LOC Fantom modifications

Hi

I'm an experienced model rocket builder, but have only recently moved towards HPR. I am currently building a stock LOC Fantom 438 (not the EXL version) for my L1 certification. After successful certification, eventually I'd like to able to fly it on J motors as well as H and I, and add an electronics bay as a step towards Level 2.

Does anyone know whether J power is possible for a Fantom, and, if so, any tips on extra strengthening I can add now, at build stage, please?

Thanks!

...I should add that when I say I'm building it 'stock' I have used U and eye bolts, kevlar shock cord etc to upgrade the recovery.

We tend to over-build our high power rockets. I have seen stock built rockets take a hammering from some fairly large motors, and come back for more... Build the rocket well, and I believe your Phantom can handle a bit of abuse.

Welcome to The Rocketry Forum!

Thanks for both the reassuring advice (and the welcome!)

I built my L2 rocket out of LOC components and wood glue. All you'll need to make the Fantom into the EXL is an altimeter bay and another section of 4" BT.

You don't need any extra strengthening techniques to fly a J in this rocket.

Ok thanks - that's good to know.

My wife did the exact same thing with her Fantom; Started stock for L1 then went with an Av bay for her L2 on a J350. Awesome flights both (see attached). As a side note; Best performance in the EXL configuration came from a Pro-X I540 WT. Hardest accelerating flight I've ever seen! The perfect rocket/motor combo. She did break a fin on a hard, High Wind recovery so she ultimately replaced the ply fins with S-Glass. That was well after the L2 flight on the J.
Best of luck!

stantonjtroy said:

My wife did the exact same thing with her Fantom; Started stock for L1 then went with an Av bay for her L2 on a J350. Awesome flights both (see attached). As a side note; Best performance in the EXL configuration came from a Pro-X I540 WT. Hardest accelerating flight I've ever seen! The perfect rocket/motor combo. She did break a fin on a hard, High Wind recovery so she ultimately replaced the ply fins with S-Glass. That was well after the L2 flight on the J.
Best of luck!

Click to expand...

Those are some really nice cert shots of your wife's Phantom. Good thing she got the certs before breaking a fin.

stantonjtroy said:

My wife did the exact same thing with her Fantom; Started stock for L1 then went with an Av bay for her L2 on a J350. Awesome flights both (see attached). As a side note; Best performance in the EXL configuration came from a Pro-X I540 WT. Hardest accelerating flight I've ever seen! The perfect rocket/motor combo. She did break a fin on a hard, High Wind recovery so she ultimately replaced the ply fins with S-Glass. That was well after the L2 flight on the J.
Best of luck!

Click to expand...

Thank you very much that's good stuff to know. Truly fantastic shots of both launches there!

Cheers!

Some shots of work in progress. Having pondered the kit itself and some detailed sims in Open Rocket, I decided to make a few customised changes. So this is now a sort of 'Fantom variant'. I opted to get new fins of a different shape (more akin to a Nike Smoke). laser cut from 3mm aeronautical birch ply, and added an extra 3mm CR to the MMT, to allow me to create an internal fin can. Having factored in the shift in CG and studied the OR sims carefully, I added 50g of lead shot mixed with 30min epoxy at the tip of the nose cone, using John Coker's method of drilled then filed cross pins to anchor the slug in place. I added a cast eyebolt, secured with a nice wide washer had in my tool box and nut. The white band is a small plastic tube off cut, which I thought might serve as a fixing point for a read only altimeter at some point. I filled the spirals on the airframe with a wood filler, sanded, then sealed them with thin coats of aliphatic resin glue (brushed on with a fine art brush) and smoothed off with progressive sanding.

Resist the overbuilding! My Fantom is overweight. My only recommendation is oversize the chute until you're comfortable with the decent rate. Maybe it's just the thin air up here, but I keep breaking fins/fillets. The Fantom will handle some J's with no mods. Just remember, Up is easy.
-Ken

new2hpr said:

Resist the overbuilding! My Fantom is overweight. My only recommendation is oversize the chute until you're comfortable with the decent rate. Maybe it's just the thin air up here, but I keep breaking fins/fillets. The Fantom will handle some J's with no mods. Just remember, Up is easy.
-Ken

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Thanks - I won't be adding any more 'extras' from here on in. The ground is softer where I'll be flying - and closer to sea level, but in any case the additions so far (the bolts etc) are very much in line with what others at my club had flown.

I made a angle iron (or angle-wood) type fin alignment guide which worked well for fin attachment. I made internal fillets and then secured the backplate. Since I'm using an anodised alu retainer I ensured the rim of the MMT was flush with the backplate, then epoxied it in, and filleted. The screw inserts for the retainer were masked off during this to avoid any inadvertent blockage.

A couple of questions:

1) The blue tape marks the my intended positioning of my rail guides (I'll be using Acme conformal guides). I've noticed some rocketeers affix the aft rail guide or button nearer to the back end, and I'm curious what the reasoning is here...?

2) This is my first time sanding a polypropylene nose cone, and of course it scratches easily, but there's still a visible moulding seam (but now with added scratches). I'd welcome any ingenious techniques how to finish the nose cone and blend out the seams without distorting the nose. (Just progressive sanding, I guess..?)

The farther back your rail guides are, the longer they will work for you. As far as the nose goes, they are relatively easy to get right. Any sort of plastic filler down the seam followed by some light sanding will do the trick. I use Superfill because it sticks to the plastic really well and sands easily. I then give the nose a light sanding all the way around then hit it with plastic adhesion promoter. Once the promotor is dried, it gets a coat of primer. Up to this stage it's still a little harry with visible sanding gouges in it. Lightly sand the primer smooth until it's shinny and do it again. A nice coat of gloss once the primer is smooth cleans it up real nicely.

grouch said:

The farther back your rail guides are, the longer they will work for you. As far as the nose goes, they are relatively easy to get right. Any sort of plastic filler down the seam followed by some light sanding will do the trick. I use Superfill because it sticks to the plastic really well and sands easily. I then give the nose a light sanding all the way around then hit it with plastic adhesion promoter. Once the promotor is dried, it gets a coat of primer. Up to this stage it's still a little harry with visible sanding gouges in it. Lightly sand the primer smooth until it's shinny and do it again. A nice coat of gloss once the primer is smooth cleans it up real nicely.

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I had not heard of plastic adhesion promoter before today, do you have a specific brand that has worked well for you?

Thanks very much that's really helpful. Any particular brand recommendations re adhesion promoters?

Sorry Dragon64 - just realised I've echoed your question!

I have used Bulldog and Duplicolor and have had good results. I think the one I am using now is Rusto plastic primer and that has worked very good.

Thanks - I'll check those out.

One school of thought on button/lug placement is to have the forward one at CG and the rear at CP. The reasoning behind this is that once the forward button leaves the rail, if the rear button isn't at CP, it'll be fighting against the aerodynamic forces of the rocket and can lead to unexpected angular momentum off the rail.

Sometimes this leads to a relatively close spacing of the buttons which might cause binding. In this case, you can move the forward button further forward a bit.

To blend out the seams on the nosecone, you can use Bondo Glazing putty or Squadron putty (white is what I use). Both of these need LOTS of ventilation when you apply them. Also, wash the nosecone in hot, soapy water to remove any mold release. It's best to do this before sanding, but better late than never. After priming (or using the adhesion promoter) and the first couple of coats of color, you should wet sand with 400-800 grit sandpaper to remove as many fuzzies/scratches as possible. Another couple of coats of color will give you a nice, smooth nosecone.

Yea to dovetail Alpha's comment, clean the cone before you start. I did check BTW and the last stuff I used was Rusto Plastic Primer. It comes out a much lighter grey than their 2 and 1 Filler primer. I like to put the adhesion promoter on then lightly sand after dried then prime the cone with the same primer as the rest of the rocket to there is no gradient difference. The Squadron stuff works well too but once you use the SuperFill you won't want to use anything else. The stuff is an easy 2/1 mix and it doesn't smell much. It's thick like cold whipped peanut butter if there is such a thing. I just dip a plastic spoon in the blue stuff twice and the white stuff once and get to mixing (more like folding). It spreads easily and sticks where you want it. I was actually surprised how well it sticks to the LOC cones. I used a popsicle stick to get it into the seam then smooth it off with a rubber glove or a credit card bent to match the radius of the cone. Fast and easy. I have tried a bunch of others over the years and get rolling and lifting when sanding, the Super Fill doesn't. It just sands like soft balsa. Good stuff and you can use it for a boat load of other things. Easily worth the money and the $22 bucks spent on it will last a VERY long time. The stuff should be on every rocketeers bench.

https://www.aircraftspruce.com/catalog/cmpages/superfil.php?clickkey=8866

stantonjtroy said:

My wife did the exact same thing with her Fantom; Started stock for L1 then went with an Av bay for her L2 on a J350. Awesome flights both (see attached). As a side note; Best performance in the EXL configuration came from a Pro-X I540 WT. Hardest accelerating flight I've ever seen! The perfect rocket/motor combo. She did break a fin on a hard, High Wind recovery so she ultimately replaced the ply fins with S-Glass. That was well after the L2 flight on the J.
Best of luck!

Click to expand...

Agree. I built a stock Fantom and did my L1 on a H180, motor ejection. Added the AV bay and did my L2 on a DD CTI J357. Best flight ever.

The DD I motors are a low altitude blast.

Thanks very much that's all useful stuff - I'll try to get some.

Thanks - here's hoping my cert flight goes to plan - then I can try out these combinations!

grouch said:

Yea to dovetail Alpha's comment, clean the cone before you start. I did check BTW and the last stuff I used was Rusto Plastic Primer. It comes out a much lighter grey than their 2 and 1 Filler primer. I like to put the adhesion promoter on then lightly sand after dried then prime the cone with the same primer as the rest of the rocket to there is no gradient difference. The Squadron stuff works well too but once you use the SuperFill you won't want to use anything else. The stuff is an easy 2/1 mix and it doesn't smell much. It's thick like cold whipped peanut butter if there is such a thing. I just dip a plastic spoon in the blue stuff twice and the white stuff once and get to mixing (more like folding). It spreads easily and sticks where you want it. I was actually surprised how well it sticks to the LOC cones. I used a popsicle stick to get it into the seam then smooth it off with a rubber glove or a credit card bent to match the radius of the cone. Fast and easy. I have tried a bunch of others over the years and get rolling and lifting when sanding, the Super Fill doesn't. It just sands like soft balsa. Good stuff and you can use it for a boat load of other things. Easily worth the money and the $22 bucks spent on it will last a VERY long time. The stuff should be on every rocketeers bench.

https://www.aircraftspruce.com/catalog/cmpages/superfil.php?clickkey=8866

Click to expand...

Superfil is very good stuff! I stopped using that red Bondo putty after using Superfil. It fills better, is sandable, and very very strong...while being light. Here is my Level 3 rocket with Superfil used to smooth out fillets and fill voids.

I missed the Superfill recommendation in Jarrett's original post. I'm definitely going to have to get some of that to try.

Thanks for the recommendation - and congratulations on such an impressive looking Level 3 bird! I'm interested to know more - is that a LOC kit-bash, entirely scratch built or what?

Where do you get superfil? Red bondo is a bit of a pain.

Tim51 said:

I opted to get new fins of a different shape (more akin to a Nike Smoke). laser cut from 3mm aeronautical birch ply, and added an extra 3mm CR to the MMT, to allow me to create an internal fin can.

Click to expand...

Where did you source the new fins from?

Zeroignite said:

Where do you get superfil? Red bondo is a bit of a pain.

Click to expand...

https://www.aircraftspruce.com/catalog/cmpages/superfil.php?clickkey=8866

The one quart kit is all you need.