Arapahoe fin layout

[foose4string]

I looked forward to having Thrustline get back in the game and re-issue the Arapahoe, and for a time, it looked like a good possibility. But, it appears that Thrustline is gone for good, and so I began acquiring parts to clone this great design. The nose cone and tail cone were purchased from BMS at NARAM this summer. The original Rocksim file was submitted to EMRR some time ago which includes the fin pattern.

I want to make efficient use of my balsa fin stock and I am having a hard time figuring out how to lay out the fins. Seems like I am getting a lot of wasted balsa when I do it. I know the main fins are split into two sections and glued together to ensure good grain orientation and strength. This was determined after seeing build pics on EMRR. The strakes could probably be done in two pieces also. Does anyone have the instructions, fin layout diagram, or suggestions on how to arrange them? I'm a using 3/32 balsa X 4" sheet and I will eventually laminate the fins once they are cut out.

 

[roadkill]

I would cut the front half of fins with grain
parallel to most of the leading edge and the
rear half with grain parallel to trailing edge.

You'll lose some wasted balsa but gain a lot of strength...

I did that with my Colonial Vipers and they can really
take a beating...

 

[brianc]

Does anyone have the instructions, fin layout diagram, or suggestions on how to arrange them?

I found my original destructions, but John photocopied them for distribution.
The picture with the balsa layout is much too dark to make out. ;(

IIRC, I just played around with the fin stencils until the pattern fell
into place... (the grain direction is as Sue mentioned).

The strakes are actually three pieces each- a single long piece and two
sloped sections fore & aft.

Good luck with your build!!

 

[tonypv]

Craig,

I'm a little late but here is a pic of the fin patterns.
I have the instructions, if you like I can scan them for you.

 

[foose4string]

Thanks for the replies. Tony, I have the fin pattern from the Rocksim file. I've already cut an laminated the fins. I oriented the grain and the split in roughly the same way as you've shown. I thought maybe there was a diagram that showed how it's all laid out on the balsa sheet. Were the 1/4" strakes already stripped on the kit version?

 

[tonypv]

Thanks for the replies. Tony, I have the fin pattern from the Rocksim file. I've already cut an laminated the fins. I oriented the grain and the split in roughly the same way as you've shown. I thought maybe there was a diagram that showed how it's all laid out on the balsa sheet. Were the 1/4" strakes already stripped on the kit version?

Craig,

The kit came with three balsa strips 3/32"x1/4"x16" for the strakes. There was a template for each end, each end has a different angle, but I can't find the ones I had.
There is no fin cutting lay out diagram in the instructions.

 

[K'Tesh]

Any chance someone has a version of this pattern with a scale for convenient printing/scaling?

Thanks!
Jim

 

[Gary Byrum]

Here's my layout pattern. I tried a lot of configs to avoid as much waste as I could, but the Arapahoe fins are such, that a lot of balsa does get used. My diagram shows I had to use a 4" x 2' long piece. The strakes btw, are drawn as a complete shape. No templates for each end. The line down the center of them is a half way point that enabled me to print the whole strake in two pieces on a 8.5" x 11" sheet of card stock. I just taped them together before I traced the pattern on to the balsa.

 

[Pepe Le Pew]

Hi Craig, In the past 4 months , I have built and flown a few Arapahoe clones. Unless you are looking to emulate every part as it came with the kit, you can change the layout of the fin on the balsa. I traced the pattern that Tony V put up in the previous post, cut the two pieces out and glued them to a piece of phenolic. This would be my pattern for many sets of fins. Then, I set the sheet of balsa in such a way that the grain runs down the leading edge of the fin. In order to get the whole fin, I cut a piece of balsa and placed it on the bottom end of where the fin pattern is. The fins are plenty strong this way and if you are diligent with your sand paper, you will eliminate any possibility for flutter that would kill your rocket.The nose cone I use come from the Estes PNC 60A bag and one cone is used for the boattail. The ARAPAHOE text is done in "earth" font if you don't have it yet. If you can, place some pics of the build as you go, this is a great little bird enjoy your build!

Joser

 

[K'Tesh]

1) I love your solution to the fin layout... I'm going to use that idea (but I'm adding fin tabs).

2) the PNC-60A kit. D'oh! Why didn't I think of that earlier? They come in pairs, are easy to sand (compared to balsa), and are much more available than the PNC-60RL or PNC-60AH I was thinking of using for the boat tail.

 

[Cl(VII)]

Everybody needs one!

 

[Pepe Le Pew]

Fin tabs.... great idea! I will be making some on the next Arapahoe!!!
Sharing ideas makes us all better builders, flyers and grows our hobby! Keep 'em coming!
Joser

 

[K'Tesh]

I'm curious... where did you mount the LL or rail buttons? I'm tempted to apply them (two lugs) to the strake opposite of the fin w/the different color.

As for fin tabs, I'm planning on two for each strake, and two for each fin. With a fin alignment guide this should guarantee that the fins are on straight and true. As for cutting the slots in the boat tail, I'm planning on using the same method I used for my Velociraptor downscale.

Uh oh... hmmm I wonder if it's possible to build a two stage version??? Hmmm... (Definitely not a good idea...)

 

[Pepe Le Pew]

The LL go right on the strake just as you have mentioned.
Fin tabs ...great idea!!!!
Keep building!!!!
I just built another Vagaboonie because it is raining here in central Florida and couldn't go flying!

 

[bradycros]

Any chance someone has a version of this pattern with a scale for convenient printing/scaling?

Thanks!
Jim

The Sandman offers water slide decals along with card stock prints of the fins and strakes for $8.

Balsa Machining offers the nose cone and boat tail (their shapes are a bit different) for a BT-60 V-2, which is what is used on the Arapahoe.

$8 bucks ain't to much to pony up and get what you want!

 

[K'Tesh]

Good to know.

Thanks!

 

[rocketron1948]

When i ordered Arapahoe-E decals from Excelisior they also included a fin pattern and plans.

Rocketron

 

[Marc_G]

Sorry to necropost, but since K'Tesh did a "5 year necropost" I figure a 5 month one isn't so bad.

I just wanted to say thanks to all the contributors in this thread. It seems I've been bitten by the Araphahoe E bug and I'll be making some in various scales this year. This thread has been helpful. Thanks!