Sniffi, review of a balsa glider

Gone (22 Sept 2021)

Lost over fence of adjacent condo last Sunday. That's the end of it.

Needed up substantial up elevator and left rudder, flies too fast. Doesn't recover well, seems the dihedral and rudder are too small. Definitely not roll off the top model.  Would prefer catapult launches.

Do it again? nah.... wasn't forgiving and flight times quite short even on occasional good launches.

Last point: don't use UHU APG for this, bendy joints.

Before flying (14 Sept 2021)

This Ikea plastic laptop table worked as a work bench for this model. 

I used double-sided tape on the edges to hold the balsa parts for planing and sanding. 

It is still available from Ikea, Klipsk bed tray at $13.90.

I planed too much off the port wing tip. Having the balsa grain going outwards is not a sure fix.

I don't have 'resin glue' at hand, so I used UHU All Purpose. Result: the joints remained flexible for a few days after gluing. The fin was glued ok, it stiffened the quickest because it was so easy to sand the edges square. The polyhedral joints do not have matching joints, it wasn't easy to sand at approximate angle, so more glue filled the gap and it takes a longer time to stiffen, currently, 3 days has lapsed and I think it may be ok for launching. To play it safe, I am giving it a few more days.

The decorative strips cut out from the plan were glued with white glue to the sanded model. I didn't have glue stick at hand and tried successfully with white glue on the small logos of 'Aero-naut' to the fin. However, the rest of the decoration wrinkled, white glue is not suitable, I might have had better success with UHU All-Purpose Glue (UHU APG).

The tail jig set the horizontal stabiliser square and the fuselage vertically to receive the wings. The dihedral jigs were spot glued to the wings' underside, and then the wings were joined to the fuselage. The mini-plane rested over the dihedral joint to keep both wings pressed against the mounting area. I left it jigged like that for 2 days to allow the UHU APG time to harden.

After UHU APG has stiffened enough (feeling a bit springy at the dihedral joint with light finger pressure), I did "bed-glides" by launching the model over my bed towards my pillow. The diving glides indicated that the single lead piece provided in the kit is enough. That is good news. It is not time to give it up-elevator yet, during the bed-glides, I noticed it was turning to the right. Slight bend at the fin seems to straighten the glides but the starboard wing hung low. Putting the model on the floor had the starboard wing down on the floor. Balancing the model inverted on my fingers confirmed that the starboard wing is heavier, the CG is to the right side of the fuselage. This is probably due to the different balsa density between the two wings. Since my port wing and tail have their tips planed off, I think I will glue a paper wing tip to the port wing to reduce the mass offset but I will leave the port tail alone.

I may remove the wrinkled decorations, it would be easy, just moisten with water and perhaps a few passes with a sanding block after the model is dried. I want to try with it on first.

At the beginning (6 Sept 2021)

This is my ongoing review of Sniffi. I got Sniffi from Rotor. It seemed simple enough, but I over-estimated myself and had to pick up lessons along the way. It has been a long while.

The kit was die-cut, everything seemed to be there except that I only found a small piece of lead, the larger piece indicated on the pictorial instruction was not found. I don't think that will be enough but since that was what I received, and the lead weight is to be concealed, I am trying it out with just one small lead weight and didn't source from my collection.

A curious warning on the instruction pamphlet says to use resin glue and not wood glue for the fuselage pieces. Perhaps the concern is warpage? Since this Sniffi appears to be a German Kit, I am going to use UHU General Purpose.

The CG indicated in pictorial instructions is confusing, I hope it is 20mm in front of the trailing edge? This would be the first time I will have a glider with such a rearward CG.

The balsa pieces were cut through, the pieces were crushed on the entry side but thankful that the exit side was clean.  The wings and tail is only of 1/16" thick sheets. Mine had hard balsa for the wings and soft balsa for the tail and fuselage. I think the wings ought to be of lighter balsa and the fuselage pieces would require heavier balsa. I suppose the heavier wing is ok because the CG seems to be near the wing's trailing edge.

I wanted to use the clean cut edges for the bottom of airfoil because I figured that some sanding on the crushed top side will make it look alright. But this is not possible for the port wing because of how the pieces are laid out on the balsa sheet.

I wanted the tail to be of lifting section, with the fin lifting to yaw the plane to circle left. I also thinned the tips to reduce the tail's weight further. Thin trailing edges allow for future adjustments, there will be a gap between the fin and elevator, better for adjustment I hope. 

I wanted the wing to have a sharper leading edge and thin trailing edge. I wanted the tips to be thinned outwards. 

Lessons learned:

• One elevator tip was cut too deeply. Only plane in the direction where the wood grain will throw out the planer, that way, it will not dig in. Even if it meant that I am planing towards myself. 
• Use new sandpaper. I was using old sanding blocks and it doesn't cut the balsa.