Estes large V-2 fins

[Flash]

I have heard of some filling these fins with expandable foam to firm them up. Could someone give me a recommendation if I should use Expandable foam and if so what type? If not, then what do you recommend?

 

[rbeckey]

I mix 20 min epoxy with an equal amount of Sig microballoon filler, put it in one half of the fin, glued and taped it, then turned it over to let the epoxyflow into the other half. I did't try to fill the whole thing, mostly the root edge. It doesn't take much to fill the thin space between the skins.

 

[jpasqual]

I was reading that the you can put the two fin halves together and leaving a tiny hole in the root edge - fill the fin with expandable foam - the kind you can buy at the hardware store. To make sure the whole fin is filled - put the fin against a bright light to see which spots are missing - good luck

 

[Vance in AK]

When you fill with the expanding foam aren't you taking a chance on overfilling & cracking the fins as the stuff expands? I've never tried it in an application like this, but have used it in construction & seen over zelous filling move things that were nailed, door frames coming to mind.
A window installer I once worked with used a "non expanding" foam around window frames for that purpose. Was the same after it cured, looked the same, and was in the same type of pressurised can with a nozzle, but did not have the expanding quality. I would think it would work great for this application.
I'm curious also as I'm going to be starting on my 4" V2 soon.

 

[Darian Rachal]

I dispensed with the vacuum formed fins altogether & traced them out on 1/4" balsa. Maybe I just do not have the patience to work with that type plastic, but I did the same thing on an Honest John kit. I know all the detail is not there, nor the exact shape when using balsa. My main concern right now is whether the balsa will stay attached to the plastic tail cone. I roughed up the joints well, drilled rivet holes, & used 30 minute epoxy.
They seem to be secure, but unfortunately I've not had a chance to fly it yet.

 

[eugenefl]

On the same subject of "plastic fin" units, I have an Honest John that has been sitting on my desk unbuilt for about 2 years now. 3 of the 4 fins have been assembled and glued to the tailcone. The problem here is that they are flexible/bendable and tend to separate at the seams with an extremely light twist. I don't want to experience a fin popping off or bending causing paint to flake off. I want a durable bird or something I don't have to refurbish because the components are flimsy.

Bottom line - I really want to ditch the plastic fins altogether and make some balsa or ply. Should I jump ship or reinforce them somehow?

My personal opinion - I really dislike these kits with 2 part plastic fins.

 

[jpasqual]

Go to this site - this might help figure out what you can do with the fins. I think this is where I got the idea about expanding foam - but they also talk about other alternative - hope this helps

https://www.ninfinger.org/~sven/rockets/hj.faq.html#c3

 

[jpasqual]

Forgot to mention - when you use expanding foam - you also need to drill small vent holes in a spot that is pretty well hidden from the public eye - this way it keeps you bird looking great

 

[sandman]

JimZ, who is also a master of vacuform plastic, suggested to glue one half of the fin to a sheet of styrene plastic (Evergreen about .020") then line up and glue the other half on.

I havn't tried it yet.

sandman

 

[Stymye]

you could try the push-pin trick I described in emrr's review of the V-2(e-motor)

https://www.rocketreviews.com/reviews/kits/est_e_v2.html

in the specific tip section of the review, I describe a way to align the fin halves
it's a very easy simple way to do it using push pins
when you fill the fin with foam..the excess will seep from and fill the pin holes.. it's easy to clean up... and your left with a very firm yet light fin.

 

[jpasqual]

Hey stymye - great Idea on the pin trick - never thought of using that - Its reminds me of an old rocket tip I found in a old Estes news magazine about pinning all three fins together to get a perfect set of identical fins when sanding them down