of filling the taper with lightweight spackeling. I'm not worried about enough weight in the front, a BT70 balsa cone(at least in the size I got) is pretty heavy plus I'll be using a ring to keep the recovery stuff in the front 1/3rd of the rocket.

 

[The EGE]

Good, good... always good to have a little bigger MMT than you think you need at first.

There's also basswood. It's stronger than balsa, not too much heavier, and you can buy it at most places that carry sheet balsa.

 

[ScrapDaddy]

Basswood is a great idea it has all the charictaristics of balsa plus a little backing, any a little off topic here but what is the exact speed of balsa?

 

[cjl]

Depends on the thickness and the fin shape, as well as the grade of balsa. A stock Fliskits Deuce will shred on D13s for example (I know this from experience), but I've also flown balsa finned rockets much faster than that on F21W motors (the fin shape was much better for high speed though).

 

[ScrapDaddy]

What would be a good estemate for a tengent clipped double delta using 1/8 balsa?

 

[The EGE]

What would be a good estemate for a tengent clipped double delta using 1/8 balsa?

Depends on how well how build it. If you use basic light (A-grade) balsa, have the leading edge perpendicular to the grain, have a poor glue joint, and don't sand or coat them, as low as 300 fps.

If you use darker (C-grade) balsa, have the leading edge with the grain, use a solid glue joint, skin it with paper, and sand it absolutely smooth and an airfoil on the edges... then it's conceivable that that fin could survive speeds up to 1500 fps.

I personally use plywood fins on anything that will fly on an E motor or above, weighs more than 6 ounces, or will go more than 800 fps. The exception is my Svetlana (heavy modified Big Daddy) which has thick, through-the-wall, high-quality balsa fins which I paper-skinned and epoxied.

High-speed survivability is 10% what material you choose, 40% how well you fabricate the fins, and 50% how well you make the glue joint.

 

[ScrapDaddy]

Would epoxy fillets be overkill?

 

[doug_kosty]

Originally I was mostly thinking of papering the fins to help them survive recovery impact. I wasn't even thinking that they had any possibility of shredding. On these smallish engines, I don't expect to hit the speed of balsa - perhaps hit the speed of my construction technique though

 

[cjl]

Would epoxy fillets be overkill?

Definitely. A good strong joint using wood glue (I personally like Titebond III) will be strong enough that the balsa will shred before the joint will. For images proving this, check out my thread on the rocketry forum archive here:

https://www.rocketryforumarchive.com/showthread.php?t=20550

Note that the fin joints are still solid on the "after" shots. Those fins were plain balsa, attached with Titebond III. A critical step to a strong fin attachment on Estes/Flis/Quest/etc style tubing is to sand the area where the fins will be attached with a fairly coarse grit of sandpaper though. You want to make sure that the glue can soak in properly, otherwise it will not get a solid bond and the fin will snap off at the root long before the balsa itself is at all strained.

Also ignore my blathering on in that thread about CF/composites/etc for my next iteration of a deuce for D motors. I was inexperienced at the time, and luckily I regained my sanity prior to the construction of a replacement deuce. I later built one with everything stock except for a single layer of 1/2 ounce fiberglass tip to tip. It has since survived a great many flights on C and D motors, and it barely weighs more than a stock deuce (the glass added something like 1/4 ounce or less). Don't overdo the reinforcements or materials for low powered rockets. They very, very rarely need more than a single layer of extremely light fiberglass, and even that is overkill most of the time.

 

[cjl]

What would be a good estemate for a tengent clipped double delta using 1/8 balsa?

Depends on the size of the fin and the grade of balsa. If you use decent balsa, align the grain correctly, and the fins aren't too big, they should be fine to mach 1 or better.

 

[ScrapDaddy]

Definitely. A good strong joint using wood glue (I personally like Titebond III) will be strong enough that the balsa will shred before the joint will. For images proving this, check out my thread on the rocketry forum archive here:

https://www.rocketryforumarchive.com/showthread.php?t=20550

Note that the fin joints are still solid on the "after" shots. Those fins were plain balsa, attached with Titebond III. A critical step to a strong fin attachment on Estes/Flis/Quest/etc style tubing is to sand the area where the fins will be attached with a fairly coarse grit of sandpaper though. You want to make sure that the glue can soak in properly, otherwise it will not get a solid bond and the fin will snap off at the root long before the balsa itself is at all strained.

Also ignore my blathering on in that thread about CF/composites/etc for my next iteration of a deuce for D motors. I was inexperienced at the time, and luckily I regained my sanity prior to the construction of a replacement deuce. I later built one with everything stock except for a single layer of 1/2 ounce fiberglass tip to tip. It has since survived a great many flights on C and D motors, and it barely weighs more than a stock deuce (the glass added something like 1/4 ounce or less). Don't overdo the reinforcements or materials for low powered rockets. They very, very rarely need more than a single layer of extremely light fiberglass, and even that is overkill most of the time.

woops then I just over built my first machbuster! What's the shred rush on a huge fin like a rectangle say...3X13inches? Standard 1/8 balsa