Thread: Discussion Alpina Magic
View Single Post
Old Nov 16, 2012, 01:22 AM
AirBornOne is offline
Find More Posts by AirBornOne
S.F. Bay Area
Joined Aug 2002
1,921 Posts
Originally Posted by John Cole View Post
You guys may already know about this detail, but thought I'd mention it anyway. My early Alpina build instructions recommend sanding away much of the veneer from the tail surfaces. Also mentioned is sanding the veneer thinner towards the wing tips, all to help shave off weight.
I believe carefully applied glass will weigh approx to film, but as already mentioned, paint will really rack up the grams.
Never heard about sanding the veneer down to 'save' weight. A wive's tale if you ask me.
Neither the Alpina or the Arriba are contest designed aircraft.
Personally I would prefer as much 'natural beef' at the extremities for cartwheel insurance.We're not talking any serious mass.
For the lightest treatment,a high grade covering would be the way to go.
MPX's instructions for film coverings specify using a balsa block wrapped with a soft cloth to smooth the film down.This works very well.
Originally Posted by Chris
I know the OP has taken this fact on board, but it bears repeating again that some old airfoils do not respond to camber change. The Alpina's Ritz foil definitely doesn't, I'm not sure about the Arriba... In such cases a modification to add flaps would be for the purpose of braking only...

The OP started this thread re: the Alpina Chris,I was speaking to Ken and his ? re: his new Arriba.Given the Arriba has spoilers,flaps for braking is prolly useless.
Originally Posted by Ken
Thanks for the response. The glass and polyurathane would be because I never have good results with a film over a solid wing surface. Poor technique.
The airfoil is a HQ 3.5/12 The instructions talk about installing flaps, the difficulty and benefits. I may ask one of the airfoil designers on the DLG group if he thinks this airfoil would respond well to flaps. Not his usual RE number range, but he knows how to run xfoil forward and backward.
I always hoped that if I had a big enough plane I wouldn't need to chase that last ounce. Not so.
Ken, My very similar planform DG-600 flies wonderfully with a solid stainless steel wingrod.I don't think you need to sweat the weight (adding gallons of epoxy & FG cloth notwithstanding of course )
The change in basic flight control with flaps linked to ailerons is phenomenal,specially considering only a few mm of travel are involved.
Your Arriba was designed near the advent of popular e-flight.Pre brushless motors and high power LiPo cells.I doubt if the intended flight regime was anything near aggressive, however with the weight you will be avoiding by using modern e-power this can raise the performance level of your Arriba significantly.Which Can benefit from added flaps.But don't sweat it.Flaps can be added later.
And remember, those nice fellas across the pond have some strong feelings about flaps vs. spoilers.
It may also be time to start your own Arriba thread so you can share your build and post some relavant photos.
AirBornOne is offline Find More Posts by AirBornOne
Last edited by AirBornOne; Nov 16, 2012 at 01:40 AM.
Reply With Quote