Looking for broken DLG boom

[msc]

Hi,
I am looking for a small section of OD 20mm tapered boom. This is to repair my new glider, which broke during shipment here.
I only need a small section, around 90mm length and thought that DLG'ers with broken booms might have this.

Let me know if you have any broken booms, I'll pay for it.

Thanks.

MS

[sherchoo]

Sad to hear on the shipping boo boo... haiz

I think i might have a section of boom but I doubt it is 20mm diameter.

Do you have a picture of the damage? Maybe someone can offer some advise on the repair method if we know the extent of the damage.

[msc]

The glider is the Cirrus F5J 3.37m. It is a 2 piece wing and the box is almost as tall as my daughter.
My brother's colleague hand carry it back from London. Even with the many fragile stickers, the box was crushed in the middle.
The wings were dented, but the boom was half cracked.

My repair plan is to glue a length of tapered tube on the inside of the broken boom. I made a rough measurement around the crack area and estimate the ID to be around 20mm-19mm, and tapered towards the tail end.

If I could get a small section of a matching tapered tube on the inside, this would make a good repair.

Any other suggestions are most welcome.

MS

[randomtask]

Hi kah marn, that crack in thr boom is a shame but i have repaired a boom which has broken completely.

What i did was similar go ur plan but instead i used many smaller cf rods on the inner walls. This way i ould ensure a perfect alignment. Outside i folled with cf cloth with another layer of fg cloth at a bias. Now the boom is.solid and i still get good launches with it.

Hope this helps. Cheers.

[sherchoo]

Found the boom but it's only 14mm OD.

By the way, the repair that Randomtask did on the plane which he flew and got the championship in last month's competition.... so the definately worth a try.

[Ghostfit]

Marn,

Wrapped the thinner section of the boom (which is about 18mm OD) with mylar as release agent and then lay a layer of carbon and glass cloth, soak with epoxy and let cure overnight. Wiggle the 'tube' out thru the smaller end and you have your sleeve for the boom internal spine repair.
Smear a little expanding PU foaming glue and you'll have a joint that's stronger than the original.

[chiadennis]

Marn

Is the fuse totally broken into 2?
If it is, couple of things that you can do.

roughen the inside of the fuse, make a foam plug so that you can lay fiberglass around the plug. make the plug as straight as possible so you wont misaligned the fuse. Spray 3M super 77 on the fiberglass cloth and wrap it around the plug. Go about 3 - 4 layers around the plug (the plug OD need to be smaller than the fuse ID and the glass cloth take up the space). Use fiberglass resin or very slow dry epoxy. Fill the inside of the fuse and also the glass wrap plug and slide the plug into the fuse.

Now come the difficult part.
If it's totally broken in 2, you need to fix the wing and the tail to eyeball the alignment. This maybe a challenge. Once the epoxy it totally cured (leave for few days) use a long stick and push out the foam plug. After that you can start on the external of the crack.


Now if the fuse is not totally broken (bent crack).
Thin CA the crack. grind 2" on both side of the crack and wrap glass cloth over it.

[msc]

These are great tips. I think I will apply a combination of Tony's and Dennis' repair method. The boom is not completely broken into 2, but the crack is about half the circumference of the boom.
Now, I need to get my hands on some thick glass cloth and carbon weave....

Hey Adnan and Sherchoo, thanks for the tips too!

I may post my repair, if successful....still trying to claim for damages from SQ.

MS

[Twyl]

Reading the initial posts I was about to advise something similar to Tony's proposal.

To be honest though, if it's not completely broken and you do not mind a little bulg in that area, then CA the cracked area making sure the fuse is strait, then sand the area down to get rid of any mold release agents and prepare a good bonding area. Wrap the section with some FG cloth and wet it out using epoxy resin (regular 5/10/30min modeling epoxy is not recommended as you will have difficulty wetting out the cloth and it will be a weaker bond). Once cured, sand it down so the step from fuse to cloth is smooth, and you are good to go.

If that just wont cut it for you, then go with the repair on the inside method.
1st. Make sure their is a clean break.
2nd. Lightly tape the two halves back together. You want it light or skimpy enough that you could pull the two halves apart if you give it a good pull.
3rd. Wrap some thin paper around the fuse with the break in the center. One wrap is fine.
4th. Make sure the paper is wrapped as tightly as possible and tap it.
5th. Run packing tape length wise over the paper. Over lap each strip until the paper is completely covered. The packing tape will act as a release agent.
6th. Mask off or cover the tail and forward areas of the fuse that you do not want to accidentally get resin on.
7th. Wrap the break area of the fuse with FG cloth 3-4 times. Make sure you go at least 5-6cm to each side of the break, more if want, but do not go further then the length of paper you have underneath.
8th. Wet the fiberglass out. If you used a dark colored packing tape you will be able to see the areas of the cloth that are not completely wet. They will look white as the wetted areas will be translucent and you will just see the color of the tape you used. Alternatively you can use dark colored paper and clear packing tape.
9th. After FG has cured, you should be able to unwrap the tape on the fuse to where the underlying paper is. If you tacked the two parts of the fuse together ligth enough you can pull them apart and have wider diameter part should at least pop out of the tube you made. If the fuse is untapered enough you might be able to get both sides out. Regardless you will not want to carefully cut the FG tube you made lengthwise. Carefull not to cut into the fuse although some minor cut/scratch will not matter as it can be sanded and painted out.
10th. Pop the cut tibe off the remaining fuse part. The packing tape should come easily off
11th. You now have a FG tube that can be overlapped and stuffed inside both parts of the fuse to act as a brace. You might be able to trim the FG tube's horizontal cut so that it does not have to overlap when you decrease it's diameter and stuff it in the fuse.
12th. Be sure to sand the inside of both sections of the fuse to get rid of any possible mold release agents from the original manufacturing. Use some good epoxy and glue everything together making sure the fuse is as strait as can be. Some temporary braces on the outside to keep things straight could be wise.

HERE's a build I did something similar to, but I did not use the fuse as the tubes mandrel, but it's fairly similar. To check out another thread on how to make ballast tubes and which I based the above repair advice on look HERE.



Best of luck with the repair!

-Jonathan

[Twyl]

Did you attempt any repair? Hope it went well.

-Jonathan

[msc]

Did you attempt any repair? Hope it went well.

-Jonathan

Not yet, too much distraction from work. Need to piroritize.