Rocketry Planet

Those tongue and groove fin edges are a fine idea. Well done, GLR.

Actually, having seen the tongue and groove fins, I would say the idea is good, but the quality is marginal. Not only were the fins not completely grooved, but the insert tabs were made of MDF, which is heavy and not durable. They would have done better if they used basswood, or even dowels for that matter. The concept, however, is good.

Harold

Can someone clarify for me?

The body tubing is all prefiberglassed - correct? But the fins are not. These fins require fiberglassing don't they? No criticism - just curious to confirm what I think is the case. Even if they do - fiberglassing only the fins and wings would be a lot less work than doing the entire rocket.

But if this is the case, I assume that a tip to tip job is not the best choice. Since the tube is already fiberglassed and cured I assume that the best bond you can get is mechanical and not chemical. Am I off base here?

From the appearance, it looks like the fins are the honeycomb with g10 facing. When I've used this material, I CA'ed the basswood edges to it, and tapered those. Then to make sure all was gonna stay put, I bagged the fins with FG. That added some additional stiffness, but the CF semi span-to-semispan sealed the deal. Those fins are on for life.

You're right about the best bond being chemical and so it's better if the tube is still green, but even if fully cured, the mechanical bond over that large a surface area pretty much insures the fins from ever coming off.

The fins are a composite. The advertisement calls it "Fly-Lite". I don't know if it is the same as this stuff that GL sells:

An inner layer of NOMEX(TM) honeycomb,
sandwiched between either thin G-10
Fiberglass or Carbon Fiber!

Steve,

That would be my guess, and maybe why the grooving was incomplete?

That would be my speculation. You've used this stuff, right? It looks great. How did you like it? Did you have any concerns about it?

GLR response:

a. Thank you for your questions, Harold, please let me know who the customer is who has "marginal quality" in his kit so I can fix it as I have not heard from anyone who has purchased kits who utilize this process. My cell number is 620-727-0045.

b. on page twenty-one (of the fifty plus page instruction book) it states " It is possible that some additional honeycomb material found in the fins may need to be removed allowing complete insertion of the edging tongue up to the point where the edging regains full thickness". And all that is necessary to do that is to simply take a hobby knife to remove any excess honeycomb. If the customer is having problems, I am always here to fix the problem and have not heard from any.

c. I chose MDF edging for several reasons:
1. availability
2. ease of machining
3. MDF edging produces the "shape" that will be strengthened in later steps (page twenty-five of the instruction book) via tip to tip fin reinforcement, a common method I chose for this kit where an easily shape-able substrate is covered by composite reinforcement, exactly like the fin material itself is made by putting composite reinforcement over a honeycomb core (and this excess stuff is purchased from manufacturer who build commercial airplanes, if this method is good enough for them, it's good enough for me).
4. Of course it is possible to get a "ding" in the fins or break something, what cannot get damaged during a flight? But with many Talon6's in service, especially in Europe and a customer in the United States with over twenty flight on his kit, this fin construction concept is solid, reliable and lightweight. If you don't like it, change it! It's your kit, knock yourself out!

d. The airframe is our DynaWind method with two wraps of ten ounce fiberglass cloth and Aeropoxy laminating resin. The fins are made from 1/4" nomex honeycomb with covering layers of fiberglass skins. This is the exact material utilized by commercial airplane manufacturers

e. I highly recommend tip-to-tip fin reinforcement to strengthen the fin to body tube joints and edging as referred to in point "c.3" above. And yes this would be a mechanical bond, not chemical. This method is more than suitable for the Nuclear Sledgehammer build and is exactly the same method of construction that has been used by Talon 6 flyers for years now (and I flew the first one for my Level 3 in March of 2001, successfully first time out of the gate)

Folks who buy a Nuclear Sledgehammer are buying a sport kit that is not the usual "three fins and a nosecone" but something that grabs attention with unique features. It is not made for 100,000 foot flights or to go mach 40. It is a sport kit made for the customer to enjoy building and to enjoy showing and flying. If there are any further questions, I can be reached at 620-727-0045, and I thank you for your thoughts.

After using it, I'll say this: It will be a cold day in hell before I ever use straight G10 in any performance oriented rocket again. It cuts very easily, basswood sticks as described, I'm guessing 2/3'rds as stiff as G10 at about 1/3 the weight. I should send some samples to Doc and he could get real numbers.

This was a very good response. It answers all of the questions I had.