Filling cluster motor mount....

[sbaryenbruch]

I am starting my Richter Recker soon and had a question about the motor mount. Are there any alternative methods for filling the gaps in the motor mount? Has anybody tried the foam in a can? Thanks for any help.
Scott B.

 

[rstaff3]

The canned foam is messy and hard to work with. Polyurethane glues like Gorilla glue might work work better. They are easier to apply and will also expand to fil gaps. I have also used tissue wetted with white or carpenter's glue successfully on modrocs.

 

[cls]

when building my RR I had reservations about the tissue-paper-and-glue method. mainly I was worried about weight - what a lot of goop to put in between those 3 MMTs!! so I made a "BT-69" diameter 1/8" plywood disc and cut 3 BT-50 holes in it. I glued that to the top of the cluster, and put just a little glue & tissue around the MMTs to seal their tops against the plywood. this works great!!

but everyone says the tissue-and-glue method works fine. I will try that on my next cluster.

 

[rstaff3]

I have only used the tissue and glue method for small gaps myself, I guess I didn't have a good mental picture of the RR. I wouldn't fill huge spaces with polyurethane either. The latter would work well if you had a thin ring to reinforce. This method is described in the review of the Cycline 3 Fun Fat Rocket on EMRR. (probably in any of the Cycline reviews there)

 

[firemanup]

I think i saw Jim Flis describe in another thread that most of that weight is from the water in the glue, and as the glue cures the water evaporates out....hence reducing the weight

 

[flying_silverad]

First I get some balsa dust and I pack any holes or gaps. Then hit it with a squirt of CA and watch the smoke! Turns pretty hard. I finish it off with a couple of coats of Elmer's Polyurethane glue.
here's a pic...
Center hole sealed!

 

[jflis]

Originally posted by firemanup
I think i saw Jim Flis describe in another thread that most of that weight is from the water in the glue, and as the glue cures the water evaporates out....hence reducing the weight

yep, that's about right (with regard to elmers and other water based glues), CA and Epoxy's don't loose such weight however.

The only real concern is if you are too agressive. I know of one case where the wetness of the glue softened the motor tubes and there was some damage when the tissue was pushed into the holes too strongly.

The gaps that you're trying to fill in the Richter Recker aren't really all that large. Smaller than 1/4" for the most part. and you don't need a *lot* of tissue. Just a small ball on each end of the motor mount for each of 3 gaps.

jim

hey hey, post 2600!

 

[cydermaster]

Originally posted by jflis
hey hey, post 2600!

I had a modem which ran at that speed - and we moan about dialup speeds!

I put a thin layer of that useless car-bodywork-finishing epoxy, which I bought by mistake, over the cured tissue/glue balls, on the engine block side of the MMT assembly. I've not flown my RR yet, so I don't know if its too heavy or not, but its near-enough airtight.

 

[rstaff3]

hey hey, post 2600! [/B]

OK, we all know you are in the lead and pulling away. At least you didn't post just to talk about your count....OOOPS....my bad