V2 LOC 4"

[BenAlbers]

Hi, some years ago i built an Estes V2 which i lost last year in the field (simply forgot to pack going home..).
I bought myself a V2 from LOC, in the Netherlands from reseller Modelraketten.nl. Although the V2 has of course a very dark history i simply like the design. I decided to use the paint scheme of the test version, and was fun to do with masking tape, spray cans etc.
I was surprised by the weight of the components, and it took some effort to make a smooth transition from boat tail to body tube ans special attention was given to the fillets of the fins. This model was my first one completely built with epoxy. I will fly on CTI Pro 38 G motors.

 

[BenAlbers]

The construction process in images...

 

[dhbarr]

Very nice! Did your model require extra weight in the nose?

 

[mwtoelle]

I have not run across a flying V-2 that did not need nose weight. Even the captured V-2s flown at White Sands need 2000 lbs. in the nose to fly correctly. On those V-2s, lead was added if the instruments did not weigh enough.

 

[BenAlbers]

Hi,

i did not do any calculations or testing on the balance, i simply built it according to LOC instructions: the bag of lead grain supplied with the model is epoxied into the nose cone. I will fly with 38 mm G motors (not heavier) so not the heaviest stuff available, it might be possible to fly it with less nose weight.

 

[qquake2k]

Great paint job. Very clever use of the laser.

 

[MaxQ]

Very Nice build.
I have one of these kits...I think I'd like to build it with your paint scheme on it.

 

[grouch]

Fantastic! You did a remarkable job, makes me want one.

 

[BradMilkomeda]

That looks very nice!

I have finally started building my own loc v2. I spent a while researching the proper epoxy and preparation for the polypropylene plastic. As I plan on using an I motor, it is likely more important than for MPR.

I have a couple questions:
What are you doing for motor retention?
What is your final weight, with nose weight?
I am a little concerned about keeping the loaded weight under 1500 grams for MPR launched.

 

[MaxQ]

That looks very nice!

I have finally started building my own loc v2. I spent a while researching the proper epoxy and preparation for the polypropylene plastic. As I plan on using an I motor, it is likely more important than for MPR.

I have a couple questions:
What are you doing for motor retention?
What is your final weight, with nose weight?
I am a little concerned about keeping the loaded weight under 1500 grams for MPR launched.

Interesting...what did you find out about epoxy and preparation for the polypropylene plastic.................................

 

[BradMilkomeda]

Interesting...what did you find out about epoxy and preparation for the polypropylene plastic.................................

Keeping it short , the instructions for this kit are odd in that they specifically recommend SCOTCHWELD 1838, which is expensive at about 50$ for a 2 oz. This lead me into the deep hole of the data sheets and technical specification of 3M structural adhesives to determine if there was any reason for this epoxy to be chosen. I was not able to see why this epoxy would be recommended. Specifically, important here is that the material of polypropylene is classified as a "low surface energy" LSE plastic . These types of plastics readily beed waters so it dances around, which is what the molecules of the adhesive do.

This results in properties such as DP190 having specified overlap shear strength of 650 psi for Wood, but only 90 psi for Polypropylene. And many of these epoxies have 1/10 the strength when above 150F!

West System's G-Flex has adhesion data on a couple different treatments for polyethylene plastic, another LSEP, which I believe is comparable. They specify adhesion data for "80-git sand", "80-git sand, flame treatment" and "alcohol wipe, flame treatment" for polyethylene. It shows that there is significant benefit for using a flame treatment. This is nothing really new, but I was surprised to see 6X strength from this treatment.

I ended up going with the G-Flex epoxy and 407 micro balloons for the fillets.

 

[BenAlbers]

Hi, the final weight of this one is 1150 gram, that is including nose weight and parachute. The parachute is a heavy one (120 gr), if neccesary to be replaced by a thin fabric one.

Motor retention is done with two small S-shapes aluminium strips attatched to the bottum plate with wood screws.

 

[MaxQ]

Keeping it short , the instructions for this kit are odd in that they specifically recommend SCOTCHWELD 1838, which is expensive at about 50$ for a 2 oz. This lead me into the deep hole of the data sheets and technical specification of 3M structural adhesives to determine if there was any reason for this epoxy to be chosen. I was not able to see why this epoxy would be recommended. Specifically, important here is that the material of polypropylene is classified as a "low surface energy" LSE plastic . These types of plastics readily beed waters so it dances around, which is what the molecules of the adhesive do.

This results in properties such as DP190 having specified overlap shear strength of 650 psi for Wood, but only 90 psi for Polypropylene. And many of these epoxies have 1/10 the strength when above 150F!

West System's G-Flex has adhesion data on a couple different treatments for polyethylene plastic, another LSEP, which I believe is comparable. They specify adhesion data for "80-git sand", "80-git sand, flame treatment" and "alcohol wipe, flame treatment" for polyethylene. It shows that there is significant benefit for using a flame treatment. This is nothing really new, but I was surprised to see 6X strength from this treatment.

I ended up going with the G-Flex epoxy and 407 micro balloons for the fillets.

Thanks!
I remember reading about flame treatment for painting Loc nose cones on a website....haven't done that...yet.
https://stason.org/TULARC/recreatio...g-Paint-to-Stick-to-LOC-and-Aerotech-Nos.html
https://faqs.cs.uu.nl/na-dir/model-rockets/construction.html
I have a Loc NC that I've made into a boat tail and applying tip to tip CF and attaching fins is the next step, so I'm looking for info on these Loc NC.

This recommended epoxy IS expensive.

https://www.skygeek.com/3m-021200-2...aign=froogle&gclid=CJ7St97Q79MCFdKLswodOvAEhw

 

[BenAlbers]

Final touch two Giant Leap rail guides: paint of body tube was sanded away locally (i love my Dremel tool), back of the 4" rail guide sanded too for better connection. Guides were glued in place using epoxy.


Parachute supplied with the model is too small: i wll use this 90cm one only for the main body, the nose cone will be recovered by a separate chute of 70 cm.
First flight hopefully saturday at FTTS-2 of our local rocketry club DRRA.

On small detail: the opening in the nose cone for adding epoxy/led has been sealed to decrease the neccesary ejection gas volume.

 

[BenAlbers]

First flight on a CTI Pro-38-1G Smoky Sam (G) motor. Wonderful straight flight. No spin, perfect recovery.

 

[BenAlbers]

[video]https://youtu.be/XH4ApVZWLOs[/video]

Slo-mo of the start...

 

[BradMilkomeda]

Congratulations on the seccessful maiden flight. Thanks for sharing the nice video.

 

[Maxter]

Great Job. Love those Smoky Sams. You might think about not using the nose cone loop as they will break. Drill a small hole 180 degrees apart and run a shock cord through them, much stronger.

 

[BenAlbers]

Hi,

after the first flight of this V2 i discovered a crack in one of the fillets. I think this occured at landing (ca 5 m/s) and obviously the strength of the fillet is not as good as i expected. Maybe a fibre as filler would be better. What do you think ?

 

[BradMilkomeda]

Hi,

after the first flight of this V2 i discovered a crack in one of the fillets. I think this occured at landing (ca 5 m/s) and obviously the strength of the fillet is not as good as i expected. Maybe a fibre as filler would be better. What do you think ?

That is a bummer dude. Do you have any picks? Is the crack in the middle of the fillet? Or at the adhesion point between the epoxy and the tail cone or fin?

 

[Jozef]

Hi,

after the first flight of this V2 i discovered a crack in one of the fillets. I think this occured at landing (ca 5 m/s) and obviously the strength of the fillet is not as good as i expected. Maybe a fibre as filler would be better. What do you think ?

Late to the party.... but it appears you used too much micro balloons in your West Systems mix. They appear to be grainy and pure white. That weakened the epoxy. I have used G-Flex and micro balloons a number of times with no cracking. Since G-Flex is a relatively slow cure, add only enough micro balloons to get a creamy consistency. Let the epoxy mix set up until it gets to a peanut butter consistence then apply your fillets. Lots of info on fillets if you search TRF

 

[Jozef]

G-Flex and micro balloon fillets on my MDRM. Also be sure the surfaces are rouged up we'll before applying fillets.

 

[BenAlbers]

Hi guys,

the crack is in the middle of the fillet. I agree that the amount of micoballoons was maybe (too?) high: the epoxy matrix that should have given the fillet its tensile strength apparently is too much broken by the microballoons. The microballoons themselves are obviously too brittle and not able to withstand the short tension peak at landing. But: the fillet that Josef shows looks like pure epoxy with a little bit of microballoons in it. The advantage of having a paste that can be handled for a long time and which stays in place after applying is no longer there (?)
For a next project I will apply a fibre filler in the epoxy. The fibre itself has its own tensile strength, and instead of weakening the epoxy it will even strengthen it...

 

[Steve Shannon]

You're exactly right about using fiber fillers. However, you could now apply a layer of fiberglass over your fillets to restore a great deal of strength.
I would not add microballoons to epoxy in any application where I wanted structural support. Microballoons enable easy sanding and mass reduction but intentionally weaken any epoxy. What makes them easy to sand is their relative softness. Being filled with gas adds no tensile strength. I would use microballoons where I wanted bulk with little mass and where I intended to add a strength layer.
West Systems puts out an excellent manual explaining their epoxies and different fillers. Here's the link:
https://www.westsystem.com/wp-content/uploads/User-Manual-2015.pdf



Steve Shannon

 

[BenAlbers]

Thanks Steve. For now I repaired the crack with some thin CA glue. I will see how it develops over the next flights, and if things become worse I may have to do some rework like you suggest. Have to do a lot of paintwork again then.....

 

[BenAlbers]

Yesterday this one flew for the second time. Again a very straight line, no spinerfect! And very imprssive this black smoke column in the blue sky! At landing again some minor crack in the fin fillets but i decided to do no specific repair now. The fins are glued with pure epoxy, there is no risk of losing the fins, and maybe the crack in the fillets do not develop further.

 

[BenAlbers]

Hi there, last week we had our last Dutch DRRA launch event of this year. I was lucky to get myself a CTI PRO 38/1 Skidmark motor which i used this day. It was a great flight, very impressive and 100% succesful. see my Facebookpost...

The event was one of the best ever: low wind, nice people, over 60 launches, nice food, a camp fire. We had great fun: the best showstopper ever. The day was ended with a synchro launch of two Patriots on D12 and D9 motors.

 

[Tyler P]

Very nice build! I like the style of the V2. It just has that early-rocketry feel, being an early rocket.