Aaarghhh!!!!

[Gus]

I wanted a project I could build in a day so I started a Launch Pad Dragonfly which I've had sitting around awhile.

Finished gluing on the aft fins and tabs, went to get something out of the bag, and out falls a fin template from inside the mylar parachute material.

I thought the fin template was what was printed on the instruction sheets, but those pictures are about 25% smaller than the actual templates, so the fins I made and epoxied on are too small. And I put in an E-engine mount instead of the D included in the kit!

I know these launch pad kits are designed with pretty tight stability margins and now I've upscaled the motor and downscaled the fins.

AAARGHHH!!!

I guess I'll just leave off the forward fins and add some nose weight.

Fortunately I have enough spare parts to build one the right way.

 

[rbeckey]

How about cutting the sanded edges of the mounted fins and glueing on extensions? Theoretically, that should be even stonger than a one piece fin.

 

[sandman]

I wanted a project I could build in a day

LOL! looks like you killed THAT idea!

Try just adding onto the leading edge and outer tip with some balsa strips.

Then cover the fin with paper or cardstock to reinforce them a bit and to cover the seams.

You can fix it!

 

[Gus]

Thanks for the suggestions, but I decided to complete it with the forward fins as I already cut them.

The next 2 pictures show how much different it came out compared to the way it was designed, and why adding on to the fins would be more of a pain than it's worth.

I'm going to RockSim it as I built it and see how much weight to add to the nose. Weighs 2.9 oz as built (without motor).

Or maybe I'll just spin test it.

Then, I'm going to wait to fly it until I go up to Sandman's field.

 

[Gus]

Here's a pic of the fin template next to the actual fins.

I'm figuring total surface area is off by about 25%.

 

[rstaff3]

D'oh, this sounds like something I might do. If it were me, I'd sim it, see what nose weight is needed, and then decide if the overall weight fits well with the target motors. If so, I'd add the weight. If it would be underpowered with the added weight, I'd add fin area.

 

[Ryan S.]

it looks better IMHO