Building Two Mega DRM At Same Time

[SAC of MMMSClub]

This is my build of the Estes Mega DRM and some mods to the kit. The plywood parts and balsa sheets are very good. All the parts test fit well.



This panel of the directions could have used a few bits of info like measurements from baseline of how far up MMT to mark for CRs. Aft most CR is 12mm up MMT, CR with notches is 75mm up MMT and forward most CR is 12mm from end but this is not really necessary as it is behind the green ring that must be enlarged on Nose Cone of rocket. They show building from Aft CR, I am building from Forward CR back.


The balsa is very good and glues up nicely, I do not like how they suggest this part of the instructions. Once you have glued two pieces of the balsa sheets together on a nonstick surface, why go to the bother of tracing and cutting and sandwiching...The Plywood core makes a great cutting guide once it is securely glued to the balsa sheets. I just glued them down, put a sheet of plastic wrap over them and weighted them down. Just be careful near the fin tab with the glue, so far no tab problems.



This panel does not give a grit value for the type of abuse you want to inflict on the glueing surface of the plastic. 60 grit should make some nice scratches for the Epoxy to grab also scratch up the cardboard too. I like JB-Weld for this application, I have been told regular epoxy will do.

 

[SAC of MMMSClub]

With the enlarged green ring(s) and MMTs and motor retainers together, I set about determining what the placement of the CRs should be.



I am also easily confused and like to mark up Fwd/Aft just because.



I test fit the motor retainer and marked up how much MMT it used.



I did what the directions say, and stuck a fin in the ring to give me the distance but, it is just a little loose so I did not like the varying distances I was getting. The green ring makes a good marking guide.



The measurements you see here are after I put the fins and rings on the MMT held together with tape and had the Mrs. C, mark MMT while I held it all firm.



So the Motor retainer uses 12mm, second CR from 0.00 is 75mm. I am going to show you the rig in next post.

Scott

 

[SAC of MMMSClub]

Here is the fin can, the green ring stays on better than the Motor retainer.



So with the MMT even with the green ring, that is the same depth as Motor retainer, then the CR and Fin Tabs of all three fins the CRs looked perpendicular to the MMT.




This is the Forward CR with one of the first modifications. Forged Eye,w washers and Nut. Simple .25 hole in CR.


Ready for assembly.



All glued up and set aside to dry.

 

[dixontj93060]

Never heard of this rocket(?).

 

[SAC of MMMSClub]

Estes Proline ii Der Red Max in 4" BT = Mega DRM

 

[GRIFFIN]

Never heard of this rocket(?).

Estes Mega Der Red Max

 

[dixontj93060]

Estes Proline ii Der Red Max in 4" BT = Mega DRM

Oh.

 

[SAC of MMMSClub]

Here are some fin shots, after they glued up the balsa sheets we just glued up the plywood cores and glued them to the balsa sheets. Cutting them out by following the plywood core at a template.



The reason I traced the fin shape was to load the corners with glue as there was some gaping at the corners. After the fins are done we will sand til the laser burn fades



Do not be afraid of loading the glue on.



Shock cord attachment with 15 feet of 3mm cord.

 

[sodmeister]

Very nice ,detailed build review....I`m enjoying very much !

My Mega DRM is waiting in the wings ,ready to be built.

Paul t

 

[SAC of MMMSClub]

Very nice ,detailed build review....I`m enjoying very much !

My Mega DRM is waiting in the wings ,ready to be built.

Paul t

Thanks Paul, I appreciate that.

I have been working mostly on the fins since my last post. The plywood core and the balsa "laminating sheets" are good stuff and dry.

As I was glueing up the individual balsa sheets to make them big enough to cover the plywood core, I have seen some warping of the balsa sheets. No big surprise as I was adding moisture(glue) in an uneven manner.

I also experienced some warping of the partial build up, and the final product of the build up. All the fins are complete as far as the build up and are in sealing stage.


Here are the final four glue ups the shine on the table is plastic wrap as wood glue will not stick to it. I would glue them flat on the table and then cover with another sheet of plastic wrap and a larger compesion aid like a package of Avery labels and then weight it down. Wife was wondering why all her big pots were on the table filled with water.:bangpan: There was some gapping at one end on several, but no big deal as it could be used at the fin tab end of the glue up.


One of the final glue ups.


I had some Minwax poly left over and thought I would use it as the first sealer filler. The fins have got one coat both sides, dried, sanded smooth with 220 grit.



As I write this they are drying and tomorrow I will give them a gentle massage with 400 grit and move on to gray primer. That really seems a shame as poly makes any wood look great, even balsa, but I have decided to do a candy apple red over metallic base

 

[SAC of MMMSClub]

This is the left overs of the fin build up, so lots of 3mm balsa to use in other projects.:horse:

 

[sodmeister]

This is the left overs of the fin build up, so lots of 3mm balsa to use in other projects.:horse:

View attachment 110612

Wow ,that`s a lot of left over !!

Things are looking good ,keep up the great posts and pictures ,very useful.

Those fins look like hardwood flooring BTW LOL


Take care

Paul t

 

[SAC of MMMSClub]

Wow ,that`s a lot of left over !!

Things are looking good ,keep up the great posts and pictures ,very useful.

Those fins look like hardwood flooring BTW LOL


Take care

Paul t

Thanks again, I think a version of the fins left just poly with the tan trim could be a woody station wagon rocket.

I hope they look as good in Candy Apple over Metallic!:fly: I have been watching vids on line on how to do a Candy Apple paint job.

Ya, there are long with grain pieces from either side of the fin, and short cross grain pieces from the ends and some big flats from over the fin tabs. Times two sides, times three fins. There has to be two pounds of balsa in that photo.:jaw:

 

[SAC of MMMSClub]

I received my MDRM recently and all I can say is those fins are crazy big once you pull them out of he package and see them. Of course they are just upscaled from the original model, but this 4 incher makes the fin size seem silly, Cool, but silly.

The Mega DRM also offers lots of potential as a starting point for HPR uses and pretty much renders any 4 inch DRM upscale clone pointless, with the accurate 4inch nose and waterslide decals.

Sorry for the Hijack. Waiting for more pics

That nose cone is a big part of the price of the kit, I bet.

Ya, You could easily slide a 38mm MMT in this rocket.

 

[kelltym88]

That nose cone is a big part of the price of the kit, I bet.

Ya, You could easily slide a 38mm MMT in this rocket.

hehehe or a 54mm :cool2:

 

[SAC of MMMSClub]

hehehe or a 54mm :cool2:

Yes, depending on how heavy you build that might be necessary.:flyingpig:

I saw the quoted 500 foot flight estimate, and thought thats a good starting point!

I am using 29mm but with 4" of room to pack chute, I have the 6 grain motor case.....

 

[kelltym88]

If one were to totally glass it and beef it up and add nose weight it could easily handle a 54/1280 case or bigger. But that's alot of work. I'll probably just put a 38mm MMT in mine and glass the fins before putting them on. Shouldn't require too much extra weight, if any. With those big beefy fins, it should be plenty stable.

 

[SAC of MMMSClub]

If one were to totally glass it and beef it up and add nose weight it could easily handle a 54/1280 case or bigger. But that's alot of work. I'll probably just put a 38mm MMT in mine and glass the fins before putting them on. Shouldn't require too much extra weight, if any. With those big beefy fins, it should be plenty stable.

OMG yes it is way over stable.

 

[SAC of MMMSClub]

I am still coating the fins and letting them dry, but they should be smooth.:yawn:

I usually use sticker paper on small fins but this seemed like a job that warranted a real sand/fill/sand treatment.

I also stopped by a recommended auto store that has auto paint and painting supplies, for some prices on Candy Apple Red transparent paint:jaw::surprised::jaw::surprised: $11.oo for a

12oz. can Ford Candy Apple Red, and I would bet two if not three cans for this beast. Luckily the silver base and clear over coat do not have to be high dollar paint.

 

[new2hpr]

A forged eye bolt in an Estes kit? It probably weighs more than the rest of the rocket!
Looks good so far.
-Ken

 

[SAC of MMMSClub]

A forged eye bolt in an Estes kit? It probably weighs more than the rest of the rocket!
Looks good so far.
-Ken

Not this one!:lol:

 

[georgeb]

Thank you for the build thread,great pics and build techniques.I have a MDRM to build. I wonder how many DRM's will be flying at the sod farm this spring. Looking forward to flying with the club

 

[SAC of MMMSClub]

Thank you for the build thread,great pics and build techniques.I have a MDRM to build. I wonder how many DRM's will be flying at the sod farm this spring. Looking forward to flying with the club

We will have quite a drag race going this spring -> summer, as I am co building two, plus yours and another with a 38mm MMT Hehehehe.......:lol:

Except i am beginning to think that the poly is going right through the balsa and filling the fins like a fuel tank... I should have done one with sticker paper just to see if it works in large scale.

 

[georgeb]

Scott,what kind of arrangement do you do with the Kevlar in the recovery part of the rocket. Do you use the elastic thats included?

 

[SAC of MMMSClub]

Scott,what kind of arrangement do you do with the Kevlar in the recovery part of the rocket. Do you use the elastic thats included?

I did not find any Kevlar in my kits so I think you are looking at the 15ft. of cord in my pics.

The cord in the photo I took is 3mm+/- climbing accessory cord from EMS. I do not know the breaking load for it, but I would bet it is rated at one thing, and breaks at another. They also have 1.5mm and 2.75mm and rate them at 75lb. and 200lb. respectively so 3mm should be more than 200lb and unlike kevlar this should have some give to it.

If I do anything with that elastic stuff, I would lay out the strong cord and the elastic strap and see how they compare. I have 15 ft. and 20 ft. of cord from EMS.

I would want to compare and see if I have enough elastic to double it, or if I can only make one run from anchor point to anchor point.

You want the strong cord to become taunt (not full about to break taunt) just before the elastic strap is about to reach same stress point.


At the Eye or (quick link) you need to attach both cord and elastic strap. On the strong cord at the point that you can stretch the elastic strap no more put a piece of tape.

Back down the strong cord toward the rocket X* inches, make a loop knot in the strong cord.

(*Nylon cord or rope is rated in falls and % for elongation to failure, I have no idea what or even if this cord will have a % elongation as it is not sold to be mission critical.):confused2:

So SWAG 1% 2 to 3 inches and make a loop. Tie off other end of elastic strap to the loop, or stretch it out doubled over and loop it and tie back to eye or quick link.

Now you have a shock cord with elastic and strong cord so if elastic fails the strong cord will hopefully hold.

That is what I have seen done and pic of on the forum, I think it was an L-3 build so it was all heavy nylon and Kevlar tubular strapping.

Maybe I will see if my kids high school has a strain gage recording meter and do a pull test on the 3mm cord.

I would really like to see how many hundreds of pounds it takes to make it fail.

I will put up pics in a bit.

 

[georgeb]

Cool,Thank you.I am looking forward to seeing the cords assembled. Easier for me to copy .

 

[SAC of MMMSClub]

Cool,Thank you.I am looking forward to seeing the cords assembled. Easier for me to copy .

op:op:op:

Hey G,
This is what I did...



Just a loop knot at the end of the cord and elastic on the quick link.



No knots just loops so it can be disassembled



As you can see the elastic is shorter than the cord and there is lots of slack in the cord, but when the cord is pulled taunt the elastic is just about at full extended stretch.

I am sure this is way over kill but separation at apogee sucks!!! your nose cone and parachute go for a ride and your hard work comes in hard and fast.

Scott

 

[georgeb]

Cool,I will do the same. Thank you Scott.

 

[sodmeister]

Well Scott, I just cracked the bag on my Mega DRM and wow ,half the bag is almost sheets of Balsa ,nice and flat and very dense ,which seems to be the norm with Estes kits.I`m very pleased ,should be a fun build ,and your play by play will come in handy.

Take care

Paul T

 

[krusty]

Subscribed

I've got a MDRM on order. It should be here in a couple of weeks!

The build looks great so far! Thanks for sharing!

Krusty