n00bs Gonna Build a Carden

[gareth.ky]

I did a test swatch with the roller to see what kind of penetration I was getting into the foam. I tore up the test piece and the adhesion between the foam and the wood was very good. No peeling or separation, the wood cracks before the bond breaks. The glue went down into the foam structure about 5mm or about 1/5 of an inch.

Is that enough? Do you all generally see more penetration than that?

I would rationally think its enough. Its composite structure and as long as the wood is properly adhered to the foam its will be strong. The wood is there to resist tension and compression loads across the parts surface. The foam resists compression. On the test panel I can't break it in my hands in tension.

[why_fly_high]

You need enough glue so that the penetration from both sides of the wing reach each other.

I am just messing with you. I would be pleased with the bond you got.

Dan

[gareth.ky]

It varies from 1/8 to 1/5 in places, depends on how porous the foam is. I sent a PM to Walt to ask him about it and he thinks its enough glue. I think we are good to go, I'm sold on the roller.

[gareth.ky]

On with the Sheeting. I did the Belly Pan, Hatch, both H-Stabs, Rudder and Turtle Deck in that order. Then I got help from Dan to do the wings (Thanks Dan!).

I used the method I like best for spreading the glue is a small foam roller that you can get at Walmart. This really gets a nice thin layer of glue evenly all over the sheet. Just keep rolling until the sheet turns a uniform color and you don't see any big globs of glue left on it. For the wings I think I used 6oz of glue and at least 1oz of that is waste that ends up in the roller. So at most there is 1.25oz of glue on each skin. Each wings had at least 400lbs on it.

I put parchment paper between the shucks and the skins. The upside of this is glue can't get through the skins (and it will!) and stick the part to the shuck. The downside is the parts tend to move around very freely until the weight is applied. Take some care and time to align the part with the shucks so its sits square. I used about 300 pounds of weight on all of the other parts in the form of various concrete blocks I got for a few cents each at Home Depot. Even with all that I didn't get good adhesion around the edges of some parts. I guess the gap between the shuck and the part was just wider there. Vacuum bagging would really help with the edges and I would probably go that rout if I was doing it again.

You want to take some care with the rudder sheeting alignment. I just joined the Fin and Rudder sheeting parts with masking tape over the plans so that they covered up the whole rudder. Put the foam over the plan and make some reference marks so you know approximately where you want the sheeting to lay down. Try and get the seam to run through the area that will be cut out for the hinge line. Don't do anything stupid when cutting off the excess sheeting. Use a sharp blade and then a sanding block to make it smooth. I chipped some parts with a dull blade and I'm regretting it now. A hobby saw works well for the curves.

So I'm sure you can see the holes in some of the parts. The hatch, belly pan and turtle deck are all cosmetic parts. They don't contribute much in the way of strength to the model. So they make great targets for lightning. I'm going to guess that I saved about 5oz off the airframe and much of that is from behind of the CG. This technique leaves the part fully sheeted so its easy to cover but it avoids large chunks of foam and the glue that goes with it. Here is the HowTo:

1.) Mark a reference line down the center of the part and the center of the sheeting.

2.) Make a template of the boundaries of 1/2 of the part.

3.) Draw your cutouts on the template and cut them out. Be smart, do triangles or cut in the same direction as the surface curvature.

4.) Place the template on the reference line and mark the cutouts. Flip and repeat for the other side.

5.) Cut out the foam with a Dremel router or hot wire tool. IMPORTANT: Keep the tool perpendicular to the surface. Put cutouts back into place with a loop of tape.

6.) Place overlapping strips of masking tape on parchment paper and cut out shapes.

7.) Use the template to position the cut out tape over the part.

8.) Then just spread glue as normal, peel off the tape and carefully align the foam part with the reference mark on the skin. Set up the part in the shuck as normal. When the glue dries you will have to pull out the routed foam pieces, none of mine stuck to the wood.

I tried a few different procedures on the hatch and belly pan. The above steps are more involved but the result is the best. The turtle deck isn't trimmed yet and it weighs 2.5oz (72g). 20g of foam was removed. I don't know how much I saved on glue because I had to work fast and didn't get the parts on the scale.

[capflyr]

Gareth great job I love the pics keep em coming your making it look so easy.

[gareth.ky]

	Quote: Originally Posted by capflyr
	Gareth great job I love the pics keep em coming your making it look so easy.

Don't be fooled, its a lot of work. Not too hard, just a lot of it. Everything about this project is big. I guess I'm about 1/3 the way through construction in 4 weekends and I'm single so I have the spare time. I don't want to discourage anyone, I'm really enjoying doing this build, just know what your in for.

This project is eating lots of 'stuff' too: 3 rolls of 3/4" masking tape, 3x 8oz bottles of Gorilla Glue ($12 each!), 3 dust masks, 4 rolls of parchment paper, 6 foam rollers, 3 sheets of poster board. I'm learning to buy consumables in bulk. I'm considering buying stock in 3M. I may be on a first name basis with all the cute checkout girls at Home Depot before this is over

I'll keep the pics coming.

[rc4flying]

	Quote: Originally Posted by gareth.ky
	I guess I'm about 1/3 the way through construction in 4 weekends and I'm single so I have the spare time. I'll keep the pics coming.

You may not be single long if you keep those Home Depot visit up.......

Nice looking work on the plane, by the way.

[Fixed Wing]

	Quote: Originally Posted by gareth.ky
	I also noticed on the rudder that at some points along the edges the panels did not contact the foam. There wasn't enough glue to foam across the gap.

Gareth,

You're doing a great job. I know you'll be pleased with your results and how the plane flies.

Regarding the edges not gluing down properly for the future you may want to use toothpicks to press the sheeting to the foam core as shown in the attached picture.

I use Elmer's Ultimate glue which is very similar to Gorilla glue like you are using. This glue typically penetrates 3 to 5 beads of foam deep. In other words when you try to peel the sheeting away from the foam after the glue has cured you'll see about 3 -5 layers of the foam beads still stuck to the sheeting that broke away.

I also use a small paint roller to spread the glue onto the skins. This method seems to spread a more consistent layer of glue and in a smaller amount than the credit card method. I have been measuring about 1.5 -2 ounces of glue in a small jello shot cup and applying that amount to each skin for a 40% sized wing.

Keep up the good work and keep the pictures coming. We are interested and do appreciate it.

Dean

[gareth.ky]

Thats a good trick Fixed Wing. I found that on the wing panel where I trimmed the skins the edges had good adhesion. On the other panel I got ahead of myself and didn't trim them before I put the glue on. That panel will need some work to get the LE to stick down.

I didn't get much done this week. I just sanded down all the skins on the parts to the shape of the foam. I'm also working on cutting out some H-Stab root caps in light ply. These are for the anti-rotation mod that Walt does. It looks easy enough and thats how 90% of the ARF's work.

What kind of filler do you all use?

Oh and one other topic; Shop Heat. Being a Caymanian I'm new to working in the cold like this. I had to go out and get a Kerosene heater for the garage. It was just too cold in there to work. some of the glues and stuff down work below 40 degreed F. I feel like a hobo every time i go warm my hands over it but it really works well! What do you all do for shop heat?

[mark786]

Gareth,
Good job on the build. I originally tried light ply for the stab root ribs but found very quickly that it wouldn't be enough. I made another set out of regular ply and threw away the light ply set.
Mark

[gareth.ky]

	Quote: Originally Posted by mark786
	Gareth, Good job on the build. I originally tried light ply for the stab root ribs but found very quickly that it wouldn't be enough. I made another set out of regular ply and threw away the light ply set. Mark

Sorry, yes what I have is birch ply, 1/8" thick if I remember. Good Catch.

[gareth.ky]

I still haven't decided on the motor for this project. I've narrowed it down to one brand and two choices. The DA 100 or the DA 85. I'm assuming that either setup would run on canister mufflers so the cost and weight of the canisters factors into this.

The case for the 85 goes something like this:

• The 85 is ~$500 cheaper than the 100
• The 85 is 1.8 pounds lighter than the 100
• It makes almost the same power as the 100

If you believe that a stock built 260 with a DA 100 weighs about 28 pounds then it will weight 26.2 pounds with no mods and a DA 85. I'm committed to doing some further lightening of the airframe, mainly in the motor box as others have done and a CF wing tube and routed out landing gear (if I can find someone to do it). I'm going to do A123 batts with a really simple setup, no regs and no power box. I'm going to do Walts mod and put the rudder servo in the base of the tail.

I'm hopeful that I can hit 25.5 pounds.

That said I'm still a little worried that the 85 will be underpowered. Everyone I have talked to says I shouldn't be. The 85 is going to have other down sides:

• Balancing the airplane will probably require cutting holes in the tail surfaces. It may even need weight.
• I'll have to butcher the pretty cowl
• The 85 is noisy and might not be IMAC legal with the optimum prop.

If you have any input on the engine choice please post. I need to make my mind up by the end of the week and place an order.

[Greyhoundman]

This is just my opinion, but if you go with the 85 you will want as much weight out of the tail as possible. You might need to lighten up the tail feathers and will definitely want the rudder on pull pull. I guess having a canister might help the cg a little but not really sure about that.

[gareth.ky]

Your right, I need to get the CG correct and I may have to settle for pull pull. I would rather have tight direct connections. With the push-pull setup 1 5955 is probably enough and the 8711 will certainly do it. I would rather cut up the tail feathers than do pull pull. The servo is about 2oz so I'd need to find 2oz at least to take out.

I could also, maybe, do a push-pull with carbon tubes and the servo up front.

Batteries will probably be mounted on top of the motor box like a 50cc.

[Neil4]

I was in the same sort of boat as you are with engine choice for Carden. I am building a 35% Dalton 260 and I was debating between the DA 100 and DA 85. I went through the pros and cons of each one and went with the DA 100. I choice the 100 because with the more weight of the 100 in the front would allow me to run a direct link to the rudder along with getting the CG right without lightening the tail surfaces which I liked. And yes as you know you will have one more canister over the 85 and that will cost a little more oviously but you will know for a fact that you will have enough power with the 100. AS you said i was worried about 85 being under powered so I went with the 100 just to be safe because you wouldn't want to buy the 85 to find it wouldn't cut it.

Oh, by the way I heard you mention going with 1 5955 for the rudder...don't do that. Go with the 8711, much more holding power. I had i 5955 in my 33% Yak 54 and it would not hold a knife edge half way through the flight. Switched to an 8711 in the rudder and it was like night and day. But go with the 5955 everywhere else, at least that is what I am doing.

Neil(sorry about the long post)