Author Topic: Twister Builds (Read 17127 times)

Bruce Guertin · « **on:** July 09, 2024, 08:59:52 AM »

As stated elsewhere in this forum I re-acquired a Twister I built 40 years ago.

As I don't plan on flying that one, I'm going to build two more (at a time) identical ones to re-acquaint myself with modelling. I've set up my building space and began construction. I have an Adjust o Jig and prepared one set of ribs already. I borrowed one years ago and just loved it. My problem is while the rib cutting on these kits is dead on, I can't get that symmetry after I cut the holes for the rods. Yes, I have the fixture for the ribs. Are there any tricks I should know, or should I just start pinning parts to the plans the way I always did it?

Because I'm a detail person, Ive weighed all the contents of each kit to try and average the weights between the two. There's a big difference between the two. one fuselage blank is 69 grams and the other 87.

Paul Smith · « **Reply #1 on:** July 09, 2024, 09:55:48 AM »

Jigs and fixtures that align gauge holes only align holes and not what really needs to be aligned.

I always make fixtures that align the LE and TE, which is the goal of the exercise.

This involves V-blocks for the LE and tapered blocks for the TE. They are mastered with an aluminum square tube.
The LE blocks are generic and will fit any model with a square-on-edge LE.
The TE blocks are cut on the miter saw for the required TE angle.
They are hot-melted to the board with the glue just on the edges, not the bottoms.

When I change to a different model I can usually leave the LE blocks in place and just change the TE angle.

Yes, there is a huge difference in weigh between several 1/2" profile bodies. The heavier body is stronger and will need less reenforcement.

Bruce Guertin · « **Reply #2 on:** July 10, 2024, 07:57:10 AM »

Is that board just a shelf from a Lowe's or Home Depot? The concept looks easy enough.

Motorman · « **Reply #3 on:** July 10, 2024, 10:18:11 AM »

Having a sweet wing jig is nice but, a flat surface and a keen eye is really all you need. Put the two spars and 1/2 the trailing edge on with no glue and see what it looks like. If it's good hit the joints with some thin CA and go from there.

Ken Culbertson · « **Reply #4 on:** July 10, 2024, 03:25:15 PM »

A Twister is a warp looking for a place to happen. You didn't think the name came from it's flying ability did you? My advice is to make sure you have a centerline painted on the fuselage as part of your finish and again on each tip rib. Makes it easy to spot the warps as they come and go. It is great to build it as straight as a good jig will allow but don't go overboard. It is also one of the easiest wings to remove warps.

Ken

Craig Beswick · « **Reply #5 on:** July 10, 2024, 07:08:08 PM »

I thought the name came from the tail, "Twisting", in flight?
Ted comes on here, perhaps he can clarify?

Paul Smith · « **Reply #6 on:** July 11, 2024, 12:33:54 PM »

Quote from: Bruce Guertin on July 10, 2024, 07:57:10 AM

Is that board just a shelf from a Lowe's or Home Depot? The concept looks easy enough.

Exactly.

I go to Home Depot and look at the "cull" rack. The wood is discounted 70%, often due to small cosmetic defects at the corners. It works well enough unless it's going into a public area of your house. 2x4's, 2x6's, plywood, laminated shelves. An 8' piece of stock with a bad spot still has plenty of good material for a modeler.

Paul Smith · « **Reply #7 on:** July 11, 2024, 12:37:51 PM »

Quote from: Ken Culbertson on July 10, 2024, 03:25:15 PM

My advice is to make sure you have a centerline painted on the fuselage as part of your finish and again on each tip rib. Makes it easy to spot the warps as they come and go. It is great to build it as straight as a good jig will allow but don't go overboard. It is also one of the easiest wings to remove warps.
Ken

When building a profile fuselage I start out by drawing a centerline as true as possible. Then I drill about four 1/8" holes spaced from the front end to the tail. Using these I can find the CL at any point in the assembly process. This is valuable in the all-important final assembly.

Bruce Guertin · « **Reply #8 on:** July 20, 2024, 08:22:37 AM »

Questions on my Twister builds.

1. What are we using for leadouts these days? I thought I had two sets of Sullivan leadout kits. Nope. McMaster Carr has a stainless .027 wire/cable. They're seven strand and I recall the leadout we had used were of a braided construction. Can I use the McMaster Carr stuff?

2. Bell crank installation. I had already moved to a suspended bellcrank 40 years ago. Is it advisable to continue that or use the eighth inch plywood platform mount?

Motorman · « **Reply #9 on:** July 20, 2024, 10:11:52 AM »

If you can do a suspended bellcrank I would do it. Just make sure you have enough strenght in the mid section. .027" is the right stuff see link.

https://brodak.com/control-line-parts/leadout-line-guide-kits/027-x-6-ft-125-leadout-wire.html

MM

Bruce Guertin · « **Reply #10 on:** July 29, 2024, 11:29:21 AM »

One thing’s for certain. My craftsmanship isn’t what it was when it comes to these models. After 40 years there’s a lot of,”How did I do this back then?” It’s been fun though.

Dave_Trible · « **Reply #11 on:** July 30, 2024, 10:31:55 AM »

I do something pretty similar to what Paul shows above. I invest in one good hardwood board at the Depot that is the most flat one on the shelf. I happen to have a forest of pretty hard balsa that is too heavy for a competitive airplane but perfect for cutting jigging blocks. I can also pin stuff down to them easily. I then tack glue them to the board where required (most of my wings are tapered-not straight). When the wing is done I knock those blocks off, sand the board a little and it's ready for the next project.

Dave

Perry Rose · « **Reply #12 on:** August 01, 2024, 09:45:27 AM »

I've built several Twister wings on the Adjusto-JIg. I set the rod hole jig so that the spars can be added while the wing is in the jig. I always put the straight part of the wing, generally the trailing edge, in the fixed end of the hole jig. In the case of the Twister either end will work. Be sure to only put the same end in the fixed piece for all ribs. You have to adjust for the center ribs as they are smaller to accommodate for the center sheeting. Also keep the rib numbers, stamped or lasered, facing the same way for all ribs. A pass of sandpaper over die cut ribs will help. After drilling the holes and your arthritis calms down put a rod in each hole, pull all the ribs together to see if the ribs need any truing up, do this with the rods on the jig stanchions so things are aligned. Watch for the center ribs just be sure the leading edge notches line up with the other ribs. Truing up the leading edge notch and trailing edge helps a lot while the ribs are in the rods. Setting the jig for the rib spacing just measure the plans, subtract 3/8" or whatever the thickness of the stanchions are and cut some cardboard spacers to put between the stanchions. Easiest way I've found to set the jig up.

Bruce Guertin · « **Reply #13 on:** August 05, 2024, 08:44:43 AM »

Quote from: Perry Rose on August 01, 2024, 09:45:27 AM

I've built several Twister wings on the Adjusto-JIg. I set the rod hole jig so that the spars can be added while the wing is in the jig. I always put the straight part of the wing, generally the trailing edge, in the fixed end of the hole jig. In the case of the Twister either end will work. Be sure to only put the same end in the fixed piece for all ribs. You have to adjust for the center ribs as they are smaller to accommodate for the center sheeting. Also keep the rib numbers, stamped or lasered, facing the same way for all ribs. A pass of sandpaper over die cut ribs will help. After drilling the holes and your arthritis calms down put a rod in each hole, pull all the ribs together to see if the ribs need any truing up, do this with the rods on the jig stanchions so things are aligned. Watch for the center ribs just be sure the leading edge notches line up with the other ribs. Truing up the leading edge notch and trailing edge helps a lot while the ribs are in the rods. Setting the jig for the rib spacing just measure the plans, subtract 3/8" or whatever the thickness of the stanchions are and cut some cardboard spacers to put between the stanchions. Easiest way I've found to set the jig up.

Good advice, Perry, as all the tips I have been given here. I referenced the forward edge of the spar to make the jig hose. This of course 1/8" too far forward which left the bottom spar interfering with the jig mounts. I noted that in my build book. I did as much as I could until I got to that point the wing had to come of the jig for the lower spar. There were a couple of wing ribs from the kit wood that had to be replaced on each wing. I have mounted the second set of ribs on the jig as you mentioned.

I have a good stock of decent wood, but I've been using the kit wood (lightend, of course). No point in using good wood on a potential lawn dart just yet. It's going well so far.

MikeyPratt · « **Reply #14 on:** August 06, 2024, 11:12:28 AM »

Quote from: Bruce Guertin on July 20, 2024, 08:22:37 AM

Questions on my Twister builds.

1. What are we using for leadouts these days? I thought I had two sets of Sullivan leadout kits. Nope. McMaster Carr has a stainless .027 wire/cable. They're seven strand and I recall the leadout we had used were of a braided construction. Can I use the McMaster Carr stuff?

2. Bell crank installation. I had already moved to a suspended bellcrank 40 years ago. Is it advisable to continue that or use the eighth inch plywood platform mount?

Bruce,
Use braided cable .027 for the leadouts; more than strong enough, switching to the suspended bell-crank mounting is a good idea that I’ve used that for years now. This also allows more Room for accessing the controls.
Post photos so we can see the end results.

Later,
Mike Pratt

Steve Helmick · « **Reply #15 on:** August 06, 2024, 03:46:25 PM »

If the ribs came with holes for jig rods burned in, use them if you wish, but I would not consider putting holes in die-cut ribs.

In fact, with die-cut ribs, you need to match them up and mark them so you put "right side up", because it's pretty certain they aren't exactly symetrical. If they're not exactly symetrical and you just go all willy-nilly throwing the ribs onto the spars, a warp is absolutely certain. You don't want that!

Steve

Bruce Guertin · « **Reply #16 on:** August 08, 2024, 01:49:17 PM »

Quote from: Steve Helmick on August 06, 2024, 03:46:25 PM

If the ribs came with holes for jig rods burned in, use them if you wish, but I would not consider putting holes in die-cut ribs.

In fact, with die-cut ribs, you need to match them up and mark them so you put "right side up", because it's pretty certain they aren't exactly symetrical. If they're not exactly symetrical and you just go all willy-nilly throwing the ribs onto the spars, a warp is absolutely certain. You don't want that! Steve

Steve, you're certainly right about the ribs. I started by making sure all the rib printing was on one side. But even at that when clamped together in a bundle there were some that were a mess. I had to replace six ribs altogether. Fortunately, the spars lots were pretty good in both depth and width. The second wing is going better than the first as I spent more time on the ribs. As I recall how things are/were done it gets easier.

I'll get some pictures posted when I can.

MikeyPratt · « **Reply #17 on:** August 15, 2024, 01:29:43 PM »

Quote from: Bruce Guertin on August 08, 2024, 01:49:17 PM

Steve, you're certainly right about the ribs. I started by making sure all the rib printing was on one side. But even at that when clamped together in a bundle there were some that were a mess. I had to replace six ribs altogether. Fortunately, the spars lots were pretty good in both depth and width. The second wing is going better than the first as I spent more time on the ribs. As I recall how things are/were done it gets easier.

I'll get some pictures posted when I can.

Bruce,

It’s a simple kit and you doing a fine job so far, build it like the instruction say and it will fly just fine (many hundreds have been built already). Don’t get to warped up making changes, just make sure it’s light and straight and it will be great. Experienced builders will make there own changes, some are good other, not so good, I’ve built a bunch of them while working at Sig Manufacturing Co). Just make sure your having fun ok with it, and welcome to the Stunt World.

Mike Pratt

Bruce Guertin · « **Reply #18 on:** August 21, 2024, 10:06:49 AM »

Well, both wings are off the wing jig finally. I loved using a jig. So much can be done simply by rotating it. Bottoms, tops, leading, and trailing edge. However, this thing is seven feet long. Because the center is so heavy it will sag in the middle without support. Before I use it again there will be some modifications to stop that.

I'm close to starting on fuselages. I always used Hobby Poxy 1 hour for laminating doublers and fuse planks. BSI only has 30 minute epoxy. With mixing, spreading, and scraping off excess that's not enough for me at this stage. I see West Systems has some epoxy adhesives that are close to the 1hour range. Has anyone used that?

Motorman · « **Reply #19 on:** August 21, 2024, 04:54:37 PM »

West system's the best. You can also use Zap Zpoxy finishing resin, just lay it on thick both parts and don't clamp up too tight.

Bruce Guertin · « **Reply #20 on:** October 16, 2024, 01:40:08 PM »

I'm picking away at it slowly. Lost a week with the weather. Tailfeathers, using my racer as a parts shelf, and a control joiner I made out of ER70 welding rod. I need to work on my setback calculations a bit. I found 2 pieces of 4.5lb 1/4 x 4 and 2 pieces of 6lb same size at Hobby Lobby the other day. All really good pieces of material, not scrap.

Ken Culbertson · « **Reply #21 on:** October 16, 2024, 04:51:23 PM »

Quote from: Bruce Guertin on October 16, 2024, 01:40:08 PM

I'm picking away at it slowly. Lost a week with the weather. Tailfeathers, using my racer as a parts shelf, and a control joiner I made out of ER70 welding rod. I need to work on my setback calculations a bit. I found 2 pieces of 4.5lb 1/4 x 4 and 2 pieces of 6lb same size at Hobby Lobby the other day. All really good pieces of material, not scrap.

I have gotten some really good 6lb wood at Hobby Lobby recently. Beware of the 4.5 for anything that requires strength. I got some 4lb 1/4" that I used for fillets and such. It cracks and snaps in two very easily. We had the best wood cutter in the business here in Dallas back in the day. Now, Hobby Lobby is our only local source.

Ken