XP-2 Rocket Glider

I was then able to use the 9/16" bit to drill out the hole for the hubs. The result was rougher that I would have liked but I was committed by this point.

The small pieces of BT5 tubing were slipped over the balsa coupler to make sure everything would fit.

The short BT5s were then glued into the pivot holes with Titebond III.

The balsa coupler was marked into two pieces, each a bit more than 1/8" thick and a miter box and razor saw were used to cut them.

It seems that when I grabbed the spruce piece for the body, I took it out of the wrong bin and it was 1/8" too deep. Running out of time, I could not get back to the hobby shop to exchange it so I marked of the correct depth.

A belt sander was then used to shrink it down to the correct depth.

The template for the front of the body was cut out and taped to the spar.

The disk sander was then used to shape the correct profile.

The plan called for 1/8x1/8 spruce to serve as stops for wing rotation. My hobby shop did not have any so I picked up basswood instead. They were cut to length in a miter box.

I smeared some Titebond II onto one of the spacer wedges and then clamped it in place on one of the shoulders to dry.

When the glue holding the spacer to the shoulder was dry, I glued the basswood stop in place.

While waiting for the shoulder to dry, I cut out the template for the standoff and used it to cut the part from balsa.

The lug was then epoxied to the top surface of the standoff.

To promote better adhesion between the body and the lug, a file was used to make a groove in the spruce body to receive the lug.

Questions:

Do the horizontal stabilizers mount to each other and then sit on top of the boom or are they mounted directly to the boom?

Are the horizontal stabilizers given a dihedral (how much) or do they stay flat?

Do I understand correctly that the airfoil on the horizontals stabs is supposed to push the tail down?

JAL3 said:

Questions:

Do the horizontal stabilizers mount to each other and then sit on top of the boom or are they mounted directly to the boom?

Click to expand...

Yes, but normally I would cut them out as a single part. The convention of only showing half the stab on plans is to save space. The stab gets glued to the underside of the boom, so you have a nice flat face to glue to.

JAL3 said:

Are the horizontal stabilizers given a dihedral (how much) or do they stay flat?

Click to expand...

No. They are flat.

JAL3 said:

Do I understand correctly that the airfoil on the horizontals stabs is supposed to push the tail down?

Click to expand...

You put the high point on the bottom so the low pressure caused by the airflow over it pulls the tail down, raising the nose. (see post #8 and the other posts about not permanently gluing it on untill you test glide and get the incidence right)

kj

With the trough dug out I mixed some more epoxy and then set the lug into the spar.

I needed to mark exactly where the hub axles would go so I finagled the pieces into place and made sure everything had clearance. I then pushed a pin through the axle to mark its location.

kjohnson said:

Yes, but normally I would cut them out as a single part. The convention of only showing half the stab on plans is to save space. The stab gets glued to the underside of the boom, so you have a nice flat face to glue to.




No. They are flat.




You put the high point on the bottom so the low pressure caused by the airflow over it pulls the tail down, raising the nose. (see post #8 and the other posts about not permanently gluing it on untill you test glide and get the incidence right)

kj

Click to expand...

Thanks for the reply.

The stabilizers are already cut. I have 3 pieces: 2 horizontal and one vertical. Should I recut the horizontals?

Also, what is the preferred method to temporarily mount them?

With the pinhole marking the correct spot for me, I glued the axle down to the shoulder with some Titebond II.

JAL3 said:

The stabilizers are already cut. I have 3 pieces: 2 horizontal and one vertical. Should I recut the horizontals?

Click to expand...

Mox nix. If you want to, recut it. If you don't, glue them together but make sure the completed stab is perfectly flat.

JAL3 said:

Also, what is the preferred method to temporarily mount them?

Click to expand...

From post #28...

kooch said:

Like Nienest on these, I would glue the pod and wings/rudder in place and then fine tune the amount of negative incidence on the stab by rubber banding it in place for the hand tosses. You want a slightly nose heavy glide on these and not a glide that "mushes" or is on the verge of a stall. Start with a few degrees of negative incidence on the stab and work out from there by sanding in additional if needed to get a glide slope you like. Note that the whole stab was at a negative angle and not just the aft elevator part of the TE.

Kevin K.

Click to expand...

kj

I was still unhappy with the damage caused by drilling the holes in the wings and decided to try and fill the gaps between the balsa wood and the bearings. I used a toothpick to fill the cavities with Titebond Molding and Trim glue since that stuff is thick and does not shrink.

kjohnson said:

Mox nix. If you want to, recut it. If you don't, glue them together but make sure the completed stab is perfectly flat.



From post #28...


kj

Click to expand...

You know, it seems amazing what I miss sometimes.

I wonder if it is the result of me posting at the same time as somebody else or if my brain is really that damaged.

Thanks.

I don't know whether it will do any good or not but I decided to try and "fair" the rough area along the launch lug and the standoff and spar. I used Titebond Molding and Trim glue to try and smooth things out.

After the axles were glued in place, I set the wings over them and proceeded to slowly sand the axles down to the right thickness. This turned out to be much easier than cutting them exactly right.

With the wings still seated on the axles, a mark was placed at the stop point with the wings extended.

A toothpick was used to poke a hole just inside of the mark and then the toothpick was used to poke the end of the Kevlar into the hole.

A minute amount of epoxy was then mixed and used to secure the Kevlar in place.

kjohnson said:

From post #28...

kj

Click to expand...

Back on this thread...

First you glue the rudder to the stab. And I agree with Kevin that the stab should be one piece with the balsa grain going length wise thru the stab.

Next, sand in some negative incidence into the rear of the spruce boom and attach the stab/rudder combo using a rubber band. See attached.

Test glide with everything in place including spent motor casing for a flat glide. If the glide is a bit nose heavy, add more negative incidence or angle.

Last, I would also glue in spruce reinforcements at the LE of the wing where it meets the spruce (or in your case bass wood) doubler on the hinge assembly. Need to make sure that hard material meets hard material when they snap into place.

Later Nienest designs as well as my own used the end grain balsa of the wing itself as the stopper. And the wing stop was the spruce boom itself.

KK

kooch said:

Back on this thread...

First you glue the rudder to the stab. And I agree with Kevin that the stab should be one piece with the balsa grain going length wise thru the stab.

Next, sand in some negative incidence into the rear of the spruce boom and attach the stab/rudder combo using a rubber band. See attached.

Test glide with everything in place including spent motor casing for a flat glide. If the glide is a bit nose heavy, add more negative incidence or angle.

Last, I would also glue in spruce reinforcements at the LE of the wing where it meets the spruce (or in your case bass wood) doubler on the hinge assembly. Need to make sure that hard material meets hard material when they snap into place.

Later Nienest designs as well as my own used the end grain balsa of the wing itself as the stopper. And the wing stop was the spruce boom itself.

KK

Click to expand...

That is very helpful and I appreciate it. There is still time to do that.

Does the presence of the rubber band have much effect in terms of weight? I understood that gliders are very picky about the least bit of weight.